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Manual - Department of Physics

1. ______________ _ CalculatiODS e A SAMPLE RESISTIVITY AND HALL VOLTAGE PROGRAMS Test Configurations Instrument Programming 2 sisien hob es han the eme nET UEA TPES PRO WEKE EAEE ESEE Program 1814 eet __________ SECTION 4 SERVICE INFORMATION 4 1 4 2 4 3 4 3 1 4 3 2 4 3 3 4 34 4 3 5 4 3 6 4 3 7 INTRODUCTION ee HANDLING AND CLEANING PRECAUTIONS 55 45 hh t rRXRRRAa PERFORMANCE VERIFICATION nus sited E 00a SOV ERE E ap xar kk ka ki aer sae aqa saa Environmental Conditions den den nba ceri ros dor Le RA AUR Warm Up Period 2545 4 ex bes neue Recommended Equipment 4 200184 ek LEED EAS E te EC IRE ET RES High Impedance Considerations pp Input Current Verification ____________ e x Input Resistance Verification Voltage Offset Verification 4 5 1 4 5 2 4 5 3 4 6 4 7 4 71 4 7 2 ADJUSIMENIS SEE AES Environmental Conditions Warm Up Period PvP rRem Recommended Test Equipment Adjustment Locations sisse
2. Rees ee Ese Sema es 4 5 Connections for Voltage Offset Adjustment pp 4 6 Connections for Common Mode Adjustment pp 47 Common Mode Adjustment Waveform 222522555552 ted Wate TE RR SH AE PE Rari 4 8 Model 7065 Block Diagram sender SERERE EGGPEERR E NEA RENT AS tr PEOR EET RS SECTION 5 REPLACEABLE PARTS 5 1 Model 7065 Component Location Drawing onn REA A REL CER E RE eves us 5 4 5 2 Model 7065 Schematic paa P ard 5 5 vi Contains information on Model 7065 features supplied accessories as well as recommended equipment SECTION 1 General Information Details installation of the Hall Card in a Model 705 or 706 Scanner outlines connections to various types of specimens and also discusses measurement considerations Covers basic applications for Hall voltage and resistivity measurement of van der Pauw bar bridge and paral lelepiped samples and includes example programs SECTION 2 Operation SECTION 3 Applications Contains performance verification adjustment and troubleshooting procedures for the Model 7065 SECTION 4 Service Information Lists replacement parts and also includes component layout and schematic drawings for the Hall card SEC
3. 2 24 Connections for Guarding Using 6167 Adapter iss cd ess ma re ehh 2 25 Equivalent Circuit for Input Guarding 2 26 Low and High Resistivity Equivalent Circuits 2 27 Gain Error LO vs HI Resistivity RE EROR ERO ira 2 28 Noise Performance LO vs HI Resistivity Setup es 5isdosesss oso aye Rd Era Saas Ea ER AR 2 29 Leakage Resistance Effects 42 dus bea erc b E OE RC KO _____ 2 30 Input Capacitance Effects osos vero ERR WES 2 31 Exponential Response of Input Voltage ranean 2 32 Multiple Ground Points Create a Ground Loop eot rad X tacens VR Ra Ee iX ER LUE 2 33 Eliminating Ground Loops Lu ies a dada da dax ERE ER d a RR e bd a a RSS RE ERE 2 34 Offset Cancellati n si ___________ SECTION 3 APPLICATIONS 3 1 Hall Effect Sign Conventions for n type Materials 3 2 Hall Effect Sign Conventions for p type Materials 3 3 Resistivity Measurement Conventions eR EC Y EROR GC KORR n WORDS RR ROT c 3 4 Hall Voltage Measurement Conventions pp 3 5 Measurement Configuration for Resistivity and H
4. 455 BUS PROGRAMMING 25542454 Reuter EE Ge Patr teehee wu Matrix Bus Commands doceo coo weer PEE wes ig M eU P be Example Programs e q e 3 s q q q 3 9 s s 9 s 4 s 9 lt s s s p s 6444 4 9 39 9 o3 c on n 2 10 2 10 1 2 10 2 2 10 3 2 104 2 10 5 2 10 6 2 10 7 2 10 8 SECTION 3 APPLICATIONS 3 1 3 2 3 3 3 3 1 3 3 2 3 3 3 34 34 1 34 2 34 3 3 5 3 5 1 3 5 2 3 5 3 3 5 4 3 6 3 6 1 3 6 2 3 6 3 3 64 3 6 5 3 7 3 71 3 7 2 3 7 3 3 74 3 8 3 8 1 3 8 2 3 8 3 MEASUREMENT CONSIDERATIONS Tm Input Voltage Levels sss ein dU ___________ Leakape Resistance 455552 nde pen lade E EE Ped Input Loading qs vie Sede Ab PIU EP OLI Fe augu Input causes nats yan ds esa ed Y XxGu qe E Electrostatic _ ______________ M P TR Ground LOOPS EN PUTEM Offsets RT aa INTRODUCTION 2 153 uya sn yaaa E panata asy codec tien eo SC en ipao ne RECOMMENDED EQUIPMENT 32e mara nho Cx or Ich Rn EUR des RE dox CIR e
5. 9 9 o3 s es 3 a s 4 s s sa san q n sq s s s 9 9 n w s q sn s e q v 9 4 v n 9 3 5 4 c HANDLING PRECAUTIONS MODEL 7065 INSTALLATION Installation in the Model 705 Scanner rm Installation in the Model 706 CONNECTIONS Card Connectors e ot e s s e s s s s q lt q s s o sn X 4 s q s q 3 s s s s 9 v s s s v on n e s e q o9 s e s s s s e v s q s c q 3 s s s w o q q q q q e v v m on Recommended Cables and Wires Cable and Wire Pr paration hate EC DECR ADR REOR ER Van der Pauw Sample Connections asses ert RR RAE ERR Ve AVENIR AR PERS Bar Sample Connections ceesesasas OT ARDOR BER OC Aa Bridge and Parallelpiped Type Sample iu ode na E Neo EAR TSS Cra eq doi ated Shorting the Current Monitor QUEUE eese pue
6. 1040 DATA 01 2002 1003 30 04 4 1050 DATA NO 2N02 1N03 53N04 4X 1060 DATA 02 2001 1003 3004 4 1070 DATA NO2 2N01 1N03 3N04 4X 1080 DATA 02 2001 3003 4004 1 1090 DATA NO2 2N01 3N05 4N04 1X 1100 DATA 02 3001 2003 4004 1 1110 DATA NO2 3N01 2N03 4N04 1X 1120 DATA 02 3001 4003 10 04 2 1130 DATA NO2 3N01 4N03 1NO4 2X 1140 DATA C02 4C01 3C03 1C04 2X 1150 DATA 02 4 01 3 03 1 04 2 1160 DATA 02 4001 1003 2004 3 1170 DATA NO2 4N01 1N03 2N04 2X 1180 DATA 02 1001 4003 2004 3 1190 DATA 02 1 01 4 03 2 04 3 3 33 APPLICATIONS Program 3 Bar Sample Resistivity HP 85 Version 19 20 30 40 50 60 70 80 30 190 110 120 130 140 150 150 170 180 199 200 210 220 230 240 250 250 270 280 230 300 510 320 350 340 350 350 370 380 580 400 410 420 430 440 450 450 470 480 490 500 3 34 CLEAR W 5 0 FIVE SECOND DELAY Pi 712 220 ADDRESS IS 12 P2707 186 ADDRESS IS 7 P3 717 705 ADDRESS IS 17 P4 722 485 ADDRESS IS 22 DISP THIS PROGRAM MEASURES DISP RESISTIVITY OF BAR TYPE SAMPLES DISP THE 7065 HALL CARD MUST DISP BE IN CARD 1 LOCATION DISP DISP PRESS PAUSE CLEAR DISP SELECT CARD RESISTIVITY SETUP DISP DISP 1 LOW RESISTIVITY DISP 2 HIGH RESISTIVITY DISP INPUT A IF A lt t OR 822 THEN 150 IF A THEN Z N 5 4X ELSE 2 C05 4X 705 COMMAND STRING DISP INITIA
7. Column 5 Row 4 State Open Low resistivity Closed High resistivity 2 7 2 Input Characteristics Table 2 4 summarizes input characteristics for the low and FROM INPUT RELAYS TO OUTPUT RELAYS A HIGH RESISTIVITY OPERATION high resistivity setups In addition to affecting the resistivity setup selection also affects input current noise and off set voltages Note that the input characteristics of the low resistivity setup are exclusive of the voltmeter which can also affect the sample under test Table 2 4 Input Characteristic Summary Low Resistivity Setup High Resistivity Setup Parameter gt 10GQ lt 0 InA lt 50 Input Impedance Input Bias Current Input Voltage Noise 0 1Hz to 10Hz bandwidth 2 7 3 Equivalent Input Circuits Figure 2 26 compares the input circuits for the low and high resistivity setups With the high resistivity setup the signal is routed through the buffer amplifier which also provides the guard for the input circuit In contrast the signal com pletely bypasses the buffer amplifier in the low resistivity mode however the guard is is still driven by the buffer amplifier FROM INPUT RELAYS TO OUTPUT RELAYS B LOW RESISTIVITY Figure 2 26 Low and High Resistivity Equivalent Circuits 2 33 OPERATION 2 7 4 Resistivity Setup Criteria The setup used depends primarily on the r
8. IZE E83 11228 R33 Figure 5 1 Model 7065 Component Location Drawing 5 4 I MONITOR AN Lo lt OD 00 won ITHLEY INSTRUMEN CLEVELAND DHID EFFECT CARD P AN D 120 NC NC gt i _ 4 NC gt 16 3301 2 Ya M 3301 LA 23 Fu ro oo 5 5 P EFFECT CARD SHEET 2 OF 2 INDEX Addenda Adjustments 4 8 Bar Sample Connections 2 11 Measurement Bridge Sample Connections Measurements Cautions Cleaning Component Location Drawing 5 1 Connections Bar Sample 241 Bridge Sample 2 16 Cable and Wire Preparation Card Connectors 241 IEEE 488 2 21 Parallelepiped Sample 2 16 Van der
9. V SOURCE USE BANANA PLUG FOR CONNECTION SC 72 BLACK WIRE TROMETER 617 ELECTRO ANALOG OUTPUT COMMON Figure 4 2 Connections for Input Resistance Verification SERVICE INFORMATION 4 3 7 Voltage Offset Verification Connections Figure 4 3 shows connection for voltage offset verification The HI terminal of the DMM is to be connected to terminal 5 of the terminal strip while the DMM LO terminal and the center contact of the sample input being verified must both be connected to analog ground as shown on the diagram This connection should be made as follows 1 Prepare the end of a Model 7025 triaxial cable by stripping 1 inch of insulation off the end and cutting off the shields see Figure 2 6 in Section 2 2 Twist together the center conductor and one end of an 5 72 wire black 3 Place the junction in a small box in between two pieces of foam to prevent air currents from affecting the reading Also keep the cable as still as possible 4 Connect the free end of the black wire to Hall Card analog ground and connect the triaxial cable to the sam ple input being tested Procedure 1 Install the Model 7065 in the scanner mainframe and turn on the power 2 Using front panel Program 6 select the matrix mode on the scanner pole 0 3 Select the DCV function and the 300mV range on the DMM 4 Temporarily disconnect the DMM and short its input Zero the DMM remove the short and reconnect
10. uW 5 Wen GD 10 HI 0 GND gt 2 E 2 WITHIN 30V OF EARTH AMPLIFIER CONFIGURATION WARNING MAINTAIN INPUTS AMD GUTPUTS o lt o w E i r P e gt w x COMMON MODE ADJUSTMENT R23 Manufacturer and Description Specifications Model gt 10MHz bandwidth 10mV div sensitivity Keithley Model 196 TEK 2235 Keithley Model 705 or 706 Keithley part R 76 10k Keithley Model 7061 INPUT 4 ADJUSTMENT INPUT 3 ADJUSTMENT INPUT 2 ADJUSTMENT INPUT 1 ADJUSTMENT CURRENT END VIEW Figure 4 4 Adjustment Locations 4 4 5 Offset Adjustments Connections Connections for making offset adjustments are shown in Figure 4 5 The HI input lead of the DMM is connected to terminal 5 of the strip while DMM LO is connected to analog ground The center connector of the sample input jack being adjusted must also be connected to analog ground on the scanner card See paragraph 4 37 for details on connecting the wire and cables together Procedure 1 With the power off install the Model 7065 in the scan ner mainframe with all shields in place 2 Using Program 6 select the matrix mode pole 0 Press ENTER 3 Close crosspoint 54 to select the high resistivity mode 4 Select the 300mV DC range on the DMM Temporarily disconnect the DMM short its input and then enable ze
11. 2 THEN 190 240 IF A 1 THEN 7 05 4 ELSE Z CO05 4X 705 COMMAND STRING 250 DISP 280 DISP INITIALIZING INSTRUMENTS 270 REMOTE P1 P2 P3 P4 PUT INSTRUMENTS IN REMOTE 280 CLEAR 7 SEND DEVICE CLEAR 290 INITIALIZE 705 300 OUTPUT P3 AQX MATRIX MODE 310 OUTPUT P3 178 PROGRAM RESISTIVITY 320 INITIALIZE 485 330 OUTPUT P4 RIX 2NA RANGE 340 WAIT 1000 SETTLING TIME 350 OUTPUT C1X ZERO CHECK ON 360 WAIT 1000 370 OUTPUT Z1X ENABLE REL 380 WAIT 1000 390 OUTPUT COX ZERO CHECK OFF 400 OUTPUT ROGIX AUTORANGE NO PREFIX 410 INITIALIZE 196 420 OUTPUT P2 ROFOSS61X AUTORANGE DCV RATE NO PREFIX 430 OUTPUT Pt U1OX 220 109 COMPLIANCE 440 DISP 220 CURRENT 500fA 1 0MA 450 INPUT I INPUT 220 CURRENT 450 I ABS I 470 IF 1 lt 5 E 13 OR I gt 1 THEN 440 480 I2 I DEFINE NEGATIUE CURRENT OF SAME MAGNITUDE 480 OUTPUT I I X PROGRAM 220 CURRENT 500 DISP ENTER SAMPLE THICKNESS CM 3 36 Program 4 6 and 8 Contact Sample Resistivity HP 85 Version Continued 510 INPUT T 520 T ABS T 530 DISP ENTER SAMPLE WIDTH 548 INPUT Wl 550 WI ABS WI 550 DISP ENTER SAMPLE Di DIMENSION CM 570 INPUT Dl 580 D ABS CDI 590 DISP ENTER SAMPLE D2 DIMENSION CM 500 INPUT D2 610 D2 ABS D2 620 DISP PRESS CONT TO MEASURE 630 PAUSE 640 MAIN MEASUREMENT LOOP 650 RESTORE CL
12. Fake ud qud IEEE 488 Bus Connections MATRIX AND TEST Model 7065 matrix Test System CONFIGURATIONS s s s e 9 s e 8 e s s 9 s sn 4 q s s w s s s 9 s q s amp e q s s e q e s e a w lt lt a mom s s n s s s m om o n n s s m s q lt q s e lt q 4 e q s 4 e s e n e q e a 9 v GUARDING METHODS Principles of cpa unra ee Di ns ae UE que P met eadein Sube Current Source Input Guarding Ne Sample Input Guarding erp chien _ ________ RENI Paw E SE ke RESISTIVITY SELECTION bia eda M as Selecting the Resistivity Setup sue Xue cea Pn ARN ACRI Input Characteristics soseer recre snide s sas Equivalent Input suec dde Resistivity Setup Criteria ciere ed xoa EROR REESE RACE E ass XR REA FRONT PANEL SCANNER PROGRAMMING ss Py p nn Entering the Matrix Mode ste REQUE E US ees dtd a E Scanner Display Formats Crosspoint Programming
13. 2 6 1 Principles of Guarding Guarding consists of using a conductor driven by a low impedance source to totally surround the leads carrying a high impedance signal If the output voltage of this low impedance source is kept at the same potential as the signal itself the result will be reduced leakage effects decreased response time and lower noise To approach the concept of guarding let us first consider the unguarded circuit shown in Figure 2 19 Here the sam ple voltage is represented by E while the equivalent resistance is Rs The cable leakage impedance is Zz and represents the actual measured voltage The sample resistance and cable impedance form a voltage divider that attenuates the sample voltage as follows 2 Es Zr Rs Thus to keep the error caused by leakage resistance under 0 1 the leakage resistance must be at least 1000 times the sample resistance For low to medium resistivity samples the leakage resistance is generally sufficiently high so as to have minimal effects However with very high resistivities the errors due to leakage resistance in unguard ed circuits can be intolerably high 2 24 OPERATION R SAMPLE RESISTANCE ES SIRE EQUIVALENT CIRCUIT Figure 2 19 Unguarded Circuit 2 25 OPERATION Guarding the circuit minimizes these effects by driving the cable shield at signal potential as shown in Figure 2 20 Here the Model 7065 buffer a
14. II GET CURRENT READING FROM 485 OUTPUT Pi FOX TURN OFF 220 OUTPUT OUTPUT P3 02 4 03 1 04 2 OPEN CROSSPOINTS BEEP CLEAR CLEAR 7 SEND DEVICE CLEAR DISP MEASUREMENTS COMPLETE DISP MEASURED CURRENT I DISP MEASURED VOLTAGE DISP PRESS CONT TO CALCULATE DISP RESISTIUITY PAUSE P U Y X X I DISP RESISTIVITY P OHM CM DISP DISP REPEAT TEST TY N INPUT AS IF ASL1 1 Y THEN CLEAR 8 GOTO 250 GOTO 950 ERROR CHECKING CLEAR CLEAR 7 SEND DEVICE CLEAR DISP SAMPLE VOLTAGE IS OVER DISP 8U 7085 LIMIT DISP DO YOU WISH TO DISP 1 RESTART MEASUREMENT DISP 2 ABORT THE PROGRAM DISP INPUT IF lt 1 OR gt 2 THEN 860 IF A 2 THEN 950 CLEAR GOTO 230 END 3 35 APPLICATIONS Program 4 6 and 8 Contact Sample Resistivity HP 85 Versiom 10 CLEAR 20 W 5000 FIVE SECOND DELAY 30 DIM A t251 U 4 40 P1 712 220 ADDRESS IS 12 50 P2 707 195 ADDRESS IS 7 60 P3 717 705 ADDRESS IS 17 70 P4 722 485 ADDRESS IS 22 80 DISP THIS PROGRAM MEASURES 90 DISP PARAMETERS TO CALCULATE 100 DISP RESISTIVITIES OF 6 OR 110 DISP 8 CONTACT SAMPLES 120 DISP THE 7065 HALL CARD MUST 130 DISP BE IN CARD LOCATION 140 DISP 150 DISP PRESS CONT 150 PAUSE 170 CLEAR 180 DISP SELECT CARD RESISTIUITY SETUP 190 DISP 200 DISP 1 LOW RESISTIVITY 210 DISP 2 HIGH RESISTIVITY 220 INPUT A 230 IF A 1 OR
15. Programming Setup Criteria RFI Safety Precautions Preceding Table of Contents Safety Symbols and Terms Static Sensitive Devices Scanner Compatibility 1 3 Tables List v Front Panel 1 Theory of Operation 4 12 IEEE 488 Bus Programmin Installation of Card In 222 Schematic Diagram 5 1 Van der Pauw Sample Service Information Connections Specifications Measurement The number following each entry indicates the page number Troubleshooting Information Verification Procedure Input Current Input Resistance Voltage Offset Warnings Warranty KEI I HLEY Service Form Model No Serial No Date Name and Telephone No Company List all control settings describe problem and check boxes that apply to problem I Intermittent 1 Analog output follows display 1 Particular range or function bad specify IEEE failure 1 Obvious problem on power up Batteries and fuses are OK 1 Front panel operational 1 ranges or functions are bad Checked all cables Display or output check one Drifts I Unable to zero I Unstable 1 Will not read applied input 1 Overload 1 Calibration only 1 Certificate of calibration required Data required attach any additional sheets as necessary Show a block diagram of your measurement system including all instruments connected whether power is turned on or not Also describe signal source Where is t
16. SERVICE INFORMATION 4 4 6 Common Mode Adjustment Procedure 1 Connect the Model 7065 to the scanner through the ct 5 Model 7061 Universal Adapter Card used as an extender Figure 4 6 shows the necessary connections for this adjust to allow access to the adjustment See the Model 7061 ment The 10kQ resistor is connected between analog ISHUCHOTE Guide for more information ground the terminal strip digital ground which 2 Make certain that all Model 7065 shields are in place and be accessed at the screw on the small power supply shield properly secured Connect the oscilloscope high input to analog ground and 3 Set the oscilloscope time base and input attenuator to connect scope low to digital ground at the shield screw Use view the waveform shown in Figure 47 shielded cable between the oscilloscope and the card and 4 Adjust the common mode potentiometer R23 for best resistor shield LO center conductor HI symmetry and minimum amplitude of the waveform 5 Turn off the power and disconnect the resistor and oscilloscope once the adjustment is complete CONNECT TO TERMINAL BLOCK ANALOG GROUND ANA 10 HI GD GND gt t 2 gt 2 E WARNING INPUTS AND OUTPUTS WITHIN 30v OF EARTH Y 7065 HALL EFFECT CARD CURRENT USE SHIELDED CABLE FOR CONNECTIONS OSCILLOSCOPE DIGITAL GROUND ACCESS POINT MODEL 7065 Figure 4 6 Conn
17. 2 3 Resistivity Select Summary _ ______ 2 4 Input Characteristic SUMMARY sus 20s os ne ______________________ 2 5 Model 705 Unit 1 Column Summary by cau esce RE 4 e 2 6 Model 705 Column Assignments pp 27 Model 706 Unit 1 Column Summary by Cards ss sssuseuesisssesesauesesnes metersues 2 8 Model 706 Column Assignments Nee pK A 2 9 IEEE 488 Bus Command Summary 2 15 suat us rg X pP Ea isse Rua epa 2 10 Voltage and Percent Error For Various Time Constants SECTION 3 APPLICATIONS 3 1 Recommended Equipment ERE RARE RA na eae ee tase eine 3 2 Measurement _________ ______________ 3 3 Crosspoint Summary for Resistivity Measurements 3 4 Crosspoint Summary for Hall Voltage Measurements 3 5 Minimum and Maximum Potentiometer Values for Hall Bar Measurements 3 6 Crosspoint Configurations for Bar Measurements 37 6 Contact Sample Resistivity Measurements 3 8 8 Contact Sample Resistivity Measurements 3 9 6 Contact Sample Hall Voltage Measurements 3 10
18. 4 Program crosspoint 54 to select low or high resistivity This crosspoint should be open for low resistivity and it should be closed for high resistivity 5 Program the Model 220 current to the desired positive current value in the range of 500fA to 100mA The max imum current that can be used will depend on the resistance of the sample remember that the maximum Model 7065 input voltage is 8 6 Close the appropriate crosspoints for the sample by pro gramming the scanner Table 3 7 or 3 8 Zero the Model 196 and enable the Model 485 relative function 7 Turn on the Model 220 output by pressing the OPERATE key 8 Note and record the voltage Vi and current readings on the Models 196 and 485 9 Turn off the Model 220 output open the presently clos ed crosspoints and close the second set of crosspoints listed in Table 37 or 3 8 Enable REL on the picoammeter then turn the Model 220 output back on Measure the voltage V 10 Program the Model 220 for a negative current of the same magnitude as is presently programmed APPLICATIONS 11 Note the Model 485 current reading and compare it to the one obtained in step 8 If the current magnitudes are not exactly the same reprogram the Model 220 as necessary so that the magnitude of the current is as close as possible to that obtained in step 8 12 Repeat steps 6 through 11 and measure V and V by closing the crosspoints indicated in the appropriate table Table 37 or 3
19. I is the current measured by the Model 485 in amperes are voltages measured by the Model 196 see Table 3 4 Note that Rac and Rup should be within 10 of one another or the sample is not sufficiently uniform Once and Rup have been calculated the average Hall Coefficient Rz ve can be determined as follows Rac Rup Ru vG 2 3 5 4 Hall Mobility Calculation Once the Hall coefficient and resistivity are known the Hall APPLICATIONS mobility can be calculated as follows Pavc Where the Hall mobility in cm V s the average Hall coefficient in cm C Pave the average resistivity in ohm cm 3 6 MEASURING BAR TYPE SAMPLES The following paragraphs discuss procedures and test con figurations for measuring resistivity and Hall voltage measurements on bar samples 3 6 1 Test Configurations Figures 37 and 3 8 show the general test configurations for making resistivity and Hall voltage measurements The two setups are very similar except for the way the voltmeter is connected For resistivity measurements Figure 3 7 the voltmeter is connected between terminal 4 and 5 of the ter minal block For Hall voltage measurements a suitable potentiometer is to be connected between terminals 4 and 5 while the voltmeter is connected between the wiper of the pot and terminal 3 of the block The crosspoints that must be closed depend on whether resistivity or Hall
20. TAIAX OUTPUT CURRENT SOURCE ANA 10 f HIGD tO 3 9 5 2 i 2 2 A CONNECTIONS 6167 GUARDED MALE TRIAX ADAPTER T get HI RELAYS GUARD OUTPUT COMMON J GND SHELL 4 ANALOG GUARD GUARD INSULATED GROUND PROTECTION IRCUIT AMPLIFIER OUTPUT FEMALE TRIAX CIRCUITS 220 CURRENT SOURCE B EQUIVALENT CIRCUIT 7065 CARD Figure 2 24 Connections for Guarding Using 6167 Adapter 2 31 OPERATION CURRENT INPUT SWITCHING BUFFER TRIAX SAMPLE RELAY K1 K8 U1 U4 INPUT 1 OF 4 g Eee ces TO CROSSPOINT TRIAXIAL CABLE 10kQ BUFFER OUTPUT PROTECTION Figure 2 25 Equivalent Circuit for Input Guarding 2 32 2 7 RESISTIVITY SELECTION The Model 7065 may be operated in either the low or high resistivity mode as discussed in the following paragraphs 2 7 1 Selecting the Resistivity Setup The SAMPLE INPUTS can be programmed for low or high resistivity by controlling the state of crosspoint 54 column 5 row 4 To select high resistivity close crosspoint 5 4 to select low resistivity open crosspoint 54 Table 2 3 sum marizes these programming states Scanner programming is discussed in paragraphs 2 8 and 2 9 Note that all four sample inputs are controlled simul taneously by selecting crosspoint 54 Table 2 3 Resistivity Select Summary
21. THEH ELSE ELSE END IF ABORT 7 7 EHAELE Fi 2 STATUS fs Si 5 IHFLIT MESSAGES A IF THEH Display variables or literals on CRT Enable SRQ interrupt Clear SRQ interrupt Prompt for and input variable Conditional branching Send IFC 3 23 APPLICATIONS 4 SAMPLE INPUTS VOLTAGE OUTPUT MODEL 220 CURRENT SOURCE MODEL CURRENT INPUT PICOAMMETER 196 DMM SOURCE CURRENT MONITOR OUTPUT 7065 CARD IEEE 488 BUS HP 85 OR IBM PC 8573A COMPUTER Figure 3 16 Test Configuration for Programs 1 2 5 and 6 3 24 APPLICATIONS 4 1 mm Te 2 5 OUTPUT MODEL 220 MODEL MODEL CURRENT CURRENT 196 DMM 485 SOURCE SOURCE PICOAMMETER INPUT 7065 CARD IEEE 488 BUS HP 85 OR IBM PC 8573A COMPUTER Figure 3 17 Test Configuration for Programs 3 and 7 3 25 APPLICATIONS SAMPLE INPUTS VOLTAGE OUTPUT MODEL 220 MODEL MODEL CURRENT 485 SOURCE 196 DMM PICOAMMETER 7065 CARD IEEE 488 BUS HP 85 OR IBM PC COMPUTER Figure 3 18 Test Configuration for Programs 4 and 8 3 26 3 8 2 Instrument Programming The instruments in the test setups are programmed as follows Model 196 The DMM is programmed for autoranging in the DCV function The instrument is programmed for the continuous trigger mode Also the data format is configured to eliminate the prefix since only numeric information is required Finally the instrument is
22. assises dia ns 2 8 Equivalent Circuit for Van Der Pauw Connections 2 9 Connections for Hall Voltage Measurements of Bar Type 2 10 Equivalent Circuit for Hall Voltage Measurements of Bar Samples 2 11 Connections for Resistivity Measurements of Type Samples 2 2 Equivalent Circuit for Resistivity Measurements of Bar Type Samples 2 13 Connections for 6 Contact Samples Nt 2 14 6 Contact Equivalent Circuit Current 1 2 Voltage 6 4 2 15 Connections tor 8 Contact Samples 2 16 8 Contact Sample Equivalent Circuit Current 1 2 Voltage 6 4 shown 2 17 Model 7065 Matrix Configuration 2 122 ed o n a REC Ex EIC RE eres 2 18 Basic Hall System Configuration sensus qu E a sepa vue av vae bx Geb Eo RU Ea qs Pl 2 19 Ung arded Circuit FTT VY R M 2 20 Guarded Circuit 2 2145 FEE Eua ou brides cmd ped am dod Ud a d dons 2 21 Guarding Jumper Configurations 2 22 Shield Removal sees 2 23 Connections for Unguarded Current Source Input
23. 1 7 1 8 1 9 1 10 INTRODUCTION FEATURES e s 9 e s s eq 3 s s q s e s sa s 9 q w s s s q e s 4 lt s lt lt q q 4 n P s ov s 9 o9 s o9 s s s s s sa s s ns q sa s s s s s sqa s 3 a n lt sa lt 3 q o 4 s q 4 sa s s ss s or oc on WARRANTY INFORMAIION MANUAL ADDENDA ________________ _ SAFETY SYMBOLS AND TERMS 76 45 23 4 e TUA RERO RUE PALA s sa SPECIFICATIONS 9 9 e s 9 e 3 44 4 s 4 s n e s s 9 m P 4 qa o lt o q o q q s q q a s v v UNPACKING AND INSPECTION 2 senses kh ed kr Gare Suns RIS ERE TR I EUR SU OR cays ewes REFACKING FOR SHIPMENT 5a oin Ert ea shee paqa ees Pues urbe ace wird dba RECOMMENDED EQUIPMENT CER ESSE NUUS EIE ab dra SCANNER COMPATIBILITY ulla AA Le de wks SOS rr TE ease SECTION 2 OPERATION 2 1 2 2 2 3 2 3 1 2 3 2 24 24 1 24 2 2 4 3 244 24 5 24 6 247 24 8 2 5 2 5 1 2 5 2 2 6 2 6 1 2 6 2 2 6 3 2 7 2 7 1 2 7 2 2 7 3 2 74 2 8 2 8 1 2 8 2 2 8 3 2 9 2 9 1 2 9 2 INTRODUCTION
24. 5C04 4X 1080 DATA NO2 2N01 1N035 5N04 4X 1090 DATA CO2 2C01 3C03 4C04 1X 1100 DATA NO02 2N01 3N03 4N04 1X 1110 DATA 02 3001 2003 4004 1 1120 DATA N02 3N01 2N05 4N04 1X 1150 DATA CO2 3C01 4C03 10C04 2X 1140 DATA NO2 3N01 4N03 1N04 2X 1150 DATA 02 4001 3003 1 04 2 1150 DATA NO2 4N01 53N03 1N04 2X 1170 DATA 02 4001 10 03 2004 3 1180 DATA 2 4 01 1 03 2 04 3 1180 DATA 02 1001 4003 2004 3 1200 DATA NO2 1N01 4N05 2N04 3X 3 44 APPLICATIONS Program 7 Bar Sample Resistivity IBM PC 8573A Version 10 CLS 20 DELAY 5000 FIVE SECOND DELAY 30 P1 12 P2 7 P3 17 P4 222 DEFINE INSTRUMENT PRIMARY ADDRESSES 40 D CHR 20 DEFINE DCL BYTE 50 NAS GPIBO CALL IBFIND NAS BRD FIND BOARD DESCRIPTOR 50 NA DEUI CALL IBFIND NAS 22 04 FIND 220 DESCRIPTOR NAS DEV2Z CALL IBFIND NA MISEX FIND 196 DESCRIPTOR 80 NAS DEV3 CALL IBFIND NA M70542 FIND 705 DESCRIPTOR 80 NAS DEV4 CALL IBFIND NAS 4855 FIND 485 DESCRIPTOR 100 CALL IBPAD M220 P1 SET 220 PRIMARY ADDRESS 110 CALL IBPAD M196 P2 SET 196 PRIMARY ADDRESS 120 CALL IBPAD M7 5 P3 SET 705 PRIMARY ADDRESS 130 CALL IBPAD M485 P4 SET 485 PRIMARY ADDRESS 140 PRINT THIS PROGRAM MEASURES THE RESISTIVITY OF BAR TYPE SAMPLES 15 PRINT THE HALL CARD MUST BE IN THE CARD LOCATION 16 PRINT 170 PRINT PRESS ANY KEY TO CONTINUE 180 AS INKEYS IF AS THEN 180 130 CLS 200 PRINT SE
25. 7065 Matrix Configuration OPERATION CRYOSTAT TEMPERATURE CONTROL D BY SAMPLE KEITHLEY EQUIPMENT r 7065 HALL CARD 705 OR 706 220 CURRENT SOURCE 48 PICOAM 196 VOLTMETER MAGNET POWER SUPPLY 5 METER IEEE 488 BUS 488 BUS CONTROLLER Figure 2 18 Basic Hall System Configuration 2 23 OPERATION Equipment in the system includes 220 Current Source Applies the current to the sample under test 485 Picoammeter Measures the current through the sam ple under test 7065 Hall Card Switches and buffers applied currents and voltages 705 or 706 Scanner Controls and supplies power to the 7065 Hall Card 196 Voltmeter Measures the voltage across the sample under test IEEE 488 Controller Provides the intelligence to control the instruments in the system Electromagnet Provides an accurately known magnetic flux for the sample under test A Hall sensor is sometimes used to measure the magnetic field as well Magnet Power Supply Supplies the necessary current for the electromagnet Cryostat Keeps the sample at the desired test temperature Temperature Control Controls the cryostat to maintain the desired temperature 2 6 GUARDING METHODS The following paragraphs discuss principles of guarding methods of guarding on the current source input and guarding of the sample inputs
26. ANY KEY TO CALCULATE RESISTIVITIES 950 AS INKEYS IF AS THEN 950 940 PA W T C2 11 D1 2 CUCIO UCS 350 PB U T 2 II D2 CUC22 UCc AD 860 PAVG PA PB 2 970 PRINT PA PA 480 PRINT PB PB 990 PRINT PAUG PAUG 1000 PRINT M M M 3 48 Program 8 6 and 8 Contact Sample Resistivity IBM PC 8573A Version Continued 1010 1020 1050 1040 1050 1050 1070 1080 1080 1100 1110 1120 1130 1140 1150 1150 1170 1180 1180 1200 INPUT REPEAT TEST 3 8 IF LEFTS AS 1 Y THEN CLS GOTO 280 GOTO 1150 CLS BEEP CALL IBCMD OBRDOZ D SEND DEVICE CLEAR PRINT SAMPLE VOLTAGE IS OVER 8V 7055 LIMIT DO YOU WISH PRINT CI RESTART THE MEASUREMENT PRINT 2 ABORT THE PROGRAM PRINT INPUT IF OR 2 THEN 1070 IF A 2 THEN 1150 CLS 60TO 290 END END PROGRAM REM 705 COMMAND STRINGS DATA 03 2004 1 DATA NO3 2N04 1X DATA CO3 3C04 4X DATA 05 5 04 4 APPLICATIONS 3 49 APPLICATIONS REFERENCES ASTM F76 84 Standard Method for Measuring Hall Mobility and Hall Coefficient in Extrinsic Semiconductor Single Crystals Annual Bk ASTM Stds 1985 10 05 155 Hemenger P M Measurement of High Resistivity Semiconductors Using the van der Pauw Method Rev Sci Instrum 1973 44 698 Look D C and Farmer JW Automated High Resistivity Hall and Photoelectronic
27. Model 220 output by pressing the OPERATE key Turn on the magnetic field and set it to the desired positive flux density B Measure and record the value of B Measure the voltage V by noting the Model 196 reading Note and record the current being measured by the Model 485 Picoammeter Measure and record through V as listed in Table 3 4 by closing the appropriate crosspoints Be sure to open crosspoints from the previous measurement and turn off the Model 220 output After closing the next crosspoints re zero the DMM and enable REL on the Model 485 before turning on the Model 220 output Reverse the magnetic flux and adjust it to the same magnitude used for positive flux measure and record the flux value Measure V through V listed in Table 3 4 now with negative flux Table 3 4 Crosspoint Summary for Hall Voltage Measurements Only those crosspoints shown can be closed for a specific measure ment except 54 which controls card input configuration for low or high resistivity samples 3 8 3 5 3 Hall Coefficient Calculations Once the voltages are measured two Hall coefficients and can be calculated as follows 25 x 10 t V V Vs Ve Rac c BI 2 5 X 107 ts V4 P V3 V Vs Rap LM S BI Where and are Hall coefficients in cm C ts is the sample thickness in cm B is the magnetic flux in gauss
28. Once the voltages are known the resistance can be calculated as follows Vi Vos Vos eee LA 2I Where R calculated resistance V measured voltage with positive current V measured voltage with negative current I applied current Vos combined offset voltage If we rearrange the above equation and combine terms we have Vi Vi R 2I Note that the offset term Vos cancels out of the equation demonstrating the nulling effect of this measurement technique Minimizing Offsets when Averaging is not Used The measurement scheme is more than adequate for null A POSITIVE CURRENT ing offsets in most situations There are several other precautions that be taken to mimimize offset effects if for some reason the averaging technique is not used 1 Make sure that the buffer amplifier offsets are properly nulled as discussed in Section 4 Note that this con sideration applies only when using the high resistivity setup because the buffers are not used in the low resistivity mode 2 Use the zero or relative features on the measuring in struments to null their offsets Typically these functions should be enabled with the sample connected and all necessary crosspoints in the measurement path closed but with no current applied to the sample 3 Use the maximum current possible without heating up the sample excessively For a given sample resistance the higher the current the higher
29. Re HALL EFFECT CONVENTIONS AND PRINCIPLES Hall Effect Sign Convention cesa ex Agar ES S dE aa arr Terminal Conventions us ido iex Basic Hall Effect Principles esses cxx vn eR eau ORE Taree sews VAN DER PAUW RESISTIVITY MEASUREMENTS cise Test Configuration vot edes Pads Ud E Learn Test Proc d Resistivity Calculations asses rr Rae 54 E AREE RAT ERR HALL VOLTAGE MEASUREMENTS d RAPERE UEBER ADR o eO d duod Test Configuration ____ er REA eK rack sees ceeds Test Proced r rS Hall Coefficient Calculations 9 Hall Mobility Calculation MEASURING SAMPLES Test Configurati ons onra AU Ep RR Ge dar dq ra dace Determining Potentiometer Values Bar Resistivity Measurements xh es id edes Hall Voltage RARE ARE RTAR Ra E e eas C AICUIANONS MEASURING BRIDGE AND PARALLELPIPED TYPE SPECIMENS Test Config rati ns Luo ed RE cas PUE PENENT Vas Vr Pe vae mapasa Resistivity Measurements iss i RR OPEN ERAT EUR AE MEE Hall Voltage
30. Revision B Document Number 7065 901 01 All Keithley product names are trademarks or registered trademarks of Keithley Instruments Inc Other brand and product names are trademarks or registered trademarks of their respective holders November 1986 December 1986 The following safety precautions should be observed before using this product and any associated instrumentation Although some in struments and accessories would normally be used with non haz ardous voltages there are situations where hazardous conditions may be present This product is intended for use by qualified personnel who recog nize shock hazards and are familiar with the safety precautions re quired to avoid possible injury Read the operating information carefully before using the product The types of product users are Responsible body is the individual or group responsible for the use and maintenance of equipment for ensuring that the equipment is operated within its specifications and operating limits and for en suring that operators are adequately trained Operators use the product for its intended function They must be trained in electrical safety procedures and proper use of the instru ment They must be protected from electric shock and contact with hazardous live circuits Maintenance personnel perform routine procedures on the product to keep it operating for example setting the line voltage or replac ing consumable materials Maintenance pr
31. W 5 Composition R 76 180k R21 R22 Resistor 22 0 5 Composition R 76 22k R23 Potentiometer 10kQ 0 5W RP 97 10k R24 R27 Resistor 22MQ 4W 10 Composition R 76 22M R28 Resistor 3300 5 Composition R 76 330 R29 R32 Resistor 1 W 5 Composition R 76 1k R33 Resistor 4 70 IW 10 Wirewound Fusible R 334 4 7 R34 R42 Resistor IMQ 4W 5 Composition R 76 IM U1 U4 IC operational amplifier OPA104 IC 519 U5 IC CMOS shift register 4094 IC 251 Ue IC CMOS quad NOR gate 4011 IC 102 IC Bus buffer 74HC241 IC 520 U8 IC CMOS 555 timer IC 521 U9 IC 12V regulator 78L12 IC 522 U10 IC 12 regulator 79L12 IC 523 011 016 IC Photovoltaic relay 3301 IC 525 Transformer TR 247 T2 Transformer TR 248 1 TP2 Pin contact 24249 VRI VR2 Zener diode 12V 100mA 1N5349B DZ 72 1 W1 W2 Connector jumper CS 476 These parts are static sensitive See paragraph 4 6 for handling precautions REPLACEABLE PARTS Table 5 2 Mechanical Parts Quantity Description 1 2 6 1 1 1 1 5 Q Lug for J8 Washer for J8 Cap for BNC and triax jacks Bracket BNC Top Analog Shield Digital Shield Bottom Assembly Shield 4 40 x 1 Phillips pan head modified screw for shields 94 40 x 3 6 Phillips pan head screws for attaching BNC bracket to PC board Keithley Part Number LU 100 WN 13 CAP 18 7065 302 7065 304 7065 307 7065 121 7065 308 REPLACEABLE PARTS
32. W Shield 10 ft MODEL 80 HALL EFFECT PACKAGE ACCURACY SPECIFICATIONS 1 year 182282 RESISTIVITY MEASURMENT ACCURACY Note Resistivity accuracies based on sample excitation voltage which produces no more than 1mW power dissipation in sample 5V maximum for high resistivity mode 3V maximum for low resistivity mode Accuracy Percent 1 10 10 1095 10 10 Sample Resistance Ohms HALL VOLIAGE LIMIT OF ERROR Notes 1 Assumes 196 DMM on 300mV range for both modes default resolution and filters 2 For better performance below 500nV in the low resistivity mode a Model 181 nanovoltmeter is recommended in place of the Model 196 DMM 3 Assumes device under test at room temperature 18 28 C 30mV p kE a 2014 22 12 20 L Z q 1 1 U p 01 21 les Pees RENNES Es 2 33 E CEE ED __ L 14 __ __ __ F J 4 5 j A j Ds CI ee GE 2 EN 10uV Hall Voltage Limit of Error EEE 100nV 2 xe 10 10 10 10 10 1012 Sample Resistance Ohms TABLE OF CONTENTS SECTION 1 GENERAL INFORMATION 1 1 1 2 1 3 14 1 5 1 6
33. WAIT W MSEC FOR READING TO SETTLE 580 ENTER P2 GET 196 VOLTAGE READING 580 IF ABS V J gt 8 THEN GOTO 880 CHECK VOLTAGE LIMITS 5002 IF 1 1 THEN ENTER If GET 485 CURRENT READING 610 OUTPUT P F X TURN OFF 220 OUTPUT 520 READ AS READ 705 COMMAND STRING 630 OUTPUT P3 OPEN CROSSPOINTS 540 NEXT J LOOP BACK FOR NEXT MEASUREMENT 650 850 CLEAR 670 CLEAR 7 SEND DEVICE CLEAR 680 DISP MEASUREMENTS COMPLETE 680 DISP MEASURED CURRENT I1 700 FOR J TO 8 LOOP AND DISPLAY MEASURED VOLTAGES 710 DISP 4 720 NEXT J 730 DISP 740 DISP PRESS CONT TO CALCULATE 750 DISP RESISTIUITY 750 PAUSE 770 R151 13831 T IT UC2 UCA UC1 UC3 780 R251 1331 T Il UCBORUCB UC5 0 UC7 0 730 R3sORI R2 2 800 DISP 810 DISP 2 820 DISP PHAU R3 830 DISP 840 DISP REPEAT TEST Y N 850 INPUT A 880 IF A 1 112 Y THEN CLEAR 8 6010 240 870 GOTO 1020 880 ERROR CHECKING 890 CLEAR 0 400 CLEAR 7 SEND DEVICE CLEAR 910 DISP SAMPLE VOLTAGE IS QVER 420 DISP 7065 LIMIT 950 DISP DO YOU WISH TO 440 DISP 1 RESTART MEASUREMENT 350 DISP 2 ABORT THE PROGRAM 960 DISP 970 INPUT A 980 IF lt 1 OR A gt 2 THEN 930 99 IF A 2 THEN 1020 1000 CLEAR 3 32 APPLICATIONS Program 2 Van der Pauw Resistivity HP 85 Version Continued 1010 GOTO 240 1020 END 1030 705 COMMAND STRINGS
34. be connected to earth ground only at a single point as shown in Figure 2 33 It is important to assure that no supp ly or power line currents flow through signal grounds Sometimes experimentation can help determine the best arrangement INSTRUMENT INSTRUMENT INSTRUMENT POWER LINE GROUND Figure 2 33 Eliminating Ground Loops 2 10 8 Offsets Offsets generated py thermals or other factors can degrade measurement accuracy particularly at low signals levels Such offsets are normally nulled out as part of the measure ment process but some precautions can be taken to reduce these effects to inconsequential levels Offsets can generally be attributed to one or more of three Sources 1 Thermal EMFs generated at relay or connector contacts 2 Buffer amplifier voltage offsets 3 Offsets inherent in the measuring instruments picoam meter or voltmeter Minimizing Offsets by Measurement Averaging In most cases an averaging measurement scheme is used to reduce the effects of such offsets In the example measurement shown in Figure 2 34 averaging is achieved by taking the measurement twice once each with positive and negative current In a the generated voltage V has the same sign as the offset voltage Vos However by rever sing the current as in the case of b the generated voltage V now has the opposite polarity although the offset voltage polarity is the same as before 2 43 OPERATION
35. by using the CHANNEL button for sequential access or by keying in the column and row numbers with the DATA keys For example to display column 5 row 2 on the Model 705 press the following 0 5 2 3 Once the desired crosspoint is displayed use the OPEN or CLOSE button to update its status as required 4 Repeat steps 2 and 3 for all crosspoints to be changed 5 To open all crosspoints simultaneously and return the display to column 1 row 1 press the RESET button 2 38 2 9 IEEE 488 BUS PROGRAMMING The Model 7065 may be controlled over the IEEE 488 bus through the host scanner as described in the following paragraphs For more detailed bus information refer to the Model 705 or 706 Instruction Manual 2 9 1 Matrix Bus Commands Table 2 9 summarizes the commands necessary to put the scanner in the matrix mode and to close open and display crosspoints The commands are further defined below Table 2 9 IEEE 488 Bus Command Summary Select matrix mode Display crosspoint nn m 705 Display crosspoint nnn m 706 Close crosspoint nn m 705 Close crosspoint nnn m 706 Open crosspoint nn m 705 Open crosspoint nnn m 706 Open all crosspoints display 1 1 Use of colon is optional Sending this command places the scanner in matrix mode opens closed crosspoints and displays col umn 1 row 1 Display B close C and open N These commands per form the indicated operation on t
36. circuit Make connections as follows 1 Connect the Model 6167 guard adapter to the Model 220 triax output Connect the Model 6167 guard output to the Model 220 GUARD jack 2 Connect the Model 6167 Input to the CURRENT SOURCE INPUT jack using a 7024 3 or 7024 10 triaxial cable NOTE This setup assumes that the guarded source input configuration is to be used See paragraph 2 6 for more information on guarding 3 Connect the four terminals of the sample under test to the SAMPLE INPUTS using supplied triaxial cables See Figure 2 6 for cable stripping instructions 4 Connect the Model 485 Picoammeter to the CURRENT MONITOR OUTPUT jack on the Model 7065 using the supplied Model 4801 low noise cable use the 4851 shor ting plug if no picoammeter is to be used 5 Connect Model 196 DMM LO to terminal 4 of the Measurement Output terminal strip and connect DMM HI terminal to terminal 5 of the terminal strip Use the dual banana plug cable for DMM connections 2 8 SC 8 BG 7 DOUBLE BANANA PLUG HI WARNING MAINTAIN INPUTS CUTPUTS WITHIN 30 OF KEITHUEY 7065 HALL EFFECT CARD 705 OR 706 SCANNER 485 PICOAMMETER 6167 ADAPTER 7024 TRIAX CABLE OPERATION SEE PARAGRAPH 2 6 FOR GUARDING CONFIGURATIONS GUARD OUTPUT COMMON epo 9 220 CURRENT SOURCE MI RESISTIVITY AMPLIFIER CONFIGURATION SAMPLE SAMPLE CURRENT IN
37. connector and their purposes and also show typical connecting schemes 2 4 1 Card Connectors WARNING Maintain inputs and outputs within 30V of earth ground Failure to observe this precaution may result in a shock hazard The layout of the Model 7065 is shown in Figure 2 3 Con nectors on the card are CURRENT SOURCE INPUT A two lug triaxial connector intended for applying the test current Note that the inner shield can be connected to source guard using one of the methods described in paragraph 2 6 The Keithley Model 220 is the recommended current source Maximum allowable input current is 100mA SAMPLE INPUTS 1 through 4 These are two lug triaxial connectors with the inner ring driven at guard potential while the shell is connected to analog ground Maximum input overload is 12V CURRENT MONITOR OUTPUT An insulated BNC con nector recommended for use with a Keithley Model 485 Picoammeter Maximum input overload is 10mA when us ing the Model 485 CAUTION Be careful not to interchange triax and BNC con nectors to avoid damaging them NOTE The caps should be kept in place on the connectors when not in use to prevent possible contamination which could degrade performance Terminal Block J2 These thumb operated spring loaded connectors accept 18 24 gauge wire Three of the terminals are intended for voltmeter connections while the re mainder allow connection to analog ground or external guard Terminal ass
38. ed The same guard potential also surrounds the contacts of the associated relay in order to minimize leakage effects of the switching circuits Note that guarding is used for both high and low resistivity configurations even though the buf fers are effectively switched out of the circuit when the card is configured for low resistivity Paragraph 2 7 covers resistivity mode selection in detail OPERATION BOTTOM SHIELD Figure 2 22 Shield Removal OPERATION SEPARATE WIRE SC 72 WHITE NOTE GUARD CONNECTION MUST BE MADE 220 CURRENT SOURCE OUTPUT 7024 TRIAXIAL CABLE ANA 10 HI GD 10 RESISTIVITY Mi RESUS TIVIT x 3 4 7065 CARD MAINTAIN INPUTS ANO 5 WITHIN 30v OF EARTH AMPLIFIER CONFIGURATION WARNING CURRENT A CONNECTIONS 220 iz EE reu SEN ES 7065 CURRENT SOURCE INPUT TO RELAYS OUTPUT COMMON Y ANALOG 7024 CABLE GROUND WHITE INSULATED WIRE 1 PE GUARD GUARD GUARD 10kQ AMPLIFIER INPUT CHASSIS VR1 PROTECTION CIRCUITS EQUIVALENT CIRCUIT Figure 2 23 Connections for Unguarded Current Source Input 2 30 OPERATION 6167 GUARDED ADAPTER CONNECT GUARD NOTE USE 6167 IN GUARDED MODE 220 CURRENT SOURCE 7024 TRIAXIAL CABLE INPUT
39. high as possible also the DMM input resistance must be substantially higher than the equivalent resistance seen at its input The worst case condition occurs when the potentiometer wiper is at the center of its adjustment range R 1 For example in the equivalent circuit of Figure 3 10 assume that R has a value of 200kQ In this case Ro 12 Rp Rp 50 0 Low Resistivity For the low resistivity setup and for values significantly less than the values listed for R in Table 3 5 better accuracy can be obtained by using a different value for than that shown in the table Using the equivalent circuit shown in Figure 3 11 the relationship between the error Rp and is given as follows Rp Ri Rp E x 100 Where Rp potentiometer value Rw input resistance of the Model 196 Rw 10M2 for 30V range 100 for 300mV ranges Note that this approximation is valid for E lt 10 Table 3 5 Minimum and Maximum Potentiometer Values for Hall Bar Measurements Resistivity Mode See Figure 3 9 3 12 Additional Recommended Introduced APPLICATIONS SAMPLE 196 DMM Figure 3 9 Hall Bar Equivalent Circuit 3 13 APPLICATIONS RpK Rp 1 K 1 KiRp Figure 3 10 Equivalent Potentiometer Circuit High Resistivity CURRENT SOURCE Figure 3 11 Equivalent Potentiometer Circuit Low Resistivity 3 6 3 Bar Resistiv
40. pressing the OPERATE key 8 Measure V by noting the reading on the Model 196 Also note the current measured by the Model 485 Picoammeter 9 Turn off the Model 220 output and open the cross points 10 Re zero the DMM enable REL on the Model 485 then turn on the Model 220 output 11 Measure and record the remaining voltages V through Vs listed in Table 3 3 by closing the appropriate cross points Be sure to open the crosspoints from the previous measurement before closing crosspoints for the present measurement Table 3 3 Crosspoint Summary for Resistivity Measurements Current Voltage Crosspoints Applied Measured Designation Closed Column Row Between Between Only those crosspoints shown can be closed for a specific measure ment except 54 which controls input configuration for low or high resistivity samples APPLICATIONS 5 4 CONTROLS RESISTIVITY 3 4 5 Q Q COLUMNS 20 3 0 4 0 CURRENT CURRENT MONITOR SOURCE OUTPUT INPUT BUFFERS TERMINALS LO BNC 485 220 PICO CURRENT AMMETER SOURCE SAMPLE Figure 3 5 Measurement Configuration for Resistivity and Hall Voltage Measurements USED FOR BAR TYPE SAMPLES 196 VOLTMETER APPLICATIONS 3 4 3 Resistivity Calculations Once the voltages and current through the sample have been measured the resistivity can be calculated as follows Two values of resis
41. sample 1 buffer Reversed polarity Sample 1 buffer negative input Select buffer 2 Sample 2 buffer negative input Reversed polarity Sample 2 buffer positive input Select buffer 3 Sample 3 buffer positive input Reversed polarity Sample 3 buffer negative input Select buffer 4 Sample 4 buffer negative input Reversed polarity Sample 4 buffer positive input Open all crosspoints 4 15 4 16 SECTION 5 REPLACEABLE PARTS 5 1 INTRODUCTION This section contains a list of replaceable electrical and mechanical parts for the Model 7065 A component layout drawing and schematic diagram are also included 5 2 PARTS LISTS Electrical parts are listed in order of circuit designation in Table 5 1 Table 5 2 summarizes mechanical parts 5 3 ORDERING INFORMATION To place a parts order or to obtain information concerning replacement parts contact your Keithley representative or the factory see the inside front cover for addresses When ordering parts be sure to include the following information 1 Hall card model number 7065 2 Unit serial number 3 Part description 4 Circuit description if applicable 5 Keithley part number 5 4 FACTORY SERVICE If the Hall card is to be returned to Keithley Instruments for repair or service perform the following 1 Complete the service form at the back of this manual and include it with the card 2 Carefully pack the card in the original packing carton 3 Writ
42. the manual The A symbol on an instrument shows that it can source or mea sure 1000 volts or more including the combined effect of normal and common mode voltages Use standard safety precautions to avoid personal contact with these voltages The WARNING heading in a manual explains dangers that might result in personal injury or death Always read the associated infor mation very carefully before performing the indicated procedure The CAUTION heading in a manual explains hazards that could damage the instrument Such damage may invalidate the warranty Instrumentation and accessories shall not be connected to humans Before performing any maintenance disconnect the line cord and all test cables To maintain protection from electric shock and fire replacement components in mains circuits including the power transformer test leads and input jacks must be purchased from Keithley Instru ments Standard fuses with applicable national safety approvals may be used if the rating and type are the same Other components that are not safety related may be purchased from other suppliers as long as they are equivalent to the original component Note that se lected parts should be purchased only through Keithley Instruments to maintain accuracy and functionality of the product If you are unsure about the applicability of a replacement component call a Keithley Instruments office for information To clean an instrument use a damp cl
43. the van der Pauw method 3 4 1 Test Configuration Figure 3 5 shows the basic test configuration for making resistivity measurements A detailed connection diagram may be found in Section 2 3 4 2 Test Procedure Use the following general procedure to measure parameters necessary to calculate sample resistivity The procedure assumes that the sample has been stabilized at the desired operating temperature and will remain at that temperature throughout the tests 1 Turn on all the instruments and allow them to warm up for the prescribed period for rated accuracy 2 Place the Models 196 and 485 in autoranging Be sure the Model 196 is in the DCV function 3 Using front panel Program 6 set the Model 705 Scan ner to the matrix mode APPLICATIONS 4 Program crosspoint 5 4 to select low or high resistivity This crosspoint should be open for low resistivity and it should be closed for high resistivity 5 Program the Model 220 current to the desired value in the range of 500fA to 100mA The maximum current that can be used will depend on the resistance of the sample remember that the maximum Model 7065 in put voltage is 8V In order to maintain proper sign con vention for the measured voltage and to minimize common mode errors program only positive currents 6 Close the crosspoints necessary to measure V as in dicated in Table 3 3 Zero the DMM and enable the REL function on the Model 485 7 Turn on the 220 output by
44. 202 FIND 220 DESCRIPTOR 80 NAS DEV2 CALL IBFIND NAS M196 FIND 185 DESCRIPTOR 80 NAS DEV3 CALL 9 7052 FIND 705 DESCRIPTOR 100 NAS DEV4 CALL IBFIND NA M4852 FIND 485 DESCRIPTOR 110 CALL IBPAD M22 P1 SET 220 PRIMARY ADDRESS 120 CALL IBPAD M196 P2 SET 196 PRIMARY ADDRESS 130 CALL IBPAD M7 5 P3 705 PRIMARY ADDRESS 140 CALL IBPAD M485 P4 SET 485 PRIMARY ADDRESS 150 PRINT THIS PROGRAM MEASURES THE RESISTIVITY OF VAN DER PAUW SAMPLES 16 PRINT THE HALL CARD MUST BE IN THE CARD 1 LOCATION 17 PRINT 180 PRINT PRESS ANY KEY TO CONTINUE 130 AS INKEYS IF THEN 130 200 CLS 218 PRINI SELECT CARD RESISTIVITY SETUP 220 PRINT 230 PRINT 1 LOW RESISTIVITY 240 PRINT 2 HIGH RESISTIVITY 250 INPUT 260 IF OR 92 THEN 210 270 A 1 THEN Z NO5 4X ELSE Z CO5 4X 705 COMMAND STRING 280 PRINT INITIALIZING INSTRUMENTS 290 UX 1 CALL IBSRE BRDOX UZ 7 SEND REMOTE ENABLE 300 CALL IBCMD BRDOZ D SEND DEVICE CLEAR 310 REM INITIALIZE THE MODEL 705 xx 220 C AOX CALL IBWRT M7 5 C PUT 705 IN MATRIX MODE 330 CALL IBURT M7052 28 PROGRAM CARD RESISTIVITY SETUP 340 REM INITIALIZE THE 485 xxx 350 C RIX CALL IBURT MA8SZ C SELECT 2NA RANGE 350 FOR I 1 TO 1000 I SETTLING TIME 370 C CIX CALL IBWRT M485 C ZERO CHECK ON 380 FOR I 1 TO 1000 I 580 C Z1X CALL IBWRT M485 C RE
45. 27 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 Landsberger Strasse 65 D 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 The Minster 58 Portman Road Reading Berkshire RG30 1EA 0118 9 57 56 66 Fax 0118 9 59 64 69 Flat 2B WILLOCRISSA 14 Rest House Crescent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 Viale San Gimignano 38 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 2FL URI Building 2 14 Yangjae Dong Seocho Gu Seoul 137 130 82 2 574 7778 Fax 822 574 7838 Postbus 559 NL 4200 AN Gorinchem 0183 635333 Fax 0183 630821 Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 1FL 85 Po Ai Street Hsinchu Taiwan R O C 886 3 572 9077 Fax 886 3 572 9031 No 2193 2 2000
46. 4 31 4 2 4 2 Resistivity Hall Voltage 5 3 3 6 5 Calculations Resistivity The resistivity of the sample is related to the measurements as follows X Ve yt Where V4 the voltage measured by the Model 196 p the resistivity in ohm cm 1 the current in amperes measured by the Model 485 t the sample thickness in cm x and y sample dimensions shown in Figure 3 12 in cm Hall Voltage The magnetic field B will generate a Hall voltage as follows LB 625 x 109 nt Where Va the voltage measured by the Model 196 in volts APPLICATIONS I the current in amperes measured by the Model 485 B the flux density in gauss t the sample thickness in cm concentration in electrons cm substitute p for hole conduction in p type materials Mobility Once the resistivity and Hall voltages are known the mobility can be determined as follows xV 105 gt Where the mobility in cm V s Va the Hall voltage measured by the Model 196 x y sample dimensions in cm Figure 3 12 B flux density in gauss Vr voltage measured by the Model 196 3 7 MEASURING BRIDGE AND PARALLELEPIPED TYPE SPECIMENS The fundamental procedures for measuring 6 and 8 contact bridge and parallelepiped type speciments are discussed in the following paragraphs 3 7 1 Test Configurations Figure 3 13 shows the test setup for 6 contact specimens a
47. 60 ERROR CHECKING CLEAR e BEEP CLEAR 7 SEND DEUICE CLEAR DISP SAMPLE VOLTAGE IS OVER DISP 8U 7065 LIMIT DISP DO YOU WISH TO DISP 1 RESTART MEASUREMENT DISP 2 ABORT THE PROGRAM DISP INPUT IF A lt t OR A gt 2 THEN 1070 IF 2 THEN 1160 CLEAR GOTO 280 END x 705 COMMAND STRINGS DATA 05 2 04 1 DATA 03 2 04 1 DATA 03 3004 4 DATA NO03 3N04 4X Pro Hal 10 20 50 40 50 50 70 80 30 190 110 120 158 140 150 150 170 180 190 200 210 220 230 240 250 270 280 280 300 310 520 330 340 350 350 370 280 380 400 410 420 430 440 450 460 470 480 490 500 APPLICATIONS gram 5 Voltage Measurement IBM PC 8573A Version CLS DELAY 5 FIVE SECOND DELAY DIM U 8 D CHRS 2 DEFINE DCL COMMAND BYTE 1 12 2 7 3 17 4 22 DEFINE INSTRUMENT PRIMARY ADDRESSES NAS GPIB CALL IBFIND NAS BRDOZ FIND BOARD DESCRIPTOR NAS DEVi CALL IBFIND NAS M220 FIND 220 DESCRIPTOR 02 CALL IBFIND NAS 195 FIND 196 DESCRIPTOR NAS DEV3 CALL 7053 FIND 705 DESCRIPTOR NAS DEV4 CALL IBFIND NAS M485 FIND 485 DESCRIPTOR CALL IBPAD M220 P1 SET 220 PRIMARY ADDRESS CALL IBPAD M196 P2 SET 185 PRIMARY ADDRESS CALL IBPAD M7 5 P3 SET 705 PRIMARY ADDRESS CALL IBPAD M485 P4 SET 485 PRIMARY ADDRESS PRINT THIS PROGRAM MEASURES HALL VOLTAGES AND COMPUTES THE PRIN
48. 8 Table 3 7 6 Contact Sample Resistivity Measurements Voltage Crosspoints Closed Current Voltage Designation Column Row Between Between Vi 3 2 41 4 6 V2 3 5 4 6 3 5 Reverse current by programming source for opposite polarity Table 3 8 8 Contact Sample Resistivity Measurements Voltage Crosspoints Closed Current Voltage Designation Column Row Between Between 41 12 4 6 44 41 44 5 7 4 6 57 22 Reverse current by programming source for opposite polarity 3 19 APPLICATIONS 3 7 3 Hall Voltage Measurements The following procedure assumes that the sample is held stable at the desired temperature throughout the tests and that the applied magnetic flux is also held constant at the desired flux density 1 2 Turn on all instruments and allow them to warm up sufficiently Select the DCV function on the Model 196 and set both the Model 196 and the Model 485 to autoranging Using Program 6 set the Model 705 Scanner to the matrix mode Program crosspoint 54 for the desired resistivity open low resistivity closed high resistivity Program the Model 220 Current Source to the desired positive current Program the scanner to close the first set of contacts listed in Table 3 9 or 3 10 Enable zero on the Model 196 and the relative function on the Model 485 Turn on the Model 220 output by pressing the OPERATE butto
49. 8 Contact Sample Hall Voltage Measurements 3 11 HP 85 and 9816 Programming Language Differences SECTION 4 SERVICE INFORMATION 4 Performance Verification Equipment 44 44s424rsseanisrenecmnetens etapes ae 4 2 Crosspoint Closed to Measure Sample Input Voltage Offset 4 3 Equipment Needed for Adjustments her aa RATER ARR RR EAR 4 4 Crosspoints to Close When Adjusting 4 5 Troubleshooting Equipment pp 4 6 Troubleshooting SECTION 5 REPLACEABLE PARTS 5 1 Electrical Parts cuota pac do rea LER RR EROR El RED EE 5 2 5 2 gt 5 3 LIST OF ILLUSTRATIONS SECTION 2 OPERATION 2 Model 705 Card Installation d e el e ea ea 2 2 Model 706 Card Installation eugene hie EE PER SPECK Rad eh 2 3 Model 7065 Conneetors ices exa rn 2 4 Single Wire PreparatiGlt Sige GE d pas qud aka ee eee es 2 5 Shielded Cable Preparation esses sper qas awas sees RE PEU ROO CE EH mas sa 2 6 Triaxial Cape 27 Connections for Van Der Pauw Samples
50. Apparatus J Phys E Sci Instrumen 1981 14 472 Van der Pauw L J A Method of Measuring Specific Resistivity and Hall Effects of Discs of Arbitrary Shape Philips Rec Repts 1958 13 1 Wieder H H Laboratory Notes on Electrical and Galvanomagnetic Measurements Yeager J R Hall and van der Pauw Measurements of Semiconductors Keithley Instrum App Note 1984 510 3 50 SECTION 4 SERVICE INFORMATION 4 1 INTRODUCTION This section contains the necessary information to service vour Model 7065 Hall Effect Card and contains the follow ing information 4 2 Handling and Cleaning Precautions Discusses handl ing precautions and cleaning methods for the Model 7065 4 3 Performance Verification Covers the procedures necessary to determine if the card is operating properly 4 4 Adjustments Outlines adjustment procedures for the Hall effect card 4 5 Theory of Operation Briefly discusses circuit operation from a block diagram viewpoint 4 6 Special Handling of Static Sensitive Devices Reviews some precautions necessary to avoid damaging static sensitive devices 4 7 Troubleshooting Gives some troubleshooting tips for the Model 7065 4 2 HANDLING AND CLEANING PRECAUTIONS Because of the high impedance of many circuits on the Model 7065 care should be taken during handling or ser vicing of the card in order to prevent possible performance degradation because of contamination The following precautions shou
51. As THEN 880 880 RH sS2 5ET T7 T CB I1 UC2 UC12 UCB UC B 300 RHD 22 5E T 07 T GOB I12 UCA UC 0 7 UCB 2 810 RHAVG RHC RHD 2 20 PRINT RHC RHC 830 PRINT RHD RHD 840 PRINT RHAUG RHAUG 950 PRINT 850 INPUT REPEAT TEST Y N A 970 IF LEFT A 1 2 Y THEN CLS 60TO 280 880 6010 1100 890 CLS BEEP 1000 CALL IBCMD BRDQ D SEND DEVICE CLEAR 3 40 Program 5 Hall Voltage Measurement IBM PC 8573A Version Continued 1010 1020 1030 1040 1050 1050 1270 1080 1100 1110 1120 1130 1140 1150 1180 1170 1180 1190 PRINT SAMPLE UOLTAGE 15 OVER 80 7065 LIMIT PRINT DO YOU WISH TO 1 RESTART THE MEASUREMENT PRINT 2 ABORT THE PROGRAM PRINT INPUT IF lt 1 OR A gt 2 THEN 1020 IF 8 2 THEN 1100 CLS 60TO 280 END END PROGRAM REM 705 COMMAND STRINGS DATA CO02 1C01 3C03 4C04 2X DATA NO2 1N01 3N03 4N04 2X DATA C02 2C01 1C03 4C04 2X DATA NO2 2N01 1N03 4N04 2X DATA 02 2001 4003 1004 3 DATA NO2 2NQ01 4N03 1N04 2X DATA 02 4001 2005 1004 3 DATA NO2 4N01 2N03 1N04 3X APPLICATIONS 3 41 APPLICATIONS Program 6 Van der Pauw Resistivity IBM PC 8573A Version 10 CLS 20 DELAY 5000 FIUE SECOND DELAY 30 DIM U 8 40 DS CHR 20 DEFINE DCL BYTE 50 P1 12 P2 7 P3 17 P4 22 DEFINE INSTRUMENT PRIMARY ADDRESSES 60 NA S GPIBQ CALL IBFIND ONA BRDOZ FIND BOARD DESCRIPTOR 70 NAS DEVI CALL IBFIND NA M2
52. BLE 485 PICOAMMETER Figure 2 9 Connections for Hall Voltage Measurements of Bar Type Samples 2 12 220 CURRENT SOURCE NOTE BUFFERS ARE BYPASSED IN LOW RESISTIVITY MODE 4 OPERATION J2 TERMINAL 5 SEE TABLE 3 5 FOR RECOMMENDED R VALUE HI R J2 TERMINAL 6 SAMPLE 3 485 PICOAMMETER 196 HI R J2 TERMINAL 3 Figure 2 10 Equivalent Circuit for Hall Voltage Measurements of Bar Type Samples 2 13 OPERATION VOLTS OHMS HI 6167 ADAPTER GUARD GH BLACK 9 o Mice 220 CURRENT SOURCE 7024 TRIAX CABLE CONNECT HIGH TO SAMPLE 22 ANA 10 4 160 9 LO AESISTIVITY 30v OF EARTH CONFIGURATION WARNING INPUTS AMD GuTPUTS 7025 TRIAXIAL CABLES KEITHLEY 3065 MALL EFFECT CARD BAR TYPE SAMPLE CONNECT HIGH TO 7065 CARD SAMPLE xt epus uiro uris LEAVE 705 OR 706 SCANNER SHIELD CONNECT TO ANALOG OUTPUT LOW UNCONNECTED 4802 COAX CABLE 485 PICOAMMETER Figure 2 11 Connections for Resistivity Measurements of Bar Type Samples 2 14 OPERATION J2 TERMINAL 5 NOTE BUFFERS ARE BYPASSED IN LOW RESISTIVITY MODE 196 DMM ist SAMPLE 220 CURRENT SOURCE 485 PICOAMMETER Figure 2 12 Equivalent Circuit for Resistivity Measurements of Bar Type Samples 2 15 OPERATION 2 4 6 Bridge and Parallelpiped Type Sample 4 Current source low and
53. C but they can be converted to run on other com puters with similar programming languages The program ming language for the Helwett Packard 9816 for example is almost identical to that of the Model 85 Table 3 11 sum marizes important differences between the two computer programming languages APPLICATIONS Program 5 8 are written for an IBM PC XT computer and some PC compatibles equipped with a Keithley Model 8573A IEEE 488 interface Note that the program listings do not include lines 1 6 of the DECL BAS file which must be added to the front of each program See the Model 8573A Instruction Manual for details NOTE These programs are intended only as examples and they may not yield optimum accuracy with all measurement conditions 3 8 1 Test Configurations Figure 3 16 shows the general test configuration necessary to run Programs 1 2 5 and 6 The necessary test fixture cryostat magnet and magnet power supply are not shown on the diagram Figure 3 17 shows the test configuration for Programs 2 and 7 and Figure 3 18 gives the configura tion for Programs 4 and 8 Table 3 11 HP 85 and HP 9816 Programming Language Differences HP 85 9816 Statement Equivalent Statement s Comments ESS 4 CHR CHR CES 2 Clear home cursor OUTPUT C DISF EHABLE IHTR ri STATUS 1 5 DISP MESSAGE IF
54. CANNER OUTPUT GUARD COMMON SC 72 BLACK WIRE 6167 7025 TRIAX CABLE ADAPTER 220 CURRENT SOURCE Figure 2 15 Connections for 8 Contact Samples 2 19 OPERATION 220 CURRENT SOURCE 485 PICOAMMETER HI 7065 BUFFERS 2 196 DMM LO NOTE HIGH RESISTIVITY MODE SHOWN BUFFERS ARE BYPASSED IN LOW RESISTIVITY MODE Figure 2 16 8 Contact Sample Equivalent Circuit Current 1 2 Voltage 6 4 shown 2 20 2 4 7 Shorting the Current Monitor Output Normally a system will be setup with a Model 485 or similar picoammeter to accurately measure the sample ex citation current As an alternative you can configure your system for use without a picoammeter by placing the Model 4851 BNC shorting plug on the CURRENT MONITOR OUTPUT jack in place of the picoammeter connecting cable This shorting plug is necessary to complete the cir cuit for the current path Note that shorting the CURRENT MONITOR OUTPUT is not necessary for bar 6 contact or 8 contact samples because the picoammeter is connected directly to the sample for those measurements In cases where a picoammeter is not used short out the picoam meter on the wiring diagram Another situation requiring use of the shorting plug is when the sample excitation current exceeds the 2mA measurement capability of the Model 485 Picoammeter In this case the Model 485 should be disconnected from the Model 7065 and the Model 4851 shorting plug connected in its place 2 4 8
55. DTH HI R 3mV NOISE UNCERTAINTY 96 0 1 10 2 3004 F TT ROOM SIGNAL VOLTAGE TEMPERATURE 30zV 196 3V RANGE 196 300mV RANGE 300nV 181 2mV RANGE 30nV 1 10 10 10 10 105 10 10 10 10 10 10 R Q Figure 2 28 Noise Performance LO vs HI Resistivity Setup 2 36 2 8 FRONT PANEL SCANNER PROGRAMMING The following Paragraphs discuss front Panel operation of the Models 705 and 706 Scanners in general terms For more complete information refer to the applicable scanner in struction manual 2 8 1 Entering the Matrix Mode Since the Model 7065 is organized into a 5 X 4 matrix see Figure 2 17 the scanner must be setup to operate in the matrix mode as follows 1 Press PRGM 6 in sequence to enter the pole selection program The unit will display the following message POLE 2 Press 0 ENTER to select the matrix mode 3 The unit will then display the status of column 1 row 1 Note that all crosspoints will be open after using Pro gram 6 2 8 2 Scanner Display Formats Model 705 Format In the matrix mode the Model 705 display format appears as follows nn m O or Where nn represents the column number m is the row O and C represent open and closed respectively Since the Model 705 can hold two cards and up to five units can be daisy chained the total number of possible columns is 50 Table 2 5 summarizes column numbers by card for unit 1 and Table 2 6
56. EAR DATA POINTER 669 DISP MEASURING 670 FOR J 1 TO 4 LOOP FOR ALL FOUR VOLTAGES 680 IF J 3 THEN RESTORE 8 OUTPUT 12 X REVERSE CURRENT 680 READ AS READ 705 COMMAND STRING 700 QUTPUT P3 AS 1 CLOSE CROSSPOINTS 710 OUTPUT Pi FIX TURN ON 220 OUTPUT 720 WAIT W WAIT FOR READINGS TO SETTLE 730 ENTER P2 V J GET 196 READING 740 IF ABS VCJ gt 8 THEN GOTO 1030 CHECK READING LIMITS 750 IF 1 1 THEN ENTER P4 11 INPUT 485 CURRENT READING 760 OUTPUT FOX TURN OFF 220 OUTPUT 770 READ AS READ 705 COMMAND STRING 780 OUTPUT OPEN CROSSPOINTS 780 NEXT J LOOP BACK FOR NEXT MEASUREMENT 800 BEEP 810 CLEAR 820 CLEAR 7 SEND DEVICE CLEAR 830 DISP MEASUREMENTS COMPLETE 840 DISP MEASURED CURRENT II 850 FOR 1 1 TO 4 DISPLAY MEASURED VOLTAGES 850 DISP 870 880 DISP 880 DISP PRESS CONT TO CALCULATE 800 DISP RESISTIUITIES 310 PAUSE 820 Pl Ut T C2 I1 DI 9 UCT12 UCS 930 P2 W1I T CO2 11 D2 UC22 UCA4 840 P3 P1 P2 2 850 DISP 1 860 DISP 2 970 DISP P3 980 DISP REPEAT TEST Y N 990 INPUT A 1000 IF A t 1 11 Y THEN CLEAR 0 GOTO 250 APPLICATIONS 3 37 APPLICATIONS Program 4 6 and 8 Contact Sample Resistivity HP 85 Version Continued 1010 1020 1030 1040 1050 1050 1070 1080 1030 1100 1110 1120 1130 1140 1150 1150 1170 1180 1180 1200 1210 3 38 60 11
57. Figure 2 6 1 Using an X Acto knife cut and strip back the outer insula tion about 1 inches 2 Remove the piece of insulation then cut away the outer shield back as far as the insulation is stripped 3 Carefully strip insulation on the inner shield one inch then cut the shield off 4 Carefully strip the insulation on the inner conductor to the desired length then twist the strands together 5 Repeat steps 1 through 4 for the remaining triaxial cables NOTE Make sure the inner and outer shields do not touch one another CUT CUT 1257 A CUT OFF INSULATION WITH X ACTO KNIFE INSULATION OVER INNER SHIELD B STRIP INSULATION AND CUT OFF INNER SHIELD C CUT OFF INNER SHIELD THEN STRIP INNER CONDUCTOR TO DESIRED LENGTH Figure 2 6 Triaxial Cable Coaxial Cable Preparation In some instances bar and bridge samples the picoam meter must be connected directly to the sample using a Model 4802 coaxial cable Before use the coaxial cable should be prepared as follows 1 Cut back the outer insulation about one inch then remove it 2 Remove the exposed shield by cutting it back as far as the insulation 3 Strip the inner insulation to the desired length then twist the strands together 2 4 4 Van der Pauw Sample Connections Figure 27 shows typical connections for measurement made using the van der Pauw method and Figure 2 8 gives an equivalent
58. I and R represent the source current and sample resistance while the leakage resistance is R 2 40 E is the voltage developed across the sample resistance by the source current I E I x Rs Ew represents the ac tual input voltage appearing at the device input of the Model 7065 Rs and R form a voltage divider that attenuates the input signal as follows Es Rz Es R Since the Model 7065 has guarded sample inputs the ef fects of leakage resistance are minimized However in ex treme cases where samples with resistance in the GQ or TQ range are being measured other steps may be necessary to further reduce leakage resistance effects as well The most obvious remedy is to make sure that the leakage resis tance is as high is possible Use only good quality cables included and make these cables as short as possible Also it is important that the sample under test text fix ture and all connectors are kept free of contamination Figure 2 29 Leakage Resistance Effects 2 10 3 Input Loading When sample resistance becomes a large percentage of the Hall card input resistance loading effects can also come into play The effects are essentially the same as for leakage resistance in fact we can use the model in Figure 2 29 with the leakage resistance R replaced by the card input resistance We can then determine the percent error for a given sample resistance as follows Rs x 100 E
59. IEEE 488 Bus Connections Connect each instrument to the IEEE 488 bus using the sup plied Model 7008 IEEE 488 cables Refer to the instrument instruction manuals for pertinent details 2 5 MATRIX AND TEST CONFIGURATIONS The following paragraphs discuss the matrix configuration of the Model 7065 and detail a basic Hall measurement system 2 5 1 Model 7065 Matrix The Model 7065 is organized into a 5 X 4 5 column by 4 row matrix as shown in Figure 2 17 Each intersection of a column and row is called a crosspoint and is designated by a small circle on the diagram By appropriate program ming a particular row can be connected to the desired col umn by closing the appropriate crosspoint The conven OPERATION tion used in this manual always designates a crosspoint in column row format For example contact 34 refers to col umn 3 row 4 of the matrix Source and measurement devices are connected to the col umns while the samples are connected to the rows For example the picoammeter and current source are con nected to columns 1 and 2 respectively while the voltmeter is connected to columns 3 and 4 Column 5 is reserved for Hall bar measurements except for 54 which selects low high resistivity operation The four sample inputs are applied to the X1 buffer amplifiers which have a very high input resistance to minimize loading In the low resistivity mode however these buffers are effectively bypassed by FET switches A
60. INPUT AS 830 IF 8 1 11 THEN CLEAR 8 GOTO 240 940 GOTO 1080 950 ERROR CHECKING 850 CLEAR 8 970 CLEAR 7 SEND DEVICE CLEAR 980 DISP SAMPLE VOLTAGE IS OVER 890 DISP 80 7065 LIMIT 1000 DISP DO YOU WISH TO 3 29 APPLICATIONS Program 1 Hall Voltage Measurement HP 85 Version Continued 1010 1020 1050 1040 1050 1060 1070 1080 1090 1109 1110 1120 1130 1140 1150 1160 1170 1180 3 30 DISP 1 RESTART MEASUREMENT DISP 2 ABORT THE PROGRAM DISP INPUT IF lt 1 OR A gt 2 THEN 1000 IF 2 THEN 1090 CLEAR GOTO 240 END 705 COMMAND STRINGS DATA C02 1C01 3C05 4C04 2X DATA N02 1N01 2N02 4N04 2X DATA C02 3C01 1C05 4C04 2X DATA NO2 3NQ01 1N03 4N04 2X DATA 02 2001 4003 1004 3 DATA 02 2 01 4 03 1 04 3 DATA C02 4C01 2C03 1C04 5X DATA NO2 4N01 2N05 1N04 3X Program 2 Van der Pauw Resistivity HP 85 Version 10 CLEAR 20 W 5000 FIVE SECOND DELAY 30 DIM 8 251 U 8 40 Pi 712 220 ADDRESS IS 12 50 P2 707 196 ADDRESS IS 7 BU P3 717 705 ADDRESS IS 17 70 P4 722 485 ADDRESS IS 22 80 DISP THIS PROGRAM MEASURES 90 DISP RESISTIVITY OF 100 DISP VAN DER PAUW SAMPLES 110 DISP THE 7065 HALL CARD MUST 120 DISP BE IN CARD LOCATION 130 DISP 140 DISP PRESS CONT 150 PAUSE 160 CLEAR 170 DISP SELECT CARD RESISTIVITY SETUP 180 DISP 190 DISP 1 BOW RESISTIVITY 200 DISP 2 HIGH RES
61. ISTIVITY 210 INPUT A 220 IF lt 1 OR gt 2 THEN 180 230 IF 8 1 THEN 7 05 4 ELSE Z C S 4X 705 COMMAND STRING 240 DISP INITIALIZING INSTRUMENTS 250 REMOTE P1 P2 P3 P4 PUT INSTRUMENTS IN REMOTE 250 CLEAR 7 SEND DEVICE CLEAR 270 INITIALIZE 705 280 OUTPUT A X MATRIX MODE 280 OUTPUT P3 5128 PROGRAM RESISTIVITY 300 INITIALIZE 485 310 OUTPUT P4 RIX 2 RANGE 320 WAIT 1000 SETTLING TIME 330 OUTPUT CIX ZERO CHECK ON 340 WAIT 1000 350 OUTPUT P4 Z1X ENABLE REL 380 WAIT 1000 WAIT FOR REL 370 OUTPUT COX ZERO CHECK OFF 380 OUTPUT ROGIX AUTORANGE NO PREFIX 380 INITIALIZE 196 400 OUTPUT P2 R F SSG1X AUTO DCV NO PREFIX 410 OUTPUT UIQX 220 109 COMPLIANCE 20 DISP 220 CURRENT 500 100 430 INPUT I INPUT 220 CURRENT 440 I ABS I POSITIVE CURRENT ONLY 450 OUTPUT I 1 X PROGRAM 220 CURRENT 460 DISP ENTER SAMPLE THICKNESS CM 470 INPUT T INPUT SAMPLE THICKNESS 480 T ABS T 49 CLEAR 500 MAIN MEASUREMENT LOOP APPLICATIONS 3 31 APPLICATIONS Program 2 Van der Pauw Resistivity HP 85 Version Continued 510 RESTORE CLEAR DATA POINTER 520 DISP MEASURING 530 FOR J i TO 8 LOOP FOR ALL 8 VOLTAGES 540 READ AS READ 705 COMMAND STRING 550 OUTPUT A CLOSE CROSSPOINTS 550 OUTPUT Pi FIX TURN ON 220 OUTPUT 570 WAIT W
62. ITS IF J lt gt 1 THEN 680 RD SPACES 25 CALL IBRD MA8SZ RDS GET 485 CURRENT READING IT1 VAL RD S CONUERT READING TO NUMERIC C FOX CALL IBURT M220X C TURN OFF 220 OUTPUT READ C READ 705 COMMAND STRING CALL IBWRT M7 5 C OPEN CROSSPOINTS NEXT J LOOP BACK FOR NEXT POINT BEEP CLS CALL IBCMD BRDOZ D SEND DEVICE CLEAR PRINT MEASUREMENTS COMPLETE PRINT MEASURED CURRENT T1 FOR J TO 8 LOOP AND DISPLAY MEASURED VOLTAGES PRINT V s Js NEXT J PRINT PRESS ANY KEY TO CALCULATE RESISTIVITY OF SAMPLE AS INKEYS IF A THEN 810 PA 1 18331 T I1 CUC204UCA4 UC12 UC3 PB 1 15381 T I1 UCB2 UCB UCS 0 UC7 lt 2 PRINT PA 3PA PRINT PB 3PB PRINT PAUG PAUG PRINT INPUT REPEAT TEST 25 IF LEFTS AS 1 Y THEN CLS 60TO 280 1058 CLS BEEP CALL IBCMD BRD0Z D SEND DEVICE CLEAR PRINT SAMPLE VOLTAGE IS OVER 8V 7055 LIMIT PRINT DO YOU WISH TO PRINT 1 RESTART THE MEASUREMENT PRINT 2 ABORT THE PROGRAM PRINT INPUT A 1000 IF lt 1 OR 2 THEN 850 E M M a H HM 3 43 APPLICATIONS Program 6 Van der Pauw Resistivity IBM PC 8573A Version Continued 1010 IF 2 THEN 1030 1020 CLS 60T0 280 19030 END END PROGRAM 1040 REM 705 COMMAND STRINGS xo 1050 DATA 01 2002 1 03 3 04 4 1050 DATA 01 2 02 1 03 5 04 4 1070 DATA CO2 2C01 1003
63. L ON 400 FOR I 1 TO 1000 NEXT I 410 C COX CALL IBWRT M485 C ZERO CHECK OFF 420 C ROGIX CALL IBWRT M485 C AUTORANGE PREFIX 430 REM INITIALIZE THE 196 xxx 440 C ROFOSZGIX CALL IBURT MISBZ CS AUTO DCU RATE NO PREFIX 450 REM INITIALIZE THE 220 450 C U1QX CALL IBURT M220X C 220 100 COMPLIANCE 470 INPUT 220 CURRENT 500 100 1 INPUT 220 CURRENT 480 I ABS I POSITIUE CURRENT ONLY 480 IF 1 lt SE 13 OR 1 gt 1 THEN 470 500 C I STRS IO X CALL IBURT M220Z C PROGRAM 220 CURRENT MM M M M 3 42 APPLICATIONS Program 6 Van der Pauw Resistivity IBM PC 8573A Version Continued 510 520 530 540 550 550 570 580 530 600 610 520 630 640 650 559 70 580 E92 700 710 720 732 740 750 750 770 780 730 800 810 820 830 840 850 850 870 880 830 300 810 820 330 940 950 850 970 880 890 INPUT ENTER SAMPLE THICKNESS CM T T ABS T CLS REM MAIN MEASUREMENT LOOP RESTORE CLS PRINT MEASURING FOR J TO 8 READ C CALL IBWRT M7 S C CLOSE CROSSPOINTS CS FIX CALL IBURT M220X C TURN ON 220 OUTPUT FOR 141 TO DELAY NEXT WAIT FOR READING TO SETTLE RDS SPACE 25 CALL IBRD MISEZ RDS GET 196 READING U J UALCRD CONVERT STRING TO NUMERIC PUT IN ARRAY IF ABS U J gt 8 THEN 820 CHECK VOLTAGE LIM
64. LECT CARD RESISTIVITY SETUP 210 PRINT 220 PRINT 1 LOW RESISTIVITY 230 PRINT 22 HIGH RESISTIVITY 240 INPUT A 250 IF Act OR 852 THEN 200 260 IF 8 1 THEN Z NO5 4X ELSE Z C05 4X 705 COMMAND STRING 270 PRINT INITIALIZING INSTRUMENTS 280 UX 1 CALL IBSRE BRD Z V SEND REMOTE ENABLE 240 CALL IBCMD BRD DS SEND DEVICE CLEAR 300 INITIALIZE THE MODEL 705 s x 310 C AOX CALL IBWRT M7O5 CB PUT 705 IN MATRIX MODE 320 CALL IBWRT M7 5 Z PROGRAM CARD RESISTIVITY SETUP 330 REM INITIALIZE THE 485 x x 340 C RIX CALL IBWRT M485 C SELECT 2NA RANGE 350 FOR I 1 TO 1000 I SETTLING TIME 369 CS CIX CALL IBWRT M485 C ZERO CHECK ON 370 FOR I 1 TO 1000 I 380 C Z1X CALL IBWRT M485 C REL ON 380 FOR I 1 TO 1000 I 400 C COX CALL IBWRT M485 C ZERO CHECK OFF 410 C R G1X CALL IBWRT M485 C AUTORANGE NO PREFIX 420 REM INITIALIZE THE 196 430 C ROFO0SS361X CALL IBURT MISBZ CS AUTO DCU RATE NO PREFIX 440 REM INITIALIZE THE 220 x 450 C UIOX CALL IBURTCM2205 0 220 10U COMPLIANCE 450 INPUT 220 CURRENT SQ FA 1 MA 1 INPUT 220 CURRENT 470 I ABS I POSITIVE CURRENT ONLY 480 IF I lt 56 13 OR 19 1 THEN 460 490 C I STRS I X ICALL IBWRT M220 C amp PROGRAM 220 CURRENT 500 INPUT ENTER SAMPLE THICKNESS 0M Z 3 45 APPLICATIONS Program 7 Bar Sample R
65. LIZING INSTRUMENTS REMOTE P1 P2 P3 P4 PUT INSTRUMENTS IN REMOTE CLEAR 7 SEND DEVICE CLEAR INITIALIZE 705 OUTPUT P3 MATRIX MODE OUTPUT P3 37 PROGRAM RESISTIVITY INITIALIZE 485 OUTPUT P4 RIX ZNA RANGE WAIT 1000 SETTLING TIME QUTPUT P4 CIX ZERO CHECK ON WAIT 1000 OUTPUT Z1X ENABLE REL WAIT 1000 OUTPUT COX ZERO CHECK OFF OUTPUT P4 ROGIX AUTORANGE PREFIX INITIALIZE 196 OUTPUT P2 4 5361 AUTC DCV RATE NO PREFIX OUTPUT Pt s UtQX 220 100 COMPLIANCE 220 CURRENT 50 fA 1 MA gt DISP INPUT I 1 085 1 1 INPUT 220 CURRENT IF I lt 5 E 13 OR I gt 1 THEN 410 OUTPUT P1 I I X PROGRAM 220 CURRENT ENTER SAMPLE THICKNESS CM DISP INPUT Z Z ABS Z DISP ENTER SAMPLE X DIMENSION CM INPUT X APPLICATIONS Program 3 Bar Sample Resistivity HP 85 Version Continued 510 520 530 540 550 560 570 580 580 500 519 620 550 649 650 650 570 680 630 700 710 720 730 740 750 760 770 780 810 820 880 300 840 350 X ABS X DISP ENTER SAMPLE Y DIMENSION CM INPUT Y 5 CLEAR MAKE MEASUREMENTS OUTPUT P3 C02 4C03 1C04 2X CLOSE CROSSPOINTS OUTPUT FIX TURN ON 220 OUTPUT WAIT WAIT FOR READING TO SETTLE ENTER P2 GET VOLTAGE READING FROM 196 IF ABS V gt 8 THEN 820 CHECK VOLTAGE LIMITS ENTER P4
66. MENT 880 PRINT 2 ABORT THE PROGRAM 890 PRINT 900 INPUT A 810 IF lt 1 OR gt 2 THEN 860 920 IF A 2 THEN 840 850 CLS GOTO 270 840 END END PROGRAM 3 46 APPLICATIONS Program 8 6 and 8 Contact Sample Resistivity IBM PC 8573A Version 10 20 40 50 52 70 80 90 100 118 120 130 140 150 150 179 180 S w 3 FP 12 p CJ GJ CO C9 sos C GW 01 Gi 143 FJ 14 PI 1 3 po 14 O4 J wm J GJ GI CJ 03 1 1 540 350 550 380 380 400 410 430 440 450 450 470 480 490 500 CLS DELAY 5 0 FIVE SECOND DELAY DIM 904 D CHR 20 DEFINE DCL COMMAND BYTE P1 12 P2 7 P3 17 P4 22 DEFINE INSTRUMENT PRIMARY ADDRESSES NAS GPIBO CALL IBFIND ONAS BRDOR FIND BOARD DESCRIPTOR NAS DEV1 CALL IBFINOCNAS M220 FIND 220 DESCRIPTOR NAS DEU2 CALL IBFIND NAS M SBZ FIND 196 DESCRIPTOR NAS DEVS CALL IBFINDCNAS M7 5 FIND 705 DESCRIPTOR ESCRIPTOR CALL IBPAD M22 P1 220 PRIMARY ADDRE CALL IBPAD M196 P22Z2 SET 135 PRIMARY DDRE CALL IBPAD M705 P3 705 PRIMARY ADDRE CALL IBPAD M485 P4X 485 PRIMARY ADDRESS PRINT THIS PROGRAM MEASURES PARAMETERS TO CALCULATE THE RESISTIVITY PRINT OF 6 OR 8 SAMPLES PRINT THE HALL CARO MUST BE IN THE CARD 1 LOCATION PRINT PRINT PRESS ANY KEY CONTINUE AS INKEYS IF AS THEN 200 CLS PRINT SELECT CAROD RESISTIVITY SETU
67. Model 7065 Hall Effect Card Instruction Manual Contains Operating and Servicing Information KEI THLEY WARRANTY Keithley Instruments Inc warrants this product to be free from defects in material and workmanship for a period of 1 year from date of shipment Keithley Instruments Inc warrants the following items for 90 days from the date of shipment probes cables rechargeable batteries diskettes and documentation During the warranty period we will at our option either repair or replace any product that proves to be defective To exercise this warranty write or call your local Keithley representative or contact Keithley headquarters in Cleveland Ohio You will be given prompt assistance and return instructions Send the product transportation prepaid to the indicated service facility Repairs will be made and the product returned transportation prepaid Repaired or replaced products are warranted for the balance of the origi nal warranty period or at least 90 days LIMITATION OF WARRANTY This warranty does not apply to defects resulting from product modification without Keithley s express written consent or misuse of any product or part This warranty also does not apply to fuses software non rechargeable batteries damage from battery leakage or problems arising from normal wear or failure to follow instructions THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING ANY IMPLIED WAR
68. NT 530 INPUT ENTER SAMPLE THICKNESS CMO T 540 T ABS T 550 INPUT SAMPLE WIDTH 8 550 W ABSCU 570 INPUT SAMPLE 01 DIMENSION CM D1 580 INPUT SAMPLE D2 DIMENSION CM3 D2 580 Di ABS D1 D2Z ABS 02 600 CLS 610 PRINT PRESS ANY KEY TO MEASURE 520 AS INKEYS IF AS THEN 620 50 REM MAIN MEASUREMENT LOOP w 640 RESTORE 65 CLS 650 PRINT MEASURING 670 FOR J TO 4 68 IF 143 THEN 710 680 RESTORE CLEAR DATA POINTER 700 C 2 I STRS CIZO X CALL IBURT M220X C0 REUERSE CURRENT 710 READ C CALL IBWRT M705 C CLOSE CROSSPOINTS 720 CS FIX CALL IBWRT M22 CS TURN ON 220 OUTPUT 730 FOR 1 1 TO DELAY NEXT WAIT FOR READING TO SETTLE 740 RD SPACES 25 CALL IBRD MISBE RD GET 196 READING 750 9 10 VAL RDS CONVERT STRING TO NUMERIC PUT IN ARRAY 760 IF ABS V J 8 THEN 1040 CHECK VOLTAGE LIMITS 770 IF 141 THEN 800 780 RDS SPACES 25 CALL IBRD OMAB85Z RD 485 CURRENT READING 790 ITi VAL RDS CONUERT READING TO NUMERIC 800 CH FOX CALL IBWRT M220 TURN OFF 220 QUTPUT 810 READ C READ 705 COMMAND STRING 820 CALL IBWRT M7 5 05 OPEN CROSSPOINTS 830 NEXT J LOOP BACK FOR NEXT POINT 840 BEEP 850 CLS 880 CALL 2 08 SEND DEVICE CLEAR 870 PRINT MEASUREMENTS COMPLETE 880 PRINT MEASURED CURRENT 11 890 FOR J TO 4 LOOP AND DISPLAY MEASURED VOLTAGES 800 0 7 910 NEXT J 920 5
69. ON LO RESISTIVITY PUT JUNCTION IN BOX AND SURROUND WITH FOAM INSULATION CONNECT TO ANALOG GROUND 1 SC 72 WIRE Lens 7025 TRIAX CABLE OUTPUT CURRENT SOURCE INPUT TRIA AESIETIVOT MONITOR OUTPUT CURRENT Figure 4 3 Connections for Voltage Offset Verification SERVICE INFORMATION 4 4 ADJUSTMENTS Offset adjustments for the four sample inputs as well as common mode rejection adjustment are covered in the following paragraphs 4 4 1 Environmental Conditions All adjustments should be made at an ambient temperature of 18 to 28 C and at a relative humidity of less than 70 4 4 2 Warm Up Period The Model 7065 should be allowed to warm up for one hour before performing the adjustments Test equipment should also be allowed to warm up for the period stated in the respective instruction manuals 4 4 3 Recommended Test Equipment Table 4 3 summarizes the equipment necessary to make the adjustments 4 4 4 Adjustment Locations Figure 4 4 shows the adjustment locations The four offset adjustments are accessible from the end of the card each control is adjacent to the associated input connector The common mode rejection adjustment can be accessed through the hole in the small digital shield Table 4 3 Equipment Needed for Adjustments DMM Oscilloscope 100nV sensitivity Scanner 10kQ Resistor Extender Card
70. P PRINT PRINT lt PRINT INPUT A IF lt 1 OR gt 2 THEN 229 IF A THEN Z 2 NOS5 4X E Z PRINT INITIALIZING INSTRU g V 1 CALL UX SEND REMOTE ENABLE CALL IBCMD BRD D SEND DEVICE CLEAR REM INITIALIZE THE MODEL 705 x C A X CALL IBWRT M705 CB 705 IN MATRIX MODE CALL IBWRT M705 Z PROGRAM CARD RESISTIVITY SETUP REM INITIALIZE THE 485 C RIX CALL IBURT MABSZ C SELECT NA RANGE FOR I 1 TO 1000 I SETTLING TIME CS CIX CALL IBWRT M485 ZERO CHECK ON FOR I 1 1000 I C Z1X CALL IBWRT MABSZ C REL ON FOR I TO 1000 I C COX CALL 485 6 ZERO CHECK OFF C ROBIX CALL IBWRT M485 CS AUTORANGE NO PREFIX REM INITIALIZE THE 196 C ROFOSSGIX CALL IBURT MISBZ US AUTO DCU RATE NO PREFIX REM INITIALIZE THE 220 C U10X CALL IBWRT M220 C 220 10V COMPLIANCE INPUT 220 CURRENT S FA 1 MA 1 INPUT 220 CURRENT 5 1 IF I lt SE 13 19 1 THEN 480 E E E NAS DEV4 CALL 8 4851 FIND 485 D 5 0 05 1 LOW RESISTIUITY RESISTIVE LSE 24 05 4 705 COMMAND STRING MENT 3 47 APPLICATIONS Program 8 6 and 8 Contact Sample Resistivity IBM PC 8573A Version Continued 510 2 520 CS I STRSCIO X CALL IBWRT M22 CS PROGRAM 220 CURRE
71. P THIS PROGRAM MEASURES 90 DISP HALL VOLTAGES AND COMPUTES 100 119 120 158 140 150 160 170 180 130 200 210 220 230 240 250 250 270 280 460 470 480 490 500 3 28 DISP IHE COEFFICIENTS DISP THE 7085 HALL CARD MUST DISP BE IN CARD 1 LOCATION DISP DISP PRESS CONT PAUSE CLEAR DISP SELECT CARD RESISTIVITY SETUP DISP DISP DISP INPUT A IF lt 1 OR gt 2 THEN 180 IF A 1 THEN 2 05 4 ELSE 7 05 4 705 COMMAND STRING DISP INITIALIZING INSTRUMENTS REMOTE P1 P2 P3 P4 PUT INSTRUMENTS IN REMOTE CLEAR 7 SEND DEVICE CLEAR INITIALIZE 705 OUTPUT 40 MATRIX MODE OUTPUT 7 PROGRAM RESISTIVITY INITIALIZE 485 OUTPUT P4 RIX ZNA RANGE WAIT 1000 SETTLING TIME OUTPUT P4 CIX ZERO CHECK ON WAIT 1000 WAIT FOR READING TO SETTLE OUTPUT ZIX ENABLE REL WAIT 1000 WAIT FOR REL TO COMPLETE OUTPUT P4 COX ZERO CHECK OFF OUTPUT P4 R GiX AUTORANGE NO PREFIX x INITIALIZE 195 OUTPUT P2 R F SSG1X AUTO DCU RATE NO PREFIX OUTPUT Pt U1 X 220 10V COMPLIANCE DISP 220 CURRENT S fA 1 MA gt INPUT I INPUT 220 CURRENT I ABS I POSITIVE CURRENT ONLY IP I lt 5 E 13 OR 12 1 THEN 420 OUTPUT Pi I I X PROGRAM 220 CURRENT DISP ENTER SAMPLE THICKNESS CM INPUT T INPUT SAMPLE THICKNESS T ABS T gt DISP ENTER FLUX DENSITY GAUSS 1 LOW RESISTIVI
72. PUT SOUACE j a TRAY PE rj CURRENT MONITOR Output 4801 COAXIAL CABLE 7025 TRIAXIAL Figure 2 7 Connections for Van der Pauw Samples 2 9 OPERATION 196 485 220 VOLTMETER CURRENT METER SOURCE o o DENOTES RELAYS ON 7065 47 DENOTES ANALOG GROUND NOTE HIGH RESISTIVITY MODE SHOWN Figure 2 8 Equivalent Circuit for Van der Pauw Connections 2 10 2 4 5 Bar Type Sample Connections Hall Voltage Measurements Use the basic scheme shown in Figure 2 9 for Hall voltage measurements on bar type samples Figure 2 10 shows an equivalent circuit Make connections as follows 1 Connect the sample to the SAMPLE INPUTS as shown in Figure 2 9 Use the supplied 7025 triaxial cables see paragraph 24 3 for preparation 2 Mount the Model 6167 guarding adapter on the Model 220 and connect the guard lead to the Model 220 GUARD terminal Connect a Model 7024 triax cable between the Model 6167 input jack and the Model 7065 Current Source Input NOTE This connecting method assumes guarded source input operation See paragraph 2 6 for more infor mation on guarding OPERATION 3 Connect the picoammeter HI input terminal directly to the sample under test through a Model 4802 coaxial cable Connect a black wire banana plug between analog ground on the terminal block and Model 485 analog out put low 4 Connect a suitable potentiometer between terminals 4 a
73. Pauw Sample 2 8 Contents Table of Crosspoint Programming Current Monitor Output Shorting Current Source Input Guarding Electrical Parts List of 5 2 Electrostatic Interference Equivalent Input Circuits 2 33 Factory Service 5 1 Figures List iv Ground Loops 2 43 Guarding Current Source Input 2 24 Principles 2 24 Sample Input 2 26 Hall Effect Principles 3 2 Sign CE Terminal Convention Hall Voltage Measurements Bar Sample 3 14 Bridge Sample Parallelepiped Sample Van der Pauw Sample 37 Hall Mobility Calculations Bar Sample Bridge Sample 3 20 Parallelepiped Sample 3 20 Van der Pauw Sample Handling Precautions High Impedance Considerations 4 2 IEEE 488 Bus 22113 Programs 2 39 3 23 CR Characteristics Loading 2 41 Voltage Levels 2 40 Installation Model 705 Scanner 2 2 Model 706 Scanner 2 2 Jacks Input and Output Leakage Resistance 2 40 Matrix Configuration 2 21 Measurements Bar Samples Bridge Samples Parallelepiped Samples 3 15 Van der Pauw Samples Offsets 2 43 Operation General 2 1 Parallelepiped Sample Connections 2 16 Measurement Performance Veri cation 4 1 Programs Example Pee Replaceable Parts Resistivity Measurement Bar Sample Bridge Sample Parallelepiped Sample 3 19 Van der Pauw 13 5 Resistivity Selection Equivalent Input Input Characteristics
74. RANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE THE REMEDIES PROVIDED HEREIN ARE BUYER S SOLE AND EXCLUSIVE REMEDIES NEITHER KEITHLEY INSTRUMENTS INC NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT INDI RECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS INC HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES SUCH EXCLUDED DAMAGES SHALL INCLUDE BUT ARE NOT LIMITED TO COSTS OF REMOVAL AND INSTALLATION LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON OR DAMAGE TO PROPERTY KEI I HLEY Keithley Instruments Inc 28775 Aurora Road Cleveland OH 44139 216 248 0400 Fax 216 248 6168 http www keithley com CHINA Keithley Instruments China Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 8610 62022886 Fax 8610 62022892 FRANCE Keithley Instruments SARL BP 60 3 All e des Garays 91122 Palaiseau C dex 33 1 60 11 51 55 Fax 33 1 60 11 77 26 GERMANY Keithley Instruments GmbH Landsberger Strasse 65 D 82110 Germering Munich 49 89 8493070 Fax 49 89 84930787 GREAT BRITAIN Keithley Instruments Ltd Minster 58 Portman Road Reading Berkshire RG30 1EA 44 118 9575666 Fax 44 118 9596469 ITALY Keithley Instruments SRL Viale S Gimignano 38 20146 Milano 39 2 48303008 Fax 39 2 48302274 JAPAN Keithley KK Ai
75. T COEFFICIENTS THE HALL CARD MUST BE IN THE CARD 1 LOCATION PRINT PRINT PRESS ANY KEY TO CONTINUE AS INKEYS IF A THEN 190 CLS PRINT SELECT CARD RESISTIVITY SETUP PRINT PRINT LOW RESISTIVITY PRINT 2 HIGH RESISTIVITY INPUT IF ASTOR A52 THEN 210 IF 1 THEN 2 05 4 ELSE 78 05 4 7705 COMMAND STRING PRINT INITIALIZING INSTRUMENTS VZ 1 CALL SEND REMOTE ENABLE CALL IBCMD OBRDOX D SEND DEVICE CLEAR REM INITIALIZE THE MODEL 705 x x C AQX CALL IBWRT M705 C PUT 705 IN MATRIX MODE CALL IBWRT M7 5 2 PROGRAM CARD RESISTIVITY SETUP REM INITIALIZE THE 485 x CS RIX CALL IBWRT M485 SELECT ZNA RANGE FOR I 1 TO 1000 I SETTLING TIME C CiX CALL IBWRT M485 ZERO CHECK ON FOR I 1 TO 1 NEXT I CS Z1X CALL IBWRT M485 C REL ON FOR I 1 TO 1000 I C COX CALL IBWRT M485 ZERO CHECK OFF C ROGIX CALL 4852 AUTORANGE NO PREFIX REM INITIALIZE THE 196 C ROFOSSCGIX CALL IBWRT MIS88Z C AUTO DCU RATE NO PREFIX REM INITIALIZE THE 220 x C UIOX CALL IBWRT M220 CS 220 109 COMPLIANCE INPUT 22 CURRENT S FA 1 QMA 1 INPUT 220 CURRENT I ABS I POSITIUE CURRENT ONLY IF I lt 5 13 OR 15 1 THEN 470 CH I STRSCI X CALL IBWRT M220 CS PROGRAM 220 CURRENT 3 39 APPLICATIONS Program 5 Ha
76. TION 5 Replaceable Parts SECTION 1 GENERAL INFORMATION 1 1 INTRODUCTION This section contains general information about the Model 7065 Hall Card and is arranged as follows 1 2 Features 1 3 Warranty Information 1 4 Manual Addenda 1 5 Safety Symbols and Terms 1 6 Specifications 1 7 Unpacking and Inspection 1 8 Repacking for Shipment 1 9 Recommended Equipment 1 10 Scanner Compatibility 1 2 FEATURES The Model 7065 Hall Card is designed to assist in making resistivity and Hall voltage measurements on several types of semiconductor specimens The unit is designed to be used in conjunction with a Keithley Model 705 or 706 Scan ner along with a suitable current source and voltmeter The Model 7065 incorporates the necessary on card switching and buffering in order to minimize measurement complex ity and maximize accuracy Key Model 7065 features include Selectable input characteristics for either high or low resistivity measurements Solid state switching is used for measurement paths for higher reliability and lower thermal emfs On card low EMI power supply to maximize isolation and minimize noise effects Provisions for guarded measurements to minimize the effects of leakage resistance and capacitance On card connection for a picoammeter to verify sample excitation current 1 3 WARRANTY INFORMATION Warranty information may be found on the inside front cover of this instruction manual Shoul
77. TY 2 HIGH RESISTIVITY APPLICATIONS Program 1 Hall Voltage Measurement HP 85 Version Continued 510 INPUT B 520 B ABS B 530 CLEAR 540 DISP APPLY TB PRESS CONT 550 PAUSE 560 MAIN MEASUREMENT LOOP 570 RESTORE CLEAR DATA POINTER 580 DISP MEASURING 580 FOR J 1 TO 8 LOOP FOR ALL 8 VOLTAGES 600 IF J 5 THEN RESTORE 8 DISP REVERSE FIELD B PRESS CONT 6 8 PAUSE 510 READ AS READ 705 COMMAND STRING 520 OUTPUT AS CLOSE CROSSPOINTS 530 OUTPUT Pi FIX TURN ON 220 OUTPUT 640 WAIT W 1 WAIT W MSEC FOR READING TO SETTLE 550 ENTER P2 4 Vid 1 GET 135 VOLTAGE READING 650 IF ABS UCJ2 28 THEN GOTO 969 CHECK VOLTAGE LIMITS 570 IF 1 1 THEN ENTER 11 GET 485 CURRENT READING 680 OUTPUT P FOX TURN OFF 220 OUTPUT 680 READ AS READ 705 COMMAND STRING 700 OUTPUT P3 AS OPEN CROSSPOINTS 710 NEXT J LOOP BACK FOR NEXT MEASUREMENT 720 BEEP 730 CLEAR 740 CLEAR 7 SEND DEVICE CLEAR 750 DISP MEASUREMENTS COMPLETE 769 DISP MEASURED CURRENT I 770 FOR 1 1 TO 8 LOOP AND DISPLAY MEASURED VOLTAGES 780 DISP 7980 NEXT J 800 DISP 810 DISP PRESS CONT TO CALCULATE 828 DISP HALL COEFFICIENTS 830 PAUSE 840 R1 25000000 T B Il 2 UC2 UCT OTUCS UCB D 850 R2 25000000 T B I10 UCA UCS 4UC7 UCB 880 R3 RI R2 2 870 DISP RHC 5R 880 DISP RHD R2 880 DISP RHAU iR3 900 DISP 910 DISP REPEAT TEST Y N 920
78. all Voltage Measurements 3 6 Plotof f vs 3 7 Test Configuration for Resistivity Measurements of Bar Sample 3 8 Test Configuration for Hall Voltage Measurement of Bar Sample 3 9 Hall Bar Equivalent tk kb T Sed re hated ene st aco ded aces acie 3 10 Equivalent Potentiometer Circuit High Resistivity 3 11 Equivalent Potentiometer Circuit Low Resistivity 3 12 Bar Sample Dimensions RE Ead aa Kap edd 3 13 6 Contact Sample Connections 9 3 14 B Contact Sample Connections Cb adi PRORA wae Feed ed eee ee ONS V dua awe 3 15 Sample Dimensions Necessary for Calculations 3 16 Test Configuration for Programs 1 2 5 and cheeks ee a ee ERR Re 3 17 Test Configuration for Programs 3 and 7 pp 3 8 Test Configuration for Programs 4 and dee od SECTION 4 SERVICE INFORMATION 4 Connections for Input Current Verification aya e RR RU AV En Y rh as 4 2 Connections for Input Resistance Verification eR RESERVE RU ER ERE Sa d as 4 3 Connections for Voltage Offset Verification 5224s Lies gods bM ae ERA EN dade ss dees 4 4 Adjustment Locations
79. at electrostatic interference is present Means of minimizing electrostatic interference include 1 Shielding Possibilities include a shielded room and pro perly shielding the test fixture 2 Reduction of electrostatic fields Moving power lines or other sources away from the test setup reduces the amount of electrostatic interference induced into the experiment 2 10 6 RFI Radio Frequency Interference is a general term fre quently used to describe electromagnetic inteference over a wide range of frequencies across the spectrum RFI can be especially troublesome at low signal levels with low resistivity samples but it can also affect high level measurements in extreme cases RFI can be caused by steady state sources such as TV or radio broadcast signals or it can be caused by impulse sources as in the case of high voltage arcing In either case the effect on the measurement can be considerable if enough unwanted signal is present The effects of RFI can often be seen as an unusually large offset or in the case of impulse source as sudden erratic variations in the measurement RFI can be minimized by taking one or more of several precautions when making Hall measurements in such elec tromagnetic environments The most obvious method is to keep all the instruments and sample as far away as possi ble from the RFI source Shielding the experiment in struments and test leads will often reduce the interference t
80. ations 4 3 3 Recommended Equipment Table 4 1 summarizes the equipment necessary to perform the verification procedures SERVICE INFORMATION Table 4 1 Performance Verification Equipment Description Specifications Manufacturer and Model Digital Multimeter Electrometer Source DC output Scanner 4801 Coax Cable 7024 Triax cable 7025 Triax Cable 4802 cable SC 72 wire SC 81 BGZ Cable 4 3 4 High Impedance Considerations Because of the high impedances involved with some of the measurements the cables should be kept as still as possi ble during the tests 4 3 5 Input Current Verification Connections Connect the Model 617 Electrometer to the sample input to be verified as shown in Figure 4 1 Use a Model 7024 triaxial cable to connect the sample input jack to the elec trometer Make sure the ground link is connected between the Model 617 ANALOG OUTPUT COMMON and chassis ground terminals 4 2 100nV DC resolution 0 006 accuracy sensitivity 8V Keithley 196 Keithley 617 Keithley 705 or 706 Supplied Supplied Supplied Supplied Supplied Supplied Procedure 1 Install the Model 7065 in the scanner mainframe and turn on the power Allow the unit to warm up for one hour 2 Using Program 6 select the matrix mode pole 0 3 Place the electrometer on the 2nA range enable zero check and zero correct the electrometer Make sure th
81. being tested through a 7024 triaxial cable Connect the voltage source low ter minal to the Model 7065 analog ground using a supplied C72 black wire Connect the second SC 72 black wire bet ween voltage source output high and electrometer analog output common Make sure the ground link is removed Procedure 1 2 4 4 Install the Hall card in the mainframe and turn on the power Using Program 6 select the matrix mode pole 0 Press ENTER Select the 20nA range on the electrometer enable zero check and then zero correct the instrument Make sure the low to ground link on the electrometer is removed and that the guard switch is in the off position Make sure the Model 617 voltage source output is turn ed off then disable zero check Wait for the reading to settle Enable the suppress feature on the electrometer Enable zero check and program the Model 617 voltage source for a value of 8V turn on the output Release zero check and allow the reading to settle Note and record the current reading as 1 Program the voltage source for an output of 8V Note the current reading on the electrometer and record the value as L 10 11 Compute the input resistance for the low resistivity setup as follows 16 R IL L Verify that the resistance calculated in step 10 is greater than 10GQ Note typical values may be as high as 100 12 Enable zero check select the 2pA rang
82. bido Building 7F 7 20 2 Nishishinjuku Shinjuku ku Tokyo 160 81 3 5389 1964 Fax 81 3 5389 2068 NETHERLANDS Keithley Instruments Avelingen West 49 4202 MS Gorinchem 31 0 183 635333 Fax 31 0 183 630821 SWITZERLAND Keithley Instruments SA Kriesbachstrasse 4 8600 D bendorf 41 1 8219444 Fax 41 1 8203081 TAIWAN Keithley Instruments Taiwan 1FL 1 Min Yu First Street Hsinchu Taiwan R O C 886 35 778462 Fax 886 35 778455 Model 7065 Hall Effect Card Instruction Manual 1986 Keithley Instruments Inc Test Instrumentation Group All rights reserved Cleveland Ohio U S A Second Printing March 1989 Document Number 7065 901 01 Rev B Manual Print History The print history shown below lists the printing dates of all Revisions and Addenda created for this manual The Revision Level letter increases alphabetically as the manual undergoes subsequent updates Addenda which are released between Revi sions contain important change information that the user should incorporate immediately into the manual Addenda are num bered sequentially When a new Revision is created all Addenda associated with the previous Revision of the manual are incorporated into the new Revision of the manual Each new Revision includes a revised copy of this print history page Revision A Document Number 7065 901 01 Addendum A Document Number 7065 901 02 Addendum A Document Number 7065 901 03
83. by the Model 196 from Table 3 9 From these two coefficients the average Hall coefficient Rave can be computed in the following manner Rave 57 2 Note that ve is in units of cm C For eight contact samples only a single coefficient Rx need be derived as follows 25 x 0t V V Vy Braen BI Where Ra Hall coefficient in cm C ts sample thickness in cm B flux density in gauss I current measured by the Model 485 in amperes V V voltages from Table 3 10 measured by the Model 196 Hall Mobility The Hall mobility can be computed from the Hall coef ficient s and average resistivity of the specimen as follows Ru n Pave Where Hall mobility in cm V s average Hall coefficient in cm C Pave average resistivity in ohm cm For 8 contact samples substitute Ry for Rz the above equation 3 8 SAMPLE RESISTIVITY AND HALL VOLIAGE PROGRAMS Three Programs are included in this section in order to demonstrate fundamental Programming techniques Pro grams 1 and 5 are intended to determine the Hall coeffi cients using the van der Pauw method and Programs 2 and 6 determine the resistivity of van der Pauw samples Pro grams 3 and 7 measure bar sample resistivity and programs 4 and 8 can be used to measure the resistivity of 6 or 8 contact bridge or parallelepiped samples Programs 1 4 are written in Hewlett Packard Model 85 BASI
84. cope TEK 2235 View waveforms Extender Card Keithley 7061 Allow circuit access 4 14 Step Item Component 08 pins 4 amp 8 U8 pin 3 T1 pins 6 2 T2 pins 1 3 U9 pin 3 Scanner programming Current source input 8 DMM Scanner programming DMM Voltage source DMM Scanner programming DMM Voltage source DMM Scanner programming DMM Voltage source DMM Scanner programming DMM Voltage source DMM Scanner SERVICE INFORMATION Table 4 6 Troubleshooting Summary Required Condition 6 DC 3 4kHz square wave 6V peak 3 4kHz 17V peak 3 4kHz 20 20 5 5 Pulse train when programming channels Pulse train when programming channels Pulse train when programming channels Close crosspoint 5 4 Connect external 5V source to center conductor Close crosspoints 2 1 and 3 1 5V 0 1 Set to 5V 5V 0 1 Open 2 1 3 1 Close 2 2 32 5V 0 1 5V 5V 0 1 Open 2 2 3 2 Close 2 3 3 3 5V 0 1 5V 5V 40 196 Open 2 3 33 Close 2 4 34 5V 40 196 5V 45V 0 196 Press RESET Reference to digital ground Chopper time base Chopper signal referred to digital ground Chopper signal referred to analog ground Referenced to analog ground 12 supply 12 supply Control strobe Control data Control clock Select high resistivity Connect source low to analog ground Set DMM to measure DCV Select buffer 1 Check out
85. d your Model 7065 require warranty service contact the Keithley representative or authorized repair facility in your area for further infor mation When returning the card for repair be sure to fill out and include the service form in order to provide the repair facility with the necessary information 1 4 MANUAL ADDENDA Any improvements or changes concerning the unit or manual will be explained in an addendum included with the unit Please be sure to note these changes and incor porate them into the manual before operating or servicing the unit 1 5 SAFETY SYMBOLS AND TERMS The following symbols and terms may be found on the in strument or used in this manual The A symbol on the instrument indicates that the user should refer to the operating instructions The symbol on an instrument shows that high voltage may be present on the terminal s Use standard safety practices to avoid personal contact with these voltages The WARNING heading used in this manual explains dangers that might result in personal injury or death Always read the associated information very carefully before performing the indicated procedure The CAUTION heading used in this manual explains hazards that could damage the unit Such damage may void the warranty 1 1 GENERAL INFORMATION 1 6 SPECIFICATIONS Model 7065 specifications are located at the front of this manual These specifications are exclusive of the scanner mainframe specif
86. e 2 4 Connections Covers the various connectors on the card and how to connect it to other instruments 2 5 Matrix and Test Configurations Discusses 7065 matrix and typical system configurations 2 6 Guarding Methods Describes methods of source input guarding and discusses sample input guarding as well as guarding principles 2 7 Low and High Resistivity Selection Covers Model 7065 setup requirements for low and high resistivity samples and summarizes input characteristics and tradeoffs for each 2 8 Front Panel Scanner Programming Summarizes pro gramming steps necessary to control the Model 7065 from the front panel of the scanner mainframe 2 9 IEEE 488 Bus Scanner Programming Reviews method to control the Model 7065 through a scanner mainframe over the IEEE 488 bus 2 10 Measurement Considerations Covers important fac tors that must be taken into account when making measurements with the Model 7065 2 2 HANDLING PRECAUTIONS Because the Model 7065 is designed for very high impe dance measurements care must be taken when handling the card to avoid contamination from foreign materials such as body oils Such contamination can drastically lower channel isolation and leakage resistances degrading per formance To avoid possible contamination always grasp the card at the edges Although the card shields protect most of the circuit board it is a good idea to avoid touching the expos ed board areas If you re
87. e and disable 16 18 19 20 21 22 23 suppress Zero correct the electrometer Turn off the electrometer voltage source output Close crosspoint 5 4 to select high resistivity by pro gramming the scanner Disable zero check wait for the reading to settle and then enable suppress Turn on the electrometer voltage source output The voltage source should still be programmed to 8V Note and record the current reading as Program the voltage source to 8V Note and record the current reading as L Compute the input resistance for the high resistivity setup as follows 16 R Il Ll Verify that the resistance calculated in step 20 is greater than 10070 Turn off the voltage source enable zero check and disable suppress Open crosspoint 5 4 and repeat steps 3 through 22 for the other three sample inputs The electrometer should be connected to the sample input being tested using the connections shown in Figure 4 2 SERVICE INFORMATION o S 2825 lt 2 525 lt E o gt 5 H 5 A 2 1 zr 5 5 c WITHIN 30v OF EARTH SAMPLE 1 SAMME MPU TRIA WARNING MAINTAIN INPUTS CuTPUTS AMPLIFIE CONFIGURATION 5 7024 v 1 TRIAXIAL 55 i f 7065 CARD GROUND LINK REMOVED SC 72 BLACK WIRE 401
88. e electrometer guard switch is in the off position 4 Disable zero check and note the reading on the electro meter display Verify that the reading is less than 100pA exclusive of noise 5 Enable zero check on the electrometer and place the unit on the 2pA range 6 Close crosspoint 5 4 to enable the high resistivity mode 7 Disable zero check and verify that the current reading is less than 0 15pA exclusive of noise 8 Enable zero check and open crosspoint 54 on the scanner 9 Repeat steps 3 through 8 for the remaining three sam ple inputs The electrometer should be connected to the sample input being tested SERVICE INFORMATION a 2525 x tait 58645 5 8 gt 2 E 5 rz o x 2 SAMME INPUT TRIAX fa 2 WARNING MAINTAIN INPUTS ANO OUTPUTS WITHIN JOY OF EARTH AMPLIFIER CONFIGURATION KEITHLF Y 7085 MALL EFFECT CARD 1 SAMPLE INPUT CURRENT MONITOR OUTPUT 7065 CARD GROUND LINK CONNECTED 7024 TRIAX CABLE COMMON TO CHASSIS 617 ELECTROMETER ANALOG GUARD OFF OUTPUT COMMON Figure 4 1 Connections for Input Current Verification 4 3 SERVICE INFORMATION 4 3 6 Input Resistance Verification Connections Connect the Keithley Model 617 Electrometer to the Hall card as shown in Figure 4 2 The electrometer should be connected to the sample input jack
89. e ATTENTION REPAIR DEPARTMENT on the ship ping label Note that is not necessary to return the scanner mainframe with the card 5 5 COMPONENT LAYOUT AND SCHEMATIC DIAGRAM A component layout drawing of the Model 7065 is shown in Figure 5 1 Figure 5 2 shows a schematic diagram of the card REPLACEABLE PARTS Table 5 1 Electrical Parts Circuit Keithley Designation Description Part Number Analog FET photon coupled HHF1 IC 524 1 7 Capacitor 25V Aluminum Electrolytic C 314 10 C8 Capacitor 6800 190 100V mica C 248 6800p C9 Capacitor 0 024E 2096 500V Ceramic Disc C 22 02 C10 Capacitor 3 3pE 100V ceramic 372 3 3 C11 Capacitor 1500PE 10 1000V ceramic disc C 64 1500p CR1 CR4 Diode rectifier 1N3595 RF 43 CR5 Diode silicon 1N4148 RE 28 CR6 Bridge Rectifier 1 5A 400PIV PF40 RF 46 E1 E17 Terminal Teflon insulated TE 105 1 J2 Connector terminal strip CS 518 6 J3 Connector insulated BNC CS 520 J4 J8 Connector triax CS 440 K1 K8 Relay reed RL 70 Q1 Q2 Transistor silicon NPN GES5818 TG 138 Q3 O14 Transistor FET 2N7000 TG 195 R1 Resistor 10 ZW 10 Composition R 1 10k R2 R6 Resistor 10 W 5 Composition R 76 10k R7 R9 Resistor 330kQ 4W 5 Composition R 76 330k R10 R13 Resistor 1MQ ZW 10 Composition R 1 1M R14 R17 Potentiometer 100kQ 0 75W RP 89 100k R18 Resistor thick film 177 1 R19 Resistor 1 8 1 R 88 30 1k R20 Resistor 180kQ
90. e programs assume that the Model 7065 is in stalled in the card 1 slot of unit 1 daisy chained units OPERATION Model 705 Program Program Comments REMOTE 717 Put 705 remote OUTPUT 717 Het Put 705 in matrix mode SB DITPHUT rives C eEBISTS 77 Close 1 1 OUTPUT 17 5 02 255 Close 2 2 zB OUTPUT 54 Close 33 OUTPUT 717 1 Close 44 T m PRESS TO PAUSE DETPHT eles BEST Open all cross points 144 Model 706 Program Program Comments 184 REMOTE Fis Put 706 in remote OUTPUT 718 SAGE Put 706 in matrix mode zB OUTPUT 12 CBB1 1x Close 1 1 4B OUTPUT 2712 0882 2 Close 2 2 zB OUTPUT 218 52882 28 Close 33 OUTPUT 718 50884 gT Close 44 LISPISPRESS s CONT CROSSPOINTS PAUSE OUTPUT 718 REATI Open all cross points 146 2 10 MEASUREMENT CONSIDERATIONS Many of the measurements made with the Model 7065 are performed on high resistivity devices and at very low cur rent levels At these levels a number of factors can affect a measurement The following paragraphs discuss some considerations when making such measurements 2 39 OPERATION 2 10 1 Input Voltage Levels The input voltage operating range for the SAMPLE INPUTS is limited to 8V for both high and low resistivity setups Applyi
91. ections for Common Mode Adjustment NOTE ADJUST POTENTIOMETER R23 FOR MINIMUM AMPLITUDE AND BEST WAVEFORM SYMMETRY Figure 4 7 Common Mode Adjustment Waveform 4 11 SERVICE INFORMATION 4 5 THEORY OF OPERATION The following Paragraphs give a brief description of the ma jor circuits in the Model 7065 Figure 4 8 shows a block diagram of the unit and the schematic diagram is located on drawing number 7065 106 found at the end of Section 5 4 5 1 Relay Switching Circuits A large part of Model 7065 operation is concerned with con necting different inputs and outputs together For that reason a number of relays and solid state switching elements are found on the card K1 through perform input or current switching for the card Each of these devices is a special low current relay with a guard shield to minimize the effects of leakage cur rents Note that the current input is protected by Q1 Q2 and VR2 to limit input compliance voltage to 12 At the output switching is performed by solid state elements U11 through U16 Each of these devices is inter nally controlled by opto coupling in order to maintain high analog to digital isolation Some of the switching elements are directly controlled from scanner mainframe signals passed through J1 while others use information derived from the serial control word For example K3 and K7 are directly controlled while K4 and K8 are switched by serial control info
92. ed Again these voltages are designated V through V as discussed in paragraph 3 5 Conventions used for bar and bridge specimens are similar and are covered in paragraphs 3 6 and 37 respectively 3 3 3 Basic Hall Effect Principles For the following discussion refer to the basic sample con figuration shown in Figure 3 1 If a current I J A is applied across the length of the sam ple a voltage is developed across that sample If a magnetic field B is subsequently applied normal perpendicular to the current the carriers are displaced from their normal paths and a voltage is developed This voltage is known as the Hall voltage Once the Hall voltage is known the Hall coefficient can be defined as follows Ry JB qnvB Where R4 Hall coefficient Ey Hall voltage J current density B magnetic field n carrier concentration q carrier charge v drift mobility Once the Hall coefficient is known carrier concentration and mobility can be calculated when used with the measured resistivity APPLICATIONS A B C D E F G H Figure 3 3 Resistivity Measurement Conventions APPLICATIONS Figure 3 4 Hall Voltage Measurement Conventions 3 4 VAN DER PAUW RESISTIVITY MEASUREMENTS The following paragraphs describe basic test configuration test procedures and calculations necessary to make resis tivity measurements using
93. en as Es The input capacitance is and Ey represents the voltage appearing at the Hall card sample input Figure 2 30 Input Capacitance Effects When the source current 15 is first applied the voltage Es across the capacitance and thus at the sample input does not instantaneously rise to its final value Instead C charges exponentially through Rs as follows 1 e RO Here for convenience we can specify in megohms in microfarads and t in seconds Because of C charging the sample input follows the ex ponential curve shown in Figure 2 31 At the end of one 2 41 OPERATION time constant R C the voltage reaches approximately 63 of final value At the end of two time constants the voltage reaches about 8690 of final value and so on Generally at least five time constants 5RsC must be allowed for better than 196 accuracy 2 3 time constants per decade of accuracy improvement Figure 2 31 Exponential Response of Input Voltage The amount of time that must be allowed will of course depend on the relative R and C values For example with a sample resistance of 100GQ and an input capacitance of 2pF typically guarding the input reduces effective capaci tance to 2pF or less a time constant of 200msec results Thus at least one second must be allowed to achieve a bet ter than 196 accuracy figure We can easily calculate percentage error figures for various RC time con
94. esistivity IBM PC 8573A Version Continued 510 Z ABS Z 520 INPUT ENTER SAMPLE X DIMENSION CMO X 530 X ABS X 540 INPUT ENTER SAMPLE Y DIMENSION CMO Y 550 Y ABS CY 550 REM MAKE MEASUREMENTS 570 CLS 580 PRINT MEASURING 580 C C02 4C03 1C04 2X CALL IBWRT M7 5 C CLOSE CROSSPOINTS 500 C FiX CALL IBURT M220X C TURN 220 OUTPUT 61 FOR I 1 TO DELAY NEXT WAIT FOR READING TO SETTLE 620 RD SPACES 25 CALL IBRD MIS8BZ RD GET 196 READING 630 V UALCRD CONVERT STRING TO NUMERIC 640 IF ABS V gt 8 THEN 830 CHECK VOLTAGE LIMITS 650 RDS SPACE 25 CALL IBRD M485 RDS GET 485 CURRENT READING 660 Ii UALCRD CONUERT READING TO NUMERIC 570 CS FOX CALL IBWRT M220 C TURN OFF 220 OUTPUT 680 484 02 4 03 1 04 2 IBWRT M7 5 CS OPEN CROSSPOINTS 699 700 CLS 710 CALL IBCMD BRDOZ D SEND DEVICE CLEAR 720 PRINT MEASUREMENTS COMPLETE 730 PRINT MEASURED CURRENT 11 740 PRINT MEASURED VOLTAGE U 750 PRINT PRESS ANY KEY TO CALCULATE RESISTIVITY 750 AS INKEYS IF AS THEN 760 770 P U Y X CX 11 CALCULATE RESISTIVITY 780 PRINT RESISTIVITY 3P3 QHM CM 780 PRINT 800 INPUT REPEAT TEST 810 IF LEFT A 1 Y THEN CLS 60TO 270 820 GOTO 940 850 CLS BEEP 840 CALL IBCMD BRDOZ D SEND DEVICE CLEAR 850 PRINT SAMPLE VOLTAGE IS OVER 8U 7065 LIMIT 850 PRINT DO YOU WISH TO 870 1 RESTART THE MEASURE
95. esistivity of the sample under test The following discussion covers general aspects and criteria Some experimentation may help to ob tain the best choice with a particular sample For sample resistances above IMQ accuracy degradation because of input loading comes into play Thus you should always use the high resistivity setup when measuring samples above 1MQ For lower sample resistances however the best configuration to use is a compromise between noise and gain error performance as we will now discuss Figure 2 27 depicts gain error versus actual sample resis tance calculated from signal voltage and sourced current The errors shown do not include possible errors caused by current source uncertainty only voltage measurement er rors are shown Total measurement uncertainty is the sum of gain error and noise uncertainty If we ignore noise uncertainty for the mo ment we see from Figure 2 27 that the obvious choice for all samples is the high resistivity setup In fact you may wish to operate the Model 7065 exclusively in the high resistivity mode if slight errors caused by noise are tolerable Hall voltages gt 5mV will yield error due to noise uncer tainty of 0 2906 2 34 Figure 2 28 illustrates measured noise voltage versus actual sample resistance The tangential lines are theoretical limits given the thermal Johnson noise resistance Obviously this limit is improved for noise due to sample resistivity if
96. from the Model 7065 card as shown in Figure 2 22 CAUTION Do not touch the board surface or any com ponents on the board as doing so may degrade performance Handle the board only by the edges 3 Place the two jumpers in the desired position s as shown in Figure 2 21 Use a pair of needle nose pliers to avoid touching the PC board 4 Replace the shield and make additional connections if necessary as outlined below before installing the card Unguarded Connections Use the basic procedure below to connect the Model 220 to the Model 7065 using Figure 2 23 as a guide Note that this configuration should be used only with the card in the low resistivity mode as discussed in paragraph 2 7 1 Connect the Model 7024 triaxial cable between the Model 220 OUTPUT jack and the Model 7065 CURRENT SOURCE INPUT 2 Connect a supplied insulated white with white banana plug wire between the Model 220 GUARD terminal and terminal 6 GD of the terminal block on the Model 7065 CAUTION Model 220 GUARD must be connected to Model 7065 guard even though the cable itself is not guarded The Model 220 guard is used to drive the protection circuits in the Hall card These cir cuits protect the source input from damage caused by excessive voltages 2 28 Figure 2 23 shows an equivalent circuit of these connec tions Current source Hl is carried through to input HI via the center conductor of the triaxial cable Source LO is con nected to
97. g female triaxial Input high to low clamped at 12V Maximum Input 100mA SAMPLE INPUTS Four two lug female triaxial Outer shell is analog ground Inner shield is driven guard Maximum In put Overload HI to analog ground or guard to analog ground 12V CURRENT MONITOR OUTPUT Insulated female BNC MEASUREMENT OUTPUTS Spring loaded terminals Accepts AWG 18 to 24 wire Maximum load 1mA Specifications subject to change without notice MAXIMUM COMMON MODE VOLTAGE analog ground to earth ground 30V peak dc to 60Hz sine wave ISOLATION Analog ground to earth ground Greater than 10 in parallel with 150pF WARMUP 1 hour to rated specifications ENVIRONMENT Operating 0 35 C up to 70 R H Storage 25 to 65 C DIMENSIONS WEIGHT 32mm high x 114mm wide x 272mm long 1 in x 4 in x 10 in Net weight 434kg 15 5 oz ACCESSORIES SUPPLIED Model 4801 Low Noise Input Cable Model 6167 Guarded Input Adapter Model 7024 3 Triaxial Cable 3 ft Model 7024 10 Triaxial Cable 10 ft Model 4802 10 Low Noise Input Cable 10 ft Model 7025 10 Triaxial Input Cable 10 ft Five supplied Model 7008 6 IEEE 488 Cable 6 ft Model 4851 BNC Shorting Plug 5 72 0 Single Conductor Insulated Wire Black 4 ft Two supplied 5 72 9 Single Conductor Insulated Wire White 4 ft BG 5 Single Banana Plug Black Two supplied BG 10 1 Single Banana Plug White BG 7 Double Banana Plug Black SC 8 2 Conductor Cable
98. he crosspoint specified by the associated parameters The Model 705 parameter for mat is Where nn specifies the column m specifies the row delimits the parameters optional Note that the nn and m values are the same as those used when programming the unit from the front panel see paragraph 2 8 For example to close column 2 row 1 send the command string C02 1X or simply 21 without the optional colon delimiter The parameter format for the Model 706 is similar and ap pears as follows nnn m Where nnn indicates the column m specifies the row delimits the column and row parameters optional Again nnn and m have the same values as when program ming the unit over the front panel For example to open column 5 row 4 send the command string N005 4X or simply N0054X without the optional colon delimiter ROX Sending this command opens all crosspoints simultaneously and displays column 1 row 1 2 9 2 Example Programs The example programs below demonstrate basic program ming procedures by setting up the unit for the matrix mode and then closing crosspoints 1 1 2 2 3 3 and 44 Follow ing operator input the program then opens all closed cross points by sending the command The programs are written in Hewlett Packard Model 85 BASIC The programming syntax for other similar com puters such as the HP9816 is virtually identical See the computer programming manual for details Note that th
99. he measurement being performed factory controlled laboratory out of doors etc What power line voltage is used Ambient temperature F Relative humidity Other Any additional information If special modifications have been made by the user please describe Be sure to include your name and phone number on this service form Specifications are subject to change without notice All Keithley trademarks and trade names arethe property of Keithley Instruments Inc All other trademarks and trade names arethe property of their respective companies KEITHLEY K eithley Instruments Inc BELGIUM Keithley Instruments V CHINA Keithley Instruments China FRANCE Keithley Instruments Sarl GERMANY Keithley Instruments G mbH GREAT BRITAIN Keithley Instruments Ltd INDIA Keithley Instruments G mbH ITALY Keithley Instruments s r l KOREA Keithley Instruments K orea NETHERLANDS Keithley Instruments SWITZERLAND Keithley Instruments SA TAIWAN Keithley Instruments Taiwan Copyright 2000 Keithley Instruments Inc Printed in the U S A 28775 Aurora Road Cleveland Ohio 44139 440 248 0400 Fax 440 248 6168 1 888 K EITHLEY 534 8453 www keithley com Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 8610 6202 2886 Fax 8610 6202 2892 3 all e des Garays 911
100. ications which may be found in the in struction manuals for those instruments 1 7 UNPACKING AND INSPECTION Upon receiving the Model 7065 carefully unpack the unit from its shipping carton and inspect the card for any ob vious signs of physical damage Report any such damage to the shipping agent immediately Save the original pack ing carton for possible future reshipment The following items are included with every Model 7065 order Model 7065 Hall Effect Card e Model 7065 Instruction Manual Standard accessories Table 1 1 Additional accessories as ordered If an additional instruction manual is required order the manual package Keithley Part Number 7065 901 00 The manual package includes an instruction manual and any applicable addenda 1 8 REPACKING FOR SHIPMENT Should it become necessary to return the Hall Card for repair carefully pack the unit in the original packing car ton or its equivalent Only the Model 7065 itself need be returned Be sure to include the following information Advise as to the warranty status Write ATTENTION REPAIR DEPARTMENT on the ship ping label e Fill out and include the service form at the back of this manual 1 9 RECOMMENDED EQUIPMENT Table 1 2 summarizes the instrumentation necessary for a Hall system This list does not include necessary user supplied equipment such as a cryostat electromagnet magnet power supply or IEEE 488 controller The Ke
101. igned to plug into the Models 705 or 706 Scan ners The Model 705 can accommodate two cards while the Model 706 can handle up to 10 scanner cards Other key features common to both scanner mainframes include Full IEEE 488 bus programmability Daisy chain operation allowing up to four slave main frames to be controlled with one master Front panel programs for easier system configuration Built in day time clock for time stamping of data 1 10 SCANNER COMPATIBILITY The Model 7065 is designed to be used with the Keithley Models 705 and 706 Scanners Note however that there are certain limitations when using the card in the Model 705 Limitations for the Model 705 involve the software revision level which must be B5 or later the software revision level is displayed as part of the power up cycle The reason for this limitation is that Rev B4 and earlier software does not support the matrix mode which must be used with the Model 7065 Earlier versions can be upgraded contact your Keithley representative or the factory for details 1 3 1 4 SECTION 2 OPERATION 2 1 INTRODUCTION This section contains information on card installation con nections test configurations and scanner programming and is arranged as follows 2 2 Handling Precautions Covers precautions that should be observed when handling the Hall effect card 2 3 Model 7065 Installation Details installation in a Model 705 or 706 scanner mainfram
102. ignments are summarized in Table 2 1 Maximum load current is 1mA Table 2 1 Terminal Strip Connections Terminal Description Analog ground Analog ground Hall Bar LO output LO output HI output Guard input OPERATION INPUT TRIAX FOR CURRENT ALAILS 104100 ALIAILSIS3M O1 TERMINAL BLOCK J2 e L Ix viia WOLINOIN ANdNI 1 3WYS IS3M 5 V NOLL VUnDI3NO2 Wd WAY HiBY3 30 AOE 810410 ONY SANANI NIVINIVA ONINY YAA V 123433 WH 990 A31H 113M BNC FOR CURRENT MONITOR OUTPUT Figure 2 3 Model 7065 Connectors 2 5 OPERATION 2 4 2 Recommended Cables and Wires Table 2 2 summarizes cables recommended for test connec tions These cables are supplied with the card as standard equipment The Model 7024 cables are intended for connecting the Model 220 current source to the Model 7065 The Model 7025 unterminated triaxial cables are intended for sample connections The coaxial cables are to be used for current monitor output connections The Model 4801 connects the card to the picoammeter while the Model 4802 allows the picoammeter to be connected directly to the sample Connecting wires between the terminal block and exter nal equipment are supplied The shielded cable dual banana plug sh
103. it to the Hall card 5 Close the crosspoint for the sample input being tested as summarized in Table 4 2 For example for sample input 1 close 3 1 4 6 6 Verify that the DMM reading is lt 10 exclusive of noise after settling If necessary select suitable DMM filter ing to quiet the reading 7 Close crosspoint 54 in order to select the high resistivity mode 8 Allow sufficient time for the reading to settle then verify that the DMM reading is less than 200 V exclusive of noise Again DMM filtering may be required to quiet the reading NOTE If the high resistivity offset reading for one of the channels is above specified limits the offset can be nulled by using the procedure discussed in paragraph 44 Table 4 2 Crosspoint Closed to Measure Sample Input Voltage Offset Sample Input Crosspoint Closed Column Row 1 3 1 2 3 2 3 3 3 4 3 4 9 Press the scanner RESET button to open all crosspoints then re zero the DMM 10 Repeat steps 4 through 9 for the remaining three sam ple inputs Be sure to connect the 7025 triax cable to the sample input being test SERVICE INFORMATION 196 DMM RED VOLTS OHMS HI RED LO BLACK SHIELDED CABLE BLACK un a v LO mi ANA 10 f HIGD GND ANALOG GROUND 7065 HALL EFFECT CARD WARNING MAINTAIN INUTS AND OUTPUTS WITHIN OF EARTM AMPUFIER CONFIGURATI
104. ithley equipment summarized in Table 1 2 is briefly described on the next page Table 1 1 Supplied Accessories Keithley Model 54 Description Low noise coaxial cable Low noise coaxial cable 10 Triaxial cable 10 Guarded input adapter 3 cable 10 triax cable BNC short 6 IEEE cable Black wire 4 White 4 Banana Plug black Banana plug white Black double banana plug 2 conductor cable with shield 1 1 1 1 2 1 2 1 1 1 1 2 pplication Connects 485 input to 7065 current monitor output Connects 485 directly to sample for bar 6 and 8 contact samples Four to connect sample to 7065 sample inputs one to connect 220 directly to sample in 6 and 8 contact samples Allows 220 to drive current source input cable at guard potential Attaches 220 6167 output to 7065 curent source input Same as above Shorts 7065 current monitor output Connects bus controller to the above instruments Connect analog ground Connect 220 guard to 7065 GD terminal Terminates black connecting wires Terminates white connecting wire Used with SC 8 to connect DMM to card Used with BG 7 to connect DMM to card Table 1 2 Recommended Hall System Equipment Keithley Model Number Description Use 196 6 Digit DMM Measure sample voltage 220 Current Source Supply sample current 485 Picoammeter Monitor sample current 705 or 706 Scanner Control Model 7065 Hall Effect Ca
105. ity Measurements Use the basic procedure below to make the necessary measurements to determine resistivity of bar type samples This procedure assumes that the sample temperature is held to the constant desired temperature throughout the test 1 Turn on all the instruments and allow them to warm up for the prescribed period for rated accuracy 2 Place the Models 196 and 485 in autoranging Be sure the Model 196 is in the DCV function 3 Using front panel Program 6 set the Model 705 Scanner to the matrix mode 4 Program crosspoint 54 to select low or high resistivity This crosspoint should be open for low resistivity and it should be closed for high resistivity 5 Program the Model 220 current to the desired value in the range of 500fA to 100mA The maximum current that can be used will depend on the resistance of the sam ple remember that the maximum Model 7065 input voltage is 8V In order to maintain proper sign con vention for the measured voltage and to minimize common mode errors program only positive currents 6 Close crosspoints 2 4 3 1 and 4 2 by programming the scanner Zero the Model 196 and enable the Model 485 relative function 7 Turn on the Model 220 output by pressing the OPERATE key 8 Note and record the voltage Vr and Ik current readings on the Models 196 and 485 9 Open all crosspoints by pressing the RESET button on the scanner and turn off the Model 220 output after measurements are c
106. ld be taken when handling the scanner card 1 Handle the card only at the edges of the board whenever possible Avoid touching any components not associated with the repair 2 Do not store or operate the card in an environment where dust could settle on the board Use dry nitrogen gas to clean dust off the card when necessary 3 If it is necessary to use solder on the circuit board or around the Teflon insulators remove the flux from these areas when the repair is complete Use Freon TMS or TE or equivalent to remove the flux Clean cotton swabs or a clean soft brush can be used to help remove the flux Once all the flux is removed swab the area with methanol then blow dry the board with dry nitrogen gas 4 After cleaning the card should be placed in a 50 C low humidity environment for several hours before resum ing normal operation 4 3 PERFORMANCE VERIFICATION The following paragraphs discuss procedures for verifying offset voltage input current and input resistance 4 3 1 Environmental Conditions All measurements should be made at an ambient temperature between 18 and 28 C and at a relative humidity less than 7096 unless otherwise noted 4 3 2 Warm Up Period The Model 7065 should be turned on and allowed to warm up for at least one hour before beginning the verification procedures Also the test equipment should be allowed to warm up for the period stated in their respective instruc tion manuals or specific
107. lded cable dual banana plug to make connections 2 16 OPERATION REAR PANEL ANALOG VOLTS OHMS HI RED OUTPUT LOW LO BLACK SHIELDED 485 PICOAMMETER CABLE 196 DMM BLACK 4802 COAX HIGH SAMPLE TRIAX 0 H CURRENT SOURCE ANA 10 7 HI GD GND LO AESISTIVITY 3 ES LI WITHIN 30V OF EARTH CONFIGURATION SAMPLE I 1 SAMPLE PUT TRAX WARNING MAMTAN INPUTS AMO GUTPUTS KEITHLEY 7085 HALL EFFECT CARD SAMPLE MPUT CURRENT MOM TOR 7025 TRIAXIAL _ CABLES 705 OR 706 SCANNER CONNECT TRIAX CENTER CONDUCTOR TO SAMPLE OUTPUT COMMON SC 72 7025 TRIAX CABLE BLACK WIRE 6167 ADAPTER 220 CURRENT SOURCE Figure 2 13 Connections for 6 Contact Samples 2 17 OPERATION 220 CURRENT SOURCE SAMPLE 196 DMM 485 PICOAMMETER NOTE HIGH RESISTIVITY MODE SHOWN BUFFERS ARE BYPASSED IN LOW RESISTIVITY MODE Figure 2 14 6 Contact Equivalent Circuit Current 1 2 Voltage 6 4 2 18 OPERATION VOLTS OHMS REAR PANEL ANALOG HI RED OUTPUT LOW 485 PICOAMMETER 196 DMM 4802 COAX BLACK TRIAX SAMPLE 1 CABLES Ov OF AMPUOHER CONFIGURATION WARNING MAINTAIN INPUTS AND wir 7065 HALL EFFECT CARD 705 OR 706 S
108. lists column numbers by unit Since column numbers can be confusing it is recommended that the Model 7065 be used in the card 1 upper slot unit 1 location to simplify programming OPERATION Table 2 5 Model 705 Unit 1 Column Summary by Card Model 7065 Column 1 top slot 2 bottom slot Table 2 6 Model 705 Column Assignments Columns Unit 2 cards per unit Model 706 Format The Model 706 display format is similar to that of the Model 705 except that an additional digit of column information is displayed nnn m O Or C Where nnn represents the column number m is the row number o or cis the status of the crosspoint open or closed Since each Model 706 has 10 card slots and up to five units can be daisy chained the total number of columns is 250 Table 27 lists column numbers by card for unit 1 and Table 2 8 summarizes column numbers by unit Again the unit should be placed in slot 1 unit 1 where possible to simplify programming 2 37 OPERATION Table 2 7 Model 706 Unit 1 Column Summary by Card Model 7065 Column COON ON QI Q N HB Table 2 8 Model 706 Column Assignments 1 50 51 100 101 150 151 200 201 250 10 cards per unit 2 8 3 Crosspoint Programming Use the basic procedure below to display and program crosspoints 1 Use Program 6 to select the matrix mode pole 0 as described in paragraph 2 8 1 2 Display the desired crosspoint either
109. ll Voltage Measurement IBM PC 8573A Version Continued 510 INPUT ENTER SAMPLE THICKNESS CMO iT 520 T ABS T gt 530 INPUT ENTER FLUX DENSITY GAUSS B 540 B ABS B 550 CLS 550 PRINT APPLY B PRESS ANY KEY TO CONTINUE 570 AS INKEYS IF AS THEN 570 580 REM MAIN MEASUREMENT LOOP 590 RESTORE 6 CLS 610 PRINT MEASURING 620 FOR J 1 TO 8 630 J lt gt 5 THEN 660 640 RESTORE PRINT REVERSE FIELD B PRESS ANY KEY TO CONTINUE BEEP 650 AS INKEYS IF AS THEN 650 650 READ C CALL IBWRT M7 5 CLOSE CROSSPOINTS 670 C FIX CALL IBWRT M22 TURN ON 220 OUTPUT 680 FOR I TO DELAY NEXT WAIT FOR READING TO SETTLE 590 RDS SPACES 25 CALL IBRD MIS8S8Z RD GET 196 READING 700 VC J VALCRDS CONVERT STRING TO NUMERIC PUT IN ARRAY 710 IF ABS UCJI 8 THEN 890 CHECK VOLTAGE LIMITS 720 IF J lt gt 1 THEN 750 730 RDS SPACE 25 CALL IBRO M485 RD 485 CURRENT READING 740 II VAL RDS CONVERT READING TO NUMERIC 750 C FOX CALL 220 TURN OFF 220 OUTPUT 760 READ C READ 705 COMMAND STRING 770 CALL IBWRT M7 5 C OPEN CROSSPOINTS 780 NEXT J LOOP BACK FOR NEXT POINT 790 BEEP 800 CALL IBCMDCBRDOZ D SEND DEVICE CLEAR 810 CLS 820 PRINT MEASUREMENT S COMPLETE 830 PRINT MEASURED CURRENT TII 840 FOR J 1 TO 8 LOOP AND DISPLAY MEASURED VOLTAGES 850 PRINT U J 5U J 869 NEXT J 870 PRINT PRESS ANY KEY TO CALCULATE HALL COEFFICIENTS 880 AS INKEYS IF
110. lthough not shown on the diagram the buffers also pro vide a driven guard for the four sample inputs to minimize the effects of leakage resistance and capacitance To demonstrate the versatility of the switching matrix let us assume that we wish to apply a current through ter minals 1 and 2 of the sample and measure the voltage be tween terminals 4 and 3 of that sample To apply the cur rent we would close 2 1 and 1 2 while to measure the voltage contacts 34 and 4 3 would be closed In this case current would flow from the source through 2 1 into ter minal 1 of the sample From there current would flow out terminal 2 through 1 2 into the picoammeter back to analog ground to complete the path The act of closing 34 and 43 would connect the voltmeter to measure the voltage between terminals 4 and 3 through the buffer amplifiers high resistivity mode More information on scanner programming may be found in paragraphs 2 8 and 2 9 while Section 3 covers measure ment methods in more detail 2 5 2 Test System The basic configuration of an IEEE 488 based Hall measure ment system is shown in Figure 2 18 A system used solely for resistivity measurements would not require the elec tromagnet or magnet power supply 2 21 OPERATION COLUMNS 3 4 e O O HI BUFFERS LO CONTROLS RESISTIVITY VOLTMETER USED FOR PICO CURRENT 6 AMMETER SOURCE SAMPLES SAMPLE COLUMN 5 ROW 4 2 22 Figure 2 17 Model
111. move the shields for any reason be sure not to touch the exposed board or any components underneath Particularly sensitive areas include the sam ple inputs from the sample input jacks to the inputs of the buffer amplifiers Dirt build up over a period of time is another possible con taminating factor To avoid potential problems operate the scanner only in a clean environment If contamination is suspected the card should be carefully cleaned using the procedure outlined in paragraph 4 2 of this manual 2 3 MODEL 7065 INSTALLATION The following paragraphs discuss Model 7065 Hall Effect Card installation in both the Models 705 and 706 Scanners Note that some connections must be made to the Model 7065 before installation as discussed in paragraph 24 WARNING Turn off the scanner power and disconnect the line cord before installing or removing scanner cards CAUTION Leave the Model 7065 in its anti static bag until ready for installation to avoid possible static damage OPERATION 2 3 1 Installation in the Model 705 Scanner Refer to Figure 2 1 and install or remove the Model 7065 Hall Card as follows 1 To install the card slide it into the desired rear panel slot with the component large shield side facing up Make sure the card edges are properly aligned with the grooves in the receptacle Once the card is fully seated lock the card by placing the tabs into the locked positi
112. mplifier which has high in put impedance and low output impedance is used to drive the inner shield Since the amplifier has unity gain the potential across the leakage resistance is essentially zero so that virtually no current flows Leakage between the in ner shield and ground outer shield may be considerable but it is of little consequence since that current is supplied by the buffer amplifier rather than by the sample signal voltage itself 7065 BUFFER Figure 2 20 Guarded Circuit In a similar manner guarding also reduces the effective cable capacitance resulting in much faster measurements on high resistivity circuits Because any distributed capaci tance is charged through the relatively low impedance of the buffer amplifier rather than by the source settling times are shortened considerably by guarding 2 26 As an example consider the situation where 10 0 resistance is being measured through a cable that has 200pF of distributed capacitance This combination results in an RC time constant of 2sec Thus at least 10 seconds must be allowed to allow the circuit to settle to within 196 of final value In contrast guarding the circuit could result in a more than hundred fold reduction in settling time 2 6 2 Current Source Input Guarding When testing high resistivity samples the current source input must also be guarded by using the driven guard from the current source itself The following paragraphs discu
113. n 10 11 14 Turn on the magnetic flux and adjust it to the desired positive value B Note and record the Model 196 voltage V as well as the sample current measured by the Model 485 Picoammeter For 6 contact speciments only measure the voltage V2 as indicated in Table 3 9 Reverse the Model 220 current polarity and note the cur rent reading on the Model 485 If necessary reprogram the current source so that the magnitude of the measured current is as close as possible to that measured in step 10 Measure the remaining voltage s as indicated in Table 3 9 or 3 10 using steps 6 through 12 of the above procedure Reverse the magnetic flux and repeat steps 10 through 13 3 7 4 Calculations Once the necessary measurements are made resistivity Hall voltage and Hall mobility calculations can be made from the data and certain sample dimensions which are outlined in Figure 3 15 Table 3 9 6 Contact Sample Hall Voltage Measurements B 31 Voltage Flux Crosspoints Closed Designation Polari Column Row 44 Current Voltage Between Between 2 6 5 1 7 4 3 1 2 4 3 44 2 1 6 5 2 1 4 3 1 2 6 5 1 2 4 3 2 1 6 5 2 1 4 3 Reverse current by programming source for opposite polarity Table 3 10 8 Contact Sample Hall Voltage Measurements Voltage Flux Designation Polarity 3 1 3 1 3 1 3 1 Crosspoints Closed Current Voltage Col
114. nd 5 of the terminal strip See paragraph 3 6 2 for details on selecting the correct potentiometer value 5 Connect VOLTS OHMS LO to terminal 3 of the strip Connect DMM HI to the wiper of the potentiometer us ing the dual banana plug shield wire Resistivity Connections Connections for determining the resistivity of bar type samples are essentially the same as for Hall voltage except for the way the DMM is connected As shown in Figure 2 11 DMM VOLTS OHMS LO should be connected to ter minal 4 of the strip and DMM HI should be connected to terminal 5 Figure 2 12 shows an equivalent circuit of the test configuration 2 11 OPERATION GUARD NOTE SEE PARAGRAPH 2 6 FOR VOLTS OHMS 6167 ADAPTER GUARDING CONFIGURATION RED BLACK 196 DMM 220 CURRENT SOURCE BLACK SHIELDED CABLE 7024 TRIAX CABLE RED POTENTIOMETER SEE TABLE 3 5 FOR VALUE OUTPUT ANA lO f Ht GD 5 3 GND RERSTIVITY 10 RESIBTIVITY MAINTAIN INPUTS OUTPUTS WITHIN 30 OF EARTH CONFIQURA TION WARNING KEITHLE S 7065 HALL EFFECT CARD 1 SAMPLE MPUT 555 7025 TRIAXIAL TE CABLES SAMPLE CONNECT HIGH TO 7065 CARD SAMPLE SC 72 BLACK LEAVE SHIELD UNCONNECTED ANALOG OUTPUT LO 705 OR 706 SCANNER ON REAR PANEL 4802 BNC CA
115. nd the setup for 8 contact samples is shown in Figure 3 14 In both cases four sample contacts are connected to the sample inputs on the Model 7065 The current source and picoammeter must be connected directly to the sample itself Section 2 covers physical connections in more detail 3 15 APPLICATIONS 3 16 4 SAMPLE 4 LO R O HI R Figure 3 12 Bar Sample Dimensions APPLICATIONS COLUMNS 5 4 CONTROLS RESISTIVITY 2 gt ROWS O O HI O 3 4 1 2 SAMPLE INPUTS 5 4 TRIAX i 220 196 DMM 485 CURRENT PICOAMMETER SOURCE Figure 3 13 6 Contact Sample Connections 3 17 APPLICATIONS COLUMNS 5 4 CONTROLS RESISTIVITY ROWS al 3 4 1 2 SAMPLE INPUTS TRIAX 3 4 a g O O HI LO J2 5 4 220 CURRENT SOURCE 485 196 DMM PICOAMMETER Figure 3 14 8 Contact Sample Connections 3 18 3 7 2 Resistivity Measurements Use the basic Procedure below to measure Parameters for 6 and 8 contact specimens As always the sample should be stabilized at the desired temperature both before and during the tests 1 Turn on all the instruments and allow them to warm up for the prescribed period for rated accuracy 2 Place the Models 196 and 485 in autoranging Be sure the Model 196 is in the DCV function 3 Using front panel Program 6 set the Model 705 Scan ner to the matrix mode
116. ng a voltage greater than 8V but less than 12V will not damage the card but accuracy of the measurement will suffer CAUTION The maximum input overload is 12 ex ceeding this value may cause damage to the Model 7065 The voltage developed across the sample will depend upon both the excitation current and the resistivity of the sam ple If the sample resistance is known you can calculate whether or not a given current will overload the inputs by using Ohms law IR For example the voltage developed across a 100kQ sample with a 100 current is E 100 x 10 100 x 10 E 10V In this case the developed voltage is above the 8V input operating range of the Hall card The solution of course is to lower the current so that the voltage is within the re quired range 2 10 2 Leakage Resistance At lower resistance levels the effects of leakage resistance are seldom a consideration because any leakage resistance is generally much higher than the resistance levels in the sample itself With high resistivity samples however leakage resistance can have a detrimental effect on the measurement Such leakage resistance can occur in the sample test fixture the connecting cables or even at the Model 7065 sample input connectors especially if these connectors are not kept clean To demonstrate how leakage resistance can affect measure ment accuracy let us review the equivalent circuit shown in Figure 2 29 Here
117. nts Details methods to measure and calculate Hall coefficients and Hall mobility 3 6 Measuring Bar Type Samples Discusses the pro cedures necessary for measuring the Hall voltage and resistivity of bar type samples 3 7 Measuring Bridge and Parallelepiped Type Specimens Outlines basic test procedures for both 6 and 8 contact samples 3 8 Sample Resistivity and Hall Voltage Programs Lists sample programs that can be used to measure and calculate Hall coefficients and resistivities of typical samples 3 2 RECOMMENDED EQUIPMENT Table 3 1 summarizes the equipment necessary for a com plete Hall measurement system The Models 196 220 485 705 and 7065 are available from Keithley Instruments while the remainder of the equipment must be obtained from other sources Table 3 1 Recommended Equipment Equipment Description Model 196 DMM Measure sample voltages Model 220 Current Source Supply sample current Model 485 Picoammeter Measure sample current Model 705 or 706 Scanner Control Hall Effect card Cryostat Set sample temperature Magnet Apply magnetic field Magnet power supply Supply magnet power Gauss meter Used to measure actual magnetic field strength 3 3 HALL EFFECT CONVENTIONS AND PRINCIPLES The following paragraphs discuss Hall effect sign and sam ple terminal conventions as well as basic Hall effect principles 3 3 1 Hall Effect Sign Conventions Figures 3 1 and 3 2 show the sign c
118. o an acceptable level In extreme cases a specially con structed screen room may be necessary to sufficiently at tenuate the troublesome signal If all else fails external filtering of the device input paths may be required In some cases a simple one pole filter may be sufficient in more difficult cases multiple pole notch or band stop filters tuned to the offending frequen cy range may be required Keep in mind however that such filtering may have other detrimental effects such as increased response time on the measurement 2 10 7 Ground Loops Ground loops that occur in multiple instrument test setups can create error signals that cause erratic or erroneous measurements The configuration shown in Figure 2 32 can introduce errors in two ways Large ground currents flow ing in one of the wires will encounter small resistances either in the wires or at the contact points These small resistances result in voltage drops that can affect the measurement Even if the ground loop currents are small magnetic flux cutting across the large loops formed by ground leads can induce sufficient voltages to disturb sen sitive measurements SIGNAL LEADS INSTRUMENT A TYPICAL GROUND LOOP CAUSES CURRENT FLOW N INASIGNALLEAD 7 POWER LINE GROUND Figure 2 32 Multiple Ground Points Create a Ground Loop OPERATION To prevent ground loops instrument signal grounds should
119. ocedures are described in the manual The procedures explicitly state if the operator may per form them Otherwise they should be performed only by service personnel Service personnel are trained to work on live circuits and perform safe installations and repairs of products Only properly trained ser vice personnel may perform installation and service procedures Keithley products are designed for use with electrical signals that are rated Installation Category I and Installation Category II as de scribed in the International Electrotechnical Commission IEC Standard IEC 60664 Most measurement control and data I O sig nals are Installation Category I and must not be directly connected to mains voltage or to voltage sources with high transient over volt ages Installation Category II connections require protection for high transient over voltages often associated with local AC mains connections The user should assume all measurement control and data I O connections are for connection to Category I sources un less otherwise marked or described in the Manual Safety Precautions Exercise extreme caution when a shock hazard is present Lethal voltage may be present on cable connector jacks or test fixtures The American National Standards Institute ANSI states that a shock hazard exists when voltage levels greater than 30V RMS 42 4V peak or 60VDC are present good safety practice is to expect that hazardous voltage is presen
120. omplete 3 6 4 Hall Voltage Measurements The following procedure assumes that the sample is held stable at the desired temperature throughout the tests and that the applied magnetic flux is also held constant at the desired density 1 Turn on all instruments and allow them to warm up sufficiently 2 Select the DCV function on the Model 196 and set both the Model 196 and the Model 485 to autoranging 3 Using Program 6 set the Model 705 Scanner to the matrix mode 4 Program crosspoint 54 for the desired resistivity setup open low resistivity closed high resistivity 5 Program the Model 220 Current Source to the desired positive current 6 Program the scanner to close contacts 2 4 3 1 4 2 and 5 3 as summarized in Table 3 6 7 Enable zero on the Model 196 and the relative function on the Model 485 8 Turn on the Model 220 output by pressing the OPERATE button 9 With no magnetic field applied adjust the poten tiometer for a reading of OV on the Model 196 10 Turn on the magnetic field and adjust it for the desired intensity 11 Note and record the Model 196 voltage Vx as well as the sample current L measured by the Model 485 Pico ammeter 12 Open all crosspoints by pressing RESET on the scanner and turn off the Model 220 output after all measure ments are completed 3 14 Table 3 6 Crosspoint Configurations for Bar Measurements Closed Crosspoints Measurement Column Row 24 3 1 2
121. on as shown in Figure 2 1 To remove the card first unlock the tabs by pulling them outward then grasp the end of the card at the edges and pull the card free of the scanner 7065 HALL CARD SCANNER CARD SLOTS 2 3 2 Installation in the Model 706 Scanner Install the Model 7065 in the Model 706 Scanner using Figure 2 2 as a guide 1 MODEL 705 REAR PANEL HANDLES 1 OF 2 To install the Hall card slide it into the desired vertical slot Looking from the rear slots are numbered from 1 to 10 left to right Note that the component large shield side of the card should face to the left of the slot Make certain the card edges are properly aligned with the top and bottom grooves in the slot Once the card is aligned with the grooves push the card as far as it will go into the slot until it is properly seated into the slot connector After the card is properly seated lock the card with the tabs as shown in Figure 2 2 To remove the card unlock the tabs by pulling them out ward as shown in Figure 2 2 Grasp the end of the card and pull it free of the mainframe 7065 HALL DR 7 INSTALLED Figure 2 1 Model 705 Card Installation 2 2 OPERATION LOCKING TABS MODEL 706 REAR PANEL C 7065 HALL CARD INSTALLATION Figure 2 2 Model 706 Card Installation 2 3 OPERATION 2 4 CONNECTIONS The following paragraphs discuss the card
122. onventions for n type and p type materials respectively Table 3 2 summarizes generally accepted units of measure Table 3 2 Measurement Units Sample dimensions Potential difference Charge Carrier concentration Drift mobility Hall mobility Current density Hall coefficient Electric field Magnetic flux density Resistivity APPLICATIONS SAMPLE Figure 3 1 Hall Effect Sign Conventions for n type Materials Figure 3 2 Hall Effect Sign Conventions for p type Materials 3 3 2 Terminal Conventions Both Hall voltage and resistivity measurements are per formed by applying a current to two terminals of a sam ple and measuring the resulting voltage at the remaining two terminals In the case of van der Pauw resistivity measurements a current is applied between two terminals while the voltage is measured between the two opposite terminals as shown in Figure 3 3 A total of eight such measurements are taken with each possible terminal and current convention In this manual these voltages are designated V through V and are covered in detail in paragraph 34 The connections for Hall voltage measurements are shown in Figure 3 4 Here current is applied and voltage is measured across the diagonal of the sample Again eight such measurements are necessary both with positive and negative current and positive and negative magnetic flux often additional measurements are taken with no flux ap pli
123. oth or mild water based cleaner Clean the exterior of the instrument only Do not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument Products that consist of a circuit board with no case or chassis e g data acquisition board for installation into a computer should never require cleaning if handled according to in structions If the board becomes contaminated and operation is af fected the board should be returned to the factory for proper cleaning servicing 2 01 7065 HALL EFFECT CARD SPECIFICATIONS 1 year 0235 C installed in scanner mainframe CONFIGURATION Input characteristics and output matrix configurable for Van der Pauw or Hall Bar measurements Input characteristics selectable for either low resistivity or high resistivity samples LOW RESISTIVITY MODE Input Voltage Operating Range 8V to 8V Input Impedance gt 10GQ in parallel with less than 420pf Input Bias Current lt 100 Input Voltage Noise lt 50nVp p 0 1 to 10Hz bandwidth Input to Output Resistance lt 300 HIGH RESISTIVITY MODE Input Voltage Operating Range 8V to 8V Input Impedance gt 100TQ in parallel with less than Input Bias Current lt 150fA at 23 C Doubles approximately every 10 C rise in ambient room temperature Input Voltage Noise lt 0 1 to 10Hz bandwidth Output Resistance lt 600 GENERAL CONNECTORS CURRENT SOURCE INPUT Two lu
124. ould be used to connect the DMM to the card while the white and black wires can be used for guard and analog ground connections respectively Table 2 2 Recommended Cables Cables Used with Model 7025 10 triaxial cables unterminated Model 4801 BNC to BNC coaxial cable Model 4802 10 BNC Cable unterminated Model 7024 triaxial cables 5 72 connecting wires with same color single plugs Sample inputs Current monitor output Current monitor output direct to sample Current source input 2 black 1 white SC 8 BG 7 Analog ground Guard Red to DMM HI term 5 black shield to DMM LO term 4 on J2 NOTE These cables are supplied 2 4 3 Cable and Wire Preparation The necessary cables wires and connectors are supplied with the Model 7065 however these cables and wires must be prepared before use as described below Single Wire Banana Plug Preparation As summarized in Table 2 2 color coded wires are provided 2 6 for making various connections between the Model 7065 and other instruments A matching color coded kanana plug is included to mate with appropriate jacks on the test instruments NOTE A banana plug should always be used to make the connection to a banana jack on an instrument to ensure proper contact The supplied SC 72 wires should be prepared and con nected to the supplied banana plugs as follows Refer to Figure 2 4 for the various steps 1 Strip the end of the wi
125. picoammeter low must be con Connections nected together The method of connection depends on whether or not current input guarding is used as follows A Unguarded Connect picoammeter analog output LO to the output common terminal of the Model 220 Cur rent Source The ground link should be removed B Guarded Connect picoammeter analog output LO to Connections for 6 contact samples are shown in Figure 2 13 while Figure 2 14 gives an equivalent circuit Figures 2 15 and 2 16 summarize the connections for 8 contact samples Make the required connections as follows the output common terminal of the Model 220 cur rent source The inner shield should be left floating 1 Connect the required sample terminals to the four SAM at the sample end The Model 6167 must be used to PLE inputs using supplied Model 7025 triaxial cables guard the cable as discussed in paragraph 2 6 2 Using the supplied 4802 coaxial cable connect the HIter 5 Regardless of the current input guarding configuration minal of the picoammeter to the indicated sample Model 220 GUARD must be connected to the ter terminal minal 6 on the Model 7065 in order to drive the protec 3 Connect a Model 7025 triaxial cable to the Model 220 as tion circuits on the card un indicated Connect current source HI center conductor 6 Connect the DMM to the Hall Card as indicated on the to the sample as shown on the appropriate diagram appropriate diagram Use the shie
126. programmed to operate with 612 digit but with no filtering filtering may be re quired in some instances especially with low voltages Model 220 The current source is programmed for a voltage compliance of 10V The current value is entered by the user to program the unit during the course of the program For Programs 4 and 8 only the current is reversed during the test by programming the Model 220 for a negative current of the same magnitude Note that no provision is includ ed for verifying that the positive and negative currents have APPLICATIONS the same magnitude Also averaging is used in all pro grams except Programs 3 and 7 Model 485 The continuous trigger mode is used and the prefix on the data string is eliminated by appropriate pro gramming The unit is zero checked at the start of each pro gram for optimum accuracy Model 705 The scanner is placed in the matrix mode and then crosspoint 5 4 is programmed in accordance with the resistivity configuration desired by the user Other cross points are programmed as required for the various measurements 3 8 3 Program Listings Programs 1 through 8 listings appear on the following pages 3 27 APPLICATIONS Program 1 Hall Voltage Measurement HP 85 Version 19 CLEAR 20 5000 FIVE SECOND DELAY 38 DIM 4 1251 U 8 40 P1 712 220 ADDRESS IS 12 50 P2 707 196 ADDRESS IS 7 BO P3 717 705 ADDRESS IS 17 70 P4 722 485 ADDRESS IS 22 80 DIS
127. proximately inch of insulation from both the red and black wires 4 Twist the shield braid and black wires together tightly Also twist the strands on the red wire together 5 Slip the wire through the back hole in the dual banana plug then place the red wire end in the hole in the banana plug without the ridge on the body 6 Slip the black shield wire end through the hole in the banana plug closest to the body ridge 7 Secure both red and black wires by tightening the screws for each banana plug these screws are accessi ble inside the body directly behind each banana plug Be careful not to tighten them too tightly 8 Strip approximately 1 inch of the insulation off the op posite end of the cable then unravel and shield and twist the strands together 9 Strip the red and black wire insulation approximately 3 8 inch OPERATION 10 Twist the black wire and shield together Also twist the red wire strands together 11 The cable is now ready for connection to the terminal block RED E A STRIP WIRES THEN TWIST BLACK AND SHIELD TOGETHER BLACK SHIELD BLACK AND SHIELD B CONNECT WIRES TO PLUG AND STRIP OPPOSITE END Figure 2 5 Shielded Cable Preparation OPERATION Triaxial Cable Preparation The one end of each Model 7025 triaxial cable must be prepared as follows before it can be connected to the sam ple under test Refer to
128. rd Not essential but recommended for best accuracy NOTE This listing does not include required user supplied equip ment such as cryostat electromagnet and power supply or IEEE 488 GENERAL INFORMATION bus controller Model 196 DMM The Model 196 is recommended for measuring the voltage across the sample under test Im portant Model 196 features include 100nV resolution High input resistance gt 1GQ on 300mV and ranges for minimum sample loading 6 digit display resolution Autoranging EEE 488 bus operation Model 220 Current Source The Model 220 Current Source is recommended for applying the current to the sample under test Key Model 220 features include 0 5pA to 101mA DC current output 10 Q output resistance Programmable voltage compliance limit Complete IEEE 488 bus programmability Model 485 Picoammeter The Model 485 Picoammeter can be used to monitor the current being applied to the sam ple under test Although not absolutely essential for a measurement system the use of the Model 485 is recom mended to maximize accuracy especially when testing high resistivity samples Important Model 485 features include 0 1pA resolution 2mA maximum input current 200uV maximum voltage burden Autoranging 4 digit display resolution EEE 488 bus operation with option 4853 Models 705 and 706 Scanners The Model 7065 Hall Effect Card is des
129. re to be connected to the banana plug approximately inch then twist the strands together 2 Unscrew the body of the matching color single banana plug and insert the stripped end of the wire through the small hole in the metal part of the plug so the wire comes through the small hole as shown in Figure 2 4 3 Wrap the wire around the plug base in the same direc tion as the plastic body screws on then screw on the plastic body securely 4 Strip the opposite end of the wire approximately inch and twist the strands together This end is to be con nected to the terminal block of the Model 7065 27 17 STRIP WIRE inch H gt B INSERT WIRE INTO HOLE AND WRAP AROUND BODY C SCREW ON PLASTIC COVER AND STRIP OPPOSITE END INCH Figure 2 4 Single Wire Preparation Dual Banana Plug Preparation A dual banana plug 7 and length of shielded two conductor cable SC 8 is provided with the Hall card These items are to be used to connect the DMM to the Model 7065 NOTE To minimize noise the dual banana plug shield wire combination should always be used to con nect the Model 7065 to the DMM instead of separate wires The dual banana plug and 2 conductor shielded cable can be prepared as follows see Figure 2 5 1 Strip back about 14 inch of outer insulation from the SC 8 shielded 2 conductor wire 2 Unravel the shield braid and twist the strands together 3 Strip ap
130. rmation The serial control information is converted to parallel by US a shift register and then buffered by U7 before being applied to the various relays or switching FETs R2 C1 CR5 and elements of U6 form a power up down fail safe circuit to prevent relays from being inadvertently closed when power is turned on or off 4 5 2 Buffers An important feature of the Model 7065 is the use of on card buffers which give the card its very high gt 10010 4 12 input impedance allowing the card to be used to measure high resistivity samples Ul through U4 are special high quality operational ampli fiers configured as non inverting unity gain amplifiers These components provide both buffering as well as a driven guard for the sample inputs Voltage offset adjust ment for these ICs is performed by through R17 in order to maintain optimum input leakage current and guard performance Resistivity setup switching is performed by FETs Q3 through Q11 In low resistivity the buffers are effectively bypassed by turning on appropriate FETs while turning off others For example when low impedance is selected Q3 Q4 Q9 and Q10 will be on while Q5 through Q8 are off Conversely in high resistivity Q5 through Q8 are on while 04 Q9 and 010 are turned off 4 5 3 Power Supply The power supply section of the Model 7065 has a two fold purpose 1 to step up the nominal 6V scanner main frame supply to 4 12V and 2 to p
131. ro Remove the short and reconnect the DMM to the Hall card 5 Close the crosspoint for the sample input you are cur rently adjusting as summarized in Table 4 4 For exam ple to measure sample input 1 close 3 1 SERVICE INFORMATION 6 Adjust the offset control for the selected sample input for a minimum null reading on the DMM less than 20 is satisfactory The controls are accessible through small holes in the bracket at the back of the card see Figure 4 4 Note that it may be necessary to use DMM filtering to minimize noise 7 Open the crosspoint now closed 8 Repeat steps 5 through 7 for the remaining three sam ple inputs Be sure to connect the sample input being adjusted to analog common and also make certain the the appropriate crosspoint is closed for the measure ment Table 4 4 Crosspoints to Close When Adjusting Offsets Crosspoint Sample Input Column Row 1 34 2 3 2 3 3 3 4 Crosspoint 54 must also be closed to select high resistivity 4 9 SERVICE INFORMATION VOLTS OHMS HI RED LO BLACK C G PUT JUNCTION IN BOX CABLE AND SURROUND WITH FOAM INSULATION CONNECT TO ANALOG ____f_ 196 DMM GROUND p 1 SC 72 WIRE J 7025 TRIAX CABLE BLACK 8 7 3 5 Bc OE Hn 5 3 FE i E ANALOG GROUND 5 8 312 Figure 4 5 Connections for Voltage Offset Adjustment 4 10
132. rovide a high degree of isolation between the digital circuits of the mainframe and the sensitive analog signal paths on the Model 7065 In order to meet these requirements a trapezoidal wave chop per step up circuit with transformer isolation is used The nominal 3 4kHz time base of the chopper is generated by U8 a 555 timer which has its operating frequency set by C8 and R19 The signal is buffered by Q13 before being applied to the chopper made up of and associated components The nominal 6V peak signal is coupled through a 112 4 step down transformer TI and then is coupled again through a 4 380 step up transformer T2 This dual transformer technique is used to ensure max imum analog to digital isolation At the secondary of T2 the nominal 17V peak AC signal is rectified by CR6 before being filtered and regulated C4 C7 and U9 provide filtering and regulation for the 12V supply and C5 C6 and U10 filter and regulate the 12V supply SERVICE INFORMATION CURRENT CURRENT SAMPLE MONITOR INPUT INPUTS OUTPUT J3 J8 J4 J7 OUTPUT RELAYS U11 U16 J2 OUTPUTS RESISTIVITY SELECT BUFFERS 03 011 01 04 RELAY CONTROL U5 U7 CONTROL FROM SCANNER 46V FROM SCANNER TO CIRCUITS MAINFRAME MU DENOTES ANALOG GROUND DENOTES DIGITAL GROUND Figure 4 8 Model 7065 Block Diagram 4 13 SERVICE INFORMATION 4 6 SPECIAL HANDLING OF STATIC 5 U
133. rror R For example assume we are measuring a sample with an equivalent resistance of 100MQ with the hall card in the low resistivity setup Under these conditions the card has a nominal input resistance of 10 0 and the Model 196 has a nominal input resistance of 1GQ 300mV 3V ranges yielding an equivalent resistance of 909 1MQ Thus the er ror in this case would be 100M9 Error x 100 100MQ 909 1MQ Error 9 996 However assume we make the same measurement with the Hall card configured for high resistivity in which case the input resistance increases to gt 100T The error caused by input loading is now reduced to 100MQ Error x 100 100MQ 10010 Error 0 000099 Here we see the importance of choosing the right resistivity setup for the sample being measured 2 10 4 Input Capacitance Virtually any circuit has at least some small amount of distributed capacitance that can slow down the response time of high impedance measurements Even if the test sample itself has minimal capacitance cable or Model 7065 card input capacitance effects can be noticeable especially if current input guarding is not used OPERATION To demonstrate input capacitance effects consider the equivalent circuit shown in Figure 2 30 Here Is and Rs represent the sourced current and sample resistance respectively The voltage developed across the sample resistance as a result of the source current Is is giv
134. scanner card analog ground through the inner cable shield and the outer cable shield connects to Model 220 chassis only Model 220 guard is connected to the guard input on the Model 7065 in order to drive the input pro tection circuits Guarded Connections The current source input should be guarded when the card is in the high resistivity mode paragraph 2 7 Figure 2 24 a shows the basic connections which are outlined as follows 1 Attach the supplied Model 6167 Guard Adapter to the OUTPUT jack of the Model 220 2 Connect the Model 6167 adapter wire to the Model 220 GUARD jack 3 Place the adapter switch in the guarded position 4 Connect the Model 7024 triaxial cable between the triax jack on the adapter and the Model 7065 Current Source Input An equivalent circuit of this configuration is shown in Figure 2 24 b Current source output HI is connected to the Hall card input HI through the center cable conductor Guard connection is made through the Model 6167 to the inner shield of the cable while output LO now appears on the outer cable shield and is connected to analog ground in the scanner card 2 6 3 Sample Input Guarding In order to minimize the effects of leakage resistance and capacitance the shield of each input cable is guarded by driving the inner shield with the output of the respective buffer amplifier as shown in Figure 2 25 Note that the outer shield is at analog ground potential and is not guard
135. se only anti static type de soldering tools and SENSITIVE DEVICES grounded tip soldering irons 6 Once the device is installed in the PC board it is usually CMOS and other high impedance devices are subject to adequately protected and normal handling can resume possible static discharge damage because of the high im pedance levels involved When handling such devices in dicated by in the parts list use the following precautions 4 7 TROUBLESHOOTING 1 Such devices should be transported and handled only in containers specially designed to prevent or dissipate R mmen Eauipment static build up Typically these devices will be received Recommended rap in anti static containers of plastic or foam Keep these parts in their original containers until ready for Table 4 5 summarizes the equipment necessary for general installation troubleshooting 2 Remove the devices from their protective containers on ly at a properly grounded work station Also ground yourself with a suitable wrist strap 3 Handle the devices only by the body do not touch the pins The troubleshooting procedure is summarized in Table 4 6 4 Any printed circuit board into which the device is to be inserted must also be grounded to the bench or table 4 7 2 Troubleshooting Procedure Table 4 5 Troubleshooting Equipment Manufacturer Description and Model DMM Keithley 196 Measure DC voltages Voltage Source Keithley 230 Apply DC voltages Oscillos
136. ss guarded and unguarded operation of the current source input and various connecting methods NOTE Although you do have the option of selecting guarded or unguarded operation there is no harm in using the guarded mode for all measurements it works for all resistivities Guarding Jumpers As shown in Figure 2 21 two jumpers set up the current source input for either unguarded or guarded operation The jumper configurations shown at the top of the diagram indicate which of two configurations apply as follows 1 Unguarded A This method can be used only for rela tively low resistivity 1050 or less resistance samples low resistivity mode 2 Guarded B This configuration is required for use with the high resistivity mode Note that the Model 6167 Guarded Adapter must be used in conjunction with the Model 220 in order to drive the inner shield of the triax ial cable at guard potential OPERATION GUARDING JUMPERS UNDER SHIELD B GUARDED SHIELD NOTE SEE TEXT FOR GUARDING RECOMMENDATIONS A UNGUARDED Figure 2 21 Guarding Jumper Configurations 2 27 OPERATION Changing Jumper Settings From the factory the Model 7065 is setup for the guarded configuration Use the following procedure to change or verify the positions of these jumpers 1 Turn off the scanner mainframe power and unplug the power line cord Remove the card from the scanner if installed 2 Remove the large analog shield
137. stants Table 2 10 summarizes voltage ratio values and percentage error values for ten different time constants where RsC Table 2 10 Voltage and Percent Error For Various Time Constants 0 632 E 36 086 Es 14 095 E 5 0 982 E 1 8 0 993 E 0 647 0 25 0 09 0 033 0 012 0 005 0 9975 Es 0 999 E 0 99966 0 9999 0 99995 2 42 2 10 5 Electrostatic Interference Electrostatic interference occurs when an electrically charged object is brought near an uncharged object thus inducing a charge on the previously uncharged object At lower impedance levels the effects of electrostatic action are not noticeable because the low impedance levels allow the induced charge to dissipate quickly At the high im pedance levels of many Model 7065 measurements how ever these charges do not readily dissipate and erroneous or erratic measurements may result These unstable read ings may be caused in two ways 1 A DC or slowly varying electrostatic field 2 AC electrostatic fields which can cause errors by driv ing the buffer amplifier into saturation or through rec tification that produces DC errors Electrostatic interference is first recognizable when hand or body movements near the sample cause fluctuations in the measurements Pickup from AC fields can be verified by checking the buffer amplifier outputs with an oscilloscope The presence of line frequency signals on the outputs are an indication th
138. su ewe E DR oO dle mile nono ed em di elec Offset QR Rud 6 pui D qd dew we Common Mode Adjustment ave ane idee THEORY OP OPERATION Se nee mare maman etre ele at been Relay Switching CITES c ids qp PPP Power d Ub desir dug ed pde SPECIAL HANDLING OF STATIC SENSITIVE DEVICES TROUBLESHOOTING uso titio des dient eT e bee RS idera es aces ted Recommended ake RD VEU NR s aire eue Troubleshooting Procedure SECTION 5 REPLACEABLE PARTS INTRODUCTION SD E IC RC oi nA E a aid WR PARIS LISD 155 er 0 ed ud Rob d e Ahad der Ru dd ORDERING INFORMATION i edd FACTORY SERVICE COMPONENT LAYOUT AND SCHEMATIC DIAGRAM LIST OF TABLES SECTION 1 GENERAL INFORMATION 1 1 Supplied sob booked aro da A ea ____________________ 1 2 1 2 Recommended Hall System Equipment 1 ka hk E sade RE AT LR EE PAR 1 3 SECTION 2 OPERATION 24 Terminal Strip Connections _____________ eq pa ea 2 2 Recommended Abies Su Roe br ____________________
139. t in any unknown circuit before measuring Users of this product must be protected from electric shock at all times The responsible body must ensure that users are prevented access and or insulated from every connection point In some cases connections must be exposed to potential human contact Product users in these circumstances must be trained to protect themselves from the risk of electric shock If the circuit is capable of operating at or above 1000 volts no conductive part of the circuit may be exposed Do not connect switching cards directly to unlimited power circuits They are intended to be used with impedance limited sources NEVER connect switching cards directly to AC mains When con necting sources to switching cards install protective devices to lim it fault current and voltage to the card Before operating an instrument make sure the line cord is connect ed to a properly grounded power receptacle Inspect the connecting cables test leads and jumpers for possible wear cracks or breaks before each use When installing equipment where access to the main power cord is restricted such as rack mounting a separate main input power dis connect device must be provided in close proximity to the equip ment and within easy reach of the operator For maximum safety do not touch the product test cables or any other instruments while power is applied to the circuit under test ALWAYS remove power from the entire test s
140. ters necessary to calculate Hall coefficients Test connection details are located in Section 2 In addition to the equipment shown a suitable magnet or electromagnet will be necessary to generate the required magnetic field 3 7 APPLICATIONS 3 5 2 Test Procedure Use the procedure below to measure data necessary to calculate Hall coefficients Note that the sample should be stabilized at the desired temperature before and during the tests Also the flux density magnitude must be kept con stant during the measurements 1 2 Turn on the instruments and allow them to warm up for the prescribed period for rated accuracy Place the Models 196 and 485 in autoranging Be sure the Model 196 is in the DCV function Using front panel Program 6 set the Model 705 Scan ner to the matrix mode Program crosspoint 54 to select low or high resistivity This crosspoint should be open for low resistivity and it should be closed for high resistivity Program the Model 220 current to the desired value in the range of 500fA to 100mA The maximum current that can be used will depend on the resistance of the sample remember that the maximum Model 7065 in put voltage is 8V In order to maintain proper sign con vention for the measured voltage program only positive currents 10 11 Close crosspoints 2 1 1 3 34 and 4 2 then zero the Model 196 and enable the Model 485 relative function Turn on the
141. the sample temperature is reduced to liquid nitrogen levels 77 K or below Below sample resistances of 10kQ however lowering the temperature will not significantly im prove noise performance because instrument noise dominates at room temperature In the resistance range of 10 10 Q Figure 2 27 shows that for the low resistivity setup best accuracy is achieved if the signal voltage sourced current I X R remains under 3V There is another very important reason for doing so the power dissipated in the sample V7 R will then remain under ImW minimizing problems caused by self heating and temperature coefficients of the sample The signal voltage generated during Hall voltage measurements is usually very small typically 20mV or less If a sample or measurement situation results in very small Hall voltages lt 5mV and the sample resistance is less than 1MQ it will be advantageous to use the low resistivity setup Hall voltages as low as 2 4 can be measured with less than 296 uncertainty in this mode by using a Model 181 Nanovoltmeter in place of the Model 196 DMM OPERATION GAIN IDEAL ACTUAL GAIN ERROR 10096 IDEAL 1 LOR dd 196 AT gt RANGE 10 LO R 196 AT lt 3V RANGE 1 0 1 0 01 0 001 1 10 10 10 10 105 10 107 10 10 10 10 SAMPLE RESISTANCE 0 Figure 2 27 Gain Error LO vs HI Resistivity Setup 2 35 OPERATION en Vp p 10Hz BANDWI
142. the voltage reducing off set effects Some compromise between low offsets and minimum sample heating may be necessary when choos ing a current value Minimizing Offset Drift Offset drift which can be cause by such factors as temperature variation can also affect measurement ac curacy In order to minimize offset drift operate the Model 7065 and the measurement instruments in a stable temperature environment Also time between measure ments should be as short as possible keeping in mind other constraints such as circuit settling times B NEGATIVE CURRENT Figure 2 34 Offset Cancellation 2 44 SECTION 3 APPLICATIONS 3 1 INTRODUCTION This section briefly discusses Hall effect Hall conventions and gives some typical measurement examples for the Model 7065 This information is intended as an overview on methods for using the Model 7065 and associated in struments for measurements References are included for more detailed information on making van der Pauw resistivity and Hall effect voltage measurements Information in this section includes 3 2 Recommended Equipment Summarizes the equipment necessary for a complete system 3 3 Hall Effect Conventions and Principles Covers Hall and terminal conventions used in this manual and discusses basic Hall effect principles 3 4 Van der Pauw Resistivity Measurements Covers the basic procedures for determining the resistivity of samples 3 5 Hall Voltage Measureme
143. tivity and ps are computed follows 1 1331 fa ts V2 V V V3 pae I SEE Net pie I Where and are resistivities in ohm cm ts is the sample thickness in cm V V represent the voltages measured by the Model 196 see Table 3 3 Iis the current through the sample in amperes as measured by the Model 485 f and f are geometrical factors based on sample symmetry and are related to the two resistance ratios and as shown below fa fs 1 for perfect symmetry Q and can be calculated using the measured voltages from Table 3 3 as follows V V Vs Ve Vs Q Vs V Q and are related as follows Q 1 f 0 693 arc cosh Q 1 0 693 A plot of this function is shown in Figure 3 6 Note that if p4 and Ps are not within 10 of one another the sample is not sufficiently uniform to determine resistivity Once and p are known the average resistivity Pavc can be determined as follows Ps 2 Pave 5111 1121 TI 21111 11 PING I 21111 NJ 100 0 8 f 0 7 0 6 0 5 0 4 Figure 3 6 Plot of f vs Q 3 5 HALL VOLTAGE MEASUREMENTS The following paragraphs discuss Hall voltage measure ments on van der Pauw type samples 3 5 1 Test Configuration The sample test configuration shown in Figure 3 5 can be used to measure the parame
144. umn Row Between Between 43 1 2 2 1 12 2 1 4 3 4 3 4 3 Reverse current by programming source for opposite polarity 3 20 APPLICATIONS NR Co 9 1 1 3 4 ts NOT SHOWN SAMPLE THICKNESS 6 SPECIMEN 8 CONTACT SPECIMEN Figure 3 15 Sample Dimensions Necessary for Calculations 3 21 APPLICATIONS Resistivity Calculations Two resistivity values and can be calculated as follows Wsts pa V Vs 2ID and Wists ps V V4 21 Where and resistivity in ohm cm ws sample width in cm ts sample thickness in cm D and D sample dimensions Figure 3 15 in cm I current measured by the Model 485 in amperes V V voltages measured by the Model 196 Table 37 6 contact Table 3 8 8 contact Once and are known the average resistivity Pave can be computed as follows Ps 2 Pave Note that pave is also given in ohm cm Hall Voltage Calculations For 6 contact samples two Hall coefficients Ra and Rin can be calculated as follows 2 5 x 107 ts Vi Va Lt Vs 2 5 x 107 ts V Va Vs Ve Ra BI 3 22 Where Ra and Hall coefficients in cm C coulomb ts sample thickness in cm B flux density in gauss I current in amperes measured by the Model 485 V Vs voltages measured
145. voltage measurements are to be taken Table 3 6 summarizes which crosspoints to close for each type of measurement APPLICATIONS BUFFERS 5 4 CONTROLS RESISTIVITY COLUMNS aes 2 3 CLOSE gt 5 CURRENT SOURCE INPUT TRIAX CLOSE ANALOG O O 4 GROUND w gt 4 3 SAMPLE INPUTS J2 TERMINALS J2 196 TERMINAL 1 0R2 HI LO 220 CURRENT SOURCE 485 LO PICOAMMETER Figure 3 7 Test Configuration for Resistivity Measurements of Bar Samples 3 10 APPLICATIONS COLUMNS COLUMNS 3 CLOSE CLOSE 2 0 3 gt tc CURRENT SOURCE INPUT TRIAX CLOSE 4 5 4 3 SAMPLE 3 INPUTS TRIAX J2 TERMINALS J2 TERMINAL 1 OR 2 220 CURRENT SOURCE 485 PICOAMMETER NOTE SEE TEXT FOR POTENTIOMETER VALUE Figure 3 8 Test Configuration for Hall Voltage Measurement of Bar Samples 3 11 APPLICATIONS 3 6 2 Determining Potentiometer Values The loading effects of the DMM and potentiometer can af fect the accuracy of both low and high resistivity measurements Table 3 5 summarizes recommended poten tiometer values along with nominal errors Additional con siderations for value selection are discussed below An equivalent circuit of the card and sample for this discus sion is shown in Figure 3 9 High Resistivity In order to minimize loading errors the equivalent resis tance seen by the buffers must be as
146. ystem and discharge any capacitors before connecting or disconnecting cables or jump ers installing or removing switching cards or making internal changes such as installing or removing jumpers Do not touch any object that could provide a current path to the com mon side of the circuit under test or power line earth ground Always make measurements with dry hands while standing on a dry insulated surface capable of withstanding the voltage being measured The instrument and accessories must be used in accordance with its specifications and operating instructions or the safety of the equip ment may be impaired Do not exceed the maximum signal levels of the instruments and ac cessories as defined in the specifications and operating informa tion and as shown on the instrument or test fixture panels or switching card When fuses are used in a product replace with same type and rating for continued protection against fire hazard Chassis connections must only be used as shield connections for measuring circuits NOT as safety earth ground connections If you are using a test fixture keep the lid closed while power is ap plied to the device under test Safe operation requires the use of a lid interlock If a D screw is present connect it to safety earth ground using the wire recommended in the user documentation The A symbol on an instrument indicates that the user should re fer to the operating instructions located in

Manual - Department of Physics

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