1、Designation: E827 08Standard Practice forIdentifying Elements by the Peaks in Auger ElectronSpectroscopy1This standard is issued under the fixed designation E827; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. 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 outlines the necessary steps for the iden-tification of elements in a givenAuger spectrum obtained usingconventi
3、onal electron spectrometers. Spectra displayed as ei-ther the electron energy distribution (direct spectrum) or thefirst derivative of the electron energy distribution are consid-ered.1.2 This practice applies to Auger spectra generated byelectron or X-ray bombardment of the specimen surface andcan
4、be extended to spectra generated by other methods such asion bombardment.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 us
5、e. It is theresponsibility of the user of this standard 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 SurfaceAnalysis (Withdrawn2012)3E983 Guide for
6、 Minimizing Unwanted Electron Beam Ef-fects in Auger Electron SpectroscopyE984 Guide for Identifying Chemical Effects and MatrixEffects in Auger Electron SpectroscopyE1523 Guide to Charge Control and Charge ReferencingTechniques in X-Ray Photoelectron Spectroscopy2.2 ISO Standards:4ISO 17973: 2002 S
7、urface Chemical AnalysisMedium-Resolution Auger Electron SpectrometersCalibration ofEnergy Scales for Elemental AnalysisISO 17974: 2002 Surface Chemical AnalysisHigh-Resolution Auger Electron SpectrometersCalibration ofEnergy Scales for Elemental and Chemical-State Analysis3. Terminology3.1 Definiti
8、ons:3.1.1 Terms used inAuger electron spectroscopy are definedin Terminology E673.4. Summary of Practice4.1 TheAuger spectrum is obtained with appropriate instru-mental parameters from a low kinetic energy limit of approxi-mately 30 eV to an upper kinetic energy limit of approximately2000 to 3000 eV
9、 or higher to include all the principal Augerelectron energies of all elements (except hydrogen and heliumwhich do not have Auger transitions).4.2 This practice assumes the existence of appropriatereference spectra from pure element or stoichiometric com-pound standards, or both, with which an unkno
10、wn spectrumcan be compared (1, 2).5It may be useful to note that althoughAuger energies in some data bases are referenced to the Fermilevel, other data collections have been referenced to thevacuum level. Auger kinetic energies referenced to the Fermilevel would be approximately 5 eV larger than val
11、ues refer-enced to the vacuum level.4.3 An element in an Auger spectrum is considered posi-tively identified if the peak shapes, the peak energies, and therelative signal strengths of peaks from the unknown coincidewith those from a standard reference spectrum of the elementor compound.1This practic
12、e is under the jurisdiction of ASTM Committee E42 on SurfaceAnalysis and is the direct responsibility of Subcommittee E42.03 on Auger ElectronSpectroscopy and X-Ray Photoelectron Spectroscopy.Current edition approved Oct. 1, 2008. Published November 2008. Originallyapproved in 1981. Last previous ed
13、ition approved in 2007 as E827 07. DOI:10.1520/E0827-08.2For 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.3The
14、last approved version of this historical standard is referenced onwww.astm.org.4Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.5The boldface numbers in parentheses refer to the list of r
15、eferences at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesNOTICE: This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International (www.astm.org) for the latest i
16、nformation15. Significance and Use5.1 Auger analysis is used to determine the elementalcomposition of the first several atomic layers, typically 1 to 5nm thick, of a specimen surface. In conjunction with inert gasion sputtering, it is used to determine the sputter depth profileto a depth of a few mi
17、crometres.5.2 The specimen is normally a solid conductor,semiconductor, or insulator. For insulators, provisions may berequired for control of charge accumulation at the surface (seeGuide E1523). Typical applications include the analysis ofsurface contaminants, thin film deposits or segregated overl
18、ay-ers on metallic or alloy substrates. The specimen topographymay vary from a smooth, polished specimen to a rough fracturesurface.5.3 Auger analysis of specimens with volatile species thatevaporate in the ultra-high vacuum environment of the Augerchamber and substances which are susceptible to ele
19、ctron orX-ray beam damage, such as organic compounds, may requirespecial techniques not covered herein. (See Guide E983.)6. Apparatus6.1 Electron Energy Analyzers: a retarding field analyzer,cylindrical mirror analyzer (single or double pass), or hemi-spherical analyzer is typically used. The calibr
20、ation of theanalyzers energy scale should be checked at regular intervals(see ISO 17973: 2002 and ISO 17974: 2002) to aid in makingreliable identifications.6.2 Standard Equipment: typically an electron gun or X-raysource is used for excitation, an electron multiplier is used foramplification of the
21、Auger electron signal, and a recordingdevice is used to output the data.6.2.1 Avacuum capability in the test chamber is required foroperation of the electron gun or X-ray source and thespectrometer, and to allow analysis without contaminationfrom the ambient gases; depending on specimen surfacecondi
22、tions, analysis is performed in the pressure range from103to 108Pa.7. Procedure7.1 Identify the peak having the largest signal strength in thespectrum and note its peak energy and characteristic shape.Note that by convention, the peak energy is measured at theenergy of the maximum intensity in the d
23、irect N(E) spectrumand at the minimum value in the derivative spectrum. Thesetwo energies will not be the same, with the derivative spectrumgiving higher peak energies.7.2 Consult a list of peak energies for elements and note thepossible energy matches. The peak position can vary by up to20 eV becau
24、se of slightly differing chemistries, so includeelements within a wide range of energies around the peakposition noted in 7.1.7.3 Consult the standard elemental spectrum for one of theelements identified by 7.2, and look for the presence ofadditional lines in the specimen spectrum that match thestan
25、dard spectrum in energy and intensity (see peak overlap in8.1.1) (1, 2). Direct and derivative standard spectra areavailable (1, 2). Compare the shape of the peaks as well. If agood match is found, label all lines from the standard spectrumthat are visible in the specimen spectrum. If a match is not
26、found, eliminate that element from further consideration andselect another element from the list found in 7.2 and repeat 7.3.7.4 If all of the elements from 7.2 have been exhausted,widen the energy range and choose additional elements.Remember, charging may shift the energy spectrum substan-tially.
27、In this event, look for the carbon and oxygen peak shapes(or other known elements) by shape and relative position todetermine the extent of charging. Correct for charging andrepeat 7.2 and 7.3.7.5 If a match is still not found, temporarily ignore the mostintense peak and repeat 7.1-7.3 for the next
28、most intense peak.Recall that relativeAuger peak intensities may change becauseof the specimen chemistry. A weaker peak may become moreintense and the primary peak may become less intense. (SeeGuide E984.)7.6 Repeat 7.1-7.3 with peaks of decreasing signal strengthuntil all peaks are positively ident
29、ified.7.7 It should be noted that since the Auger signal strengthvaries proportionally with the concentration of the elementdetected, an element present at a small concentration mayregister only its strongest Auger peak(s). The identification ofsuch weak peaks should be verified by optimizing the si
30、gnal-to-noise ratio in separate scans, for example, by repetitivescans of the energy range of interest.7.8 When extending the technique to Auger transitionsgenerated by an X-ray source, it is important to note that thekinetic energy of theAuger electrons does not change when theenergy of the inciden
31、t X-rays is changed. This may allow theAuger peaks to be distinguished from the photoelectron peaks.7.9 Auger features generated by incident ions may haverelative intensities and energies that differ substantially fromthose generated by electrons or X-rays (3).8. Interferences8.1 The procedure for p
32、ositive elemental identificationgiven in Section 7 is valid except when the characteristic shapeof an Auger peak is subject to change (which is not caused byinstrumental parameters such as different analyzer resolutions).This can arise from two situations:8.1.1 Peak overlap occurs when Auger peak en
33、ergies fromtwo or more different elements coincide within the energywidth ranges of the peaks. The spectrum of a possiblecomponent element can be subtracted from the composite data.This subtraction or spectrum stripping can be performednumerically, and the residual intensity can be compared withrefe
34、rence spectra for another possible element (4). Sometimes,for qualitative analysis, spectrum stripping can be adequatelyperformed by an experienced eye. It may be necessary to takeadditional data on an expanded scale (perhaps with increasedenergy resolution and improved signal-to-noise ratio) to per
35、-form the spectrum stripping with the desired precision.8.1.2 Changes in peak energy, peak shape, or relative signalstrengths of peaks may be due to Auger chemical effects orE827 082matrix effects. (See Guide E984.) In this case, the referencespectrum should be that of the particular compound contai
36、ningthe element.8.2 In spectra obtained using X-ray generation there willgenerally be photoelectron peaks in the spectrum. These mayinterfere with the Auger peaks. As noted above, if possible,changing the energy of the incident X-rays will change thekinetic energy of the photoelectron peaks, while t
37、he kineticenergy of the Auger peaks will be unchanged.9. Discussion9.1 The state-of-the-art in Auger electron spectroscopy nowallows routine qualitative analysis without too many interpre-tational difficulties. It is assumed that the practitioner employscommon practice in generating an Auger spectru
38、m in order touse this procedure. Under normal circumstances, all elements(except hydrogen and helium) present on a specimen surfacebeing analyzed can be detected with a sensitivity limit of 1atomic % or better.9.2 Electron Beam ExcitationTypical parameters used forelectron beam excitation are 2 to 3
39、0 keV beam energy and1010to 106A beam current. The beam energy and beamcurrent are selected to obtain sufficient Auger signal strengthand an appropriate beam size and analysis depth. High electronbeam current densities may cause electron beam damage incertain specimens. (See Guide E983.) If phase-se
40、nsitive detec-tion is used for obtaining the Auger spectrum, typical modu-lations used are 2 to 6 eVppsinusoidal or square-wave at 5 to10 kHz.9.3 X-Ray ExcitationTypical parameters used in thesource for X-ray excitation are 5 to 50 mAelectron emission at10 to 15 keV energy, resulting in a power diss
41、ipation of 100 to1000 W.9.4 Because this practice for chemical identification relieson comparison with reference spectra, the unknown spectrumshould ideally be generated using the same spectrometer typeand instrumental parameters employed for the reference spec-tra. Practical situations do not alway
42、s meet these ideal condi-tions; therefore, systematic spectrum differences should betaken into consideration when comparing with the standardspectra, such as the electron background shape which changeswith differing spectrometer type or primary electron beamenergy.9.5 Peaks other than those arising
43、from interferences re-ferred to in Section 8 can arise from ionization loss peaks(electron excitation), photoelectron peaks (X-ray excitationand electron excitation) (5), ion-excited Auger peaks, orcharging effects.9.5.1 Ionization loss peaks from primary electrons mayappear in the Auger spectrum, p
44、articularly when the primarybeam energy is relatively low. Changing the primary beamenergy shifts the loss peak energy by the same amount and losspeaks may thus be identified. It is usually recommended thatthe primary beam energy should be at least three times greaterthan the Auger energies of inter
45、est to minimize the occurrenceof these loss peaks.9.5.2 Photoelectron peaks from characteristic X-rays (forexample, Mg K) will occur in the spectrum. Changing thecharacteristic X-rays (for example, from Mg Kto Al K) willmove the photoelectron peaks relative to the Auger spectrum.9.5.3 Auger transiti
46、ons can also be excited in certain mate-rials by ion beams typically used in sputter depth profiling (forexample, Ar+, 15 keV). Such materials include magnesium,aluminum, and silicon.Their ion excitedAuger signal strengthsincrease with beam energy.9.5.4 Charging effects are manifested by shifts of t
47、he entirespectrum and are particularly prevalent during the analysis ofinsulating surfaces. Severe charging may introduce spuriouspeaks. Differential charging on the specimen may causemultiple spectral shifts. Unusually sharp peaks or peaks whoseenergy position shifts in subsequent spectra are usual
48、ly indica-tive of charging. Instrumental adjustments are necessary toeliminate this problem. Care should be used in Auger peakidentification since such effects change the Auger peak energyand shape.10. Keywords10.1 AES; Auger electron spectroscopy; spectroscopy; sur-face analysisREFERENCES(1) Sekine
49、, T., Nagasawa, Y., Kudoh M., Sakai, Y., Parkes, A. S., Geller,J. D., Mogami, A., and Hirata, K., Handbook of Auger ElectronSpectroscopy, JEOL, Tokyo, 1982.(2) Childs, K. D., Carlson, B.A., LaVanier, L.A., Moulder, J. F., Paul, D.F., Sitckle, W. F., and Watson, D. G., Handbook of Auger ElectronSpectroscopy, 3rd Edition, Physical Electronics Inc., Eden Prairie,1995. ISBN: 0-9648124-0-1.(3) Grant, J. T., Hooker, M. P., Springer, R. W., and Haas, T. W.,“Comparison of Auger Spectra of Mg, Al, and Si Excited byLow-Energy Electron and Low-Energy Argon-Ion Bombard
