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EA 125 Energy Analyser User's Guide

1. EAC300 PASS ENERGY PCB j lo 1044 05 ISSUE 4 Figure 29 EAC adjustment potentiometers Upper section position of RV 1 on EAC 2000 outer card lower section position of RV 5 on the EAC 300 inner outer cards After you have found equal peak energies for the pass energies if possible check also the energy positions of some other lines in the spectrum For example you could measure a survey spectrum e g from 100 eV to 1300 eV kinetic energy step 0 5 eV pass energy 70 eV Cross check the peak positions with reference to Table 7 on page 62 the differences should not be much larger than 1 eV It is not worthwhile making a more accurate comparison of the peak energies as the measured values can be changed by different methods of sample preparation chemical shifts etc and there are many differences in the published values of peak energies in the literature Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 65 EA 125 Energy Analyser User s Guide Preamplifier Threshold Adjustment July 2002 SN Please note Read these instructions thoroughly before starting this test procedure Attention Ensure that the multipliers are switched off before carrying out this procedure Never remove the front panel with the multiplier HV switched on Up to 3 6 kV are present inside the unit Please note Due to the sensitivity of the circu
2. T Oo O 450k ull Ip NEBEN esse DE EN 08 eet DE L b 2 Ag4p S Ag 3p Mg K i Mg KO Mg Ke Ag4d S0k a es Lee dio ee pM CuL9 Ag 3d f i Al KO Ag 3d CuLo v ye eee ee ee nee Ln Edi pee e ando nd EPETEE EEE peer Serene Mrppusun utin E 200 400 600 800 1000 1200 Kinetic Energy eV Figure 25 Analyser test dirty XPS spectrum Figure 26 shows a similar spectrum taken with a new X ray source The absence of the C and O 1s lines indicates a cleaner sample and the absence of any ghost peaks indicates an uncontaminated anode 1000k4 M delLeeelell Hanne SE E t ERR tll d t 800kl X M e u j o n 5 c ao E f i Pet asien A E eE SE Kasten 200k disriescisisseczle F E en EEE EE ERARE 0t C er RE E E m EE Podesecetesscesess Bas sarsasln else 200 400 600 800 1000 1200 Kinetic Energy ev Figure 26 Analyser test clean XPS spectrum The flux of X rays emitted from the source is sometimes reduced due to a build up of sputtered material onto the Al window Obviously this also reduces the observed intensity Wy Omicron July 2002 Nano Technology Version 2 1 8 Typical Experiments Factory Tests 52 EA 125 Energy Analyser User
3. EA125 ANALYSER LENS SCREENS EA125 ANALYSER LENS SCREENS FOR CHAMBERS FOR STANDARD OMICRON FOR STANDARD OMICRON MUMETAL CHAMBERS MUMETAL CHAMBERS WITHOUT MUMETAL SCREENS Mu metal shielding for EA 125 and EA 125 HR analyser lens all Figure 5 dimensions in mm v Omicron Version 2 1 NanoTechnology July 2002 4 Unpacking and Installation 19 EA 125 Energy Analyser User s Guide 4 Unpacking and Installation EA 125 Analyser Supplied as a Component Please note This Chapter is intended primarily for the user supplied with an EA125 analyser as a component but the information will be useful to all users who have to remove an EA 125 from a system and subsequently refit it The EA 125 analyser vacuum hardware is shipped on a four wheeled shipping frame and contained in a wooden crate 88 cm x 72 cm x 110 cm 165 kg separate from the electronics crate 83 cm x 78 cm x 67 cm 72 kg Attention All OMICRON instruments have been carefully packed before leaving the factory Before unpacking please inspect the transport case for damage If any damage can be seen or a rattling noise can be heard when moving the boxes do not unpack and contact your local OMICRON agent immediately Please note All parts are clean to vacuum standards e Always use suitable polythene or cotton gloves for handling e Lift the analyser only by the large flange using the supplied handles e Take great care when unpacking especi
4. eeeeees 16 47 wiring electronics 25 resolution and operating parameters analyser eost inu 47 X retarding Tallo oorr emere 40 XPS test analyser 50 Ola y ANNE o tents iE cet teme bue iens 15 Z S zoom ENS tee 38 SAG CANA SITZE rennen 10 zoom lens curve nnnnsnneennneneennnnn 39 safety information 4 11 July 2002 Womicron Version 2 1 Decontamination Declaration 86 EA 125 Energy Analyser User s Guide Decontamination Declaration If performing repair or maintenance work on instruments which have come into contact with substances detrimental to health please observe the relevant regulations If returning instruments to us for repair or maintenance work please follow the instructions below Contaminated units radioactively chemically etc must be decontaminated in accordance with the radiation protection regulations before they are returned Units returned for repair or maintenance must bear a clearly visible note free from harmful substances This note must also be provided on the delivery note and accompanying letter Please use the attached attestation declaration at the end of this manual Harmful substances are defined in European Community Countries as materials and preparations in accordance with the EEC Specification dated 18 September 1979 Article 2 and in the USA as materials in accordance
5. Find 3 Find peaks Fina To identify the elements present we press the FIND button and choose a FWHM of 3 and a sensitivity of 2 That delivers a list of 20 peaks Which peak fitting and background subtraction method should be used There is a lot of refinement in defining the right background procedure A linear background subtraction is the least necessary A Shirley background helps to eliminate contributions to the data from the scattering of low energy electrons A Tougaard background gives higher accuracy than Shirley The amount of work increases from linear to Tougaard and the result still varies on choices you have to make about the peak shape parameters To keep it simple with acceptable accuracy we recommend to use the automatic peak finding routine Only if necessary when peaks start to overlap the peak fitting submenu is required Peak List 537 5 25190 1090 24820 108 5 4435 4 Identify and Select Peaks 3 290 An overview spectrum has been acquired Identify the peaks with help of a database For the quantification select one peak of each element or chemically shifted species Working through the list by pressing n on the Name column we identify the elements a suggestions from a database comes up for us to choose from This selection automatically invokes a concentration display which includes already the element specific sensitivity factor We select just one convenient XPS peak per element The
6. WOomicron LL NanoTechnology EA 125 Energy Analyser User s Guide Version 2 1 July 11 2002 Limburger Stra e 75 65232 Taunusstein Germany Tel 49 0 6128 987 0 Fax 49 0 6128 987 185 Preface 2 EA 125 Energy Analyser User s Guide Preface This document has been compiled with great care and is believed to be correct at the date of print The information in this document is subject to change without notice and does not represent a commitment on the part of OMICRON NanoTechnology GmbH Please note Some components described in this manual may be optional The delivery volume depends on the ordered configuration Please note This documentation is available in English only Attention Please read the safety information on pages 11 to 12 QD before using the instrument Trademarks Channeltron is a registered trademark of Galileo Electro Optics Corporation Viton is a registered trademark of DuPont Dow Elastomers Kapton is a registered trademark of DuPont Films Swagelok is a registered trademark of the Crawford Fitting Company MULTIPROBE ESCAPROBE and MULTISCAN LAB are registered trademarks of OMICRON NanoTechnology GmbH Other product names mentioned herein may also be trademarks and or registered trademarks of their respective companies Table 1 Related manuals Vy Omicron July 2002 Nano Technology Version 2 1 Preface 3 EA 125 Energy Analyser User s Guide Copyright No part o
7. Potentiometer Mains On Off o J Mains Input Cable Figure 11 Connection diagram upgradable and multi channel detection FB Channeltron front bias C central Channeltron channel 1 11 12 13 inner Channeltron s O1 O2 O3 outer Channeltron s Vy Omicron July 2002 Nano Technology Version 2 1 5 Getting Started 30 EA 125 Energy Analyser User s Guide Setting up the Software Please refer to the EIS Software manual for more details Fit the Omicron SAC and ComputerBoards IEEE cards into the PC Install the Omicron SAC Device Driver if necessary the ComputerBoards GPIB Library and the EIS program from the EIS CD The Shutdown and restart the computer Configure the GPIB card to control an EAC 2000 or EAC 300 using the cbconf32 exe configuration program Configure EIS for your system i e Set the analyser controller and detector types in the Configuration dialogue box in EIS For Multi channel Analysers Only Set the energy dispersion factors A print out of these is supplied with your EA 125 test data The software should now be set up to start a measurement For further details on how to do this please refer to the EIS Software manual July 2002 Vy Omicron NanoTechnology Version 2 1 6 Operation 31 EA 125 Energy Analyser User s Guide 6 Operation Assuming a suitable excitation source and sample in an appropriate geometry are available and when the vacuum press
8. m zZ W A S Ei c EK h ps E 9a fringe field plate pass energy potential c j vacuum level R e n A D np i S 1 EARTH POTENTIAL SEES Fermi level of sample and first lens element o o E3 Eb e o E a SAMPLE b SPECTRUM c ANALYSER Figure 14 Workfunction of the sample and spectrum of electrons ejected by X rays Although the true kinetic energy of the electron leaving the sample Ex depends on the work function of the sample ps the measured kinetic energy Ex only depends on the work function of the analyser a The energy distribution of electrons has the following features Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 36 EA 125 Energy Analyser User s Guide e The spectrum low energy cut off is at Ek s Below this energy electrons have insufficient kinetic energy to overcome the work function of the sample however this may be overcome by biasing the sample e A large peak at low kinetic energy is due to the true secondary electrons e The centre of the spectrum has peaks corresponding to the discrete states from which the electrons are ejected e The high energy cut off occurs when electrons are ejected from the Fermi level where E is defined to be zero i e at E hv Os Note that the true kinetic energy scale cannot be measured directly because s which varies from sample to sample is not known only the quantity Ej ds can be determined
9. the power supplies before connecting or disconnecting any cables Make sure all high voltage plugs are secured before switching any one of the electronics units on e Ensure all units are off and disconnected from the mains supply before making the connections as shown in Figure 9 e Before making the connections check the resistance of all pins to each other and to earth ground Resistance should be infinite except across the channel electron multiplier e Connect all channeltron pulse counting cables according to Figure 10 for non upgradable single channel systems and according to Figure 11 for upgradable single channel and multi channel systems e Connect all other cables to the analyser EAC power supply and computer according to their manuals e Ensure the preamplifier is firmly attached to the mounting on the EA 125 flange in order to be properly grounded Attention All connectors which were originally supplied with fixing screws must always be used with their fixing screws attached and tightly secured e Plug in all units and switch on the EAC 2000 300 power Setting up the Pulse Counting Electronics Please note For full details for the pulse counting electronics please refer to the CPC 125 65 M manual for upgradable and multi channel systems and the CPC 125 65 S manual for single channel systems as listed in Table 1 on page 2 It is advisable to bake out the vacuum system prior to operation Atten
10. 3 Channeltron multiplier power supplies 4 Pulse preamplifier 5 Receiver 6 PC with EIS software Vy Omicron July 2002 Nano Technology Version 2 1 5 Getting Started 25 EA 125 Energy Analyser User s Guide FILTERED PLUG VACUUM IEEE CABLE OPTICALLY COUPLED VACUUM FEEDTHROUGH OPTICALLY COUPLED Figure 9 Electronics wiring overview for EA 125 The Channeltron multiplier power supply unit generates up to 3 6 kV and is switched ON OFF remotely from the EAC 2000 300 with slow start up This link is optically de coupled A pulse preamplifier detects electron pulses and filters out the system ground noise using a high speed comparator circuit with adjustable threshold for background noise rejection The electrical signal is converted to an optical signal within the preamplifier unit and then transmitted to the receiver via a 5 m long optical fibre link Both pulse TTL and analogue signal outputs are provided The digital TTL output pulses are input into the pulse counter board the analogue voltage output is proportional to count rate and is provided for a user supplied DVM or X Y recorder Vy Omicron July 2002 Nano Technology Version 2 1 5 Getting Started 26 EA 125 Energy Analyser User s Guide Attention Installation procedures may only be carried out by authorised personnel qualified to handle lethal voltages Switch off all units and wait for a few minutes for discharge of
11. CEM supplies e Locate the HV adjust pot on the relevant CEM HV unit See CPC 125 65 Manual Vy Omicron July 2002 Nano Technology Version 2 1 6 Operation July 2002 34 EA 125 Energy Analyser User s Guide Turn it counter clockwise until the count rate reduces to close to zero Increase the high voltage by turning the HV adjust pot clockwise until the channeltron is operating at the desired voltage Repeat for remaining channels until all channeltrons are operating at the desired voltage Replace the top panel on the CEM supplies Replace the CEM supplies into the equipment rack Vy Omicron NanoTechnology Version 2 1 7 Theory of Operation 35 EA 125 Energy Analyser User s Guide 7 Theory of Operation The following discussion is by no means exhaustive It is merely meant to define the relevant parameters in analyser operation Further details can be found in textbooks on electron spectroscopy see page 82 for a selective list Radiation of wavelength hv ejects electrons from electronic states with different binding energies in the sample leading to a range of ejected electron kinetic energies If the sample is at earth potential electrons ejected from a state with binding energy E are emitted from the sample with a true kinetic energy Ex given by Ek hv E 0 where 9 is the work function of the sample A schematic spectrum of electrons ejected by X rays is shown in Figure 14 gt O c
12. EA 125 Energy Analyser User s Guide 1 Introduction EA 125 Spectrometers This manual is a guide to the installation setting to work and operation of the vacuum electronic and computer hardware for an EA 125 Energy Analyser and includes information on experimental procedures to assist the new user The EA 125 Energy Analyser forms part of a complete EA 125 hemispherical spectrometer system for XPS AES UPS ISS and synchrotron applications featuring an energy resolution better then 10 meV FWHM 6 meV in the high resolution EA 125 HR versions a multi element universal lens with selectable analysis area and acceptance angle Channeltron pulse counting with gt 10 Mcps count rate per channel a kinetic energy range up to 2000 eV and data acquisition and analysis software More detailed information about the channeltron detection systems electronics computer hardware and software may be found in the related manuals in Table 1 on page 2 Throughout this manual the word electrons is used to denote electrons or ions unless the description specifically relates to electrons such as in the section on the operation of the channeltron electron multipliers EA 125 Vacuum Hardware The vacuum hardware of the EA 125 Energy Analyser comprises 1 a multi element electrostatic lens with 30 mm working distance to collect electrons from the sample and focus them on the entrance of the hemispherical energy analyser The lens may also accelerate o
13. FWHM eV 0 70 0 85 0 25 0 006 0 003 Table 6 Characteristic photon line widths Typical measured peak widths for XPS can be derived as shown by the following example taking typical values of E 0 7 eV for Mg Ka En 0 3 eV for a core level electron Ea 0 6 eV analyser energy resolution to give Em the resulting measured peak width as Em 1 0 eV Vy Omicron July 2002 Nano Technology Version 2 1 8 Typical Experiments Factory Tests 49 EA 125 Energy Analyser User s Guide 8 Typical Experiments Factory Tests This section is aimed at providing an inexperienced user tips on running some typical experiments The experiments described are those used to test the EA 125 in the Omicron factory prior to shipment Standard analysers are tested for XPS and AES and high resolution HR analysers are also tested for HRUPS Analysers purchased with an EAC 2000 ISS control unit are further tested for ISS and those purchased with an X ray monochromator are tested for monochromated XPS For further details of these please refer to the related manuals listed in Table 1 on page 2 Vy Omicron July 2002 NanoTechnology Version 2 1 8 Typical Experiments Factory Tests 50 EA 125 Energy Analyser User s Guide X ray Photoelectron Spectroscopy XPS The factory XPS tests consist of running a series of experiments with a Mg anode X ray source and an Ar ion etched polycrystalline Ag sample Various maximum inten
14. Once the set up has been optimised low intensity is usually caused by a dirty sample or a poor X ray source The cleanliness of the sample surface is checked by looking for the presence of the Carbon 1s and Oxygen 1s lines The quality of the X ray source is checked by looking for the presence of ghost peaks These are peaks which arise from different X ray excitation energies from contaminants on the anode These may include O Ka at 524 9 eV from oxidation of the anode or Cu La at 929 7 eV from the substrate following degradation of the anode In twin anode laboratory sources cross talk is often observed resulting in small ghost peaks corresponding to the different excitation energy Ghost peaks can be easily identified using the EIS element library with the excitation energies of the suspected X ray contaminants Please see the EIS Software Manual The presence of ghost peaks from O Ka usually confirms oxidation of the anode a condition which can also broaden the characteristic X ray line width Figure 25 shows an XPS broad survey scan taken with a contaminated Mg anode X ray source and a dirty Ag sample All of the expected peaks are observed but also small C 1s and O 1s peaks indicating that the sample is not clean There are also ghost peaks due to O Ka and Cu La X rays Vy Omicron July 2002 NanoTechnology Version 2 1 8 Typical Experiments Factory Tests 51 EA 125 Energy Analyser User s Guide
15. User s Guide 2 Safety Information A Important Please read this manual and the safety information in all related manuals before installing or using the instrument Please read this manual and the safety information in all related manuals before installing or using the electronics equipment The safety notes and regulations given in this and related documentation have to be observed at all times Check for correct mains voltage before connecting any equipment Do not cover any ventilation slits holes so as to avoid overheating The EA 125 Energy Analyser may only be handled by authorised personnel AN Warning Lethal Voltages Adjustments and fault finding measurements may only be carried out by authorised personnel qualified to handle lethal voltages Lethal voltages are present inside the filtered plug EAC 2000 125 EAC 300 125 and parts of the instrument during operation Lethal voltages are present at unconnected plugs July 2002 A Always All connectors which were originally supplied with fixing screws must always be used with their fixing screws attached and tightly secured Always disconnect the mains supplies of all electrically connected units before venting pumping down or opening the vacuum chamber opening a control unit case c touching any cable cores or open connectors c touching any part of the in vacuum components Leave for a few minutes after switching off for any
16. Vy Omicron July 2002 Nano Technology Version 2 1 5 Getting Started 24 EA 125 Energy Analyser User s Guide 5 Getting Started Bakeout dg Please note Bakeout is generally recommended but absolutely necessary only for UHV operation For UHV work a bakeout procedure should be performed whenever the system has been to atmospheric pressure and at other times after extended periods at poor pressure to improve the quality of the vacuum Attention The vacuum chamber pressure must not exceed 10 mbar at any time during bakeout All non bakeable items in the bakeout zone such as cables pipes preamplifiers etc should be removed prior to bakeout Viewports and ceramic feedthroughs should be covered with aluminium foil for protection The recommended bakeout temperature is 180 C recom mended bakeout time is 15 hours Take care to avoid localised hot spots Allow the system to cool to room temperature before applying high voltage to the channeltrons The temperature of the big analyser flange can take more than 12 hours to cool to below 50 C Electrical Connections Attention After bakeout check that there are no short circuits between any channeltron and front bias feedthroughs and 9 way feedthrough pins and that none of them are connected to any external part of the EA 125 vacuum hardware earth ground The complete system comprises the following units 1 EA 125 2 EAC 2000 125 optional EAC 300 125
17. are selected then an effective slit width may be calculated by taking the average of the two widths i e 3 5 mm to determine the analyser resolution see also section Peak Width Measurement on page 48 Vy Omicron July 2002 Nano Technology Version 2 1 3 The Hemispherical Analyser 17 EA 125 Energy Analyser User s Guide Outline Dimensions hs 124 era _ 124 A MCD DETECTION ELECTRONICS ENCLOSURE 230x280x110 450 OD FLANGE 7 285 Q u ti Y i 4 54 y 150 OD ROT CF FLANGE q bod r J 131 m L 291 5 E MUMETAL 150 5 SCREEN 259 uc Dun 159 409 T Y ROTARY DRIVE ON H MCD VERSION ONLY 274 6 ELECTROSTATIC x SCREEN j Tm 50 a rg For details of the mu metal le 2 shielding see Figure 5 below Iu 3o 4 SAMPLE POSITION EA125 ANALYSER WITH LENS SCREENS FOR STANDARD OMICRON MUMETAL CHAMBERS Figure 4 Analyser with Universal Lens all dimensions in mm The standard length of the mu metal screen is 259 mm Magnetic Shielding For optimum energy resolution the EA 125 analysers are provided with one layer or two layers for HR versions of mu metal shielding around the input lens and the analyser hemispheres to prevent magnetic field penetration into the analyser Preferably
18. as shown in Figure 19 As the beam has passed from potential V4 to V2 there has also been a change of energy The angular extent of the beam is minimised by placing the pupil at the focal length of the lens This produces a zero beam angle and hence the angular extent of the beam is solely defined by the pencil angle 0 Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 40 EA 125 Energy Analyser User s Guide Window Pupil Image Figure 19 Lens apertures to define beam The quantities r 8 and V in the object window and image plane are related by the law of Helmholtz Lagrange ra 04 Vi sq 0 Var The product of r 0 and V is conserved So as the retarding ratio V V2 is increased the linear and or angular magnification must also increase Vy Omicron July 2002 NanoTechnology Version 2 1 7 Theory of Operation 41 EA 125 Energy Analyser User s Guide Pulse Counting Operation In an electron spectrometer electrons ions which arrive at the input of the Channeltron detector generate secondary electrons which are then accelerated down the Channeltron by a positive voltage bias 2 kV to 3 kV at the output These electrons strike the Channeltron wall producing additional electrons progressively down the Channeltron to the output where between 10 to 10 electrons arrive primary electron output secondary electrons Figure 20 Electron amplification in a Channe
19. changes has dramatically increased please contact Omicron Service using the procedures given on page 83 Low Kinetic Energy Cutoff too High All spectra display a low kinetic energy cutoff When the low energy cutoff appears too high the problem is usually caused by stray electrostatic or magnetic fields For applications in which low kinetic energy electrons are analysed it is strongly recommended that mu metal shielding is employed It is also very important that great care is taken to interface the mu metal of the system with that of the analyser lens Also check that no other instruments on the system are injecting magnetic fields into the analysis area Any removable magnets should be taken well away from the system Check that the sample or anything in the sample region is not charging as in Peak Energy Changes with Time on page 58 Poor Resolution XPS Check for oxidation of anode see X Ray Photoelectron Spectroscopy on page 50 Check for sample surface contamination If the resolution requires very low temperatures are you sure exactly how cold the sample is Check the analyser supply voltages at the filtered plug see the EAC Electronics for EA 125 Technical Reference Manual Vy Omicron July 2002 Nano Technology Version 2 1 9 Troubleshooting 60 EA 125 Energy Analyser User s Guide Low Intensity Usually caused by experimental setup geometry etc Check that the position of the sample and source are optimised
20. depth versus electron energy Ebel 1985 The diagram gives the escape depth as function of the electron kinetic energy for mainly metals can be given in different approximations 1M F Ebel R ntgen Photoelektronen Spektrometrie In Grasserbauer Dudek Ebel Angewandte Oberfl chenanalyse Springer 1985 Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 70 EA 125 Energy Analyser User s Guide Equation Comment Literature Good fit to the experimental data E is kinetic energy in Dench A Ad E eV and d are measured in Angstrom For metals A Seah B E d 538 B 0 13 d is the interlayer distance in the sample Ebel p168 or the atom diameter The diagram shows clearly that for bigger atoms A is larger than for smaller But one has to know the interatomic distance of the material X 0 41 d VE Asymptotic approximation for Exi gt 150 eV takes into account the material used The excitation energy sometimes can be chosen to shift the kinetic energy of the level investigated into this range Ertl K p pers p 77 Ae E Approximation around a kinetic energy of 1 keV Is better Ebel 1981 approximation than NE as long as no absolute values H fner p but rather relative dependency on energy is required 69 tabulated Good choice Jablonski et al 9 NIST Tougaard measurement on the Best choice Tougaard individual system The typical escape depth f
21. excitation source producing electrons from a sample open the instrument control page in the EIS software and set a suitable pass and kinetic energy see Chapter 4 of the EIS Software Manual e Switch the multipliers on and slowly apply the high voltage to the multipliers by turning the 10 turn potentiometer slowly up to the value given either on the EA set up record sheet provided with your analyser or the previously determined optimum operating value If at this point you see a reasonable spectrum then proceed to optimise If you cannot find a reasonable count indication please refer to the Trouble Shooting section of this manual which starts on page 57 Channeltron High Voltage Setup Each channeltron is individually setup in the Omicron factory before shipment As the channeltron ages however the required operating voltage must be increased To do this Vy Omicron July 2002 Nano Technology Version 2 1 6 Operation 33 EA 125 Energy Analyser User s Guide simply increase the output adjust potentiometer on the front panel of the CEM supplies One full turn is approximately equal to 300V The desired operating voltage is approximately 100V above the onset of the count rate plateau Please see the theory of pulse counting operation section of this manual In multi channel EAs all channels are adjusted simultaneously with this potentiometer u Please note The channeltron lifetime will be reduced if the high voltage is applied at p
22. operating voltage will need to be gradually increased during early operation This is normal behaviour and eventually the operating voltage should level out It is difficult to give a normal expected lifetime of channeltrons as their lifetime is limited by the total accumulated output charge A figure of around 10 accumulated counts should be attainable The lifetime is also very much dependent on the environment in which they are operated and will be very much reduced in contaminated systems Pump oil and other reactive materials are particularly harmful For information regarding the replacement of channeltrons please contact Omicron Service following the procedure on page 83 Multi channel Analysers The observed intensity in an analyser can be multiplied by up to a factor of seven by simply positioning extra detectors channeltrons at different positions in the exit plane When the kinetic energy is scanned these extra detectors will measure spectra which are offset in energy from the true spectra by an amount proportional to the pass energy and also to the position of the detector relative to the centre channel Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 43 EA 125 Energy Analyser User s Guide Energy Dispersion Outer Hemisphere Electron ion Trajectories Inner Hemisphere Inlet Aperture Exit Apertures Channeltron Detector Array up to 7 may be fitted E dE E E dE Fi
23. stored energy to discharge Vy Omicron NanoTechnology Version 2 1 2 Safety Information 12 EA 125 Energy Analyser User s Guide A Venting Make sure all parts of the EA 125 Energy Analyser have gained room temperature and disconnect all cables from the base flange before venting the vacuum chamber A Never e Never exceed a pressure of 1 1 bar inside the vacuum chamber e Never have in vacuum components connected to their electronics in the corona pressure region i e between 10 mbar and 10 mbar so as to avoid damage due to corona discharge This product is only to be used e within a dedicated UHV system e under ultra high vacuum conditions e indoors in laboratories meeting the following requirements gt altitude up to 2000 m c temperatures between 5 C 41 F and 40 C 104 F speci fications guaranteed between 20 C 68 F and 25 C 77 F gt relative humidity less than 80 for temperatures up to 31 C 88 F decreasing linearly to 50 relative humidity at 40 C 104 F c pollution degree 1 or better according to IEC 664 c overvoltage category II or better according to IEC 664 c mains supply voltage fluctuations not to exceed 10 of the nominal voltage Vy Omicron July 2002 Nano Technology Version 2 1 3 The Hemispherical Analyser 13 EA 125 Energy Analyser User s Guide 3 The Hemispherical Analyser The EA 125 is based on a 125mm mean radius electrostatic hemisp
24. the element and the specific level excited The following diagram shows the general behaviour of the cross section versus the atomic number 100 1 000 Cross section C 1s Al Ka Scofield 041 0 10 20 30 40 50 60 70 80 90 Atomic Number Fig 2 Calculated cross sections Scofield Scofield has calculated total cross sections o for photoemission The calculation is for free atoms and for AlKa 1486 6 eV and with different cross sections for MgKa 1253 6 eV These cross sections are used in the EIS database of the Omicron data acquisition software Other software packages like Spectra and Presents used by VG and by Omicron use cross sections very similar to Scofield s The MultiPak package from PHI applies different ones Ebel gives a power series approximation for the cross sections dependent on the atomic number Angle Correction The photoelectron line intensity varies with the angle between the photoelectron emission direction and the X ray beam It is a well pronounced effect The highest XPS intensity is found at 09 90 for most atomic levels The given angular correction is applicable for polycrystalline samples i e randomly oriented atoms For XPS on single crystals XPD the angular distribution is different J H Scofield J Elec Spectr Rel Phenom 8 1976 129 137 11 see also Wagner et al Surf Interf Analysis 3 1981 211 Vy Omicron July 2002 Nano Technology Version
25. 016 b 0 2175 Rel Std Dev 3 57 Area Pass Energy Retard Ratio Fig 4 Fit for the Berresheim Parameters as performed by PHI MultiPak In general acceptable parameters for the EA 125 are a 6 55 and b 0 45 in high magnification mode for the largest slits This transmission function can be built into PRESENTS as well using the VAMAS format of the transmission function see PRESENTS manual When using the full VAMAS description one should include also the more accurate mean free path equation The accuracy will improve considerably when the parameters a and b are determined for the current experimental setup This facility is built into PHI MultiPak Possible further improvements This method includes a possible variation of the area the EA looks at A set up with a dual anode X ray source and a monochromated X ray source will give a different transmission function In the former case the sample is illuminated more ore less homogeneously and the EA lens cuts out the probed area With the X ray monochromator the probed area is rather defined from the monochromated X ray spot The above mentioned method allows for measurement of the transmission function quite easily The software EIS can transfer the measured CRR and FAT data into an EXCEL spreadsheet Here the ratio of the two spectra can be calculated and multiplied by E yielding the transmission function for this set up It is not even necessary to find an analytic fit fu
26. 2 1 Appendix 72 EA 125 Energy Analyser User s Guide Definition of 0 0 is the angle between the photon direction X ray source and the electron direction lens of the analyser This angle is given from the chamber geometry For Omicron s Multiprobe MXPS system the angle is 80 The angle between the direction of the incident x ray and the detected photoelectron is 0 Angular Function 0 The angular distribution of the intensity is basically described by the differential cross section do dQ uio Ea 1 4 cos 8 1 dQ 4r 4 Intensity This formula describes the intensity variation with angle B is the asymmetry parameter It depends on the angular symmetry of the atomic level excited and varies with element number Z At the so called magic angle 54 7 the relative intensity is 1 independent of p 12 J W Cooper Phys Rev A47 1993 1841 Deviations froms the dipole approximation are discussed in V Nefedov I S Nefedova J Electr Spectr Relat Phenom 107 2000 131 137 Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 73 EA 125 Energy Analyser User s Guide Asymmetry Parameter I ee ee eer ee All S subshetls Ebel gives a power series approximation with atomic number The coefficients a b c are tabulated in p at tbZ c z a oL The diagram shows calculated values of the asymmetry parameter VG AEl Kratos Vorian PHI Leybold out ESC
27. 2220 228 20 2002 20 Figure 7 Mounting holes of the EA 125 analyser sssssse 21 Figure 8 Mu metal spiral positions u4ssssnnssnnnnnnnnennnnnnnnnnnnnnnnennnnnnennnnnnnne 22 Figure 9 Electronics wiring overview for EA 125 eee 25 Figure 10 Connection diagram non upgradable single channel version 28 Figure 11 Connection diagram upgradable and multi channel detection 29 Figure 12 Internal connections cernere eerie a ee der 31 Figure 13 9 way cable plug and feedthrough pin layout ssssseeeeses 32 Figure 14 Sample work function and electron spectrum eesse 35 Figure 15 The hemispherical analyser schematic diagram ssssssssssssss 37 Figure 16 Trajectories in a lens with two cylindrical electrodes 38 Figure 17 Lens with three cylindrical electrodes eeeeeeeeeeeeeeeeeeeeeeeeeee 38 Figure 18 Zoom lens CUrve ice eoe L oen coin uocis conce debct e sn cinta der no te cp Denblnerndelene 39 Figure 19 Lens apertures to define beam Qiete mene 40 Figure 20 Electron amplification in a Channeltron schematic diagram 41 Figure 21 Channeltron operating plateau sesseeeeseeeenenneenee enn 41 Figure 22 Multichannel analyser energ
28. 24 rp cavese 24 Electrical Connectloris oiii Hei 24 Setting up the Pulse Counting Electronics cece eee eee eee e eee e eee e enna 26 Setting up the Software ana eerte tes Lem Rep de au Ere ted a Serena ede 30 For Multi channel Analysers Only ssssssem 30 B ODGLPALIOT cop eai aat ERREUR AITNE Tass arena naan A 31 9 Way Plug and Feedthrough Pin Assignments eeeeeeeeeseeeeeeeee 32 Pulse Counting Operation 22 22 eet e tbe itp dtr ial utu oed ates us 32 Channeltron High Voltage Setup 22444440nnnnnnnnnnnnnnnnnnnnnnnnnnnnannnnnnnnnnnnnnnnnn 32 Multi channel Analyser High Voltage Adjustment sssssssss 33 T gt Theory of Operation erre terere E SEa aaaea aianei ENEKE Skiens 35 The Hemispherical Analyser 2 een 36 The Universal Lens nes Haan eu Erna 37 Electrostatic Input LenS nee HR R une 38 Einzel Lens TID 38 ZOOM Lens ek bikini bb binnen 38 The Law of Helmholtz Lagrange 44444ss4ssnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 39 WOmicron July 2002 NanoTechnology Version 2 1 Contents 7 EA 125 Energy Analyser User s Guide Pulse Counting Operation este ee ein RR 41 Channeltron Operating Plateau uusss44nnnnnnnnnnnannnnnnnnnnnnnnnnnnnnnnn 41 Channeltron Lifetime Expectancy Replacement uen 42 Multi channslAalySel S rn ie curet heb
29. 8 Mean Free Pallio re EE REPE oie EO Ee EAE A 69 Angle Correction rr T 71 Analyser Transmission issn ia t ertet des t dett IR Ede toed etc E de cond dere tad here 73 Mois i MEET rr Me ed E c ret E CN 76 Example d eL ERREUR UMEN URE E ERR EL ER CENTRES RR EUER HER EUR Ree nah 78 Further Improvements eesssssssssssssesesseeeeeeeeee enne nnnnni nnne rennes 80 Spectra and Data Compilations seesssssssssssesess ene 81 Surface Analysis General Literature eeeeeseeesseeeeeeeeeeeneeeennennnnnnn 82 Service at OMICRON e 83 WINX Sas caste dec Stes 84 Decontamination Declaration eeeeeeeeeeeeeeennenneneennenennnnnnnnnnnnnnnn nnn nnns 86 Vy Omicron July 2002 Nano Technology Version 2 1 Contents 8 EA 125 Energy Analyser User s Guide List of Figures Figure 1 The EA 125 hemispherical analyser major components 13 Figure 2 EA 125 U1 entrance and exit plates na 15 Figure 3 Multichannel detection entrance and exit plates sssesessssssessssss 16 Figure 4 Analyser with Universal Leris 1o trt eirca ren vid ann 17 Figure 5 Mu metal shielding for analyser lens ssssssse 18 Figure 6 EA 125 shipping arrangement 2 4 4 224 2244 00 2
30. A3 ESCALAB ES 200 300 IEE 15 0 i Band et al give tabulated values for oh per Ne er mj The diagram Shows B as a function of Z F from Reilman gy ei ea ECL Analyser Transmission The literature describes a lot of different methods for determining the transmissions function of the analyser Here we deal with only the simplest two of them First Approximation The study of the EA 125 transmission function Ruffieux et al is based on a paper by Cross and Castle which is applicable to any spectrometer that can be operated both in Constant Analyser Energy CAE and Constant Retard Ratio CRR mode The advantage of this method is its simplicity independence on the sample and on the inelastic mean free path of the electrons It can easily be used by any researcher to characterise the behaviour of his specific instrumental set up To determine the required transmission function two XPS spectra are measured one in CRR the other in CAE mode Their ratio R is fitted by T CAE _ PE RR CHARORR E kin REx 13 M Band Yu I Kharitonow M B Trzhaskovskaya At Data Nucl Data Tables 23 1979 443 14 R F Reilman A Msezane S T Manson J Electron Spectrosc Relat Phenom 8 389 1976 LT Weng G Vereecke M J Genet P Bertrand W E Stone Quantitative XPS Part I Experi mental Determination of the Relative Analyser Transmission Function of Two Different Spectrome ters A
31. Critical Assessment of Various Mehtods Parameters Involved and Errors Introduced Surf Interf Analys 20 179 192 1993 6 p Ruffieux P Schwaller O Gr ning L Schlapbach P Gr ning Q C Herd D Funnemann J Westermann Rev Sci Instr 71 10 3634 3639 1 Y M Cross J E Castle J Electr Spectr Relat Phenom 22 1981 53 Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 74 EA 125 Energy Analyser User s Guide PE and RR are the pass energy and the retard ratio of the spectra involved x is the fit parameter 6x 12 mm Slit 50 6 mm Slit 2 0 48 Si 15 4 m 3 30 ll 107 di 20 0 5 5 Tory 10 600 800 1000 1200 1400 200 400 600 800 1000 1200 1400 Kinetic Energy eV Fig 3 The ratio between transmission in CRR and CAE mode is shown for two different slits Ruffieux et al The transmission in CRR mode T CRR is known to be proportional to Exn therefore the transmission in CAE mode is E kin T CAE We find that the transmission factor of the EA 125 for the CAE mode is proportional to Exin 0 for most measuring set ups This dependence is predicted by theory for an ideal analyser derived from the Helmholtz Lagrange law The required correction on a spectrum measured in CAE mode would be to multiply with E kin The energy dependent correction for the transmission function and the mean free path multiply to a corr
32. D 20 http srdata nist gov xps Electron Elastic Scattering Cross Section Database SRD 64 http www nist gov srd National Institute of Standards and Technology NIST USA Electron Inelastic Mean Free Path Database SRD71 http nist gov srd Standard Test Data for XPS http www acg nist gov std 2 G Ertl J K ppers Low Energy Electrons and Surface Chemistry VCH M nchen 1985 3 M F Ebel M F Schmidt M Ebel A Vogel J Electr Spectrosc Relat Phenom 34 313 1984 J E Castle M A Baker The Feasibility of an XPS Expert System demonstrated by a rule set for carbon contamination Journal Electr Spectr Rel Phenom 105 1999 245 256 Vy Omicron July 2002 Nano Technology Version 2 1 Surface Analysis General Literature 82 EA 125 Energy Analyser User s Guide Surface Analysis General Literature 1 2 3 4 5 6 7 8 July 2002 D Briggs and M P Seah 1992 Practical Surface Analysis Vol 1 and 2 John Wiley amp Sons Chichester J M Walls Editor Methods of Surface Analysis Cambridge University Press UK H Ibach Editor 1977 Topics in Current Physics 4 Electron Spectroscopy for Surface Analysis Springer Verlag Berlin Heidelberg New York J H Moore C Davis and M A Coplan 1989 Building Scientific Apparatus Addison Wesley Publishing Company Inc J F Watts 1990 Microscopy Handbooks 22 An introduction to Surface Analysis by
33. E width of natural energy distribution of electrons at that energy level and E finite energy resolution of the analyser The Natural Line Widths of Electronic Levels E In general the natural distribution of electron energies varies from level to level from element to element with the excitation process and to a lesser extent from environment to environment Typical values can be from some meV for free atoms in the gaseous phase up to several eV for energy bands in solids The natural line widths are usually dominated by the lifetime broadening arising from the finite lifetime of excited ionic states The Width of the Photon Line Inducing Emission E The line width of the exciting photon is often the major limitation on the resolving power of the instrument Table 6 gives widths E at half height for some characteristic photon lines Typical values range from a few meV VUV discharge lamp to 0 85 eV unmonochromated Al Ka 1486 6 eV The theoretical linewidth of ultra violet radiation from a VUV discharge lamp is limited by two processes Doppler broadening and self absorption In practice however the pressure of the discharge gas usually broadens the linewidth to between 3 and 7 meV An X ray monochromator will improve the resolution by reducing the width of the exciting X radiation to about 0 2 eV to 0 3 eV Mg Koz Al Ka Al Ka He Ne monochromated Energy eV 1253 6 1486 6 1486 7 21 2 16 7
34. Electron Spectroscopy Oxford University Press UK D P Woodruff and T A Delchar 1994 Modern Techniques of Surface Science Cambridge University Press UK S H fner 1995 Photoelectron Spectroscopy Principles and Applications 2nd ed Springer Verlag Berlin Heidelberg New York V S Smentkowski Trends in sputtering Progress in Surface Science 64 2000 1 58 Vy Omicron NanoTechnology Version 2 1 Service at OMICRON 83 EA 125 Energy Analyser User s Guide Service at OMICRON Should your equipment require service e Please contact OMICRON headquarters or your local OMICRON representative to discuss the problem An up to date address list is available on our website under http www omicron de om adr html or via e mail reply service under contact info omicron de e Make sure all necessary information is supplied Always note the serial number s of your instrument and related equipment e g head electronics preamp or have it at hand when calling If you have to send any equipment back to OMICRON e Please contact OMICRON headquarters before shipping any equipment e Place the instrument in a polythene bag e Reuse the original packaging and transport locks e Take out a transport insurance policy For ALL vacuum equipment e Include a filled in and signed copy of the Declaration of Decontamination form which can be found at the back of the equipment manual No repair of vacuum equipment without a lega
35. M12 tapped holes in the outer edge of the analyser base flange 3 Use the lifting handles to fix the crane chains to the analyser or remove 3 of the bolts which hold the analyser dome to the base flange and replace them with suitable lifting eye bolts Attention The analyser s centre of gravity is off centre so it will tilt if not held firmly Guide the analyser by carefully pushing the base flange to keep the lens in a vertical orientation 4 Unbolt the four M10 bolts which hold the analyser to the support bracket on the shipping frame Use a crane to carefully lift the analyser out of the frame while simultaneously holding it firmly 5 With the analyser suspended remove the three lens support screws which retain the input lens protection tube see Figure 6 Then Vy Omicron July 2002 Nano Technology Version 2 1 4 Unpacking and Installation 22 July 2002 10 unbolt the nuts and bolts which hold the tube to the rotatable flange of the spacing collar and remove the input lens protection tube Fit the spacer to the rotatable mounting flange on the analyser rather than fitting it to the UHV chamber as this makes inserting the lens easier The spacer also has a rotatable flange for use in connecting it to the vacuum chamber It is recommended that initially both of these flanges are only loosely assembled until the analyser is correctly positioned If the analyser is to be fitted to a mu metal chamber use the two screws
36. Pa Sa Pu Sp This is the basic instruction Find the intensity and then divide by o A and T As we usually do not know c the factor of proportionality we can only calculate the relative number of atoms DAT spectrum are proportional to the number of atoms in the probed volume We can scale the sum of the p to be 100 Let us call p the corrected intensity The corrected or reduced intensities in a Weight Percent When the concentration of an element is to be given in weight percent we have to multiply the p with the atomic weight A Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 69 EA 125 Energy Analyser User s Guide How to Measure the Peak Intensity Intensity is measured as peak area after the background is subtracted We take the peak area not peak intensity as this is more independent of the pass energy chosen Height sensitivity factors would have to specify the line width as well An area measurement has less statistical uncertainty than the height Mean Free Path Relative peak intensities can be changed dependent on the kinetic energies of the electrons Switching the excitation energy between MgK and AIK will change the relative peak intensities even when the cross section does not change because the electrons travel at a different kinetic energy and are absorbed differently AUSTRITTSTIEFE A 10 20 50 100 200 500 1000 1500 ELEKTRONENENERGIE eV Fig 1 Escape
37. Phi MultiPak format is available only from EIS V2 1 Contents ADS UACK od en Ricans P dante ES GEN ae Be ie Bio e E 67 IMMTFOCUGUION Er LEE 67 Parameters scc tege e e TRE P Te E VER ENTE XR TER landen 68 Mean Free Path i eec e ree Rer rre Pea re diner ee dei deer dere d 69 Angle GC ONS GNOME s eo ii tod olii ti tul bottle xt ue tte ox cele 71 Analyser Transmission 2 0 ccccceccceeteteccee note ceeeneteceeecenecceeneteceeenenecenenenereeente 73 ipi oc Pee HN M p a CUP Ee E n 76 cj 78 Further Improvements Srnice a a g nennen nennen rne rne a 80 Spectra and Data Compilations eeesssssssssssesssene 81 Abstract In this document we give a recipe to get a quantitative XPS analysis of an unknown sample using the Omicron EA 125 and the corresponding software package The parameters that have to be known measured calculated or approximated are discussed We focus on viable solutions rather than on an exhaustive presentation We give numbers or equations for each parameter so that a program can deal with them A procedure is given to calculate the sample composition Introduction X ray photoelectron spectroscopy XPS is a widely used and versatile tool to study the chemical composition within the surface region of solids Here we give a basic introduction on how to do the first steps into quantitative XPS analysis Here we discuss polycrystalline samples with a homoge
38. a fixed percentage of the kinetic energy determined by the slit sizes Vy Omicron July 2002 Nano Technology Version 2 1 8 Typical Experiments Factory Tests 55 EA 125 Energy Analyser User s Guide High Resolution Gas Phase Ultraviolet Photoelectron Spectroscopy HRUPS The gas phase UPS tests are usually only performed on HR analysers and are used to measure the ultimate resolution The tests consist of resolution measurements of the Ne excited Xe 5p line A gas cell is mounted onto the end of the light capillary of a HIS 13 VUV discharge lamp which is mounted perpendicular to the analyser lens Apertures in the gas cell allow the photoelectrons to leave and enter the analyser lens No extra potentials are applied to the gas cell It is essential that these tests are performed on a very well magnetically screened chamber as the photoelectrons have very low kinetic energies 4 eV A mu metal chamber or stainless steel chamber with mu metal lining is used and special care is taken to interface the mu metal with that of the analyser lens To achieve the best performance the magnetic field should be less than 10 mGauss everywhere in the system The EAC controller used for the test depends upon the ordered configuration The highest resolution is achieved with the dedicated EAC 300 HR with extremely low ripple and noise levels The guaranteed resolution specification is therefore higher with an EAC 300 than with an EAC 2000 The 1
39. ally of ceramic feedthroughs Do not rest the analyser on ceramic feedthroughs or on the viewport Unpacking e Remove the top and one side of the wooden crate by carefully unscrewing all screws Inside the crate the analyser is mounted on a metal shipping frame Vy Omicron July 2002 Nano Technology Version 2 1 4 Unpacking and Installation 20 EA 125 Energy Analyser User s Guide 4 ee L I wa 1 unbolt nuts CI and bolts aa t d TI e I ad o i remove three lens s i j UT 1 support screws amp D er a b Figure 6 EA 125 shipping arrangement a Shipping frame b Detail input lens protection tube e Lift the shipping frame together with the analyser out of the wooden crate two people needed Caution grasp the shipping frame not the analyser e Check for completeness using the enclosed packing list e Doa thorough visual check for any accidental transport damage e Keep the analyser in its protective packaging until it can be directly bolted onto the system Attention After unpacking keep the analyser frame and lens cover safely stored for use if the analyser has to be removed from the system Electrical Check Before fitting the analyser to the vacuum system check that there are no short circuits between any channeltron and front bias feedthroughs and 9 wa
40. ample Holder Check that the working distance is accurately set to 30 mm Check that the analyser is in the correct magnification mode High magnification for small spot Check that the sample is orientated correctly with respect to the lens Check that material from the sample holder has not been sputtered onto the sample Check the analyser supply voltages at the filtered plug see the EAC Electronics for EA 125 Technical Reference Manual Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 61 EA 125 Energy Analyser User s Guide Appendix EAC Adjustment The aim of these instructions is to produce a constant peak position independent of the pass energy A constant offset throughout the whole kinetic energy range from the respective literature values is normal and can be compensated by setting the analyser work function WorkF to the appropriate value Attention Lethal Voltages Adjustments and fault finding measurements as well as installation procedures and repair work may only be carried out by authorised personnel qualified to handle lethal voltages Tools required 4 EA 125 with electronics complete set of cables software PC 5 baked UHV system with X ray source 6 well known sample with a feature that can be used for accurate peak positioning e g silver 3d5 2 for XPS or Fermi edge for UPS 7 insulating potentiometer trimmer Attention Some potentiometer trimmers are anti static and are
41. by calibration ds can however be estimated since the spectrum cuts off at Ex 0s The offset of the spectrum by 6 is not as important as might be imagined since it is the kinetic energy measured with the analyser which is important This can be seen from the following The ejected electrons pass through the first lens element and are then retarded by an amount R determined by the lens voltages before entering the analyser The analyser is a band pass filter only transmitting electrons with energy very near to the pass energy Ep which are then stopped in the detector Therefore the electrons have a measured kinetic energy of R Ep But note that the analyser also has a work function 4 Therefore electrons which have been transmitted by the analyser with a retardation of R and a pass energy of E would have had a kinetic energy of Ex R E 05 hv E which is independent of the sample work function s Note that the software measures oae R E unless you set the workfunction parameter A typical value of for the work function 4 for the EA 125 is between 4 2 and 4 8 eV The Hemispherical Analyser In the hemispherical analyser two concentric hemispheres of mean radius Ro are mounted with the common centre of O see Figure 15 on page 37 A potential V is applied between the surfaces so that the outer is negative and the inner positive with respect to Vo which is the median equipotential surface between the hemispheres and the entrance a
42. cause the Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 47 EA 125 Energy Analyser User s Guide greatest concentration of atomic energy levels is at low binding energies e In AES however there is a tendency for peaks of interest to occur at low kinetic energies In addition Auger peaks tend to be broader than photoelectric peaks and high energy resolution is not as critical in AES as it is in XPS High resolution will provide the narrowest peaks with reduced sensitivity This is used to obtain accurate peak positions and derive chemical information in XPS from narrow scan spectra The transmission of the analyser also depends on the mode used For further information please refer to the XPS Quantitative Analysis with the Omicron EA 125 in the Appendix on page 67 and also to Y M Cross J E Castle J Electr Spectr Relat Phenom 22 1981 53 Analyser Resolution The analyser is a band pass energy filter for electrons at a specific energy E and has a finite energy resolution AE which is dependent on the chosen mode of operation and specific operating conditions The energy resolution of the analyser is given approximately by d 2 AE E 2 0 2Ro where d slit width Ro mean radius of hemispheres a half angle of electrons entering the analyser at the entrance slit in radian units The finite energy resolution of the analyser is dependent on the electron pass energy or retardation th
43. d for it is wise to derive quantitative information only for count rates of up to one or two million counts per second For an intense peak a loss in count rate around the maximum would result in relative broadening of the peak In extreme cases N gt 8 Mcps a peak fitting routine might even suggest the distorted peak to be composed of two Gaussians Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 45 EA 125 Energy Analyser User s Guide Error in 0 0 0 2 0 4 0 6 0 8 1 0 Nps Mcps Figure 24 Difference between true count rates Niue and observed count rate Nobs against Nobs in of error In the EA 125 multi channel systems each channeltron measures a different part of the spectrum at any particular instant in time These spectra are summed giving no significant loss in energy resolution and if M is the number of channels then the measured multi channel count rate N is approximately M times the count rate for a single detector The true count rate for the multi channel system NM u then becomes M Ns N Die Sa ar IN aT true where 1t is the single channel dead time This can be written in the same form as equation 1 above M M No true M 1 z N obs Ty is the effective dead time for all M detectors and is related to the single channel dead time by the following equation Ty M Thus although each channel has a dead time of 70 ns t
44. d to be 10 ns or 70 ns per channel To put it in perspective this result says that with this counting System that is capable of counting up to 10 Mcps per channel 7 deadtime 100 ns already at a count rate of 1 Mcps the loss in peak height is nearly 10 96 a ES Ox x oo gt N Q t 70ns Nob Ntr 1 Ntr t 4 Observed Count Rate Mcps O N O A OC Q NOO 0 20 40 60 80 100 True Count Rate Mcps Fig 5 Dead time counting losses There are measures to cope with this limitation Wy Omicron July 2002 Nano Technology Version 2 1 Appendix 78 EA 125 Energy Analyser User s Guide Use a detector with a high maximum count rate but do not use the limit The peak height or area should be proportional to the X ray intensity A solution could be to work at an input intensity where it still is linear When and as the dead time is defined and well known the spectrum can be corrected with the above equation before measuring the peak height or area Using the peak area instead of the peak height already reduces the error Example Measurement Start with a scan over a wide energy range say from binding energy E 10 eV to 1260 eV Make sure that the number of points is not more than 4000 i e for this overview scan choose an energy step width of more than 0 32 eV Presents can handle up to 4000 points only Choose the circular entrance aperture of 6 mm Note the angle between the EA lens and the X ray sou
45. e EA 125 Energy Analyser should always be used with mu metal shielding around the analysis area Otherwise it might not meet the specified performance figures This particularly applies to low energy UPS and Auger applications i e kinetic energies below 200 eV Vy Omicron July 2002 Nano Technology Version 2 1 Preface 4 EA 125 Energy Analyser User s Guide Warning Lethal Voltages Adjustments and fault finding measurements as well as installation procedures and repair work may only be carried out by authorised personnel qualified to handle lethal voltages Attention Please read the safety information in the relevant manuals before using the instrument Conditions of CE Compliance OMICRON instruments are designed for use in an indoor laboratory environment For further specification of environmental requirements and proper use please refer to your quotation and the product related documentation i e all manuals see individual packing list The OMICRON SPECTALEED complies with CE directives as stated in your individual delivery documentation if used unaltered and according to the guidelines in the relevant manuals Limits of CE Compliance This compliance stays valid if repair work is performed according to the guidelines in the relevant manual and using original OMICRON spare parts and replacements This compliance also stays valid if original OMICRON upgrades or extensions are installed to original OMICRON syste
46. e slit width and the acceptance angle of the lens system The following table lists some examples of typical parameters for various techniques and the calculated analyser resolution Technique Pass Slit Kinetic Calculated Step Dwell energy width energy analyser size time E eV mm range Ex resolution eV s eV AE eV XPS 50 6 100 1500 1 5 0 5 0 2 Broadscan XPS 20 6 20 0 6 0 05 0 5 Narrowscan UPS 5 1 0 5 0 03 0 002 1 Fermi edge HRUPS 0 5 1 0 1 0 003 0 0005 1 Gas phase Please note that the slit width is the effective slit widths of both the entrance and exit slits in the dispersive direction Table 5 Analyser operating parameters and resolution Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 48 EA 125 Energy Analyser User s Guide Peak Width Measurement When the analyser is used to measure peak position and peak shape precisely for chemical information as in XPS and to some extent in AES the measured peak width is important and should be reduced to the lowest possible level for high resolution analysis The peak width as a measure of resolution is defined as the full width at half maximum FWHM of a specific peak Measured peak width is a convolution of several contributing line widths assumed to be Gaussian and is usually given as Em E E E where Em measured peak width E width of photon line inducing emission
47. ection factor of 0 99 kin 0 28 0 71 kin kin Corr 18 This is a general electron optical conservation law See e g Cross and Castle Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 75 EA 125 Energy Analyser User s Guide Configure PRESENTS This can be installed into the PRESENTS STARTUP INI file In the section Process under subheading Linear we put Process Linear 0 28 Note Other values in section do not alter The value should always be positive even though it will be used as a negative power The item header Linear is case sensitive Second Approximation Deviations from the ideal behaviour occur for small retard ratios in combination with the large 6 x 12 mm slit However the transmission function is predictable and smooth for any parameter range and fits are possible using different fit functions The first approximation was quite good already and easy to implement The next step is to fix the region of low retard ratio and to include variations of the transmission for different pass energies A general fit function can be given which works well for the EA 125 P Epass a2 a R7 P P is the peak area RR is the retard ratio RR Exin Epass 19 K Berresheim M Mattern Klosson W Wilmers Fresenius J Anal Chem 341 1991 121 124 Vy Omicron July 2002 NanoTechnology Version 2 1 Appendix 76 EA 125 Energy Analyser User s Guide a 30 0
48. er test factory test analyser 49 AES odii asi Gba wx Ee wi HANS 53 fault finding aeas dee er Gordan nds 4 11 ARUP S zd i tre dete debe att 55 feedthrough iui et ere retedete 32 Pic pe 50 field correction sssssss 13 analyser test experiments 49 analysis area 14 G angular acceptance 14 general literature 82 aperture lens essssesss 39 Qgrourd dedecore xen 26 66 B H DAK SOU MEN 24 Helmholtz Lagrange law 39 hemispherical analyser 13 36 C HRUPS test analyser 55 CAE MOG A dre debes 14 46 card size IE EE Ga runter 10 IEEE interface card size 10 SAC Lcid d d ebd IR OR atr ee 10 input lens teint rte ut 14 CE compliance conditions of 4 installation 22 nn 20 chamber pressure een 24 channeltron 15 25 41 K accumulated counts 42 kinetic energy ssseeseseeesss 3 ce 42 lili tiere EE 42 L voltage plateau sses 42 lens computer requirements 10 aperture under 39 connections electrical 24 Einzel i oett 38 CODYTIOI canat a AER R o Ta ok na Xx 3 magnification ssuessssss
49. etes teste ette ia tale uter ESTEE LEE 42 Energy Dispersion u ae 43 Statistics of COUMUNG un Re Re Rehau 43 Modes of Analyser Operation lee ka 46 Constant Retard Ratio CRR Scan Mode 44444snnnssennnnnnnnnnnnnnn 46 Constant Analyser Energy CAE Scan Mode ceeeceeeeeeeeeeeettteeeeeeees 46 Selection of Analyser Mode 2 0 2220 46 Analyser RES OOM sa cc opo een 47 Peak Width Measurement eoo oe add 48 8 Typical Experiments Factory Tests uuuuuuuuunnnnnnennnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 49 X ray Photoelectron Spectroscopy XPS cccceesseseceeeeeeeeeeeeeseneaeeeeeeeeeteeeeeaeaes 50 Auger Electron Spectroscopy AES 2244444000nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 53 High Resolution Gas Phase Ultraviolet Photoelectron Spectroscopy HRUPS 55 9 5 Troublesh6o0ling euren 57 AD DONGIX dE 61 EAC Adj stmMment Eom 61 Peak Information Tables for SilVer cccccceeeeseeeeenceeeeeeeeeeeeeeeneeeeeeeeeeeeee 62 Prep aration Pp 62 AQUSIMEHLPFOCEAUrE ME 63 Preamplifier Threshold Adjustment ssssssm nnn 65 XPS Quantitative Analysis with the Omicron EA 125 67 Content eo eM cated rad tbe ead eti Mei ed ert setet i aud 67 ADSISOGE o rene eee te As danas eren eere eeu eb Fede ie n RO EE EUN Ore ERR EE TEMERE EE ETE 67 NO dU CION RS E E 67 i r 6
50. f this manual may be reproduced or transmitted in any form or by any means electronic or mechanical including photocopying and recording for any purpose without the express written permission of OMICRON NanoTechnology GmbH Warranty OMICRON acknowledges a warranty period of 12 months from the date of delivery if not otherwise stated on parts and labour excluding consumables such as filaments sensors etc No liability or warranty claims shall be accepted for any damages resulting from non observance of operational and safety instructions natural wear of the components or unauthorised repair attempts Normal Use The EA 125 Energy Analyser is an electrostatic analyser for measuring the kinetic energy of electrons arising from photo emission experiments e g XPS UPS XPD Auger and ions from ion scattering spectroscopy ISS experiments The EA 125 Energy Analyser shall always be used e in conjunction with an EAC 2000 125 or EAC 300 125 control unit e inside a suitable vacuum chamber explicitly specified for this purpose e in high vacuum i e base pressure lt 10 mbar e with original cable sets which are explicitly specified for this purpose e with all cabling connected and secured if applicable e with all electronics equipment switched on e in an indoor research laboratory environment e by personnel qualified for operation of delicate scientific equipment e jin accordance with all related manuals Please note Th
51. for intensity Check that the sample surface is clean Check that the analyser is in the correct magnification mode Check that each channeltron is on the count rate plateau see Channeltron High Voltage Setup on page 32 and Channeltron Operating Plateau on page 41 Check the analyser supply voltages at the filtered plug see the EAC Electronics for EA 125 Technical Reference Manual Peaks at Wrong Energy Check that the sample or anything in the sample region is not charging as in Peak Energy Changes with Time on page 58 Check that the work function has been set correctly in the EIS Software usually 4 5 eV Check that the peaks in question are not ghost peaks see XPS section of Chapter 8 on page 49 Check the analyser supply voltages at the filtered plug see the EAC Electronics for EA 125 Technical Reference Manual Noise Counts Observed with Channeltron HV OFF Check the Preamp threshold settings see Section 6 on page 65 Check that earth loops have been avoided by ensuring that all ground connections to the electronics and spectrometer system are common Check that all cables are routed well away from sources of noise such as mains power controllers switch mode power supplies or ion and plasma sources Check that no high voltage breakdown e g in an X ray source etc is occurring on the system Check for noisy instruments on the system Try switching each instrument off in turn Intensity Observed from the S
52. gions of the EAC see the EAC manual for further details Ensure that the spectra you obtain have good statistics for an accurate measurement Accurately determine the peak position with the cursor or with the Peak information window of both peaks Make a note of the difference in Peak position and turn the potentiometer RV1 EAC 2000 or RV5 EAC 300 a half turn clockwise See Figure 29 for the position of the relevant potentiometer Repeat the measurement as you did in 3 above Again accurately determine the peak position If the difference is less then continue with another half turn of the relevant potentiometer Otherwise turn RV1 5 one turn anticlockwise and repeat 3 above Continue adjusting the potentiometer until the peaks have their maximum at the same energy The accuracy with which this procedure can be performed depends upon the peak shape and width and also the kinetic energy of the peak An accuracy of lt 0 05 eV should be attainable with the suggested XPS peak whereas an accuracy of lt 10 meV should be attainable with the UPS Fermi edge Please note Four complete turns of the potentiometer are normal July 2002 Vy Omicron NanoTechnology Version 2 1 Appendix 64 EA 125 Energy Analyser User s Guide ev ENERGY PCB e o L ISSUE 2 EAC2000 PASS 1087 05 OUTER JO
53. gure 22 Multi channel analyser energy dispersion The energy offset from the centre channel is equal to the pass energy multiplied by an individual dispersion factor for the position of the channeltron in the exit plane E Ep xD where E Energy Offset Ep Pass Energy and D Dispersion Factor The EIS software is configured to take the energy dispersion into account when scanning in MCD mode and offset the acquired spectra by the correct amount before summing each channel After calibration there should be no significant loss in resolution when scanning in MCD mode compared to scanning in single channel mode Details of the software MCD Scanning Algorithm and details of how to calibrate the dispersion factors can be found in the EIS Software Manual Statistics of Counting In the pulse counting process the maximum counting speed is limited by the following components the channeltron the preamplifier and the computer interface board Special attention has been paid to extend this limit from the more common maximum of 100 kcps to a count rate of 14 Mcps as measured for periodic pulses The following results should make clear however that even with such a high count rate the maximum reliable number of counts per second i e with a low percentage of error is much lower for statistical pulses Here we will only deal with the results of more rigorous treatments that can be found in the literature 1 WC Elmer NUCLEONIC Jan 1950
54. he effective dead time for 5 or 7 channels is 14 ns and 10 ns respectively The high count rate capabilities of the EA 125 are fully proven Observed count rates of over 70 Mcps have been achieved Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 46 EA 125 Energy Analyser User s Guide Modes of Analyser Operation The kinetic energy can be scanned either by varying the retardation ratio whilst holding the analyser pass energy constant known as Constant Analyser Energy or CAE or by varying the pass energy E whilst holding the retard ratio constant known as Constant Retard Ratio or CRR Both of these modes are selectable from the computer system Constant Retard Ratio CRR Scan Mode In the CRR mode electrons entering the analyser system from the sample are retarded by the lens stack by a constant proportion of their kinetic energy so that the ratio of electron kinetic energy to analyser pass energy is kept constant during a spectrum The retard ratio k is defined as k Ek 70a E Ek Ep Ep Throughout the scan range the pass energy of the analyser is continuously varied to maintain a constant retard ratio Sensitivity and resolution are also proportional to the pass energy and therefore kinetic energy in this mode Sensitivity is reduced at lower kinetic energies The ESCA sensitivity for transition metals is therefore reduced when compared with that of Al or Si In this mode the analysed sample area and
55. herical deflection analyser composed of two concentric hemispheres The inner and outer hemispheres are biased negative and positive with respect to the pass energy of the analyser The analyser disperses electrons according to their energy across the exit plane between the two hemispheres and focuses them in the angular dimension from the entrance to the exit plane Variable slits are located at the entrance and exit of the analyser These are selected and changed by means of external rotary feedthroughs For the non upgradable single channel version the entrance and exit slits are coupled and can be controlled by a single rotary feedthrough A schematic of a multi channel EA 125 is shown in Figure 1 Hemispherical Analyser Viewport ds I3 Exit Slit Rotary Drive Channeltron Connection Feedthroughs Entrance Slit Rotary Drive Filtered Plug Lens and Analyser Voltages Electrostatic Lens Figure 1 The EA 125 hemispherical analyser major components Preamplifier to Channeltron connection cables not shown Jost field correctors are used to provide accurate field termination at the entrance and exit planes A hole in the outer hemispherical detector is used as a beam dump for high energy electrons and as a facility which permits the sample to be viewed and aligned through the lens stack Vy Omicron July 2002 Nano Technology Version 2 1 3 The Hemispherical Analyser 14 EA 125 Energy Analyser User s Guide The analy
56. ible and to vary the energy of the beam to the pass energy of the analyser The resolution obtainable with a hemispherical analyser can be significantly increased by reducing the pass energy of the analysed electrons The universal lens consists of 11 cylindrical electrodes held at different potentials Close to the gap between the various elements the potential gradients generate lines of equipotential which refract charged particles crossing them This effect is shown schematically in Figure 16 for a lens with two cylindrical electrodes V V 2 NITIITIIIIIIIIIIIISS OWN NV Z wa zur SSS ELECTRON TRAJECTORIES LINES OF EQUIPOTENTIAL Figure 16 Trajectories in a lens with two cylindrical electrodes By employing a three cylinder arrangement it is possible to accelerate or retard the electrons by varying amounts and keep the focusing properties constant The schematic layout of a lens with three cylindrical electrodes is shown in Figure 17 TT Figure 17 Lens with three cylindrical electrodes Einzel Lens If the potentials applied to V4 and V in Figure 17 were equal the three cylinder lens would not change the energy of the transmitted electrons but there would still be a focusing effect This arrangement is known as an Einzel lens This type of lens design is employed in the first stage of the Universal lens and is used to set the magnification and angular acceptance Zoom Lens If the potential
57. iometer Rear Bias DC Supplies Earth Stud a Front Bias I Z Mains On Off Mains Socket Fringe Field Mains Input Cable i N Warning Disconnect mains supplies before removing cover Mains On Off Optical ins Socket Signal Anal O Input Ow Green LEDS Red LED DC Power Check Signal Indication EA 125 Energy Analyser User s Guide EA 125 Detector Maunting Flange FB Note The letters M and FB are punched onto the flange surface next to the appropriate feedthrough connector Front Bias Adjust potentiometer below front bias connector From Filtered Plug Chamber To Computer ogue Output Socket Figure 10 Connection diagram non upgradable single channel version July 2002 WOmicron NanoTechnology Version 2 1 5 Getting Started 29 EA 125 Energy Analyser User s Guide EA 125 Detector Mounting Flange i Note The letters indicating Channeltron and Front 03 15 02 01 n C FB Bias connection positions are punched into the b d 2 i m E detector flange lll from filtered plug chamber optical fibre cables O ud u u o o o o o o o MULTICHANNEL PREAMP MS DC MULTICHANNEL RECEIVER Mains Mains On Off Socket MAINS FB From EAC IEEE Card MULTIPLIER SUPPLIES Mains Input Cable Mains Socket Output Adjust
58. ion of this lens varies with retard ratio and therefore kinetic energy in CAE mode as a result of the law of Helmholtz Lagrange The analysis area is defined by the combination of the selected analyser entrance aperture and the magnification of the entire lens The magnification of the entire lens is a product of the magnifications of the two discrete lenses The angular acceptance is defined solely by the selected magnification mode This is limited by physical apertures in the lens and therefore remains nearly constant throughout the entire energy range UNIVERSAL LENS analysis area diameter for magnification mode magnification angular acceptance 9 d g P 6 mm entrance aperture mh e s mem e 0 o Lm a r Table 2 Lens specifications universal lens Note that the spot sizes are defined as FWHM of an approximately Gaussian profile Due to the law of Helmholtz Lagrange the magnification varies slightly with the retard ratio A small retard ratio means in general a smaller magnification larger spot size and a higher angular acceptance The values given in Table 2 are an average valid for a retard ratio range from about lt 5 to gt 100 covering most applications Vy Omicron July 2002 Nano Technology Version 2 1 3 The Hemispherical Analyser 15 EA 125 Energy Analyser User s Guide The Detector One five or seven channel electron multipliers Channeltron s are placed across the exit plane of the analy
59. its in the preamplifier unit it is important to route all cabling to the preamplifier unit away from any sources of noise e g mains cables sources of RF power Make sure that all leads are connected correctly to the system and do not disconnect any lead during the test procedure Start up the system as normal Ensure that there are no counts present i e switch off any X ray sources electron guns etc Make sure the red multiplier LED on the front panel of the EAC 300 or the EAC 2000 is not lit Remove the front panel on the preamplifier unit Switch the mains to the multiplier unit on again making sure the red multiplier LED on the front panel of the EAC 300 or the EAC 2000 is not lit Set the multimeter 10MQ to read DC MILLIVOLTS For EA 125 single channel non upgradable version connect the positive lead of the multimeter to test point 3 and the negative lead to test point 4 For all upgradable EA 125 versions connect the positive lead of the multimeter to the red socket test point 3 and the negative lead to the black socket test point 4 next to the test points Adjust RV1 to set the pulse threshold voltage to about 50 mV Please note Do not set threshold voltages of less than 50 mV on multi channel analysers Disconnect multimeter and observe LED it should not flash or be on continuously If the LED is flashing continuously the odd flicker is OK then the threshold voltage is set at a level
60. lly binding signed decontamination declaration e Wear suitable cotton or polythene gloves when handling the equipment e Re insert all transport locks if applicable e Cover the instrument with aluminium foil and or place it in a polythene bag Make sure no dust or packaging materials can contaminate the instrument e Make sure the plastic transport cylinder if applicable is clean e Fixthe instrument to its plastic cylinder if applicable Vy Omicron July 2002 Nano Technology Version 2 1 Index 84 EA 125 Energy Analyser User s Guide Index Sal deus 26 66 A Einzel lens eeessesesseeessse 38 adjustment of EAC sssssss 61 electrical connections 24 adjustment potentiometers EAC 64 electron optics seeusuuuus 37 adjustmeris nee 4 11 electronics wiring 25 AES test analyser teet 53 energy amplifiers output ssssssse 25 kinetie iiis Ern aes 3 analyser resolution ssseessssssssss 47 factory test 49 SDOCHNUFTIG ale 15 mode selection ceres 46 entrance aperture 14 operating parameters and resolution 47 experiments analyser test 49 resolution isipin epoke eK 47 experiments typical 49 MOONY 2 PC 35 analyser removal from UHV system 20 F analys
61. lower than the electronic noise and may have to be increased up to 50 100 mV Vy Omicron NanoTechnology Appendix 66 EA 125 Energy Analyser User s Guide If thresholds in excess of 60 mV are required then earth loop noise should be reduced by checking all ground connections to the electronics and spectrometer system are common Also check that the cables are not routed near sources of any noise due to radio frequencies which may emanate from badly suppressed transistor switching circuits e g mains power controllers switch mode power supplies ion and plasma sources Attention Operating with high threshold voltages necessitates using high multiplier voltages a condition which can reduce Channeltron operating life time e Repeat the above procedure for setting the threshold voltage for the remaining channels e Switch the mains supply off to the multiplier unit e Replace the front cover on the preamplifier unit Vy Omicron July 2002 NanoTechnology Version 2 1 Appendix 67 EA 125 Energy Analyser User s Guide XPS Quantitative Analysis with the Omicron EA 125 Version 1 3 09 02 01 D Funnemann Omicron Vakuumphysik GmbH Taunusstein Full implementation of the techniques described in this paper requires the use of the PRESENTS Data Presentation Package For information about this software please contact OMICRON Sales using the telephone numbers on the front of this manual or by email to sales omicron de The
62. ltron schematic diagram The statistical nature of the multiplication process results in a Gaussian distribution of pulse heights at the output from a channeltron Channeltron Operating Plateau As the voltage applied to a channeltron is increased the gain increases and the output pulse height increases As more and more output pulses exceed the threshold set in the preamplifier the observed count rate increases When the gain is large enough for the smallest pulses in the distribution to exceed the threshold a plateau is reached and no further increase in count rate is observed with higher voltages as shown in Figure 21 At very high voltages the observed count rate again increases due to the feedback of positive ions generated within the channeltron This should always be avoided as the observed pulses do not result from an input and operating channeltrons in this condition considerably reduces their lifetime lonic feedback region Plateau Count Rate Operating region Desired Maximum Operating Operating Voltage Voltage Applied Voltage 2 1kV 2 8kV pp g Figure 21 Channeltron operating plateau The onset of the plateau is reached at approximately 2 kV for new channeltrons and this slowly increases as the channeltron ages The desired operating voltage is approximately 100V above the onset of the plateau In Figure 21 the applied voltages marked with an Vy Omicron July 2002 Nano Technology Versi
63. ly stable supplies It is therefore very important that no noise is picked up onto the supply lines Earth loops should always be avoided by ensuring that all ground connections to the electronics and spectrometer system are common All cables should be routed well away from sources of noise such as mains power controllers switch mode power supplies or ion and plasma sources Figure 28 shows an MCD gas phase UPS spectrum A typical resolution of around 4 meV is shown Vy Omicron July 2002 NanoTechnology Version 2 1 8 Typical Experiments Factory Tests 56 EA 125 Energy Analyser User s Guide acl Ne I Excited Xe 5p line 15k E se 9 e i E 10k 5000 4 RII MmIelLMbellD Be lle belee ldpelbl07I lle7I ReeeITT lle711I14e 7TTelIe a oo ee Tree unu ee IDEAE EEE Ier m f 452 453 453 454 454 455 455 456 Kinetic Energy eV Figure 28 Analyser test HRUPS spectrum Wy Omicron July 2002 NanoTechnology Version 2 1 9 Troubleshooting 57 EA 125 Energy Analyser User s Guide 9 Troubleshooting Before proceeding to attempt to troubleshoot any suspected problem with the EA 125 please ensure the following All cables are connected as shown in section 5 of this manual The pressure in the system is below 10 7 mbar All electronics are switched on All Green voltage supply LEDs are lit on all four electronics units The nine IN TOL LEDs on the rear
64. mm slits are used and the pass energy in CAE mode is reduced to below 1 eV usually 0 5 eV to achieve the highest resolution The resolution achieved is best in low magnification mode as the angles into the analyser are smaller However due to the low acceptance angle in low magnification mode very low count rates are observed and so the high magnification mode is more practical and is usually used Xe gas is leaked into the gas cell until the pressure in the chamber rises to approximately 10 mbar This is due to the gas which has leaked through the apertures in the cell so the pressure inside the cell is much higher Operation of the channeltrons in this high pressure region is usually avoided however the gas used is inert and extremely pure 99 99997 so does not harm the channeltrons The line width of the Ne radiation is reduced to a minimum by reducing the pressure of the Ne gas in the discharge lamp This reduces the pressure broadening in the discharge This also has the undesired effect of reducing the photon flux and hence observed intensity The energy position of the observed peaks is not fixed and in particular depends upon the pressure of the Xe in the gas cell Varying this pressure changes the ionisation potential within the cell and therefore the kinetic energy of the emitted photoelectrons This means that it is essential that the pressure is stable whilst making a measurement High resolution can only be achieved with extreme
65. ms following the attached installation guidelines Exceptions Omicron cannot guarantee compliance with CE directives for components in case of e changes to the instrument not authorised by OMICRON e g modifications add on s or the addition of circuit boards or interfaces to computers supplied by OMICRON The customer is responsible for CE compliance of entire experimental setups according to the relevant CE directives in case of e installation of OMICRON components to an on site system or device e g vacuum vessel e installation of OMICRON supplied circuit boards to an on site computer e alterations and additions to the experimental setup not explicitly approved by OMICRON even if performed by an OMICRON service representative Vy Omicron July 2002 Nano Technology Version 2 1 Preface 5 EA 125 Energy Analyser User s Guide Spare Parts Omicron spare parts accessories and replacements are not individually CE labelled since they can only be used in conjunction with other pieces of equipment Please note CE compliance for a combination of certified products can only be guaranteed with respect to the lowest level of certification Example when combining a CE compliant instrument with a CE 96 compliant set of electronics the combination can only be guaranteed CE 96 compliance Vy Omicron July 2002 Nano Technology Version 2 1 Contents 6 EA 125 Energy Analyser User s Guide Contents dirum TEE 2 COP VINO sr
66. n Please note In the following instructions the workfunction of the analyser is assumed to have been set to O eV The peak positions will therefore be shifted by approx 4 5 eV to a smaller kinetic higher binding energy e Switch off the EAC 2000 300 and wait for minimum of 15 minutes until all capacitors have been discharged Careful High voltages e Loosen the 4 screws on the top cover and remove the cover Attention Warning Lethal Voltages The voltages present inside the EAC unit are LETHAL Do not attempt this adjustment unless you are authorised personnel qualified to handle lethal voltages In particular the Focus cards in the EAC 300 require extreme care e Locate the potentiometer RV 1 for the EAC 2000 and RV5 for the EAC 300 on the PE outer module see relevant part of Figure 29 on July 2002 V Omicron Version 2 1 Appendix 63 EA 125 Energy Analyser User s Guide page 64 The potentiometer can be reached through the top of the unit Connect all cables of EA 125 and X ray source UPS Lamp Switch all electronics units on and start the software Allow for a warming up period of 30 min Adjustment procedure 1 Measure a spectrum of the Feature you have chosen in single channel mode Select 1 channel in EIS configuration dialogue Adjust your sample for maximum intensity Measure a spectrum at the lowest pass energy and the highest pass energy you are using making sure that you are not outside the valid operating re
67. nction An unknown spectrum can be transferred to and corrected in the EXCEL sheet Checks Before comparing the atomic composition of different samples measured within several months the researcher should make sure that the analyser is suitable for the purpose The measured parameters should be stable reproducible and behave linear Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 77 EA 125 Energy Analyser User s Guide Count Rate Stability The count rate should be stable with time Over a period of 1h the peak area of a Cuz peak was checked to be stable within 0 5 Peak Position Peak positions should not change with time or upon switching pass energy For XPS the peak position is stable within 50 meV Reproducibility Measurements should be reproducible A measurement made on a different sample of the same element is reproducible within less than 50 meV Count Rate Linearity The counting system should have a linear response The simple assumption that the detector response might be linear is not valid for modern excitation sources delivering a very high photon flux Surprising results might appear when the detector linearity is experimentally tested Shea Gilmore et al For a detection system with dead time zq the relation between the observed count rate N os and the true count rate N true is given by N true Na N T 1 true The dead time for the EA 125 MCD 7 channel detection system was determine
68. nd exit slits are both centred on Ro Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 37 EA 125 Energy Analyser User s Guide If Ey is the kinetic energy of an electron travelling in an orbit of radius Ro we call E the pass energy then the relationship between E and Vo is given by the expression R Ry R R eVo E Figure 15 The hemispherical analyser schematic diagram The voltages on the inner and outer hemispheres are V and V respectively and these are given by Where E is the mean analysing energy or pass energy of the analyser This produces an inverse squared 1 R field in the region between the hemispheres Please see reference 4 in Surface Analysis General Literature on page 82 for further details The Universal Lens This section is intended as a brief introduction into the main aspects of the electron optics of the universal lens For a detailed description please refer to King George C 5 Electron and lon Optics In Experimental methods in the physical sciences Volume 29A Academic Press Inc 1995 Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 38 EA 125 Energy Analyser User s Guide Electrostatic Input Lens The universal lens is a multi element electrostatic input lens fitted at the entrance to the analyser The purpose of the lens is to allow a collection of electrons from larger solid angles than would otherwise be poss
69. nd note the rate at which the spectrum is shifting e Enter the Instrument Control page of the EIS software e Select and then deselect 1 10 Energy scaling e Switch into CRR mode and then back into CAE mode or vice versa e Repeat the 10 identical scans again noting the rate at which the spectrum is shifting Vy Omicron July 2002 Nano Technology Version 2 1 9 Troubleshooting 59 EA 125 Energy Analyser User s Guide If the rate at which the spectrum shifts has dramatically increased please contact Omicron Service using the procedures given on page 83 Peak Intensity Changes with Time Check that the sample or anything in the sample region is not charging as in the Peak Energy Changes with Time section above Check that each channeltron is on the count rate plateau see Channeltron High Voltage Setup on page 32 and Channeltron Operating Plateau on page 41 Check the analyser supply voltages at the filtered plug see the EAC Electronics for EA 125 Technical Reference Manual If all of the above can be ruled out perform the following test e Ensure the EAC 2000 300 has been switched on for gt 30 minutes e Run 10 identical scans and note the rate at which the intensity is changing e Enter the Instrument Control page of the EIS software e Switch between all three magnification modes and back e Repeat the 10 identical scans again noting the rate at which the intensity is changing If the rate at which the intensity
70. neous depth profile For a user who wants more accurate results we give hints for further improvement The first part compiles parameters and information required for the calculation The emphasis is on making the information available in a shape that can be handled easily An example is given which details the recipe on how to apply the routines within the data processing software Presents Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 68 EA 125 Energy Analyser User s Guide Parameters Which are the parameters to know For an accurate quantitative analysis the peak areas intensities and energy positions of core level peaks are to be determined The measured intensity P of core level i is proportional to the number of atoms n Ertl K ppers Pi C 6 OAT eni Pi Peak Intensity i peak label C factor of proportionality Oi cross section for photoemission for core level i o angular distribution factor A effective mean free path of the electrons in the sample T transmission function of the analyser including the detection efficiency and the possible area variation with Ej n number of atoms in the analysed volume Relative Number of Atoms We want to find the number of atoms ni of a specific element Solving for n yields 1 P 1 A pi c O PAT c Relative quantification is accomplished by taking the ratio of the measured peak areas divided by the respective correction factors s na Np
71. on 2 1 7 Theory of Operation 42 EA 125 Energy Analyser User s Guide are for new channeltrons only the plateau onset and end voltages will rise as the channeltron ages The electron pulse is then routed to the preamplifier which filters out the system noise using a high speed threshold comparator circuit The electrical signal is converted to an optical signal which is transmitted to the receiver unit via an optical fibre link The receiver unit converts the optical signal to a TTL electronic pulse which is then counted by the computer The optical link isolates the pulse counting system usually a computer from the spectrometer and maintains low noise data levels The optical receiver provides both digital TTL output pulses for the pulse counter and an analogue voltage which is proportional to the count rate Normally 10 V correspond to 1 Mcps million counts per second The output polarity and range are jumper selectable on each receiver board see the CPC 125 65 M and CPC 125 65 S manuals listed in Table 1 on page 2 Channeltron Lifetime Expectancy Replacement The normal behaviour of a channeltron as it ages is for the plateau voltage to steadily increase during early operation This voltage levels out on to a plateau After this plateau is reached the channeltron should last for a considerable period with very little increase required Omicron try not to significantly age channeltrons before shipping This often means that the
72. operating parameters and resolution three electrode lens 38 analyser aan eat 47 transport damage ssssse 19 operation mode two electrode lens 38 CAE button teste 14 46 typical experiments 49 CRR A Dp E T Ae kr 14 46 optical fibre sssssssssssssss 25 U output amplifiers 25 UHV installation 20 UHV system analyser removal from 20 P universal lens 14 17 pass energy ssssesseee 37 electron optics ssssssse 37 peak width eesssssssssss 48 operation eeessseseeeeee 38 photo emission seseseusuuss 3 Unpacking uns on oon virt ovo en ior idt bes 19 preamplifier pulse 25 pulse COUNTING ret 27 V pulse counting operation 41 variable slit mechanism 15 pulse counting setup 26 voltage plateau channeltron 42 voltage ratio lens 40 R voltage lethal 4 11 ratio retarding 444442 2 40 related manuals ssssse 2 W removal from UHV system 20 Warranty a see 3 resolution
73. or metals is between 5 and 20 Angstrom for oxides between 15 40 and for polymers 40 100 In cases only one material class like metals is used it is sufficient to use the approximation A E The required correction on a measured spectrum would be to divide by A En When the photoelectron is looked at an angle e from the sample normal a correction factor has to be applied e A cos e if spectra taken at different angles are to be compared M P Seah S Gilmore S J Spencer Applied Surface Science 144 145 1999 132 M P Seah G C Smith M T Anthony Surface and Interface Analysis 15 1990 293 G Ertl J K ppers Low Energy Electrons and Surface Chemistry VCH M nchen 1985 S H fner Photoelectron Spectroscopy Principles and Applications Springer 1995 Springer Series in Solid State Sciences Vol 82 A Jablonski S Tilinin J Electron Spectrosc Relat Phenom 74 1995 207 7 National Institute of Standards and Technology NIST USA Electron Inelastic Mean Free Path Database SRD71 http nist gov srd ns Tougaard J Vac Sci A14 1996 pp 1415 S Tougaard Quases xs REELS Software for Quantitative REELS Determination of Ineleastic Scattering Cross Sections Internet www quases com Vy Omicron July 2002 NanoTechnology Version 2 1 Appendix 71 EA 125 Energy Analyser User s Guide Cross Section The cross section for photoelectron excitation depends on the photon energy
74. other peaks are deleted from the list Name Z Position Area Conc 1 a Tougaard Formalism for quantitative surface analysis by electron spectroscopy J Vac Sci Technol A8 3 1980 2197 WOmicron July 2002 NanoTechnology Version 2 1 Appendix 80 EA 125 Energy Analyser User s Guide Cis 6 290 8054 16 4 N1s 7 403 8067 9 1 O1s 8 537 5 52918 36 8 Si2p 14 108 5 14509 36 2 Mo3d5 2 42 231 5 2353 0 9 Ag3d5 2 47 373 5 3046 0 6 100 These concentrations Conc 1 still have to be corrected using the emission angle p After application of the correction quotient we get to C2 96 which has to be rescaled to give a sum of 100 Note that the effect of the D correction on the final result is not a big one Name p Corr Quot C2 Concentration C1s 0 45 1 10 14 9 17 0 Nis 0 50 1 11 8 2 10 0 O1s 0 55 1 12 32 8 38 0 Si2p 1 05 1 24 29 1 33 7 Mo3d5 2 1 18 1 27 0 7 0 8 Ag3d5 2 1 20 1 27 0 5 0 5 100 Concentration 40 35 30 25 20 El Concentration 96 15 10 0 i i E 0 um C1s N1s O1s Si2p Mo3d5 2 Ag3d5 2 Further Improvements We made some zero order approximations or assumptions in the analysis In general the elements present have another peak showing in the spectrum It is a good check to use the other peak instead of the main one to cro
75. p 26 34 2 H Neat Kernphysikalische Me verfahen zum Nachweis f r Teilchen und Quanten Karlsruhe 1966 p396ff Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 44 EA 125 Energy Analyser User s Guide 3 P Weinzierl M Drosg Lehrbuch der Nuklearelektronik Wien New York 1970 p 12 and 283 In a counter with a dead time t the observed count rate N in counts per second is given by obs uM 1 1 N one Niue is the true number of electrons ions entering the channeltron The dead time of the counting system channeltron pre amplifier receiver and counter card is t 70 ns 14 MHz other options are 80 ns and 130 ns The following diagram shows a calculation of formula 1 for that special case 1 0 s 4 P4 4 0 8 we S4 P d und s Real 0 6 me 8 LU E 304 m L PA 0 2 0 0 0 2 0 4 0 6 0 8 1 0 Niue Mcps Figure 23 Observed Real count rates N ps versus true count rates Nue as calculated from equation 1 The Ideal straight line is shown for comparison Another version of the graph shown in Figure 23 for count rates up to the maximum of 14 Mops is shown in XPS Quantitative Analysis with the Omicron EA 125 Count Rate Linearity in the Appendix on page 77 Figure 24 gives the difference between N and Nps in of error It shows that although the counter is capable of more than 10 MHz unless the loss in observed counts is correcte
76. panel of the EAC 2000 or EAC 300 are lit A suitable sample and source are present in a geometry producing electrons After all of the above have been checked please read through the following titles and if any describes your problem follow the given instructions Problem Page No Counts Observed in Software 57 Peak Energy Changes with Pass Energy 58 Peak Energy Changes with Time 58 Peak Intensity Changes with Time 59 Low Kinetic Energy Cutoff too High 59 Poor Resolution 59 Low Intensity 60 Peaks at Wrong Energy 60 Noise Counts Observed with Channeltron HV OFF 60 Intensity Observed from the Sample Holder 60 If none of the above titles describes your problem or none of the suggestions help cure the problem please contact Omicron Service using the procedures given on page 83 No Counts Observed in Software July 2002 u Please note The most common cause of no counts is a cable either disconnected or connected incorrectly Please double T check all cables before proceeding Using the EIS Software Instrument Control page set a suitable KE PE and Magnification mode Click the checkbox to switch the Multipliers ON Vy Omicron NanoTechnology Version 2 1 9 Troubleshooting 58 EA 125 Energy Analyser User s Guide Check that both the red MULTIPLIER ON LEDs one on the EAC 2000 300 and one on the Multiplier Supply light Check that the LEDs on the front of the Preamp light Check that the Output adju
77. r retard the electrons relative to the energy at which they left the sample and provide variable magnification and angular acceptance to select the sample analysis area 2 a set of slits at the entrance to the energy analyser to alter the transmission characteristics and resolution of the analyser 3 a hemispherical energy analyser with 125 mm mean radius 1809 double focusing geometry 4 a set of slits at the exit of the energy analyser corresponding to the number of electron multipliers in the detector and 5 a detector consisting of an array of 1 5 or 7 Channeltron electron multipliers The hemispherical energy analyser is mounted on a stainless steel flange under a hemispherical stainless steel cover see Figure 1 Magnetic shielding is provided by 1 layer or 2 layers in the EA 125 HR of mu metal shielding within the stainless steel flange and cover The EA 125 Energy Analyser is mounted on the vacuum system by a NW 100 CF 6 OD flange Vy Omicron July 2002 Nano Technology Version 2 1 1 Introduction 10 EA 125 Energy Analyser User s Guide Versions of the EA 125 Four versions of the EA 125 and EA 125 HR Energy Analysers are available e EA 125 U1 with a single detector which cannot be further upgraded e EA 125 U7 1 with a single detector which can be upgraded to a 7 channel detector e EA 125 U7 5 with a 5 channel detector which can be further upgraded e EA 125 U7 with a 7 channel detector which cannot be furthe
78. r upgraded Computer Operation The operations of the lens analyser and detector are controlled via an IEEE interface from a PC based computer to an EAC 2000 125 or EAC 300 125 spectrometer control unit The IEEE interface is in turn controlled by EIS Electron and lon Spectroscopy Software which also acts as the communication link between the user and the computer This software also communicates with a SAC counter board and processes the signal Both the IEEE board and the SAC counter board reside in the computer EA 125 Energy Analyser Computer Requirements The recommended minimum computer requirements for the operation of EIS Electron and lon Spectroscopy Software for use with the EA 125 analyser are as follows e IBM PC compatible computer e Two 2 spare PCI slots for full length cards e 200 MHz Pentium or Celeron processor e 64 MB memory e 4GB HDD EIS uses approximately 10 MB e SVGA graphics 1024x768 capable e 17inch monitor e Microsoft Windows NT 4 0 operating system Hardcopy output is supported to any Windows NT compatible device The SAC and IEEE interface cards fit into spare expansion slots of the host computer The SAC requires a PCI slot The slot should be at least 120 mm tall with a depth of at least 240 mm The ComputerBoards IEEE interface card requires that the PCI slot should be at least 120 mm tall Vy Omicron July 2002 NanoTechnology Version 2 1 2 Safety Information 11 EA 125 Energy Analyser
79. r d doc telas ead mt cti Em E ipd ELE 3 lure 3 sna 3 Conditions OF CE Compliance dns tess ee en Rouen deba sua deb guae aea 4 Contents aiiin ba tainen Pda Ea wc dia Sur Pav a vce VD 6 B gEgcr ETE 8 Listof kablesz aun sta RR 8 1 iugere TeiiTo eee 9 EA 125 Spectrometers oo o Ec Reb EG Eee 9 EA 125 Vacuum Hardware ssssse emen 9 Vetsions arihe E125 ccm a a tem a a dea ucl n ELE 10 Computer Operation n i Ra xo AR ea dama ea na sun Da oo R dM anna Teksi 10 EA 125 Energy Analyser Computer Requirements sssssssss 10 2 Safety Information en erra nessun d edes 11 3 The Hemispherical Analyser eene nennen nennen nennen nennen nnns 13 The Electrostatic Input Lens ssssssssssseessseeeeeeeenennene nnne nnne 14 The Detector ic os He NEAR ECEREHRR RR EAR e ERE HR SERRA E eR ahnen 15 The Variable Slit Mechanism nee 15 Outline Dimensi n Sars nona dope ein 17 Magnetic Shielding teet eto we ete ee 17 4 Unpacking and Installation eeeeeeeeeeeeeeeeeeeeeeeeeee enne nnne nnn 19 EA 125 Analyser Supplied as a Componernt usssssssssseeenennnnnnnnnnnnnnnnnnnnnnnnnnen 19 Unpacking T M 19 Electhcal CHECK RU RM CC cstelimner tate ce 20 Vacuum Installation and Removal sse 20 5 Getting Started oio obuia ben itc rni mu Eod
80. rce When switching between a dual anode source and a monochromatic source the angle changes Check that the peak intensity is not higher than about 3 Mcps per channel In case it is reduce the X ray power The pass energy chosen should be a good compromise between good count rate statistics and resolution Zn Rcgc ET ccc Ols Ze 32 265 7189415 537 5 23964 71 3 14781 36 108 5 4927123 3 20kl 23854 18140 53 290 6046 845 3 14474 19812 99 402 5 6604 331 3 Ag3d3 2 24141 12014 12 373 5 4004 708 3 Mo3d3 2 3 476 10256 67 231 5 3418 891 3 V NZ a O 2 oa i g aA e ES N EEEE A bal SEEE TERENE Nis i i Cls Si2p1 22p3 2 1 Ag3d3 2 H Mo3d3 2 5000 mm Een demere PII Pacte ta b DE E n n i N i j i i J f I hd qpuE L pep 1000 800 600 400 200 o Binding Energy Fig 6 Peak measurement information Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 79 EA 125 Energy Analyser User s Guide Data Processing using Presents A 1 Smooth On the acquired spectrum we work with the tools buttons First of all we smooth the spectrum with Savitzky Golay method and choose a smooth factor of 2 Al e0 28 2 Corrections Make sure the axis label is Binding Energy Apply the correction E This corrects for the mean free path and for the transmission function
81. rd aperture combinations Vy Omicron July 2002 Nano Technology Version 2 1 3 The Hemispherical Analyser 16 EA 125 Energy Analyser User s Guide Multi channel Analyser EA 125 U7 Upgradable Analysers EA 125 U7 1 and 5 The entrance and exit slit mechanisms in seven channel and upgradable systems can be operated independently to give a wide range of combinations The entrance and exit slit arrays have separate independent rotary drive mechanisms The entrance apertures are identical to those in the non upgradable version The exit apertures consist of 3 sets of 7 apertures one for each of the 7 possible channeltrons Table 4 below gives the standard aperture dimensions Entrance aperture plate Exit slit s plate Figure 3 Multi channel detection entrance and exit plates layout Multi channel detection 7 channel and upgradable analysers Analyser Entrance Analyser Exit Rotary drive position Entrance aperture Position Exit slit dimensions dimensions 360 6 mm x 12 mm 1 1 mm x 10 mm 270 6 mm diameter 2 3 mm x 10 mm 180 2 mm diameter 3 5 mm x 11 mm 90 1 mm diameter The 5 mm dimension in Position 3 reflects 0 AA the width of the focus plate aperture and channeltron entrance behind the exit slit Table 4 EA 125 multi channel analyser standard aperture combinations If a 6 mm entrance slit and a 1 mm exit slit
82. ressures gt 10 mbar this is normal for all 7 channel electron multipliers Multi channel Analyser High Voltage Adjustment If it is suspected that any channel in a multi channel analyser needs to be individually adjusted please follow the procedure listed below A Warning Lethal Voltages Adjustments may only be carried out by authorised personnel qualified to handle lethal voltages Lethal voltages are present inside the CEM supplies Extreme caution should be exercised when carrying out any adjustments inside this unit e Pump down the system and bake the spectrometer as normal e Remove the CEM supplies from the equipment rack e Connect all cables e Connect a source of electrons to the spectrometer i e switch on an excitation source e Connect a multimeter to the rate meter output of the channel in question on the receiver unit e Open the Instrument Control page of the EIS software e Choose a suitable set of parameters which give around 100 kcps and enter these into the checkboxes e Switch ON the multiplier voltage by clicking in the Multiplier checkbox e Increase the front panel multiplier control dial slowly to the value at which you have been operating observing the ratemeter output If the onset of the count rate plateau has not yet been reached or if you believe that the voltage is too high count rate approaching the ionic feedback region continue as follows e Remove the top panel on the
83. rge enough to ensure that the pass energy does not exceed 200 eV the maximum pass energy of the EAC 2000 throughout the entire scan The measured intensity is the peak maximum minus the background measured approximately 40 eV above the peak 390 eV This figure is then divided by the beam current which is measured with a 20 V positive bias on the sample Figure 27 shows an AES spectrum of Ag OO Ze Be Ze i t A PEPE PAR PEET EPPP E E RERE RE ELE REPE S 9 2200kF E Renee EER oe Se EEEE Intensity CP i i i i i 260 280 300 320 340 360 380 400 Kinetic Energy eV Figure 27 Analyser test AES spectrum As in XPS the most common problem with the AES test is low intensity caused by a dirty sample Again this is checked for by looking for the presence of C and O lines The C KLL line appears at the same energy as the lower energy Ag MNV line at 260 eV If this Vy Omicron July 2002 Nano Technology Version 2 1 8 Typical Experiments Factory Tests 54 EA 125 Energy Analyser User s Guide peak appears more intense than the higher energy Ag MNV line at 293 eV this is a good indication that the sample is not clean The other cause of low intensity is the position and focusing of the primary electron beam This must be focused into a very small spot at the centre of the analyser analysis area to achieve the maximum performance The analyser resolution remains
84. s 39 counting potentials dude eid 38 literature scan a 43 three electrode 38 uc qe E 43 two electrode iid siete derat 38 CRR mode sees 14 46 voltage ratio ssssssssse 40 ZOOTDI s cite ene iius 38 D lens potentials decontamination equal irte Dore D oes 38 declaration sseeeesss 86 nequal sin dents 38 proforma oneee eere anini 87 lethal Voltages 4 11 lifetime channeltron 42 E limitations esses 12 EAC 2000 ictor eo ra eau se engen 3 line width EAC adjustment uuuus 61 Induced tt deeds 48 EAC adjustment potentiometers 64 Daturgls ooi seen ee 48 July 2002 Womicron Version 2 1 Index 85 EA 125 Energy Analyser User s Guide literature selection analyser mode 46 COUDUEIG 2 53 croci eer mp maven sheet ee 43 service procedure 83 Gener le niert 82 setup software aee tese tetets tert eur Abk a certus 30 M setup magnification lens 39 pulse counting ore 26 measurements fault finding 4 11 software setup c0seeeeeeeeeeeeeeeeees 30 modes of operation 14 46 statistics of counting 43 multi channel system 16 T O theory analyser ss 35
85. s Guide and is often very difficult to detect Usually the only way to detect this is to examine the window and look for discolouration The resolution observed is usually limited by the X ray line width and remains nearly constant for a given set of analyser parameters Pass Energy and slit sizes Oxidation of the anode can cause a broadening of the line width which can limit the ultimate resolution obtainable This is detected by the presence of large ghost peaks from O Ka X rays Vy Omicron July 2002 Nano Technology Version 2 1 8 Typical Experiments Factory Tests 53 EA 125 Energy Analyser User s Guide Auger Electron Spectroscopy AES The AES tests involve measuring the intensity of the Ag MNN peak per nA of beam current As in XPS an Ar ion etched polycrystalline Ag sample is used with an electron source operating with a primary beam energy of 5 keV The electron source is positioned at an angle of 45 to the analyser lens and the sample is mounted with its normal in the direction of the lens The largest entrance and exit slits are used and the analyser is operated in CRR mode The primary electron beam is focused into a small spot on the sample and electrons from large angles are required so the high magnification mode is used A retard ratio of 4 is used to ensure a resolution of 0 5 of the kinetic energy If a retard ratio of 5 is used the analyser operates with a resolution of 0 4 The retard ratio chosen must be la
86. s applied to V4 and V3 are not equal the three cylinder lens will either accelerate or retard the transmitted electrons It is possible to calculate a range of values Vy Omicron July 2002 Nano Technology Version 2 1 7 Theory of Operation 39 EA 125 Energy Analyser User s Guide which must be applied to V2 to keep the object to image distance constant whilst varying the ratio through which the electrons are accelerated or retarded This is known as a zoom lens curve as shown in Figure 18 10 0 VAN 5 0 2 07 0 5r 0 2 F 0 1 0 2 0 5 1 0 2 0 5 0 10 0 VJV Figure 18 Zoom lens curve Note that for any given accelerating retarding ratio V3 V4 there are two values for V2 V which both focus the electrons to the same point An advanced version of this type of zoom lens design is employed in the second stage of the Universal lens and is used to set the pass energy of the analyser The Law of Helmholtz Lagrange Apertures are used in electrostatic lenses to define the beam A window aperture defines the radial size of the beam and a pupil aperture defines the angular extent of the beam Figure 19 shows a schematic of an electrostatic lens produced by the different potentials V4 and V illustrating the definition of the beam by the window and pupil apertures The lens produces an image of the window The radial size of the image is determined by the magnification M of the lens M rz ri where r and rz are
87. ser The Channeltron amplifies the current of a single electron ion by a factor of about 10 The small current pulse present at the output of the Channeltron is passed through a vacuum feedthrough and then directly into the preamplifier From here the signal is passed on to a pulse counter for processing and production of an electron ion energy spectrum For further details on the detection electronics please refer to the CPC 125 65 M or S electronics manuals listed in Table 1 on page 2 The Variable Slit Mechanism Non upgradable Single Channel EA 125 U1 The variable slit mechanism used with a single Channeltron is provided with five different linked pairs of entrance and exit apertures The pairs of apertures can be selected from outside the vacuum system by a rotary drive which moves the slit plates through a rack and pinion Table 3 below gives the standard aperture combinations Entrance aperture Rotary drive Exit slit plate position plate 360 O 270 180 O o 90 LLIL L 0 co Figure 2 EA 125 U1 entrance and exit plates layout Single Channel Detection non upgradable Rotary drive position Entrance aperture Exit slit dimensions dimensions 360 6 mm x 12 mm 6 mm x 12 mm 270 6 mm diameter 6 mm x 12 mm 180 2 mm diameter 6 mm x 12 mm 90 1 mm diameter 1 mm x 12 mm 0 1 mm x 12 mm 1 mm x 12 mm Table 3 EA 125 U1 standa
88. ser can be operated in Constant Analyser Energy mode CAE mode or Constant Retard Ratio mode CRR mode The Electrostatic Input Lens The input lens collects the electrons from the source and focuses them onto the entrance aperture of the analyser whilst simultaneously adjusting their kinetic energy to match the pass energy of the analyser The lens is also designed to define the analysis area and angular acceptance of electrons which pass through the hemispherical analyser The lens design employs a double lens concept whereby two lenses are stacked one above the other The first lens as seen from the sample selects the analysis area spot size and angular acceptance This is an Einzel lens i e it does not change the energy of the electrons and therefore has a constant magnification throughout the entire energy range This lens can be operated in three discrete magnification modes high medium and low In high magnification mode the focal plane is near to the sample and the lens accepts a wide angle of electron beams from a small region In low magnification mode the focal plane is further from the sample and the lens accepts only a small angle of beams but from a larger area The medium magnification mode is in between the two The second lens retards or accelerates the electrons to match the pass energy of the analyser and uses a zoom lens function to ensure that the focal point remains on the analyser entrance aperture The magnificat
89. sheet s trade name product name manufacturer chemical name and symbol danger class precautions associated with substance first aid measures in the event of an accident Is the equipment free from potentially harmful substances Yes O No Lr The manufacturer reserves the right to refuse any contaminated equipment component without written evidence that such equipment component has been decontaminated in the prescribed manner 4 Decontamination Procedure Please list all harmful substances gases and by products which have come into contact with the vacuum equipment components together with the decontamination method used SUBSTANCE DECONTAMINATION METHOD continue on a separate sheet if necessary 5 Legally Binding Declaration Organisation Address Tel Fax Name Job title hereby declare that the information supplied on this form is complete and accurate Date Signature Company stamp Vy Omicron July 2002 Nano Technology Version 2 1
90. sities at given resolutions peak FWHM are guaranteed for the Ag 3d peak with an X ray source power of 300W The experimental set up is optimised for maximum sensitivity The X ray source is mounted perpendicular to the EA lens with the sample tilted at 45 The X ray source is positioned as close to the sample as possible without causing shading The largest entrance and exit slits are used to ensure the largest Etendue the product of analyser analysis area and acceptance angle as the sample is flooded with X rays The CAE mode is used and the pass energy is varied to achieve a range of EA resolutions The measurements are repeated in all magnification modes Count rates of over 2 Mcps per channel are observed at an X ray source power of 300W so the power is reduced to protect the channeltrons The high voltage is kept at 15 kV and the emission current is reduced The measured intensity is then simply multiplied by the same ratio to give the performance at 300W The linearity of the EA 125 performance with X ray power has been verified experimentally The channeltrons are also protected by starting broad survey scans at 100 eV to avoid the huge secondary electron background at low kinetic energy The most common problem encountered during XPS tests is low intensity The observed intensity is strongly dependent upon the geometry of the experimental set up and therefore only under optimum conditions will the maximum intensity be observed
91. ss check the elemental distribution This check gives a good indication of the remaining error For the accuracy possible see also L T Weng et al Quantitative XPS Part Il Surf Interf Analysis 20 193 205 1993 Vy Omicron July 2002 Nano Technology Version 2 1 Appendix 81 EA 125 Energy Analyser User s Guide For a more detailed and sophisticated approach the reader is referred to Ertl K ppers Here is a list for possible further improvements for the quantitative analysis Additionally to the Si2p peak at about 99 5 eV there is a Si2p shifted peak from SiOz which we have neglected So we could differentiate between elemental Si and Si in SiO Similar There is an elemental Carbon and a shifted Carbon peak at 284 eV We could differentiate between elemental Carbon and Carbon in a CO molecule The finding of C O and CO questions our assumption of a homogenous sample We rather have a contamination layer on top Ebel 1984 gives a description of how to deal with it quantitatively Ona similar footing The Si oxide may be an overlayer How to find out quantitatively is described in Ebel 1985 chapter 7 1 see Ref 1 The above mentioned hints give the foundation for quantitative XPS analysis The route to becoming an expert is outlined in a paper by Castle and Baker Spectra and Data Compilations National Institute of Standards and Technology NIST USA X ray Photoelectron Spectroscopy Database SR
92. st dial on the CEM Supplies is turned up to the operating value Check the Preamp threshold settings see Section 6 on page 65 Check that the entrance and exit slits are located in an indent position Check that the sample is in position by viewing through the high energy beam dump and lens Select low magnification mode large spot and double check the alignment of the exciting source Disconnect the fibre optic cable from channel 1 of the receiver Check that red light is emitted from the fibre optic Firmly reconnect fibre optic Connect a digital multimeter to the monitor cable connected to the analogue output from the receiver and check that an analogue voltage is present Peak Energy Changes with Pass Energy A common problem observed when the EAC has not been finely adjusted to a specific analyser often after maintenance of the EAC See EAC Adjustment on page 61 in the Appendix Peak Energy Changes with Time This effect is usually caused by an insulating sample becoming charged This can be avoided by careful use of electron and ion flood guns Conducting samples may also behave this way if they are not well grounded If the sample itself is not charging there could be an insulator close to the sample e g on the sample holder charging and deflecting the beam If all of the above can be ruled out perform the following test e Ensure the EAC 2000 300 has been switched on for gt 30 minutes e Run 10 identical scans a
93. the analyser should be mounted in a mu metal chamber and a strip of mu metal formed into a spiral is provided for the user to fit between the input lens mu metal cover and the analyser mounting port The mu metal spiral completes the magnet circuit between the analysis chamber and the lens cover to minimise magnetic field penetration into the analysis space If the user has a stainless steel chamber the mu metal cover for the input lens is extended almost to the end of the lens and a mu metal spiral is not provided Vy Omicron July 2002 Nano Technology Version 2 1 3 The Hemispherical Analyser 18 EA 125 Energy Analyser User s Guide steel Please note The energy resolution of High Resolution HR SN analysers cannot be guaranteed if fitted to a stainless chamber For details on fitting the mu metal spiral see page 22 160 OD ROT CF FLANGE 150 OD ROT CF FLANGE TT 259 329 POSITION FOR 254 LONG PoRT 09 699 5 MUMETAL SPIRAL 160 OD ROT CF FLANGE F 991 5 t MUMETAL SCREEN POSITION FOR 254 LONG PORT 99 5 MUMETAL SPIRAL POSITION FOR 329 409 POSITION FOR 203 LONG PORT 203 LONG PORT 274 6 ELECTROSTATIC 478 8 INNER MUMETAL SCREEN SCREEN 474 6 ELECTROSTATIC SCREEN 10 5 i E 930 X 1 10 5 274 6 ELECTROSTATIC ee 930 Y ri i 4 4 ey 301 i 304 y dg 304 BMfI ogo Sait EA125HR ANALYSER LENS SCREENS
94. the emission angle remain almost constant throughout the whole kinetic energy range Constant Analyser Energy CAE Scan Mode In the CAE mode of operation the analyser pass energy is held constant and the retarding voltage is changed thus scanning the kinetic energy of detected electrons A range of analyser pass energies is available for selection from the control unit The resolution obtained in CAE is constant throughout the whole kinetic energy range The sensitivity however is inversely proportional to the kinetic energy and at lower kinetic energies is improved over that obtained with CRR The improvement may be so great that a reduction in the X ray power may be necessary to bring the signal within range of the detector and pulse counting system often by up to a factor of 10 At the same X ray power the signal intensity at the high kinetic energy end is comparable to that obtained with CRR In the CAE mode the analysed sample area and the emission angle may vary slightly with the kinetic energy but this is dependent on the type of lens design Selection of Analyser Mode The CAE mode has the advantage of fixed resolution at all kinetic energies and is used in XPS over the range 150 eV to 2000 eV Below 150 eV the CRR mode is more common in both AES and XPS Consider now the nature of XPS and AES techniques e n XPS the user is frequently concerned with peaks at energies close to the photon energy typically 1500 eV simply be
95. thus conducting for your own safety please ensure that your Trimmer is Insulating The following instructions were written for silver as an example It is possible of course to use other samples in which case only the measurement parameters have to be varied Whichever sample is used it should be clean conductive grounded and give high intensity peaks whose positions are well known Vy Omicron July 2002 Nano Technology Version 2 1 Appendix Peak Information Tables for Silver 62 EA 125 Energy Analyser User s Guide MgKa Excitation 1253 6 eV with corrected Work Function Sample Ag Polycrystalline foil 99 9985 Alfa No 944752 or Goodfellows No Ag000465 If AIKa excitation 1486 6 eV is used add 233 eV to all the kinetic energy E kin values of the core level peaks The E kin and binding energy E bin values of the Auger peaks remain unchanged Silver peaks Ag poly 4p 4s 3d 5 2 3d 3 2 3p 3 2 3p 3s MAVV M5VV E bin eV 58 97 368 374 573 604 718 895 5 901 5 E kin eV 1195 6 1156 6 885 6 879 6 680 6 649 6 535 6 358 1 352 1 Other Peaks O1s OKVV Cis C KVV E bin eV 531 6 745 3 284 6 990 E kin eV 722 0 508 3 969 263 6 Table 7 Peak information for silver sample He I Excitation with corrected Work Function The Fermi edge will be observed at 21 2 eV Preparatio
96. tion Do not bake the electronics In order to avoid severe damage to the electronics all units and cables must be removed from the UHV system prior to bakeout When operating the CPC electronics for the first time after venting the system should be allowed to pump for at least 4 hours Always make sure the chamber base pressure is 10 mbar Attention Under no circumstances should the CPC electronics be operated in conjunction with chamber pressures 10 mbar Vy Omicron July 2002 Nano Technology Version 2 1 5 Getting Started 27 EA 125 Energy Analyser User s Guide l5 Please note The Channeltron lifetime will be reduced when operating the CPC electronics at pressures gt 10 mbar this is 7 normal for all channel electron multipliers Before switching on the pulse counting electronics make sure e the mains voltage on the multiplier supplies unit is switched off e the chamber pressure is 10 mbar e the red MULTIPLIER ON light on the front of the EAC 300 or EAC 2000 is not lit Vy Omicron July 2002 Nano Technology Version 2 1 5 Getting Started Channeltron Signal Input 28 Mains Input Cable Rear Bias Single Channel Preamplifier Optical Output PLED DC Supplies Optical Fibre Cable A 3 m SCD CEM Supplies Unit O amp cen onoff m m o S a E Output Adjust Potent
97. to fix the provided mu metal spiral to the appropriate position on the mu metal lens cover The position of the mu metal spiral depends on the port length to which the analyser is to be fitted as shown in Figure 8 Note that the mu metal spiral will be in contact with the mu metal port tubulation when the analyser is fitted to the system Analyser mounting flange F Mu metal spiral fixing position for 254 mm port length Mu metal spiral fixing position for 203 mm port length Figure 8 Mu metal spiral positions Check that the spacer provided brings the lens stack to the correct working distance for the lens analyser type Supporting lugs are provided on the analyser base flange to assist when lifting the analyser to the vacuum vessel Check that the lens assembly cannot clash with other vacuum fixtures The mu metal spiral may need to be tightened to allow it to slide freely into the end of the port Once fitted in the port the spiral has Vy Omicron NanoTechnology EA 125 Energy Analyser User s Guide Version 2 1 4 Unpacking and Installation 23 EA 125 Energy Analyser User s Guide sufficient lateral rigidity to allow it to slide into position without bending sideways 11 Fit the analyser to the vacuum system using a new 100 mm copper gasket and tighten the bolts evenly 12 Evacuate the chamber to a pressure of below 10 mbar and bake the system as described on page 24
98. ure is below 10 mbar the analyser is ready for operation Figure 12 shows the destination of the various voltages on the spectrometer Note however that the spectrometer electrodes are not readily accessible as test points All voltage checks should be carried out at the filtered plug 9 way feedthrough as shown in Figure 13 Please see the EAC 2000 or EAC 300 manuals as listed in Table 1 on page 2 for further details See the CPC 125 65 M Multi Channel and CPC 125 65 S Single Channel manuals for further details on the Channeltron pulse counting electronics OUTER HEMISPHERE INNER HEMISPHERE FOCUS 1 FRINGE FIELD PLATE FOCUS 2 E l e o ie I MEDIUM HIGH SAMPLE Figure 12 Internal connections FB Front Bias M Multiplier Output s The numbers refer to the pin numbers in Figure 13 Vy Omicron July 2002 Nano Technology Version 2 1 6 Operation 32 EA 125 Energy Analyser User s Guide 9 Way Plug and Feedthrough Pin Assignments 9 WAY VOLTAGE CABLE PLUG 9 WAY FEEDTHROUGH FOR EA 125 ANALYSER FOR EA 125 ANALYSER ATMOSPHERIC SIDE Figure 13 9 way plug and related feedthrough pin layout Pulse Counting Operation e Set the 10 turn potentiometer OUTPUT ADJUST on the multiplier supplies unit to Zero e Switch the multiplier supplies unit on e Switch on the receiver unit e Set the analyser entrance and exit slits to the largest possible settings e With an
99. with the Code of Federal Regulations CFR 40 Part 173 240 Definition and Preparation No repair will be carried out without a legally binding signed declaration July 2002 Vy Omicron NanoTechnology Version 2 1 Decontamination Declaration 87 EA 125 Energy Analyser User s Guide Declaration of Decontamination of Vacuum Equipment and Components The repair and or service of vacuum equipment components can only be carried out if a correctly completed declaration has been submitted Non completion will result in delay The manufacturer reserves the right to refuse acceptance of consignments submitted for repair or maintenance work where the declaration has been omitted This declaration may only be completed and signed by authorised and qualified staff 1 Description of components Type Serial No 2 Reason for return 3 Equipment condition Has the equipment ever come into contact with the following e g gases liquids evaporation products sputtering products toxic substances yes O No L1 e corrosive substances Yes O No L1 e microbiological substances incl sample material Yes O No L1 e radioactive substances incl sample material Yes O No L1 e ionising particles radiation o B y neutrons Yes O No L1 For all harmful substances gases and dangerous by products which have come into contact with the vacuum equipment components please list the following information on a separate
100. y dispersion ssseeeeeeneeeeeee 43 Figure 23 Observed vs true count rates ssssssssssssseeeeenn enn 44 Figure 24 age error in count rates os eed ona Gee er roe i con Greer ala rasen 45 Figure 25 Analyser test dirty XPS spectrum sssssssseeeeseeeennenneneennn 51 Figure 26 Analyser test clean XPS spectrum semet detecte Eee buenas 51 Figure 27 Analyser test AES spectrum 444244444440nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 53 Figure 28 Analyser test HRUPS spectrum eesseseseeesseeneeenenenen nne 56 Figure 29 EAC adjustment potentiometers 64 List of Tables Table T Related Manuals uia on Gece nde retos eror en 2 Table 2 Lens specifications universal IONS cccccccsesecccceceeeeeesceeeseeceeseeaeceesessaaaeees 14 Table 3 EA 125 U1 aperture combinations sssesssssseseeeneennee 15 Table 4 EA 125 multichannel analysers standard aperture combinations 16 Table 5 Analyser operating parameters and resoution ssesssessssss 47 Table 6 Characteristic photon line widths ss2s2sssseneennnannnnnnnnnnnnennnnnnnnnn 48 Table 7 Peak information for silver sample ccsceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeaaeaeeeeeeeees 62 Wy Omicron July 2002 Nano Technology Version 2 1 1 Introduction 9
101. y feedthrough pins and that none of them are connected to any external part of the EA 125 vacuum hardware For information on the internal connections see Figures 12 and 13 on pages 31 and 32 Vacuum Installation and Removal Please note These instructions should also be studied before removing the analyser from a system The analyser weighs some 65 kg and should therefore be supported by a suitable frame when mounted on the UHV system The support could use the two lifting handles two 150 mm lengths of stainless steel rod with knurled grips screwed into the two M12 tapped Vy Omicron July 2002 Nano Technology Version 2 1 4 Unpacking and Installation 21 EA 125 Energy Analyser User s Guide holes provided in the edge of the base flange see Figure 7 Alternatively a support could use the four M10 x 15 tapped holes in the base plate Suitable lifting equipment should be available for lifting the analyser by attaching three chains to the eye bolts provided HANDLE MOUNTING HOLES TAPPED HOLES M10 x 15 DEEP Figure 7 Mounting holes of the EA 125 analyser Please note All parts are clean to vacuum standards Always wear suitable polythene or cotton gloves and use clean non magnetic tools To install the EA 125 analyser to your vacuum system please follow the steps below 1 After unpacking please wait until all parts have gained room temperature 2 Screw the two lifting handles into the

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