ASTM E1217-2011 Standard Practice for Determination of the Specimen Area Contributing to the Detected Signal in Auger Electron Spectrometers and Some X-Ray Photoelectron Spectromet.pdf

1、Designation: E1217 11Standard Practice forDetermination of the Specimen Area Contributing to theDetected Signal in Auger Electron Spectrometers and SomeX-Ray Photoelectron Spectrometers1This standard is issued under the fixed designation E1217; the number immediately following the designation indica

2、tes the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes methods for determin

3、ing thespecimen area contributing to the detected signal in Augerelectron spectrometers and some types of X-ray photoelectronspectrometers (spectrometer analysis area) when this area isdefined by the electron collection lens and aperture system ofthe electron energy analyzer. The practice is applica

4、ble only tothose X-ray photoelectron spectrometers in which the speci-men area excited by the incident X-ray beam is larger than thespecimen area viewed by the analyzer, in which the photoelec-trons travel in a field-free region from the specimen to theanalyzer entrance. Some of the methods describe

5、d here requirean auxiliary electron gun mounted to produce an electron beamof variable energy on the specimen (“electron-gun method”).Other experiments require a sample with a sharp edge, such asa wafer covered with a uniform clean layer (for example, gold(Au) or silver (Ag) and cleaved to obtain a

6、long side(“sharp-edge method”).1.2 This practice is recommended as a useful means fordetermining the specimen area viewed by the analyzer fordifferent conditions of spectrometer operation, for verifyingadequate specimen and beam alignment, and for characterizingthe imaging properties of the electron

7、 energy analyzer.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard

8、to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E673 Terminology Relating to Surface Analysis3E1016 Guide for Literature Describing Properties of Elec-trostatic Electron Spectrome

9、ters2.2 ISO Standards:4ISO 18115:2001 Surface Chemical AnalysisVocabularyISO 18516:2006 Surface Chemical Analysis Auger Elec-tron Spectroscopy and X-ray Photoelectron Spectroscopy Determination of Lateral Resolution3. Terminology3.1 DefinitionsSee Terminology E673 andISO 18115:2001 for terms used in

10、Auger electron spectroscopyand X-ray photoelectron spectroscopy.4. Summary of Practice4.1 Electron-Gun MethodAn electron beam with a se-lected energy is scanned across the surface of a test specimen.The beam may be scanned once, that is, a line scan, or in apattern, that is, rastered. As the electro

11、n beam is deflectedacross the specimen surface, measurements are made of theintensities detected by the electron energy analyzer as afunction of the beam position for selected conditions ofanalyzer operation. The measured intensities may be due toelectrons elastically scattered by the specimen surfa

12、ce, toelectrons inelastically scattered by the specimen, or to Augerelectrons emitted by the specimen. The intensity distributionsfor particular detected electron energy can be plotted as afunction of beam position in several ways and can be utilized1This practice is under the jurisdiction of ASTM C

13、ommittee E42 on SurfaceAnalysis and is the direct responsibility of Subcommittee E42.03 on Auger ElectronSpectroscopy and X-Ray Photoelectron Spectroscopy.Current edition approved Nov. 1, 2011. Published December 2011. Originallyapproved in 1987. Last previous edition approved in 2005 as E1217 05. D

14、OI:10.1520/E1217-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of

15、this historical standard is referencedon www.astm.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.to o

16、btain information on the specimen area contributing to thedetected signal and on analyzer performance for the particularconditions of operation. This information can be used todetermine the analysis area (see Terminology E673 orISO 18115:2001).4.2 Sharp-Edge MethodA sample with a sharp edge isscanne

17、d through the focal area of the analyzer with its sharpedge perpendicular to the scanning direction (knife edgeexperiments). As the sample is moved to different positions,measurements are made of the intensity of a characteristicphotoelectron peak of the sample surface (for example, Au 4fpeak if the

18、 sample was covered with gold) for selectedconditions of the analyzer operation. The measured intensity ismaximum when the sampled area is completely contained bythe sample surface, and minimum when there is no overlapbetween the analysis volume of the analyzer and the samplesurface. The length of t

19、he intermediate region will depend onthe size of the analysis area. The area of the photoelectron peakcan be plotted as a function of sample position. The behaviorof this curve can be used to assess the width of the analysis areain the scanning direction.5. Significance and Use5.1 Auger electron spe

20、ctroscopy and X-ray photoelectronspectroscopy are used extensively for the surface analysis ofmaterials. This practice summarizes methods for determiningthe specimen area contributing to the detected signal (a) forinstruments in which a focused electron beam can be scannedover a region with dimensio

21、ns greater than the dimensions ofthe specimen area viewed by the analyzer, and (b) by employ-ing a sample with a sharp edge.5.2 This practice is intended as a means for determining theobserved specimen area for selected conditions of operation ofthe electron energy analyzer. The observed specimen ar

22、eadepends on whether or not the electrons are retarded beforeenergy analysis, the analyzer pass energy or retarding ratio ifthe electrons are retarded before energy analysis, the size ofselected slits or apertures, and the value of the electron energyto be measured. The observed specimen area depend

23、s on theseselected conditions of operation and also can depend on theadequacy of alignment of the specimen with respect to theelectron energy analyzer.5.3 Any changes in the observed specimen area as afunction of measurement conditions, for example, electronenergy or analyzer pass energy, may need t

24、o be known if thespecimen materials in regular use have lateral inhomogeneitieswith dimensions comparable to the dimensions of the specimenarea viewed by the analyzer.5.4 This practice can give useful information on the imagingproperties of the electron energy analyzer for particular con-ditions of

25、operation. This information can be helpful incomparing analyzer performance with manufacturers specifi-cations.5.5 Information about the shape and size of the area viewedby the analyzer can also be employed to predict the signalintensity in XPS experiments when the sample is rotated and toassess the

26、 axis of rotation of the sample manipulator.5.6 Examples of the application of the methods described inthis practice have been published (1-7).55.7 There are different ways to define the spectrometeranalysis area. An ISO Technical Report provides guidance ondeterminations of lateral resolution, anal

27、ysis area, and samplearea viewed by the analyzer in AES and XPS (8), andISO 18516:2006 describes three methods for determination oflateral resolution in AES and XPS. Baer and Engelhard haveused well-defined dots of a material on a substrate todetermine the area of a specimen contributing to the meas

28、uredsignal of a small-area XPS measurement (9). This area couldbe as much as ten times the area estimated simply from thelateral resolution of the instrument. The amount of intensity infringeor tailregions could also be highly dependent on lensoperation and the adequacy of specimen alignment. Sche-i

29、thauer described an alternative technique in which Pt aperturesof varying diameters were utilized to determine the fraction oflong-tail X-ray contributions outside each aperture on themeasured Pt photoelectron signal compared to that on a Pt foil(10). In test measurements on a commercial XPS instrum

30、entwith a focused X-ray beam and a nominal lateral resolution of10 m (as determined from the distance between the positionsfor 20% and 80 % of maximum signal when scans were madeacross an edge), it was found that aperture diameters of about100 m and 450 m were required to reduce the photoelectronsig

31、nals to 10 % and 1 %, respectively, of the maximum value(10). Knowledge of the effective analysis area is importantwhen making tradeoffs between lateral resolution and detect-ability. In scanning Auger microscopy, the area of analysis isdetermined more by the radial extent of backscattered electrons

32、than by the radius of the primary beam (11, 12, 13).6. Apparatus for the Electron-Gun Method6.1 Test Specimen, preferably a conductor, is required andis mounted in the Auger electron or X-ray photoelectronspectrometer in the usual position for surface analysis. It isrecommended that the test specime

33、n be a metallic foil withlateral dimensions larger than the dimensions of the field ofview of the electron energy analyzer. The test specimen shouldbe polycrystalline and have grain dimensions much less thanthe expected spatial resolution of the analyzer or the width ofthe incident beam on the speci

34、men in order to avoid artifactsdue to channeling or diffraction effects. The specimen surfaceshould be smooth and be free of scratches and similar defectsthat are observable with the unaided eye (see 8.6). It isdesirable that the surface of the test specimen be cleaned by ionsputtering or other mean

35、s to remove surface impurities such asoxides and adsorbed hydrocarbons; the degree of surfacecleanliness can be checked with AES or XPS measurements.6.2 Electron GunAn electron gun must be available onthe spectrometer to provide a beam of electrons incident on thetest specimen surface with energy ty

36、pically between 100 eVand 2000 eV (the normal range of detected energies inAES andXPS). The gun must be equipped with a deflection system sothat the electron beam can be deflected to different regions of5The boldface numbers in parentheses refer to the list of references at the end ofthis practice.E

37、1217 112the specimen surface. The width of the electron beam (FWHM)at the test specimen should be less than the spatial resolutiondesired in the following measurements.6.3 Electronic Equipment, is required to scan the electronbeam on the surface of the test specimen and to record anddisplay the sele

38、cted signals.6.3.1 Equipped SpectrometerSome commercial spec-trometers, particularly those designed for scanning Augermicroscopy, have electronic instrumentation, which can beused to scan the electron beam across the test specimensurface, either on a selected line or on a raster pattern withselected

39、 dimensions. The selected analyzer signals may berecorded in a computer system or be displayed directly on anoscilloscope or X-Y recorder.6.3.2 Unequipped SpectrometerIf the spectrometer is notequipped with instrumentation for scanning the electron beam,this instrumentation will have to be provided.

40、 A line scan canbe accomplished with a suitable wave-form generator (eithertriangular or sawtooth) or a programmable power supply.Another dc supply may be required to define the position of theline on the specimen, that is, in the direction orthogonal to thescan. Raster scans can be made with two wa

41、veform generatorsor two programmable power supplies.7. Procedure for the Electron-Gun Method7.1 Choose the energy of the electron beam incident on thesurface of the test specimen. This choice should be madedepending on the nature of the tests to be made. For example,electron energies between 100 eV

42、and 2000 eV may be chosenfor Auger electron experiments with specific choices related tothe energies of Auger electron peaks of particular interest. InX-ray photoelectron spectroscopy experiments with magne-sium characteristic X-rays, electron energies between approxi-mately 254 eV and 1254 eV might

43、 be chosen to determine theanalyzer performance for the binding-energy range between 0eV and 1000 eV.7.2 Choose the type of scan for the electron beam on the testsurface, either line scan or raster scan (6.3). If a line scan isselected, choose the position of the line on the specimen.7.2.1 A line sc

44、an is a relatively simple procedure and can bemade for two orthogonal directions. This method for determin-ing the active area of the analyzer may suffice for manyapplications but has the disadvantage that the active area maynot be symmetrical about the two scan lines (1, 2). The rasterscan method a

45、llows convenient observation of any instrumen-tal asymmetries.7.2.2 The following suggestions are made if the instrumentis not already equipped with instrumentation to scan theelectron beam. The specific suggestions are made to generate araster scan for an electron gun equipped with deflection plate

46、s.Line scans can be made in a similar way. An analogousprocedure would be used for an electron gun operated with anelectromagnetic deflection system.7.2.2.1 Use of Waveform GeneratorsIn this approach, usetwo waveform generators to generate triangular waveforms atfrequencies typically in the range of

47、 0.5 kHz to 1 kHz. Thewaveforms are amplified and coupled through a transformer tothe deflection plates of the electron gun, one output beingdesignated for horizontal deflection and the other for verticaldeflection. A resistive center-tap is connected across eachtransformer output with the midpoints

48、 grounded. The wave-forms are also connected to the horizontal and vertical inputs ofan oscilloscope.Adjust the frequencies of the oscillators so thatthere is a uniform intensity distribution on the oscilloscope,that is, absence of any Lissajous figures. Select the gains of theamplifiers to deflect

49、the electron beam across the test specimenby amounts corresponding at least to the anticipated analyzerfield of view; for a desired deflection on the test specimen, themaximum deflection-plate voltage will scale with the selectedelectron energy. Make a line scan with a single waveformgenerator and with the scan voltage applied to either thehorizontal or the vertical deflection plates. Apply a dc voltageto the other deflection plates to select the position of the line onthe specimen.7.2.2.2 Use of Programmable Power SuppliesProgram acomputer to control th