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PLO-10i OPERATION AND SERVICE MANUAL

1. 8 19 RE 28 CRYSTAL POWER DISSIPATION VS CRYSTAL RESISTANCE ccce emen nennen 8 20 PLO 10 PHASE LOCK OSCILLATOR 1 GENERAL DESCRIPTION The INFICON Phase Lock Oscillator was developed specifically to support the use of the quartz crystal microbalance in the measurement of lossy films and in liquid applications In addition to accurately tracking the frequency of heavily damped crystals the PLO 10 provides a dc voltage that is proportional to the crystal s conductance 1 resistance This provides additional information in the study of lossy films and viscous solutions The PLO utilizes an internal oscillator referred to as a Voltage Controlled Oscillator VCO to drive the crystal The crystal current is monitored and the frequency of the oscillator is adjusted until there is zero phase between the crystal voltage and current Assuming that the crystals electrode capacitance has been effectively cancelled this point of zero phase between the crystal current and voltage is the exact series resonant point of the crystal The magnitude of the current at this point is directly proportional to the crystal s conductance This current is converted to a voltage demodulated and amplified to create a dc voltage proportional to crystal conductance The PLO contains a phase detector that continuously monitors the phase difference between the crystal s current and voltage At frequencies below the crystal s resonant frequency the
2. Connect a frequency counter to the Frequency Output Connect a voltmeter to the Conductance output The center conductor on the BNC connector is positive with respect to ground Connect the crystal holder with a crystal installed to the PLO by means of the 12 inch coax cable Plug the wall mount power supply into the wall and plug the power plug into the PLO 10 Refer to Figure 2 Figure 3 and Figure 4 for a complete system connections The green Lock LED should come on the frequency should indicate the correct crystal frequency and the voltmeter should indicate something between 5 millivolts and 4 volts Check the capacitance cancellation by pressing and holding the Reset switch The green Lock LED should light Keeping the Reset switch pressed adjust the fine capacitance trimmer clockwise by about 5 degrees The yellow Reset LED should flash Back the trimmer counterclockwise to the point where the Reset LED just stops flashing The capacitance cancellation should be checked and readjusted every time the environment of the crystal and holder is changed For example 1 crystal and holder are moved from air to liquid or liquid to air the capacitance cancellation should be checked and readjusted Remove the crystal The red Unlock LED should light The green Unlock LED should go off The Sweep Rate LED should not flash Ifthe Sweep Rate LED flashes the capacitance is under compensated 2 2 UNDERSTANDING AND SETTING UP TH
3. For example the decay length for a 5 Mhz crystal in water at 20 C is 2 5x 10 m 0 25 microns 8 5 DISSIPATION METHOD The Dissipation Method 1 an alternate way of measuring the crystal to determine the properties of the film and or the liquid In this method the crystal is driven at its resonant frequency by an oscillator then the crystal shorted and both the resonant frequency and the oscillation decay time are measured The crystal dissipation is related to Q and R as follows Equation 10 pekt ol Where D Dissipation Q Quality Factor R resistance in Q L inductance in H D can be determined from R if L is known It has been shown that L will remain constant unless there is an acoustic resonance in the film on the crystal Independent studies have shown that as long as the effect of the parasitic capacitance Cs is properly cancelled the results provided by the PLO 10 System are in good agreement with those obtained by the Dissipation Method 8 6 ELECTRICAL DESCRIPTION OF THE QUARTZ CRYSTAL Figure 18 shows the equivalent circuit of a quartz crystal The circuit has two branches The motional branch which contains the L R amp C is the branch that is modified by mass and viscous loading of the crystal The shunt branch which contains the lone Cs element represents the shunt capacitance of the crystal electrodes and any cable and fixture capacitance 8 8 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATO
4. 10 REFERENCES eereosevvevensenvevenseneenensenennenssvennennsnennenssvennennsvennennsvennennsvennennsvennsvennennsvennevnsvennevnseesnee 10 1 vi FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU Table of Figures RE I EQUIVALENT PHASE ERROR DUE IMPERFECT CAPACITANCE 1 4 RE 2 SYSTEM 8 001 0000000000000000 A etti tesa senes 2 3 RE 3 FRONT CONNECTIONS teo te eeepc ctore Fee o Ul ee ve ye EET aed 2 4 RE 4 REAR CONNECTIONS cccccccessessscecececsesesseaececceseseseseceeecseseasecesececseeaaeceeeescseeaaeceecescsensaaeeeeeeeens 2 5 RE 5 RESISTANCE VS CONDUCTANCE 2 02000000000000000000000000000000000000 00 3 1 RE 6 CAPACITANCE ADJUSTMENTS inicia td vae Ere Ue a 4 2 7 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION 5 2 RE 8 CRYSTAL POWER DISSIPATION VS CONDUCTANCE 0 01 20 010000000 0000000000000000 6 1 RE 9 PLO 10 ASSEMBLY 2 innen e 6 2 RE 10 INFICON 1 CRYSTAL ELECTRODE 2 2 7 4 9010 01 1000000 nennen etnies ee 7 2 RE 11 INFICON 1 CRYSTAL AS SEEN FROM THE FRONT 7 2 RE
5. 65 1993 2910 Sullivan C K and Guilbault G G Commercial Quartz Crystal Microbalances theory and applications Biosensors and Bioelectronics 14 1999 663 670 3 Sauerbrey 2 Phys 155 1959 206 Gabrielli C et al Calibration of the Electrochemical Quartz Crystal Microbalance J Electrochem Soc 139 9 1991 2657 gt Denison D R Linearity of Heavily Loaded Quartz Crystal Microbalance J Vac Sci Technol 10 1973 126 5 Behrndt H Long Term Operation of Crystal Oscillators in Thin Film Deposition J Vac Sci Technol 8 5 1971 622 7 Lu Chih shun Mass determination with piezoelectric quartz crystal resonators J Vac Sci Technol 12 1 1975 578 Rodahl M and Kasemo B Frequency and dissipation factor responses to localized liauid deposits on a QCM electrode Sensors and Actuators B37 1996 111 116 9 Ward M D and Delawski E J Radial Mass Sensitivity of the Quartz Crystal Microbalance in Liquid Media Anal Chem 63 1991 886 10 Cernosek R W et al Analysis of the radial dependence of mass sensitivity for Modified electrode quartz crystal resonators Anal Chem 50 1998 237 Lu Chih shun Monitoring And Controlling Techniques For Thin Film Deposition Processes AVS Course Material published under the auspices of The Education Committee American Vacuum Soiety 1981 p 64 65 l Vig J R UV Ozone Clean
6. Describing a molecule having no separation of centers of positive and negative electrical charge that would make the molecule assume certain orientations more than others in an electric field GLOSSARY 9 1 O D Organic Picofarad Plasma Cleaning PLO Quadrature current Redox RTD Shunt Capacitance Silanization Teflon Ultrasonic cleaning UVO cleaning 9 2 GLOSSARY PLO 10 PHASE LOCK OSCILLATOR Abbreviation for Outside Diameter Usually use in specifying a tube size in the form inch I D x inch O D where inch are the dimensions In chemistry organic refers to a species containing carbon Certain small ions and compounds containing carbon such as carbon dioxide are usually not considered to be organic but rather are classed as inorganic 10 farads A common unit of capacitance abbreviated as pfd By definition 1 farad will store a 1 Coulomb charge when connected across a 1 volt potential A method that utilizes plasma reaction at the surface of the sample and volatile by products are removed by the vacuum pump The basic instrumentation required this process includes a reaction chamber a power supply and a vacuum source The sample being cleaned is put into the chamber which is evacuated by the vacuum pump Gas oxygen is introduced into the chamber and converted to reactive plasma by the power supply For more information visit http www marchplasma com Phase Lock Oscillator A type
7. 12 FREQUENCY VS TEMPERATURE OF INFICON 1 AT CUT CRYSTAL FOR 90 7 7 RE 13 FREQUENCY VS TEMPERATURE OF INFICON 1 AT CUT CRYSTAL FOR 25 7 7 RE 14 CHC 100 CRYSTAL HOLDER idilio 7 10 RES CRYSTAL INSTALLATION A i eee ee and 7 11 RE 16 FREQUENCY CHANGE VS WT GLYCEROL ccsessssccececeesssseceeececsesssaeceecceesensaeeeeccecsensasaeeeeeees 8 6 RE 17 RESISTANCE CHANGE VS WT GLYCEROL csecsssccececsessseceeececsessaeceeccecsesnaeceeececsensasaeeeeeees 8 7 REI 8 CRYSTAL EQUIVALENT CIRCUITS Ein ann isn eee ici 8 9 RE 19 POLAR PLOT CRYSTAL ADMITTANCE 2 2 1 0400000000001000000000000000000 enitn t rennen 8 10 RE 20 ADMITTANCE VS FREQUENCY MAGNITUDE AND PHASE OF HIGH Q CRYSTAL 8 11 RE 21 ADMITTANCE VS FREQUENCY REAL AND IMAGINARY COMPONENTS OF HIGH Q CRYSTAL 8 11 RE 22 POLAR ADMITTANCE PLOT OF HIGH Q CRYSTAL 1222112 1 0010000000000000000000000 8 en 8 12 RE 23 POLAR ADMITTANCE PLOT OF LOW Q CRYSTAL 4 42 200000 04200000000000000000000000000008 4 8 13 RE 24 ADMITTANCE VS FREQUENCY REAL AND IMAGINARY COMPONENTS OF LOW Q CRYSTAL 8 13 RE 25 ADMITTANCE VS FREQUENCY MAGNITUDE AND PHASE OF LOW 8 14 RE 26 NON ZERO PHASE LOCK 4 355 inen i eee eee 8 15 RE 27 FREQUENCY ERROR DUE IMPERFECT CAPACITANCE
8. 80 ohms Pery in watts 0 125 20 80 80 1 25E watts or 125 pW a Crystal Resistance 4000 Pay in watts 0 125 20 4000 4000 3 87E watts or 3 87 pW THEORY OF OPERATION 8 19 PLO 10 PHASE LOCK OSCILLATOR Crystal Power vs Crystal Resistance 250 200 5 150 2 5 T gt 100 50 0 e o ite T o oO N o N e 8 N Crystal Resistance ohms Figure 28 Crystal Power Dissipation vs Crystal Resistance 8 20 THEORY OF OPERATION 9 GLOSSARY Conductance Crystal Bandwidth Crystal Holder Crystal Q Elastic Hydrocarbon Hydrophilic Hydrophobic LD Kynar Lipid Molar mass Mole nonpolar PLO 10 PHASE LOCK OSCILLATOR Symbol for angstrom a unit of length equal to 10 meter The ability to conduct Conductance is the inverse of resistance Conductance 1 Resistance or Resistance 1 Conductance The units of resistance are Ohms V A and the units of conductance are Siemens S A V Abbreviation for chlorinated polyvinyl chloride a resin patented by Goodrich it has excellent mechanical strength and stability over temperature and offers good resistance over a selective range of chemicals Refers to the crystal s frequency response range bounced by th
9. AROUND 2 EXTENDED ELECTRODE FRONT_SIDE REAR SIDE SENSING ELECTRODE CONTACT ELECTRODE Figure 10 INFICON 1 Crystal Electrode Configuration The figure below shows a INFICON 1 diameter as seen from the front side 1 CRYSTAL AS SEEN FROM FRONT SIDE Figure 11 INFICON 1 Crystal as Seen From The Front Side 7 1 2 CRYSTAL PARAMETERS Polished one inch diameter crystals that are commonly available for liquid work have the typical values as listed below Type Frequency Electrode Resistance Q Factor Range MHz Material ohms 5 MHz 4 976 5 020 Gold 10 120 000 9 MHz 8 976 9 036 Gold 7 55 000 7 2 CRYSTALS HOLDERS AND FLOW CELL PLO 10 PHASE LOCK OSCILLATOR 7 1 3 CRYSTAL SURFACE FINISH Studies have shown that electrode surface roughness can cause large apparent mass loadings due to the liquid that is trapped within pores at the crystal surface INFICON s crystals are optically polished to 50 average surface roughness to minimize this effect Polished crystals are required to obtain good agreement between theory and measurement during liquid immersion experiments Polished crystals are also required to obtain measurements reproducibility from crystal to crystal Non polished crystals R 1 8 microns are also available at reduced costs for applications that do not require the accuracy and reproducibility of the polished crystals 7 1 44 CRYSTAL ELECT
10. H38 2 Yang Mengsu and Thompson Michael Multiple Chemical Information from the Thickness Shear Mode Acoustic Wave Sensor in the liquid Phase Anal Chem 65 1993 1158 27 8 J Martin W Cernosek and J J Spates Sensing Liquid Properties with Shear mode Resonator Sensors in Proceeds from Transducers Eurosensors IX Stockholm Sweden 1995 Kanazawa K Characterization of Operating Behavior of the PLO 10 A Report Submitted to Maxtek Inc by Process Monitor April 2000 p 6 REFERENCES
11. Hz error in a five thousand ohm crystal The second reason is that the effective phase error caused by a non zero net quadrature current is inversely proportional to the real current which is inversely proportional to the crystal resistance In other words the effective phase error is proportional to the crystal resistance For instance a net unbalance of 1 pfd leads to an effective phase error of 0 02 degrees for a ten ohm crystal but 1t leads to a 2 degree error for a one thousand ohm crystal and a 10 degree error for a five thousand ohm crystal Examples A ten ohm 5 MHz crystal will have a Q Quality Factor of about 120 000 The bandwidth is equal to the crystal frequency divided by Q Thus the bandwidth of this crystal would be about 42 Hz To a first approximation near zero phase the frequency error per degree of phase error is given by the following formula Frequency Error Phase Error in radians Bandwidth Or Frequency Error 1 2 57 3 Phase Error in degrees Bandwidth For the above ten ohm crystal the frequency error caused by a one degree phase error is 42 114 6 or approximately 0 37 Hz For a one thousand ohm crystal one degree of phase error results in a 37 Hz error and for a ten thousand ohm crystal the frequency error is 370 Hz per degree of phase error Now the effective phase error caused by a non zero quadrature imaginary current is given by the following formula Effective Phase error arctang
12. IN INFICON CRYSTAL 7 10 7 3 2 HOLDER CARE AND HANDDLING esses enne nennen entren nest 7 12 7 3 3 CONSIDERATIONS FOR BUILDING YOUR OWN HOLDER 7 13 7 4 FLOW EEEL ersehen see 7 13 8 THEORY OF OPERATION ssesssseonennenesnennenesnennenesnennenesnennenesnennenesnennenennennenennennenennennenennennenennene 8 1 8 1 SAUERBREY EQUATION eere te eere ee Et 8 1 8 2 Z MATCH EQUATION diia 8 2 8 3 THICKNESS CAECULA TION oett ee nn Ri Erna 8 3 8 4 LIQUID MEASUREMENTS croire Ense 8 4 8 4 1 DECAY LENGTH OF SHEAR WAVE IN LIQUID eese 6 7 8 5 DISSIPATION METHOD entren teer Eb Eine ee teat nee ao ated e dien 8 8 8 6 ELECTRICAL DESCRIPTION OF THE QUARTZ CRYSTAL eee 8 8 8 7 CHARACTERIZING THE CRYSTAL 2 22 00000 8 15 8 7 1 FREQUENCY ERRORS re ere tg E 8 16 8 7 2 FREQUENCY ERROR DUE TO PHASE 202202 0 2 2 8 17 8 7 3 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION 6 17 8 8 FREQUENCY ERRORS DUE TO IMPERFECT CAPACITANCE CANCELLATION 8 17 8 9 CALCULATING CRYSTAL POWER tnter ottenere e nn ets 8 19 9 GLOSSARY serenvenverenvenverenseneerenseneerenseneenensenensensenensenennensenennensenennensenennensenennensenensensenensensenennensenssnennene 9 1
13. change in Hz C the sensitivity factor of the crystal in Hz ng cm 0 056 Hz ng cm for a 5 MHz crystal 20 CRYSTALS HOLDERS AND FLOW CELL 7 3 PLO 10 PHASE LOCK OSCILLATOR 0 081 Hz ng cm for a 6 MHz crystal 20 0 181 Hz ng cm for a 9 MHz crystal 20 Am the change in mass per unit area in g cm The minimum detectable mass change is typically a few ng cm and limited by the noise specifications of the crystal oscillator and the resolution of the equipment used to measure frequency shifts For example the INFICON RQCM has a frequency resolution of 0 03 Hz 4 6 MHz therefore its minimum detectable mass change is 0 37 ng cm The Sauerbrey equation relies on a sensitivity factor Cf which is a fundamental property of the QCM crystal Thus in theory the QCM mass sensor does not require calibration This ability to calculate the mass sensitivity from first principles is obviously a very attractive feature of these devices However it is very important to notice that the Sauerbrey equation is only strictly applicable to uniform thin film deposits originating from a low pressure i e vacuum gas environment Thick deposits and operation in liquid environments or in contact with lossy films relies on the use of more complex equations relating the frequency shifts to mass loading and often requires calibration of the setup for accurate results Several articles have been published on simple ways to cal
14. low Q crystal the bandwidth can be quite large and small phase errors can result in significant frequency errors See the equations in the error discussion section 8 7 CHARACTERIZING THE CRYSTAL MEASUREMENT The INFICON Phase Lock Oscillator used on the Crystal Measurement Card was developed specifically to support the use of the quartz crystal microbalance in the measurement of lossy films and in liquid applications In addition to accurately tracking the frequency of heavily damped crystals the PLO 10 also tracks the crystal s resistance This provides additional information in the study of lossy films and or viscous solutions The PLO utilizes an internal oscillator referred to as a Voltage Controlled Oscillator VCO to drive the crystal The crystal current is monitored and the frequency of the oscillator is adjusted until there is zero phase between the crystal voltage and current Assuming that the crystal s electrode capacitance has been effectively cancelled this point of zero phase between the crystal current and voltage is the exact series resonant point of the crystal The magnitude of the current at this point is directly proportional to THEORY OF OPERATION 8 15 PLO 10 PHASE LOCK OSCILLATOR the crystal s conductance This current is monitored by the PLO 10 and displayed as crystal resistance The PLO contains a phase detector that continuously monitors the phase difference between the crystal s current and voltage At fre
15. media The following guidelines are recommended for general handling of the holders Always keep the holder clean and dry when not in use Always use clean room grade gloves while handling the holder and its components Never handle the holder with bare hands as human skin oils may deposit on it and react with your experiment Always ensure that your holder is compatible with your experiment environment Never submerge the holder unassembled or without a crystal Never submerge the holder pass its terminal connector at the end of the rod Always rinse the holder generously with deionized water and thoroughly blow dry using filtered air after each experiment This is especially important if the holder has been exposed to oxidizing acids CRYSTALS HOLDERS AND FLOW CELL PLO 10 PHASE LOCK OSCILLATOR Always act fast in the event that liquids or chemicals have entered the crystal cavity in the holder Immediately clean the holder using the following procedure o Remove the crystal to expose the crystal cavity o Remove both Pogo contact pins from their sockets Use a pair of tweezers or gloved fingernail grab the Pogo head firmly and pull it straight out of its socket o Rinse the holder the crystal cavity and the Pogo sockets generously with deionized water to remove all traces of chemicals and thoroughly blow dry the whole holder using filtered air Ensure all liquids that may have been trapped in
16. of electronic circuit in which the frequency and the phase ofthe Voltage Controlled Oscillator VCO is locked to the frequency and the phase of a reference signal in our case the signal from the sensing crystal Refers to the imaginary component of the current through the shunt capacitance Cs An oxidation reduction reaction the term redox is obtained from the first few letters of reduction and oxidation Resistance Temperature Detector A device that changes its resistance as a function of temperature Effective capacitance due to the electrodes on the crystal This is the unwanted capacitance we try to cancel out along with the capacitance in the cable and the holder of course while adjusting the Fine amp Coarse capacitance cancellation on the PLO 10 CM The chemical conversion of hydroxyl OH groups which often act as adsorption sites on silica or glass stationary chromatographic phases with silane coupling agents to give the inactive O SiR3 grouping Silanization can neutralize surface charges thus eliminating non specific binding DuPont Company s registered trademark of Perfluoroalkoxy Fluorocarbon Resin a class of Teflon that offers excellent inertness to aqueous acid and aqueous alkaline superior resistance over a wide range of pH Visit www dupont dow com for more information This method utilizes high frequency ultrasonic and high intensity sound waves into a liquid producing cavitations rapid format
17. siemen Solving for Ray Rery 100 Conductance in volts Rsource The Crystal Drive Source Resistance is 20 O so in ohms 100 Conductance in volts 20 Q Examples l Conductance output voltage 1 000 volt Rey in ohms 100 1 000 20 80 Q 2 Conductance output voltage 0 015 volts Rey in ohms 100 0 015 20 6667 20 6647 6 647 Resistance vs Voltage 10000 00 1000 00 Equivalent Resistance R 10 00 NJ X Y IN P J 100 00 1 0 00 0 25 0 50 0 75 1 00 1 25 1 50 7 0 2 2 50 2 75 3 00 3 25 3 50 Conductance Voltage V Figure 5 Resistance vs Conductance Voltage CALCULATING CRYSTAL RESISTANCE 3 75 3 1 4 00 PLO 10 PHASE LOCK OSCILLATOR 4 ADJUSTING THE CAPACITANCE CANCELLATION Proper adjustment of Capacitance Cancellation is critical in obtaining accurate results with high resistance crystals See Section 1 2 3 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION The cancellation adjustment should be performed with the crystal holder and crystal in the measurement environment For instance 1 liquid measurements are to be made insert the crystal and its holder into the liquid where the measurement will be made With the crystal and holder in the measurement environm
18. 00 2 3E watts or 2 3 uW Crystal Power vs Conductance Voltage 250 0 200 0 150 0 100 0 Crystal Power uW 0 6 0 8 1 21 4 6 8 281 321 3 4 3 6 Conductance Voltage volts Figure 8 Crystal Power Dissipation vs Conductance Voltage CALCULATING CRYSTAL POWER 6 1 PLO 10 PHASE LOCK OSCILLATOR 5 3 PIN 605400 NN CHASSIS STAND X2 P N 605407 2 56 X 1 4 SCREWS X12 Figure 9 PLO 10 Assembly 6 2 CALCULATING CRYSTAL POWER PLO 10 PHASE LOCK OSCILLATOR 7 CRYSTALS HOLDERS AND FLOW CELL An essential part of the PLO 10 Oscillator is the sensing crystal Careful handling of both the crystal and the crystal holder must be observed to ensure proper and reproducible measurements Furthermore the sensing crystal the crystal holder and the connecting cable must be orientated and connected correctly in order for the PLO 10 to work properly This is especially true if you design your own crystal or holder If you have purchased a INFICON crystal holder and cable the installation is simple Follow the instructions below If you plan to build your own crystal or holder or cable see Section 7 3 2 HOLDER CARE AND HANDLING 7 1 1 INCH DIAMETER CRYSTALS INFICON pioneered the standard AT cut 5 MHz 1 inch diameter crystals for use in liquid applications The AT cut quartz is
19. 1 7 12 CRYSTAL PARA METERS fen e ee ida 7 2 7 1 3 CRYSTAL SURFACE FINISH iia ee 7 3 7 1 4 CRYSTAL ELECTRODE MATERIALS nengone eene aerie tee i E E akore ea 7 3 7 1 5 CRYSTAE THICKNESS see ae ee en ER ERR ER dq 7 3 7 1 6 MASSSENSITIVILY rcnt a p eem en dudes 7 3 7 1 7 STABIEITY s ee teen Eee 7 4 7 1 8 CRYSTAL FIFE EXPECTANCY cda 7 5 7 1 9 TEMPERATURE COEFFICIENT 5 eee pepe ce ea e 7 5 7 2 CRYSTAL CARE 2 4440 0 7 7 7 2 1 GRYSTAL GLEEANING x a Sr AS e RR aptis 7 8 7 2 1 1 General Cleaning eo Deere eorpore ier tis 7 8 7 2 1 2 Organic hydrocarbon contaminants sess 7 8 7 2 1 3 Biomaterials lipids proteins and similar 7 8 7 2 1 4 Lipid vesicles on SiO 7 8 7 2 1 5 Polystyrene removal nro rennen nnne 7 9 7 2 2 ELECTRODE SURFACE MODIFICATIONS entente enne enters 7 9 12 2 Siret eden iir A tt qii ES 7 9 7 2 2 2 SELF ASSEMBLED MONOLAYERS enn eene 7 9 72 2 3 PHYSICAL VACUUM DEPOSITION FYD ron T 7 9 7 3 CRYSTAEHOEDERS 5 5 rete t PER ee 7 9 7 3 1 HOW INSTALL CRYSTAL
20. 10i Models 1 1 3 1 2 CHARACTERIZING THE PLO une Luo epe 1 3 1 2 1 FREQUENCY 56 1 3 1 2 2 FREQUENCY ERROR DUE TO PHASE 1 3 1 2 3 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION 1 3 1 2 4 CONDUCTANCE ERRORS esses estet teet EO E 1 5 1 3 SPECIFICATIONS uses ii ede denda 1 6 1 4 ACCESSORIES rent 1 7 2 UNDERSTANDING AND SETTING UP THE INFICON 410 2 1 2 1 NORMAL OPERATION rca AE EA A ERATE ERE 2 1 22 li INO IO 2 1 3 CALCULATING CRYSTAL 5 5 0 3 1 4 ADJUSTING THE CAPACITANCE CANCELLATION eesesverserenversvsensensnnensensnsenennensenensensenennene 4 1 4 1 ADJUSTING CAPACITANCE CANCELLATION TRIMMER CAPACITORS 4 1 4 2 WORKING WITH VERY LOW 5 5 422 222 01 5 00000000000000000000040000000544 4 3 5 FREQUENCY ERRORS DUE TO IMPERFECT CAPACITANCE CANCELLATION 5 1 6 CALCULATING CRYSTAL POWER eeseseesesversvsenverensenvesenvenenneneenennensenenneneenenneneenennensensnnensensnnene 6 1 7 CRYSTALS HOLDERS AND FLOW CELL sesseseevesverevvesenneneerenseneerenseneenenneneenenseneenenseneenenseneenene 7 1 7 1 1 INCH DIAMETER CRYSTALS S roncin r a ener enne enne a 7 1 7 1 1 ELECTRODE 7
21. 4000 5000 6000 Delta Frequency Hertz 7000 8000 9000 10000 Frequency Change vs Wt Glycerol 100 Wt Glycerol 10 20 30 40 50 60 70 80 90 Theory m RQCM m Figure 16 Frequency Change Wt Glycerol 8 6 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATOR Resistance Change vs Wt Glycerol 5000 4000 3000 2000 Delta Resistance ohms 1000 0 20 40 60 80 100 Wt Glycerol Figure 17 Resistance Change vs Wt Glycerol 8 41 DECAY LENGTH OF SHEAR WAVE IN LIQUID As mentioned in the section above when an oscillating crystal is in contact with a liquid there will be a decrease in the resonant frequency and an increase in the motional resistance The decrease in the resonant frequency is caused by the additional mass of the vibrating liquid The increase in motional resistance is caused by the power dissipation of the shear wave that radiates into the liquid The decay length of the shear wave into the liquid is defined by Equation 9 Where Lp Decay length in m p Density of the liquid in contact with the electrode in kg m THEORY OF OPERATION 8 7 PLO 10 PHASE LOCK OSCILLATOR Viscosity of the liquid in contact with the electrode in kg m sec 0 Angular frequency at series resonance 277
22. 4A U coax 888023 Adapter BNC Male to SMB Jack 888026 Adapter BNC male to binding posts 803081 Power Cord 803312 Capacitance Tuning Tool 900037 Power Supply 100 250VAC to 12VDC Refer to INFICON Price List for more accessories and other products GENERAL DESCRIPTION 1 7 PLO 10 PHASE LOCK OSCILLATOR 2 UNDERSTANDING AND SETTING UP THE INFICON PLO 10 There are several LED s on the PLO 10 to indicate its operation The green Lock LED is on when the frequency is locked to a connected crystal s resonant frequency The Red Unlock LED will be on whenever the frequency is not locked The Yellow Sweep Rate LED flashes each time the frequency ramp is reset to its low starting point The Reset switch allows you to force the VCO to its lowest frequency independently of the Integrator output The Reset switch also forces the Lock LED on thus turning off the quadrature current injection The Quadrature current injection must be off to properly adjust the capacitance cancellation To insure that the VCO ramps up in frequency a small amount of quadrature current is injected into the current to voltage buffer whenever the PLO is unlocked This current is equivalent to a shunt capacitance of about 1 5 pfd As soon as lock is detected the quadrature current is turned off 2 1 NORMAL OPERATION The PLO 10 comes set up for operation with a INFICON cable and crystal holder Ifa INFICON cable and crystal holder is being used then n
23. 6 CRYSTAL FACE ISOLATION PLO 10i Models only The PLO 10i Models provide transformer isolation of the crystal front face electrode This feature allows user to connect the crystal face to an electrochemical instrument such as a potentiostat 1 2 CHARACTERIZING THE PLO 1 2 1 FREQUENCY ERRORS The first thing we want to know regarding the performance of the PLO is What is the magnitude of the frequency error we can expect from the PLO 10 In any oscillator and sensing crystal system the error in the frequency measurement is a function of both the oscillator and the sensing crystal The same is true for phase locked loops Any phase error will introduce a frequency error and this frequency error will be inversely proportional to the sensing crystal s These errors are over and above any change in crystal frequency due to temperature changes There are four important parameters that determine the frequency error of the PLO and sensing crystal system or indeed any oscillator and sensing crystal system The first two the zero phase error and the electrode capacitance cancellation errors are characteristics ofthe PLO The second two are characteristics of the crystal the Q of the crystal and the conductance l resistance of the crystal 1 2 2 FREQUENCY ERROR DUE TO PHASE ERROR Given some finite zero phase error the resulting frequency error depends on the sensing crystal s the higher the the lower the error For phase e
24. ATION 8 13 PLO 10 PHASE LOCK OSCILLATOR offset The PLO 10 provides a mechanism for canceling out the imaginary current effectively putting the center of the crystal back on the real axis The true series resonant frequency of the crystal is then the point where the conductance circle crosses the real axis This is the frequency at which the inductive and capacitive impedance s in the L R amp C branch cancel out and the crystal looks like a pure resistance of value imp LEVEL DIV MARKER 4 986 314 DOOHz D 200 00 6 UDF 1 5398E 3 D 30 000deg MARKER 4 986 314 DODHz PHASE CUDF gt 16 983deg E I AA TATT 111 CIC LI A CENTER 4 986 314 OODHz SPAN 20 000 DODHz AMPTD 10 OdBm Figure 25 Admittance vs Frequency Magnitude and Phase of Low Q Crystal 8 14 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATOR FULL SCALE 200 MARKER 4 987 9586 SOOHz ne PHASE REF 0 Odeg MAG CUDF 115 86E 3 REF POSN 0 Odeg PHASE UDF gt D 092deg CRYSTAL BANDWIDTH CENTER 4 987 964 000 2 SPAN 200 DOOHz AMPTD 10 OdBm Figure 26 Non zero Phase Lock Figure 26 shows the result of a non zero phase lock Note that the frequency difference between the top of the conductance circle and the bottom is equal to the bandwidth of the crystal For a high Q high conductance low resistance crystal the bandwidth is very narrow and small errors in phase lock angle are insignificant For a
25. E INFICON PLO 10 PLO 10 PHASE LOCK OSCILLATOR Figure 2 System Connections UNDERSTANDING AND SETTING UP THE INFICON PLO 10 2 3 PLO 10 PHASE LOCK OSCILLATOR SMB CABLE er POTENTIOSTAT gt ore SMB TO BNC ADAPTOR E REF CE WE OG WORKING ELECTRODE CRYSTAL HOLDER CHC 100 SHOWN COUNTER ELECTRODE REFERENCE ELECTRODE Figure 3 Front Connections 2 4 UNDERSTANDING AND SETTING UP THE INFICON PLO 10 PLO 10 PHASE LOCK OSCILLATOR E TO AC OUTLET POWER SUPPLY FREQUENCY COUNTER PLO 10 REAR BNC TO BINDING POST ADAPTOR VOLTMETTER METER LEADS Figure 4 Rear Connections UNDERSTANDING AND SETTING UP THE INFICON PLO 10 2 5 PLO 10 PHASE LOCK OSCILLATOR 3 CALCULATING CRYSTAL RESISTANCE The PLO 10 provides a de output voltage proportional to conductance Conductance is the inverse of Resistance Thus Conductance 1 Resistance or Resistance 1 Conductance The units of resistance are ohms volts per ampere and the units of conductance are siemens amperes per volt The PLO 10 Conductance Output is inversely proportional to the sum of crystal resistance plus the Crystal Drive Voltage source resistance Thus Conductance Output 100 Rery Rsource The Conductance Output scaling is 100 volts per
26. For Aluminum with a density of 2 7 gm cn this is equivalent to approximately 2 7 This intrinsic dependence of resonance CRYSTALS HOLDERS AND FLOW CELL 7 5 PLO 10 PHASE LOCK OSCILLATOR frequency of a sensor crystal on temperature is generally small in experiments in gas phase when operating at or near its turn around point The turn around point is where the temperature coefficient of the crystal is zero That is there is no change in resonance frequency due to a change in the temperature of the crystal at the turnaround point INFICON 1 inch crystals are optimized for two operating temperatures namely 90 and 25 These crystals have very good temperature stability when operating close to their specified temperature Even though AT cut crystals are designed to minimize the change in frequency due to temperature the effect of temperature can be significant when attempting to resolve small mass frequency changes over long periods of time This frequency change due to temperature is magnified when the sensor crystal is submerged in liquids This is due to the coupling of the shear mode oscillation with the temperature dependent viscosity and density of the fluid For experiments in liquid phase in which the frequency is to be monitored over long periods of time the temperature must be controlled to at least 0 1 C and preferably better In electrochemical experiments this is often achieved with temperature controlled baths a
27. OPERATION AND SERVICE MANUAL CAPACITANCE EM qu pi 4 rin e SWEEP UNLOCK e LOCK PLO 10 Series Phase Lock Oscillator IPN 605800 Rev G OPERATION AND SERVICE MANUAL PLO 10 Series Phase Lock Oscillator IPN 605800 Rev G INI ICON Instruments for Intelligent Control www inficon com reachus inficon com Due to our continuing program of product improvements specifications are subject to change without notice 2007 INFICON Trademarks The trademarks of the products mentioned in this manual are held by the companies that produce them INFICON is a trademark of INFICON Inc All other brand and product names are trademarks or registered trademarks of their respective companies Disclaimer The information contained in this manual is believed to be accurate and reliable However INFICON assumes no responsibility for its use and shall not be liable for any special incidental or consequential damages related to the use of this product Disclosure The disclosure of this information is to assist owners of INFICON equipment to properly operate and maintain their equipment and does not constitute the release of rights thereof Reproduction of this information and equipment described herein is prohibited without prior written consent from INFICON Two Technology Place East Syracuse NY 13057 9714 Phone 315 434 1100 See
28. R I Figure 18 Crystal Equivalent Circuit Because a crystal s impedance is minimum at resonance it is convenient to characterize a crystal in terms of admittance Admittance is the inverse of impedance Y 1 Z thus the admittance reaches a maximum at resonance While impedance is proportional to the voltage developed across a device when it is subjected to a current the admittance is proportional to the current through the device when it is subjected to a voltage At any frequency the admittance of a quartz crystal is a complex value that can be expressed in terms of magnitude and phase or in terms of a real and imaginary value The relationship of these two representations is shown in Figure 19 THEORY OF OPERATION 8 9 PLO 10 PHASE LOCK OSCILLATOR IMAGINARY COMPONENT OR QUADRATURE REAL COMPONENT Figure 19 Polar Plot of Crystal Admittance Figure 20 shows the conductance in terms of magnitude and phase while shows the same information in terms of imaginary and real part of conductance 8 10 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATOR REF LEVEL DIV MARKER 4 987 964 DODHz D 0 20 DODE 3 MAG UDF 115 B4E 3 D Odeg 30 000deg MARKER 4 987 S984 OOOHz PHASE UDF 3 877deg PHASE BANDWIDTH MAGNITUDE DEG Rr ed X10 SIEMENS 45 3 120 0 100 3 45 60 CENTER 4 987 964 DODHz SPAN 20D DODHz AMPTD 10 OdBm Figure 20 Admittance vs Frequency Magnitude and Phase o
29. RKER 4 986 414 DOOHz PHASE REF 0 Odeg MAG lt UDF gt 1 S215E 3 REF POSN O Odeg PHASE UDF 13 518deg FREQUENCY 4 986414 MHz RESISTANCE 6570 Q 1 700 CRYSTAL MEASURED IN GLYCEROL AND WATER SOLUTION FROM AIR TO SOLUTION RESISTANCE CHANGED FROM 8 60 TO 6570 FREQ CHANGED FROM 4 987966 TO 4 987414 MHz Af 526 Hz CIRCLE TOP 4 984964 MHz TRUE SERIES RESONANCE 4 986414 MHz EFFECTIVE PHASE ERROR CIRCLE BOTTOM 4 987914 MHz BANDWIDTH BOTTOM TOP CIRCLE 4 987914 4 984964 MHz 2 950 Hz CENTER 4 986 314 DOOHz SPAN 20 DOD DOOHz AMPTD 10 DdBm Figure 23 Polar Admittance Plot of Low Q Crystal REF LEVEL DIV MARKER 4 986 314 OOOHz 0 0 200 00 6 REAL CUDF gt 1 3851E 3 0 0 200 00 6 MARKER 4 988 314 000Hz IMAGINARY IMAG CUDF gt 363 72E 6 KIO SIEMENS REAL CONDUCTANCE 0 8 10 SIEMENS 0 6 0 100 0 2 80 0 4 60 fh 0 CENTER 4 986 314 DOOHz SPAN 20 000 DOOH AMPTD 10 0dBm gt 2 KHz Figure 24 Admittance vs Frequency Real and Imaginary Components of Low Q Crystal The conductance of the L R amp series arm creates the circle in the polar plot with its center on the real axis The effect of the shunt capacitance conductance is to offset the circle vertically Figure 23 shows a heavily loaded crystal in which the offset is obvious It is the imaginary quadrature current through the shunt capacitance that creates the THEORY OF OPER
30. RODE MATERIALS INFICON s crystals are available in a variety of electrode materials including Gold Platinum Aluminum Silver Titanium etc INFICON also offers Gold electrode crystals with an additional 5102 outer layer to create a hydrophilic surface needed for some biological applications 7 15 CRYSTAL THICKNESS INFICON AT cut 1 inch diameter crystals are plano plano Their physical thickness is determined by a frequency constant and their final frequency The frequency constant for an AT cut crystal is 1 668E5 Hz cm or 65 5 kHz x in Therefore the crystal thicknesses for various frequencies are as follows 5 MHz AT cut thickness 333 microns 0 013 inch 6 MHz AT cut thickness 227 microns 0 0109 inch 9 MHz AT cut thickness 185 microns 0 007 inch 7 1 6 MASS SENSITIVITY The quartz crystal microbalance is an extremely sensitive sensor capable of measuring mass changes in the nanogram cm range with a wide dynamic range extending into the 100 ug cm range Sauerbrey was the first to recognize the potential usefulness of the technology and demonstrate the extremely sensitive nature of these piezoelectric devices towards mass changes at the surface of the QCM electrodes The results of his work are embodied in the Sauerbrey equation which relates the mass change per unit area at the QCM electrode surface to the observed change in oscillation frequency of the crystal Af Am where Af the observed frequency
31. a of the magnitude of the frequency error caused by imperfect capacitance cancellation For a 10 crystal a one picofarad capacitance imbalance results in a 0 018 degree phase error and a 0 0067 Hz frequency error For a 100 crystal the phase error is 0 18 degrees and the frequency error is 0 67 Hz For a 1000 crystal the phase error 15 1 8 degrees and the frequency error is 67 Hz For a 5000 Q crystal the phase error is 9 degrees and the frequency error is 1 635 Hz A two picofarad capacitance imbalance will result in approximately twice the above error 8 18 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATOR Frequency Error vs Crystal Resistance Freq Error due to a 5 pfd Frequency Error Hz Freq Error due to a 2 pfd ranaritanre Freg Error due to a 1 pfd capacitance Crystal Resistance ohm Figure 27 Frequency Error Due to Imperfect Capacitance Cancellation 8 9 CALCULATING CRYSTAL POWER Crystal power can be calculated as follows Crystal power Pery Rery Crystal current i Rs Ray Hence Poy i Ra Vo Rs Raj Ray Where Voc Open Circuit crystal drive voltage 125 mV R Crystal drive source resistance 20 ohms Rey Crystal resistance value in ohms Examples 1 Crystal Resistance
32. andall Self Assembled Monolayers on Gold Generated from Aliphatic Dithiocarboxylic Acids Langmuir 14 1998 6337 6340 12 Duan Lili and Garrett Simon J Self Assembled Monolayers of 6 Phenyl n hexanethiol and 6 p Vinylphenyl n hexanethiol on Au 111 An Investigation of Structure Stability and Reactivity Langmuir 2001 17 2986 2994 p E Hockberger et al Cellular engineering control of cell substrate interactions in Nanofabrication and Biosystems H C Hoch L W Jelinski and H G Craighead Eds Cambridge University press 1996 276 299 2 Buttry Daniel Applications of the to Electrochemistry in A Series of Advances in Electroanalytical Chemistry edited by Allen Bard Marcel Dekker 1991 p 23 33 2 C Lu and O Lewis Investigation of film thickness determination by oscillating quartz resonators with large mass load J Appl Phys 43 1972 4385 Martin Stephen J Spates James J Wesendorf Kurt O Thomas Schnneider and Robert J Huber Resonator Oscillator Response to Liquid Loading Anal Chem 69 1997 2050 2 Muramatsu H Tamiya Eiichi and Karube Isao Computation of Equivalent Circuit Parameters of Quartz Crystals in Contact with Liquids and Study of Liquid Properties Anal Chem 60 1988 2142 25 Geelhood S J Frank C W and Kanazawa K Transient Quartz Crystal Microbalance Behaviors Compared Journal of the Electrochemical Society 149 2002 H33
33. ce measurements are meaningful over the range of 0 0001 to 0 04 siemens a crystal resistance of 10 KO to 5 Q Two characteristics of the PLO limit the range of the conductance measurement The first is the zero drift of the demodulator and amplifier and determines the minimum measure able conductance This drift can amount to 0 00005 siemens The second characteristic is the non zero source impedance of the crystal drive voltage This source impedance 20 appears in series with the crystal resistance and the conductance output is proportional to the conductance of the crystal and source combination The equation for crystal resistance 15 Rery 100 Vcond 20 GENERAL DESCRIPTION 1 5 PLO 10 PHASE LOCK OSCILLATOR 1 3 SPECIFICATIONS 0 5 degrees Frequency error vs phase error and crystal Q Q 100 000 0 087 ppm per degree Q 10 000 0 87 ppm per degree Q 1 000 8 7 ppm per degree 010 40 millisicmen 010 50 C Controls Reset Switch Capacitance Adjustment Trimmer Course and Fine Indicators Green Lock LED Yellow Sweep Rate LED 125 mV rms 1 6 W x 3 2 H x 4 8 D 3 Ibs 1 6 GENERAL DESCRIPTION PLO 10 PHASE LOCK OSCILLATOR 1 4 ACCESSORIES Part Number Description 172205 CHT 100 Crystal Holder Teflon SMB Connector 173205 CHC 100 Crystal Holder CPVC BNC Connector 184204 CHK 100 Crystal Holder Kynar SMB Connector 828007 Cable SMB Plug SMB Plug I length RG17
34. chosen for its superior mechanical and piezoelectric properties and the angle of cut can be adjusted to obtain a zero temperature coefficient at a desired operating temperature The 1 inch diameter was chosen to allow enough distance between the active area of the crystal and the mounting o ring This improves the overall stability of the crystal by reducing the frequency changes due to mounting stress 7 1 1 ELECTRODE CONFIGURATION Figure 10 below shows INFICON 5 1 crystal electrode patterns The left figure shows the Y inch diameter front electrode also called sensing electrode with an extended electrode that wraps around the edge of the crystal and extends into a semicircle shown in the top half of the right figure The lower half of the right figure shows 4 inch diameter rear electrode also called contact electrode This configuration enables both electrical contacts to be made on the backside of the crystal allowing measurement in conductive liquids The oversized front electrode inch in diameter as oppose to inch diameter rear electrode was chosen to ensure a more consistence deposition across the active area of the crystal The exposed area of the front electrode is 0 212 in 137 mm but the active oscillation region displacement area is limited to the overlapping area of the front and rear electrodes 0 053 in or 34 19 mm CRYSTALS HOLDERS AND FLOW CELL 7 1 PLO 10 PHASE LOCK OSCILLATOR WRAP
35. current leads the voltage and the phase goes to 90 degrees as the frequency separation continues to increase see Figure 20 Above the resonant point the current lags the voltage and the phase go to minus 90 degrees As the frequency increases through the resonant frequency the phase goes from plus 90 through 0 to minus 90 It is interesting to note that the phase angle is 45 degrees when the VCO frequency 15 one half of the crystal s bandwidth above or below the crystal s resonant frequency The output of the phase detector is fed into an integrator The integrator accumulates the phase error such that any positive phase error causes the integrator output to climb a negative phase causes the integrator output to fall With zero phase error the Integrator output holds steady The integrator output is connected to the VCO Thus if the VCO frequency is initially below the crystal resonant frequency the phase will be positive producing a positive output at the phase detector This causes the Integrator output to climb which causes the VCO frequency to increase When the VCO frequency matches the resonant frequency of the crystal the phase will decrease to zero the phase detector output will go to zero the Integrator output will hold steady and the VCO frequency will be locked to the crystals resonant frequency If the crystal s resonant frequency moves up or down a phase difference between the crystal voltage and current will develop pro
36. cut quartz 0 095 kg sec V For example moving the crystal from air to pure water 20 Equation 7 and Equation 8 predict a decrease in f of 714 Hz and an increase in R of 357 4 respectively Note that at pure water 20 C has a density pr of 998 2 kg m and a viscosity nL of 1 002x10 N Excellent agreement between the frequency and resistance equations and the experimental results has been 2 making QCM an excellent tool for the evaluation of fluid properties Application examples include in situ monitoring of lubricant and petroleum properties The tight correspondence between theory Equation 7 and Equation 8 and the PLO is clearly illustrated by Figure 16 and Figure 17 respectively Note that some of the discrepancy in the resistance curve could arise from an error in estimating the active electrode area The PLO 10 utilizes the PLO technology which allows the sensor crystal to operate under heavy viscous loading INFICON Crystal Holders support operation in gas and liquid environments and provide single electrode exposure to liquids as required for compatibility with electrochemical QCM measurements The PLO 10 will maintain oscillation up to a series resonance resistance of about 5 It will support crystal operation in highly viscous solutions up to 88 weight percentage of glycerol THEORY OF OPERATION 8 5 PLO 10 PHASE LOCK OSCILLATOR 1000 2000 3000
37. d Unlock LED s The green Lock LED will come on when the capacitance is grossly out of adjustment Continue turning the course trimmer clockwise until the Unlock LED comes on The adjustment is getting close Press and hold the reset button Slowly continue to turn the trimmer clockwise until the yellow Sweep LED begins to flash If you continue to turn clockwise the Sweep LED will cease flashing but 4 2 CALCULATING CRYSTAL POWER PLO 10 PHASE LOCK OSCILLATOR this is not the point you want Back off the course adjustment until the flashing begins again then continue to the point where the flashing just stops The course adjustment is now complete Install a crystal into the holder Now depress and hold the Reset button Slowly adjust the fine trimmer clockwise until the flashing of the Sweep LED begins again and then back off until it just stops The capacitance compensation adjustment is now complete Release the Reset button and assuming the crystal is not dead or out of range the PLO 10 will lock on it 4 2 WORKING WITH VERY LOW Q CRYSTALS Very low Q crystals require very close adjustment of the compensating capacitance to insure a successful lock To adjust the compensation capacitance one pushes the Reset button and adjusts the capacitance to the point where the Sweep LED just ceases to flash With very low Q crystals the PLO may not lock upon release of the Reset button The Unlock LED will be on and the Sweep LED will be flashin
38. deposited 8 2 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATOR mass Notice that the units of the frequency constant for quartz is length time or velocity Also note that if the acoustic impedance ratio is equal to one quartz on quartz then Equation 4 reduces to Equation 3 8 3 THICKNESS CALCULATION Film thickness is often the parameter of interest in many QCM applications Thickness can be derived from Equation 4 as follows Jim m tan R ad Pr TR f where TK thickness of the film in cm Equation 5 Am change in mass per unit area in g cm calculated from the Lu and Lewis equation Pr density of film material in g cm If the period of oscillation is measured rather than the frequency l period can be substituted for frequency resulting in the following equation See INFICON TechNote RTK 101 for details discussion TK Pa R tanz Pr AR 5 where Period of unloaded crystal in seconds Equation 6 Period of loaded crystal in seconds Although the above equation still involves a number of simplifying assumptions its ability to accurately predict the film thickness of most commonly deposited materials has been demonstrated The basic measurement is period which can be thought of as a measurement of equivalent quartz mass The actual film mass on the crystal is then found by applying the acoustic impedance correction facto
39. ducing a phase detector output The non zero phase detector output will drive the Integrator output up or down until the phase is zero once again thus keeping the VCO frequency locked to the crystal s resonant frequency Once the frequency of the VCO is locked to the series resonant frequency of the GENERAL DESCRIPTION 1 1 PLO 10 PHASE LOCK OSCILLATOR crystal the in phase component at zero phase error there is no out of phase component of the crystal current is demodulated to a DC voltage The amplified output of the demodulator is provided at the Conductance output 1 1 FEATURES 1 1 1 VERY WIDE FREQUENCY RANGE The PLO 10 supports a wide frequency range from 3 8 to over 6 MHz It will support both 5 and 6 MHz crystals and with a low limit of 3 8 MHz it will support 1 2 MHz of frequency shift on a SMHz crystal Also available is the PLO 10 2 to support higher frequency crystals Its frequency range is 5 1 to over 10 MHz 1 1 2 SUPPORT FOR VERY LOW HIGHLY DAMPED CRYSTALS The PLO 10 will reliably lock to crystals with resistance of 5 KQ or less In most cases it will maintain lock up to a resistance of 10 It will support crystal oscillation in highly viscous solutions of more that 88 glycol in water 1 1 3 DIRECT REAL TIME MEASUREMENT OF CRYSTAL RESISTANCE The PLO 10 provides a de voltage output that is proportional to the crystal s conductance Conductance is the inverse of resistance Based on the measured conduc
40. e frequency values cross at half the resonance frequency s magnitude It is defined as f Q resonance frequency crystal Q A device that houses the crystal and provides connections to the crystal s electrodes via a coaxial connector A figure of merit used in describing the sharpness of the crystal response It is also called crystal quality factor Flexible or springy the property of immediately returning to its original size shape or position after being stretched squeezed flexed etc A compound containing only the elements carbon and hydrogen Water loving attracted to water molecules and polar molecules Water hating not attracted to water molecules or polar molecules Abbreviation for Inside Diameter Usually use in specifying a tube size in the form inch 1 D x inch O D where inch are the dimensions Pennwalt s registered trademark of Polyvinilidene Fluoride PVDF a homopolymer of 1 1 di fluoro ethene is a tough thermoplastic that offers unique properties including high chemical inertness low permeability to gases and liquids resistance to radiation and excellent mechanical strength and toughness Visit www atofinachemicals com for more detailed information An organic compound found in tissue and that is soluble in nonpolar solvents The mass of a mole of substance the same as molecular weight for molecular substances That amount of a substance containing the same number of units as 12 g of carbon 12
41. elects to refund the purchase price the equipment shall be the property of INFICON This warranty is in lieu of all other warranties expressed or implied and constitutes fulfillment of all of INFICON s liabilities to the purchaser INFICON does not warrant that the product can be used for any particular purpose other than that covered by the applicable specifications INFICON assumes no liability in any event for consequential damages for anticipated or lost profits incidental damage of loss of time or other losses incurred by the purchaser or third party in connection with products covered by this warranty or otherwise 4 INFICON www inficon com reachusQinficon com Table of Contents OPERATION AND SERVICE MANUAL sesseseevevneseenenseneenenseneenenseneenenneneenensenenseneenenseneenenneneenenseneenanseneenee I 1 GENERAL DESCRIPTION 1 1 1 1 EA TURES see 1 2 1 1 1 VERY WIDE FREQUENCY 1 2 1 1 2 SUPPORT FOR VERY LOW O HIGHLY DAMPED 1 2 1 1 3 DIRECT REAL TIME MEASUREMENT OF CRYSTAL 5 8 0202 1 2 1 14 ELECTRODE CAPACITANCE 1 2 1 1 5 1 2 1 1 6 CRYSTAL FACE ISOLATION PLO
42. ence between the crystal voltage and current will develop producing a phase detector output The non zero phase detector output will drive the Integrator output up or down until the phase is zero once again thus keeping the VCO frequency locked to the crystal s resonant frequency Once the frequency of the VCO is locked to the series resonant frequency of the crystal the in phase component at zero phase error there is no out of phase component of the crystal current is demodulated to a DC voltage 8 7 1 FREQUENCY ERRORS The first thing we want to know regarding the performance of the crystal measurement is What is the magnitude of the frequency error we can expect from the crystal measurement portion of the PLO 10 In any oscillator and sensing crystal system the error in the frequency measurement is a function of both the oscillator and the sensing crystal The same is true for phase locked loops Any phase error will introduce a frequency error and this frequency error will be inversely proportional to the sensing crystal s These errors are over and above any change in crystal frequency due to stress temperature adsorption and humidity changes There are four important parameters that determine the frequency error of the PLO and sensing crystal system or indeed any oscillator and sensing crystal system The first two the zero phase error and the electrode capacitance cancellation errors are characteristics of the PLO The
43. ent imaginary current real current And since current is proportional to conductance Effective Phase error arctangent imaginary conductance real conductance The conductance of a one picofarad capacitor at 5 MHz is 31 4 microsiemens The conductance of a ten ohm crystal at resonance is 100 millisiemens FREQUENCY ERRORS DUE TO IMPERFECT CAPACITANCE 5 1 CANCELLATION PLO 10 PHASE LOCK OSCILLATOR Effective Phase error arctangent 31 4 6 100 3 0 018 degrees In other words a one picofarad capacitance unbalance will result in an effective phase error of only 0 018 degrees when measuring a ten ohm crystal However when measuring a one thousand ohm crystal the effective phase error will increase to 1 8 degrees and it will increase to 9 degrees when measuring a five thousand ohm crystal Combining these two errors we can get an idea of the magnitude of the frequency error caused by imperfect capacitance cancellation For a 10 Q crystal a one picofarad capacitance imbalance results in a 0 018 degree phase error and a 0 0067 Hz frequency error For a 100 Q crystal the phase error is 0 18 degrees and the frequency error is 0 67 Hz For a 1000 Q crystal the phase error is 1 8 degrees and the frequency error is 67 Hz For a 5000 Q crystal the phase error is 9 degrees and the frequency error is 1 635 Hz A two picofarad capacitance imbalance will result in approximately twice the above error Frequency Error vs Crystal Resista
44. ent press and hold the Reset switch Pressing and holding the Reset switch forces the VCO to its minimum frequency turns on the Lock LED and turns off the quadrature current injector Forcing the VCO to its minimum frequency insures that the crystal is being driven at a frequency far from its resonant frequency where its impedance is essentially due only to the shunt electrode capacitance With the quadrature current injector turned off the measured current is due only to the net shunt capacitance The measured net shunt capacitance is the capacitance of the cable holder and crystal electrodes minus the compensation capacitance If the capacitance is under compensated the phase of the measured current leads the voltage a phase angle of plus 90 degrees If the capacitance is over compensated it lags the voltage a phase angle of minus 90 degrees The Yellow Sweep LED is used to determine whether the crystal capacitance is over compensated or under compensated The Sweep LED flashes whenever the crystal capacitance in under compensated If the Sweep LED is not flashing turn the fine compensation clockwise until it begins to flash then back up until it just stops If it is flashing turn the fine adjustment counter clockwise until it just stops flashing This is a very fine adjustment Go back and forth until you are sure you are right on the edge The sensitivity of the fine adjustment is approximately 0 05 pfd per degree In situations where
45. f High Q Crystal REF LEVEL DIV MARKER 4 987 964 DOOHz 0 0 20 000 REAL UDF 114 94E 3 0 0 20 DODE 3 MARKER 4 987 964 OOOHz IMAC UDF 5 8860 meme T LIT em SUSCEPTANCE PEA CONDUCTANCE X10 SIEMENS IMAGINE BANDWIDTH X10 SIEMENS RREN ere ye CIL LLL LIC EI puse O Fer HSA Exe ERES CENTER 4 987 964 DODHz SPAN 200 000Hz AMPTD 10 OdBm ds 80 60 40 Figure 21 Admittance vs Frequency Real and Imaginary Components of High Q Crystal THEORY OF OPERATION 8 11 PLO 10 PHASE LOCK OSCILLATOR When the above complex conductance is plotted in polar coordinates one obtains a circle as shown in Figure 22 The vector V indicates the magnitude and phase of the crystal current divided by the applied voltage The real part of the conductance is indicated by the vector and the imaginary part is indicated by the vector 1 FULL SCALE 200 00E 3 MARKER 4 987 966 SODHz PHASE REF Ddeg MAG UDF gt 115 66E 3 REF POSN 0 Odeg PHASE UDF gt D 092deg OSCILLATOR LOCK POINT OSCILLATOR PHASE ERROR OF 15 DEGREES FREQUENCY 4 987966 MHz RESISTANCE 8 60 BANDWIDTH 38Hz Q 130 000 ZERO PHASE ERROR LOCK POINT TRUE SERIES RESONANCE CENTER 4 987 964 000 2 SPAN 200 ODOHz AMPTD 10 OdBm Figure 22 Polar Admittance Plot of High Q Crystal 8 12 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATOR FULL SCALE 2 SODOE 3 MA
46. f the coaxial must connect to the front electrode and the center conductor must connect to the rear electrode of crystal In addition the coaxial cable must be free of kinks knots etc to avoid unbalanced capacitance in the cable Note that a one foot of well balance RG174A U coaxial cable has approximately 29 picofarads The total capacitance of the crystal the crystal holder and the cable must be within the PLO 10 s capacitance compensation limits between 40 and 200 7 4 FLOW CELL The FC 550 Flow Cell is designed to be used with any of INFICON s 100 series crystal holders The FC 550 is made from Kynar The cell has two stainless steel inlet and CRYSTALS HOLDERS AND FLOW CELL 7 13 PLO 10 PHASE LOCK OSCILLATOR outlet tubes with a 047 I D x 062 O D compatible with 0 062 I D tubing A Viton O ring provides sealing between the cell and the face of the sensor crystal The cell is used in place of the Crystal Retainer Ring Once installed in a probe it creates a flow chamber of approximately 0 1 mL CRYSTALS HOLDERS AND FLOW CELL PLO 10 PHASE LOCK OSCILLATOR 8 THEORY OF OPERATION Sauerbrey was the first to recognize the ability of the Quartz Crystal Microbalance QCM to measure very small mass changes on the crystal surface His seemingly simple equations have been used for many years and in many different applications 8 1 SAUERBREY EQUATION Equation 1 Af C x Am Where Af Freque
47. fail to fulfill any of these conditions actually exhibit more complicated frequency mass correlations and often require some calibration to yield accurate results 8 2 Z MATCH EQUATION Sauerbrey s original assumptions were of course questionable and indeed work with crystals heavily loaded with certain materials showed significant and predictable deviations between the measured mass and that predicted by Equation 3 Lu and Lewis analyzed the loaded crystal as a one dimensional composite resonator of quartz and the deposited film which led to the equation shown below which is also referred to as the Z Match equation Eras tan E TR 7 2 2 Am change mass per unit area in g cm Equation 4 where y Paka 2P N Frequency Constant for AT cut quartz crystal 1 668 x 10 Hz x cm Density of quartz 2 648 g cm fy Resonant frequency of unloaded crystal in Hz f Resonant frequency of loaded crystal in Hz Z Factor of film material FE Acoustic Impedance Ratio Hy p Density of material g cm shear modulus of quartz 2 947x10 g cm s shear modulus of film material in g em s This equation introduces another term into the relationship which is the ratio of the acoustic impedance of quartz to the acoustic impedance of the deposited film The acoustic impedance is associated with the transmission of a shear wave in the
48. g This is normal Even so it may be possible to lock on the crystal by slowly adjusting the fine capacitance counterclockwise until the Sweep LED again ceases to flash Lock is evidenced by the Lock LED turning on or by a value of greater than 8 millivolts at the Conductance output Once lock is achieved the true series resonant point can be found by adjusting the capacitance for maximum conductance The limits of the crystal bandwidth can be determined by adjusting the capacitance and reading the maximum frequency and the minimum frequency just before the PLO loses lock ADJUSTING THE CAPACITANCE CANCELLATION 4 3 PLO 10 PHASE LOCK OSCILLATOR 5 FREQUENCY ERRORS DUE TO IMPERFECT CAPACITANCE CANCELLATION There are two reasons that proper capacitance cancellation is so important with high resistance crystals The first is that to a first approximation the frequency error resulting from a given phase error is proportional to the bandwidth of the crystal The bandwidth of the crystal is proportional to the crystal s resistance A ten ohm crystal might typically have a bandwidth of 42 Hz while a one thousand ohm crystal will have a bandwidth of 4 200 Hz five thousand ohm crystal will have a bandwidth of 21 000 Hz Since the frequency error for a given phase error is proportional to the bandwidth a phase error that would result in a 0 5 Hz frequency error in a ten ohm crystal will cause a 50 Hz error in a one thousand ohm crystal and 250
49. he following guidelines are recommended for general handling of the sensor crystals Keep the crystals in a clean environment Store them in their original package until use Never handle the crystals with bare hands Always use plastic tweezers around the edge of the crystal during handling Do not touch the center of a sensor crystal as any oil dirt dust or scratches will quickly degrade the quality of the crystal When using a chemical agent to clean the crystal ensure that the crystal electrode material s will not be damaged by the chemical Never use cleaner that will etch the quartz surface Always rinse with deionized water or another appropriate pure liquid before drying the crystal Always use a flow of dry oil free non reactive gas e g filtered nitrogen to blow CRYSTALS HOLDERS AND FLOW CELL 7 7 PLO 10 PHASE LOCK OSCILLATOR dry the crystal It is better to chase liquid off the crystal than to let it evaporate off the crystal Never wipe the crystal even soft lint free cloth will scratch the crystal 7 2 1 CRYSTAL CLEANING The surface properties of the sensor crystal determine the interaction of sample material with the surface Therefore the developments of proper procedures for cleaning are required to obtain meaningful and reproducible measurements This section provides the basic information you need to develop a cleaning procedure suited to your sample surface preparation CAUTION Whe
50. holder to the PLO but don t install a crystal If the Sweep LED is flashing press and hold the Reset button and then turn the fine trimmer counter clockwise until it just stops flashing Go back and forth a few times to get a feel for the point where the Sweep LED just stops flashing Release the Reset button and the Sweep LED should begin to flash again Install a crystal The PLO should lock Even so press and hold the Reset button and again adjust the fine trimmer to the point where the flashing just stops The capacitance cancellation adjustment is now perfect Remember to check this adjustment whenever the crystal holder is moved or changed to a new environment If you could not find the proper zero capacitance point using the fine trimmer alone then we have found the following approach which is best for adjusting the coarse trimmer First adjust the fine trimmer so that it is 50 meshed and the rotor plates are below the shaft with the oscillator upright You can see these plates through the oversize adjustment hole See Figure 6 Next connect a cable and crystal holder if you haven t already done so Don t install the crystal at this point STATOR PLATES SILVER ADJUST 5 ROTOR PLATES GOLD o COARSE ADJUST STATOR PLATES ROTOR PLATES SILVER GOLD Figure 6 Capacitance Adjustments Do not press the reset button now slowly turn the course trimmer clockwise while watching the Lock an
51. ibrate the mass sensitivity of QCMs for electrochemical applications and for vacuum thin film deposition processes and some useful calibration guidelines are also described herein Many studies have shown that the crystal s sensitivity is approximately Gaussian The maximum sensitivity is in the center of the crystal and it tapers off towards the edge of the active area The mass sensitivity distribution has also been shown to become slightly more confined to the electrode region as the mass loading is increased 7 1 7 STABILITY A sensor crystal cannot distinguish the difference between a frequency shift due to deposited material or that due to other disturbances Thus any extraneous factors other than the deposited mass which may cause the quartz crystal to change its resonant frequency must be properly controlled Factors that can influence the stability of a sensor crystal are categorized as follows The crystal itself Improper design localized stress damage to the crystal The crystal holder Improper seating of the crystal large mechanical coupling between the crystal and the holder Thermal input Radiation from evaporation source radiation from substrate heater bombardment by charge particles energy released by condensates Stress Thermal stress stress release in the deposited materials Temperature See section 7 1 9 for data on frequency versus temperature for INFICON s crystals Other facto
52. ing of Surfaces in Treatise on Clean Surface Technology Vol 1 ed By K L Mittal Plenum Press 1987 p 1 26 Cohen Y Levi S Rubin S and Willner I Modified Monolayer electrodes for electrochemical and PZ analysis Novel immunosensor electrodes J ElectroAnal Chem 417 1996 65 Minunni M Guilbault G G and Hock B Quartz Crystal microbalance as a biosensor Anal Lett 28 1995 749 Patel Rupa Zhou R Zinszer K Josse F and Cernozek R Real time Detection of Organic Compounds in Liquid Environments Using Polymer coated Thickness Shear Mode Quartz Resonators Anal Chem 72 2000 4888 Stange T G et al STM and AFM Characterization of Polystyrene Spin coated onto Silicon Surfaces Langmuir 8 1992 920 5 Vig J R UV Ozone cleaning of surfaces A review in Surface contamination Genesis Detection and Control K L Mittal Ed Plenum Press NY 1979 Pages 235 253 16 Krozer A and Rodahl Michael X ray Photoemission spectroscopy study of UV ozone oxidation of Au under ultrahigh vacuum conditions J Vac Sci Technol A 15 3 1997 1704 REFERENCES 10 1 10 2 PLO 10 PHASE LOCK OSCILLATOR 17 Prime K L Whitesides G M Science 252 1991 1164 Prime K L Whitesides G M J A Model System Using Self Assembled Monolayers Am Chem Soc 1993 v 115 10714 10721 18 Colorado Jr Ramon Villazana Ramon J and Lee R
53. ion and collapse of minute cavities in a cleaning liquid For more information visit http www aqueoustech com images UltrasonicPrimer PDF Ultra Violet Ozone The UVO cleaning method is a photo sensitized oxidation process in which the contaminant molecules are excited and or dissociated by the absorption of short wavelength UV radiation Near atomically clean surfaces can be achieved using this method The basic instrumentation required this process includes a UVO chamber a gas oxygen supply or an exhaust system For more information visit http www jelight com uvo ozone cleaning htm PLO 10 PHASE LOCK OSCILLATOR VCO Voltage Controlled Oscillator An oscillator circuit designed so that the output frequency can be controlled by applying a voltage to its control or tuning port Viscoelastic Having or exhibiting both viscous and elastic properties Viscosity The internal friction of a fluid caused by molecular attraction which makes it resist a tendency to flow Viton DuPont Dow Elastomers registered trademark of Fluoroelastomer offers superior mechanical properties and resistance to aggressive fuels and chemicals well known for its excellent heat resistance Visit www dupont dow com viton for more detailed information GLOSSARY 9 3 PLO 10 PHASE LOCK OSCILLATOR 10 REFERENCES Martin Stephen et al Effect of Surface Roughness on the Response of Thickness Shear Mode Resonators in Liquids Anal Chem
54. n developing a cleaning procedure always perform a test run on a crystal before committing to a larger batch cleaning Follow the crystal handling guidelines throughout the cleaning process to protect the crystal quality Avoid using high pH cleaners since they will etch the crystal surface 7 2 1 1 General Cleaning For general purpose applications such as electrochemistry and liquid or viscoelastic film experiments 1t is usually sufficient to use ultrasonic cleaning method to clean the crystals in a solution of non basic detergent in deionized water Immediately rinse liberally with deionized water and dry in a gentle flow of filtered nitrogen gas 7 2 1 2 Organic hydrocarbon contaminants UV ozone treatment is a powerful tool for removing hydrocarbon impurities which have been adsorbed from the ambient air This method utilizes irradiation with ultra violet light that breaks up the organics on the surface of the sample being cleaned A flow of air or a weak vacuum carries off the organics This method does not affect the quartz surface it is low cost and is very efficient Oxygen plasma cleaning is another effective method that will remove organic matters In this method the plasma reaction breaks up organic matters at the surface of the sample being cleaned into smaller molecules and a vacuum pump removes them from the surface of the sample 7 2 1 3 Biomaterials lipids proteins and similar biomolecules Start by treating the cr
55. nce 100000 000 10000 000 1000 000 100 000 Freq Error due to a 5 pfd capacitance imbalance Frequency Error Hz o ct S Freq Error due to a 2 pfd capacitance imbalance 0 100 Freq Error due to a 14 1 pfd capacitance imbalance Crystal Resistance ohm Figure 7 Frequency Error Due to Imperfect Capacitance Cancellation 5 2 FREQUENCY ERRORS DUE TO IMPERFECT CAPACITANCE CANCELLATION PLO 10 PHASE LOCK OSCILLATOR 6 CALCULATING CRYSTAL POWER Using the PLO conductance voltage output crystal power can be calculated Refer to Section 3 CALCULATING CRYSTAL RESISTANCE crystal resistance Ray is given as 100 Veona 20 where Conductance Voltage Crystal power Poy i Ray Since lery Vsoc 20 Ray or 100 Hence Pay i Ray Veona 100 Vsoc 100 Veona 20 Pory Vio Veona 100 1 20 Veona 100 Vsoc Voltage of source open circuit 125 mV open circuit source voltage crystal drive Then Pery 0 125 Veona 100 1 20 V eona 100 Examples 1 Conductance output voltage 1 000 volt Pay in watts 0 125 1 100 1 20 1 100 1 25E watts or 125 wW 2 Conductance output voltage 0 015 volts Pay in watts 0 125 0 015 100 1 20 0 015 1
56. ncy change in Hz C Sensitivity factor of the crystal in Hz ng cm 0 0566 Hz ng cm for a 5 MHz crystal 20 0 0815 Hz ng cm for a 6 MHz crystal 20 C 0 1834 Hz ng cm for a 9 MHz crystal 20 C Am Change in mass per unit area in g cm The Sauerbrey equations assumed that the additional mass or film deposited on the crystal has the same acousto elastic properties as quartz This assumption resulted in a sensitivity factor Cr which is a fundamental property of the crystal as shown in equation 2 Equation 2 2nx f ENE Where n Number of the harmonic at which the crystal is driven Resonant frequency of the fundamental mode of the crystal in Hz Density of quartz 2 648 cm Effective piezoelectrically stiffened shear modulus of quartz 2 947 101 g cm sec Solving these equations for Am yields Equation 3 U Tp 2nx f Where THEORY OF OPERATION 8 1 PLO 10 PHASE LOCK OSCILLATOR Js Resonant frequency of unloaded crystal in Hz f Resonant frequency of loaded crystal in Hz It is important to note that under these assumptions the change in frequency is a function of mass per unit area Therefore in theory the QCM mass sensor does not require calibration However keep in mind that the Sauerbrey equation is only strictly applicable to uniform rigid thin film deposits Vacuum and gas phase thin film depositions which
57. nd jacketed cells It is always good practice to wait at least 30 minutes before performing any accurate measurements after the crystal comes in contact with a new medium This allows the crystal to come to equilibrium with the medium If temperature control is not possible or practical attempts should be made to measure the temperature of the solution around the crystal during the experiments and perform temperature compensation In short each PLO 10 user must determine the effect of temperature on the experiments being performed and either control the temperature accordingly or measure the temperature and compensate for it Freq Change vs Temp INFICON AT cut for 90C Delta Frequency Hz 0 10 20 30 40 50 60 70 80 90 100 110 120 Temperature C 7 6 CRYSTALS HOLDERS AND FLOW CELL PLO 10 PHASE LOCK OSCILLATOR Figure 12 Frequency vs Temperature of INFICON 1 AT Cut Crystal for 90 C Freq Change vs Temp INFICON AT cut for 25C 275 250 225 3 200 gt 175 5 150 125 100 75 50 25 0 25 0 10 20 30 40 50 60 70 80 90 100 110 120 Temperature Figure 13 Frequency vs Temperature of INFICON 1 AT Cut Crystal for 25 7 2 CRYSTAL CARE AND HANDLING It is essential that a sensor crystal is clean and free of foreign matter that may react with the experiment inducing errors in the measurements T
58. nternal coaxial cable CRYSTALS HOLDERS AND FLOW CELL 7 9 PLO 10 PHASE LOCK OSCILLATOR INDEX PIN POGO PIN CONNECTS TO BNC CENTER POGO PIN CONNECTS TO BNC HOUSING FEMALE BNC OR SMB JACK Figure 14 CHC 100 Crystal Holder 7 3 1 HOW TO INSTALL A CRYSTAL IN A INFICON CRYSTAL HOLDER 1 Identify the Front and Rear Sides of the crystal See Section 7 1 1 2 Clean amp Dry the Crystal Holder cavity then insert the Crystal with the Front Side Sensing Electrode exposed The Wrap Around Extended Electrode MUST be in the 60 region as in Figure 15 below 2 CRYSTALS HOLDERS AND FLOW CELL PLO 10 PHASE LOCK OSCILLATOR E 60 N HOLDER CRYSTAL Figure 15 Crystal Installation 3 Place the Retainer Ring over the Crystal with the Notch mating to the Index Pin 4 Mount and turn Retainer Cover approximately Y turn Then with a gloved finger or cotton swab gently press the Retainer Ring down at the Notch to make sure that it stays mated to the Index Pin Finish tightening the Cover until 1t s snug CRYSTALS HOLDERS AND FLOW CELL 7 11 PLO 10 PHASE LOCK OSCILLATOR 1 32 HOLDER CARE AND HANDLING With a robust design INFICON crystal holders require little care However the crystal holder is in direct contact with the sensor crystal and your experiment environment Thus care must be taken to ensure its cleanliness eliminating any contaminants that may react with the crystal or the experiment
59. o initial adjustments should be needed During normal operation with a crystal installed and connected to the oscillator the green Lock LED will be on and the frequency output will reflect the crystal resonance The red Unlock LED will be off If the Unlock LED is on Sweep Rate LED should slowly flash Continuous sweeping of the frequency range indicates that the crystal s resonant frequency is outside of the PLO s frequency range or the crystal s conductance is below the conductance threshold No flashing of the Sweep Rate LED when the Unlock LED is on can mean one of two things First if the VCO frequency is sitting at its low limit it means the electrode capacitance is over compensated Second in some cases even though the crystal conductance has fallen below the threshold necessary to indicate lock the internal signals are still sufficient to keep the VCO locked to the crystal In that case the PLO really is locked and the VCO frequency will be sitting at the crystal frequency somewhere between its minimum and maximum frequencies If the VCO frequency is sitting at its low limit press and hold the Reset switch and adjust the fine capacitance trimmer a few degrees clockwise not more than ten until the Reset LED begins to flash 22 CHECKOUT Make sure the wall mount power supply is specified for the voltage in your lab 120 240 volts UNDERSTANDING AND SETTING UP THE INFICON PLO 10 2 1 PLO 10 PHASE LOCK OSCILLATOR
60. only the deposited material is stripped and not the crystal electrodes The amount of times that a crystal can be reused greatly depends on its condition after each experiment or stripping Needless to say careful handling and cleaning of the crystal is required to maximize its re usability Noisy or erratic measurement indicates that the crystal is about to fail It might even be difficult to obtain a stable baseline Spurious signals might become evident in electrochemical QCM experiments Visually traces of consumption and wear can often be seen on the crystal surface Edges of the sensor crystal might become cracked and the deposited film even the electrode starts to show scratches and tears The crystal motional resistance R does reflect the influence of deposited material on the performance of a crystal This resistance is associated with the damping of acoustic waves by the electrodes deposited materials and the supporting structure This resistance increases as more material is being deposited onto the erystal This resistance value can be used to determine when a crystal reaches a maximum loading 7 1 9 TEMPERATURE COEFFICIENT The temperature coefficient of quartz crystals is normally specified in units of parts per million per degree of temperature change A one part per million change in frequency of the sensing crystal corresponds to an indicated thickness change of approximately 7 4 for a material with a density of 1 0 gm cm
61. osity and density of the liquid Kanazawa s solution for the change in resonant frequency of the crystal due to liquid loading is shown in Equation 7 3 Af f MP T Ha Pa Where fa Resonant frequency of unloaded crystal in Hz Equation 7 pa Density of quartz 2 648x103 kg m shear modulus of quartz 2 947x10 Pa p density of the liquid in contact with the electrode in kg m 7 viscosity of the liquid in contact with the electrode in N Sec m Liquid loading also dampens the resonant oscillation of the crystal causing an increase in series resonance resistance R of the crystal Afand AR measurements are both routinely used as independent indicators of mass loading and viscosity at the crystal liquid interface of the QCM resonator during chemical and electrochemical depositions in solution A Butterworth Van Dyke equivalent circuit model Figure 18 was applied to derive a linear relationship between the change in series resonance resistance AR of the crystal and 17 under liquid loading Using the relations in this study the change in resistance AR can be put in the form Equation 8 Af arlo n 2 f 32 4 o ex See Section 8 6 for a detail discussion 8 4 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATOR Where AR change in series resonance resistance in A active area of INFICON 1 inch crystal 3 419 10 m piezoelectric constant for an AT
62. quencies below the crystal s resonant frequency the current leads the voltage and the phase goes to 90 degrees as the frequency separation continues to increase see Figure 21 Above the resonant point the current lags the voltage and the phase go to minus 90 degrees As the frequency increases through the resonant frequency the phase goes from plus 90 through 0 to minus 90 It is interesting to note that the phase angle is 45 degrees when the VCO frequency is one half of the crystal s bandwidth above or below the crystal s resonant frequency The output of the phase detector is fed into an integrator The integrator accumulates the phase error such that any positive phase error causes the integrator output to climb a negative phase causes the integrator output to fall With zero phase error the Integrator output holds steady The integrator output is connected to VCO Thus if VCO frequency is initially below the crystal resonant frequency the phase will be positive producing a positive output at the phase detector This causes the Integrator output to climb which causes the VCO frequency to increase When the VCO frequency matches the resonant frequency of the crystal the phase will decrease to zero the phase detector output will go to zero the Integrator output will hold steady and the VCO frequency will be locked to the crystal s resonant frequency If the crystal s resonant frequency moves up or down a phase differ
63. r The Lu and Lewis equation is generally considered to be a good match to the experimental results for frequency changes up to 40 relative to the unloaded crystal Keep in mind that the Z match equation strictly applies to elastic lossless films Films which behave viscoelastically such as some organic polymer films with large thickness or viscosity will exhibit significant deviations from both Equation 3 and Equation 6 THEORY OF OPERATION 8 3 PLO 10 PHASE LOCK OSCILLATOR 8 4 LIQUID MEASUREMENTS QCMs have been used as gas phase mass detectors with lossless films for many years However only recently has their applications been extended to liquids and with viscoelastic deposits In these cases both frequency and series resonance resistance of the quartz crystal are important to completely characterize the material and or the liquid in contact with the crystal electrode The development of QCM systems for use in liquids opened a new world of applications including electrochemistry and micro rheology More recent developments have focused on tailoring electrode surface chemistry 1 e specialized polymer coatings so that these devices can be applied as discriminating mass detectors for many applications including specific gas detection environmental monitoring biosensing and basic surface molecule interaction studies When the QCM comes in contact with a liquid there is a decrease in frequency that is dependent upon the visc
64. ror per degree of phase error is given by the following formula Frequency Error Phase Error in radians Bandwidth THEORY OF OPERATION 8 17 PLO 10 PHASE LOCK OSCILLATOR Or Frequency Error 1 2 57 3 Phase Error in degrees Bandwidth For the above ten ohm crystal the frequency error caused by a one degree phase error is 42 114 6 or approximately 0 37 Hz For a one thousand ohm crystal one degree of phase error results in a 37 Hz error and for a ten thousand ohm crystal the frequency error is 370 Hz per degree of phase error Now the effective phase error caused by a non zero quadrature imaginary current is given by the following formula Effective Phase error arctangent imaginary current real current And since current is proportional to conductance Effective Phase error arctangent imaginary conductance real conductance The conductance of a one picofarad capacitor at 5 MHz is 31 4 microsiemens The conductance of a ten ohm crystal at resonance is 100 millisiemens Effective Phase error arctangent 31 4e 6 100e 3 0 018 degrees In other words a one picofarad capacitance unbalance will result in an effective phase error of only 0 018 degrees when measuring a ten ohm crystal However when measuring a one thousand ohm crystal the effective phase error will increase to 1 8 degrees and it will increase to 9 degrees when measuring a five thousand ohm crystal Combining these two errors we can get an ide
65. rrors below 10 degrees the frequency error is 0 087 PPM per degree for crystals with a Q of 100 000 Thus a one degree phase error in the PLO results in a 0 44 Hz frequency error for a SMHz crystal with a of 100 000 For a 5 MHz crystal with a Q of 10 000 the error is 10 time greater or 4 4 Hz per degree Frequency Error degree df f PI 360 Q 1 23 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION The effect of imperfect electrode capacitance cancellation can also be viewed as an equivalent phase error This error is directly proportional to crystal resistance The equivalent phase error due to a non zero shunt capacitance equal to 1 pfd is one degree for a crystal with a series resistance of 556 Q Since the equivalent phase error is proportional to the crystal resistance a 1 pfd residual capacitance error will result in a 10 degree equivalent error for a sensing crystal with a resistance of 5 56 GENERAL DESCRIPTION 1 3 PLO 10 PHASE LOCK OSCILLATOR Polar Plot of Crystal Conductance IMAGINARY AXIS DIRECTION OF INCREASING FREQUENCY 250 SIEMENS CRYSTAL WITH 4 pfd NET SHUNT CAPACITANCE N EFFECTIVE PHASE ERROR DUE TO NON ZERO SHUNT CAPACITANCE REAL AXIS 1 2 3 4 5 x 100 SIEMENS 4KQ CRYSTAL WITH 0 pfd NET SHUNT CAPACITANCE Figure 1 Equivalent Phase Error Due to Imperfect Capacitance Cancellation 1 4 GENERAL DESCRIPTION PLO 10 PHASE LOCK OSCILLATOR 1 24 CONDUCTANCE ERRORS Conductan
66. rs that can affect stability are humidity shock vibration and change in pressure Controlling those conditions is a must to insure accurate measurements of 7 4 CRYSTALS HOLDERS AND FLOW CELL PLO 10 PHASE LOCK OSCILLATOR small mass changes over long periods of time 7 1 8 CRYSTAL LIFE EXPECTANCY It is difficult to predict the useful life of a crystal since it depends on many factors Some of these factors The quality of the quartz The amount of deposited material The stress generated in the crystal due to deposited material The acoustic losses in the deposited material The design of the oscillator circuitry Other aspects that affect the crystal life include the type of the deposited material splitting of source material resulting in non uniform films film flakes that landed on the crystal s active area and of course physical damage to the crystal such as chipping cracking or peeling of the electrode etc In general a sensor crystal can be used until its frequency drops below 50 of its uncoated value However for the reasons stated above crystal failures often occur well before a 40 shift in frequency is reached The sensor crystals are considered expendable However a crystal may be reused up to 20 times on average in experiments that don t physically alter the crystal electrode In experiments where a film is deposited the crystal can be stripped using a chemical etchant Care must be taken so
67. second two are characteristics of the crystal the Q of the crystal and the conductance 1 resistance of the crystal 8 16 THEORY OF OPERATION PLO 10 PHASE LOCK OSCILLATOR 8 7 2 FREQUENCY ERROR DUE TO PHASE ERROR Given some finite zero phase error the resulting frequency error depends on the sensing crystal s the higher the the lower the error For phase errors below 10 degrees the frequency error is 0 087 PPM per degree for crystals with a of 100 000 Thus a one degree phase error in the PLO results in a 0 44 Hz frequency error for a SMHz crystal with a Q of 100 000 For a 5 MHz crystal with a Q of 10 000 the error is 10 time greater or 4 4 Hz per degree Frequency Error deg df f 1 360 Q 8 7 3 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION The effect of imperfect electrode capacitance cancellation can also be viewed as an equivalent phase error This error is directly proportional to crystal resistance The equivalent phase error due to a non zero shunt capacitance equal to 1 pfd is one degree for a crystal with a series resistance 556 Since the equivalent phase error is proportional to the crystal resistance a 1 pfd residual capacitance error will result in a 10 degree equivalent error for a sensing crystal with a resistance of 5 56 8 8 FREQUENCY ERRORS DUE TO IMPERFECT CAPACITANCE CANCELLATION There are two reasons that proper capacitance cancellation is so important with high resistance cr
68. side the sockets are removed o Generously rinse the Pogo contact pins with deionized water occasionally squeeze the pins to push out any liquids that may have been trapped inside the pins Thoroughly blow dry the pins using filtered air o Install the Pogo pins back into their sockets Use the tip of a pair of tweezers and push down on each PogoQ pins to verify their deflection 7 3 3 CONSIDERATIONS FOR BUILDING YOUR OWN HOLDER You MUST consider the following aspects when building your own crystal holder The holder must be designed so that when a crystal is installed its front electrode sensing electrode is connected to the housing shell of the SMB Crystal Connector on the PLO 10 and the rear electrode is connected to the center pin of the SMB Crystal Connector The crystal should be clamped as close as possible to the edge of the crystal to avoid damping of the crystal s oscillations The holder clamping mechanism should have a positive stop to avoid excessive clamping force on the crystal If the crystal is to be used in a conductive fluid or conductive gas the rear electrode must be sealed from the conductive environment to avoid an electrical short between the electrodes The electrodes should be designed so the rear electrode and the electrodes contacts can be sealed Only the front electrode should be exposed The connecting cable must be coaxial all the way from SMB on the PLO 10 on up to the crystal The shield o
69. tance output voltage the crystal resistance is easily calculated 1 14 ELECTRODE CAPACITANCE CANCELLATION The total quartz crystal impedance includes a shunt capacitance due to the capacitance of the crystal electrodes and holder in parallel with the series resonant arm The total current through the crystal is the sum of the current through the shunt capacitance plus the current through the series resonant arm The physical motion of crystal is reflected in the values of L and C in the series arm of crystal only and therefore we want to subtract out or otherwise cancel the current through the shunt electrode capacitance The INFICON PLO includes a method of canceling the electrode capacitance insuring that the measured crystal current does not include the current through the electrode capacitance and therefore is essentially the current through the series resonant arm of crystal only 1 15 AUTOLOCK When the PLO 10 loses lock the VCO is ramped up to the maximum frequency at which time it is automatically reset to the minimum frequency and a new scan is initiated To insure that the VCO ramps up in frequency a small amount of quadrature current is injected into the current to voltage buffer whenever the PLO is unlocked This current is equivalent to a shunt capacitance of about 1 5 pfd As soon as lock is detected the quadrature current is turned off 1 2 GENERAL DESCRIPTION PLO 10 PHASE LOCK OSCILLATOR 1 1
70. the crystal resistance is very high over 1 KQ a net capacitance of over 0 5 pfd can result in a significant frequency error so try to get this adjustment to within a couple of degrees Remember to keep the Reset switch depressed while making this adjustment 4 1 ADJUSTING CAPACITANCE CANCELLATION TRIMMER CAPACITORS Setting up the capacitance cancellation is fairly straightforward The thing to remember is that there are two variable capacitors a course and a fine with the total compensation capacitance being the sum ofthe two These trim capacitors have no stops so it s not obvious when they are at their minimum or their maximum The capacitors have circular rotor plates that mesh into fixed stator plates The capacitance is at a maximum when the plates are fully meshed and a minimum when rotor plates are above the stator plates and not meshed As the capacitors are rotated clockwise they go through a full cycle from maximum to minimum and back to maximum Or depending on where you start they may go first toward a minimum then to a maximum and then back toward a minimum To avoid confusion we always want to be turning clockwise as we approach the desired capacitance and we want the capacitance to be decreasing ADJUSTING THE CAPACITANCE CANCELLATION 4 1 PLO 10 PHASE LOCK OSCILLATOR If you are using a crystal holder and cable supplied with your PLO 10 then you should not have to change the course adjustment Connect the cable and crystal
71. to choose from Contact us if you don t see one that fits your needs If you choose to do your own crystal surface modification use the following guidelines 7 2 2 1 SPIN COATING Thin films nm to microns of polymers and other materials can be applied by spin coating Polystyrene is a common material spin coated on QCM sensor crystals UV Ozone treatment can be used to change the hydrophobicity of organic polymeric coatings 7 7 2 2 2 SELF ASSEMBLED MONOLAYERS SAM Self assembling monolayers can be laid down on gold or silver surface by thiolization 18 or on SiO by silanization to control surface properties 7 2 2 3 PHYSICAL VACUUM DEPOSITION PVD Thin films of metals or metal oxides can be applied by sputtering or thermal evaporation in a vacuum chamber To ensure quality and reproducible films careful attention to cleanliness must be observed both in the vacuum chamber and in the preparation of the crystals prior to coating INFICON is an expert in PVD Consult us for any special needs 7 3 CRYSTAL HOLDERS Figure 14 shows a INFICON CHC 100 Crystal Holder without a crystal the crystal retainer or the retainer cover It has a cavity for a 1 inch diameter crystal Inside the cavity there are two Pogo pins providing connections to the crystal s front and rear electrodes Note the locations of the Pogo pins These pins are internally connected to the BNC connector SMB Jack for CHT 100 and CHK 100 holders via an i
72. www inficon com Copyright 2000 All rights reserved Reproduction or adaptation of any part of this document without permission is unlawful First Edition February 2000 Revision A May 2000 Revision October 2000 Revision December 2001 Revision D March 2003 Revision E February 2005 Revision F October 2007 Revision G November 2007 WARNING All standard safety procedures associated with the safe handling of electrical equipment must be observed Always disconnect power when working inside the controller Only properly trained personnel should attempt to service the instrument Warranty INFICON warrants the product to be free of functional defects in material and workmanship and that it will perform in accordance with its published specification for a period of twenty four 24 months The foregoing warranty is subject to the condition that the product be properly operated in accordance with instructions provided by INFICON or has not been subjected to improper installation or abuse misuse negligence accident corrosion or damage during shipment Purchaser s sole and exclusive remedy under the above warranty is limited to at INFICON s option repair or replacement of defective equipment or return to purchaser of the original purchase price Transportation charges must be prepaid and upon examination by INFICON the equipment must be found not to comply with the above warranty In the event that INFICON
73. ystal in an UV ozone chamber for 10 minutes then immerse it into a 1 1 5 solution of hydrogen peroxide 3096 ammonia 25 and deionized water heated to a temperature of about 75 C for 5 minutes 22 Immediately rinse liberally with deionized water and dry in a gentle flow of nitrogen gas Immediately before measurement treat the crystal with UV ozone for 10 minutes 7 2 1 4 Lipid vesicles on SiO surfaces Treat the crystal in an UV ozone chamber for 10 minutes then immerse it into water with 2 of sodium dodecyl sulfate SDS at room temperature for 30 minutes 23 Rinse generously with deionized water and blow dry with filtered nitrogen gas Immediately before measurement treat the crystal with UV ozone for 10 minutes 7 8 CRYSTALS HOLDERS AND FLOW CELL PLO 10 PHASE LOCK OSCILLATOR 7 2 1 5 Polystyrene removal To clean polystyrene PS off a crystal immerse the crystal into a 1 1 solution of hexane and deionized water and treat it in an ultrasonic bath for I minute Rinse thoroughly with deionized water and blow dry with filtered nitrogen gas 7 22 ELECTRODE SURFACE MODIFICATIONS A QCM will response to anything that has mass Thus it is imperative for the QCM user to develop a condition where the QCM will only responsed to the substance of interest This usually involves a chemically or biologically sensitive layer applied to the surface of the crystal INFICON offers a wide variety of standard electrode materials for you
74. ystals The first is that to a first approximation the frequency error resulting from a given phase error is proportional to the bandwidth of the crystal The bandwidth of the crystal is proportional to the crystal s resistance A ten ohm crystal might typically have a bandwidth of 42 Hz while a one thousand ohm crystal will have a bandwidth of 4 200 Hz A five thousand ohm crystal will have a bandwidth of 21 000 Hz Since the frequency error for a given phase error is proportional to the bandwidth a phase error that would result in a 0 5 Hz frequency error in a ten ohm crystal will cause a 50 Hz error in a one thousand ohm crystal and 250 Hz error in a five thousand ohm crystal The second reason is that the effective phase error caused by a non zero net quadrature current is inversely proportional to the real current which is inversely proportional to the crystal resistance In other words the effective phase error is proportional to the crystal resistance For instance a net unbalance of 1 pfd leads to an effective phase error of 0 02 degrees for a ten ohm crystal but it leads to a 2 degree error for a one thousand ohm crystal and a 10 degree error for a five thousand ohm crystal Examples A ten ohm 5 MHz crystal will have a Q Quality Factor of about 120 000 The bandwidth is equal to the crystal frequency divided by Q Thus the bandwidth of this crystal would be about 42 Hz To a first approximation near zero phase the frequency er

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