1、Designation: E 2108 05Standard Practice forCalibration of the Electron Binding-Energy Scale of anX-Ray Photoelectron Spectrometer1This standard is issued under the fixed designation E 2108; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes a procedure for calibrating theelectron binding-energy (BE) scale of an X-
3、ray photoelectronspectrometer that is to be used for surface analysis withunmonochromated aluminum or magnesium Ka X-rays ormonochromated aluminum Ka X rays.1.2 It is recommended that the BE scale be calibrated afterthe instrument is installed or modified in any substantive way.Also, it is recommend
4、ed that the instrumental BE scale bechecked, and if necessary, recalibrated at intervals chosen toensure that BE measurements are statistically unlikely to bemade with greater uncertainty than a tolerance limit, specifiedby the analyst, based on the instrumental stability and theanalysts needs. Info
5、rmation is provided by which an analystcan select an appropriate tolerance limit for the BE measure-ments and the frequency of calibration checks.1.3 This practice is based on the assumption that the BEscale of the spectrometer is sufficiently close to linear that theBE scale can be calibrated by me
6、asurements of referencephotoelectron lines made near the extremes of the working BEscale. In most commercial instruments, X-ray sources withaluminum or magnesium anodes are employed and BEs aretypically measured over the 01000 eV range. This practicecan be used for the BE range from 0 eV to 1040 eV.
7、1.4 The assumption that the BE scale is linear is checked bya measurement made with a reference photoelectron line orAuger-electron line that appears at an intermediate position. Asingle check is a necessary but not sufficient condition forestablishing linearity of the BE scale.Additional checks can
8、 bemade with specified reference lines on instruments equippedwith magnesium or unmonochromated aluminum X-raysources, with secondary BE standards, or by following theprocedures of the instrument manufacturer. Deviations fromBE-scale linearity can occur because of mechanical misalign-ments, excessiv
9、e magnetic fields in the region of the analyzer,or imperfections or malfunctions in the power supplies. Thispractice does not check for, nor identify, problems of this type.1.5 After an initial check of the BE-scale linearity andmeasurements of the repeatability standard deviation for themain calibr
10、ation lines for a particular instrument, a simplifiedprocedure is given for routine checks of the calibration atsubsequent times.1.6 This practice is recommended for use with X-rayphotoelectron spectrometers operated in the constant-pass-energy or fixed-analyzer-transmission mode and for which thepa
11、ss energy is less than 200 eV; otherwise, depending on theconfiguration of the instrument, a relativistic equation could beneeded for the calibration equation. The practice should not beused for instruments operated in the constant-retardation-ratiomode at retardation ratios less than 10, for instru
12、ments with anenergy resolution worse than 1.5 eV, or in applications forwhich BE measurements are desired with tolerance limits of 60.03 eV or less.1.7 On instruments equipped with a monochromated alumi-num Ka X-ray source, a measurement of the position of aspecified Auger-electron line can be used,
13、 if desired, todetermine the average energy of the X rays incident on thespecimen. This information is needed for the determination ofmodified Auger parameters.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the use
14、r 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:2E 456 Terminology Relating to Quality and StatisticsE 673 Terminology Relating to Surface AnalysisE 902 Practice
15、 for Checking the Operating Characteristicsof X-Ray Photoelectron SpectrometersE 1016 Guide for Literature Describing Properties of Elec-trostatic Electron SpectrometersE 1078 Guide for Specimen Preparation and Mounting inSurface Analysis1This practice is under the jurisdiction of ASTM Committee E42
16、 on SurfaceAnalysis and is the direct responsibility of Subcommittee E42.03 onAuger ElectronSpectroscopy and X-Ray Photoelectron Spectroscopy.Current edition approved Nov. 1, 2005. Published December 2005. Originallyapproved in 2000. Last previous edition approved in 2000 as E 2108 00.2For reference
17、d 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
18、shohocken, PA 19428-2959, United States.E 1523 Guide to Charge Control and Charge ReferencingTechniques in X-Ray Photoelectron Spectroscopy2.2 ISO Standards:3ISO 9001:2000, Quality Management SystemsRequirementsISO 15472:2001, Surface Chemical AnalysisX-Ray pho-toelectron SpectrometersCalibration of
19、 Energy ScalesISO 18115:2001, Surface Chemical AnalysisVocabulary3. Terminology3.1 DefinitionsFor definitions of terms used in X-rayphotoelectron spectroscopy and surface analysis, see Terminol-ogy E 673 and ISO 18115. For definitions of terms used instatistics, see Terminology E 456.3.2 Symbols and
20、 AbbreviationsTable 1 shows definitionsof the symbols and abbreviations used in this practice.4. Summary of Practice4.1 A procedure is given for calibrating the BE scale of anX-ray photoelectron spectrometer equipped with one or moreof the following sources of characteristic Ka X rays: magne-sium (M
21、g) source; unmonochromated aluminum (Al) source;or monochromated Al source. This procedure is based on ISO15472. In a first calibration for particular operating conditionsof the instrument, or after the instrument has been modified,measurements are made of the binding energies of specifiedcore level
22、s of copper and gold, and these values are then3Available from American National Standards Institute, 25 W. 43rd St., 4thFloor, New York, NY 10036.TABLE 1 Definitions of Symbols and Abbreviationsa measured energy scaling errorBE binding energy, in eVb measured zero offset error, in eVcinumber of cou
23、nts in the i-th channeleV electron voltsEcorrcorrected result for the binding energy corresponding to a given Emeas,ineVEelembinding energy of a frequently measured element at which the indicated binding energy scale is set, aftercalibration, to read correctly, in eVEKkinetic energy of a peak, with
24、reference to the Fermi level, in eVEmeasa measured binding energy, in eVEmeas naverage of the measured binding energies for the peak, n,inTable 3,ineVEmeas nione of a set of measurements of binding energy for the peak, n,inTable 3,ineVEref nreference values for the position of peak, n,inTable 3, on
25、the binding energy scale, in eVEppeak binding energy, in eVE0binding energy for first data channel at lower binding energy than the channel with the maximum number of counts,for a peak, in eVFWHM full width at half maximum peak intensity above the background, in eVg channel energy separation, in eVh
26、vAleffective X-ray energy from an unmonochromated Al X-ray source, in eVhvAlmoneffective X-ray energy from a monochromated Al X-ray source, in eVhvMgeffective X-ray energy from an unmonochromated Mg X-ray source, in eVi index to represent channel number, where i = 0 represents the first channel at l
27、ower binding energy than thechannel with the maximum number of counts, for a peak, in eVj number of repeat measurements for a new peakk number of repeat measurements for the Au 4f7/2,Cu2p3/2and Ag 3d5/2or Cu L3VV peaks in the repeatabilitystandard deviation and linearity determinationsm number of re
28、peat measurements for the Au 4f7/2and Cu 2p3/2peaks in the regular calibrationsn designation of the peak identifier in Table 3p parameter in Eq A1.1 defined in Eq A1.2q parameter in Eq A1.1 defined in Eq A1.3r parameter in Eq A1.1 defined in Eq A1.4txStudents t value for x degrees of freedom of a tw
29、o-sided distribution for a confidence level of 95 %U95total uncertainty of the calibrated energy scale at a confidence level of 95 %, in eVU95c(E) uncertainty at a confidence level of 95 % arising from the calibration using the Au 4f7/2and Cu 2p3/2peaks atbinding energy E, assuming perfect scale lin
30、earity, in eVU951uncertainty of e2or e3at a confidence level of 95 % from Eq 7,ineVU95cluncertainty of the calibration at a confidence level of 95 % in the absence of a linearity error, from Eq 12 and Eq13,ineVXPS X-ray photoelectron spectroscopya Auger parameter, in eVa8 modified Auger parameter, i
31、n eVDnoffset energy, given by the average measured binding energy for a calibration peak minus the reference energy, ineV, for n =1,2,3,4inTable 3, for a given X-ray sourceDEcorrcorrection to be added to Emeas, after calibration, to provide the corrected result for the binding energy, in eVDEcorr nv
32、alue of DEcorrfor peaks 1 and 4 in Table 3,ineVDEndrift of the binding-energy scale following a calibration for peaks 1 and 4 in Table 3,ineVDf the average of D1and D4from Eq 16,ineVDhv difference between hvAlmonand hvAl,ineVd value for the tolerance limit of energy calibration at a confidence level
33、 of 95 % (set by the analyst), in eVe2measured scale linearity error at the Ag 3d5/2peak from Eq 4,ineVe3measured scale linearity error at the Cu L3VV peak from Eq 5 or Eq 6,ineVsRmaximum of sR1, sR2or sR3, and sR4,ineVsRnrepeatability standard deviation for the seven measurements of the binding ene
34、rgy of peak, n,inTable 3,ineVsRnewrepeatability standard deviation for a new peak, in eVE2108052compared with corresponding reference energies (1).4Thelinearity of the BE scale is checked at a single point on thescale using a measurement of the position of either a specifiedcore level of silver (mon
35、ochromated Al source) or a specifiedAuger-electron transition of copper (Mg source or unmono-chromated Al source) (1,2); additional checks can be made, ifdesired, with secondary standards. Procedures are given fordetermining the components of an uncertainty budget in BEmeasurements and for determini
36、ng the uncertainties of BEmeasurements (at the 95 % confidence level) at various timesfollowing a calibration. The analyst can thus establish toler-ance limits, for example, at the same level of confidence, basedon the instrument stability and the analysts needs so that BEmeasurements statistically
37、are likely to be made within theselimits during specified time intervals following a calibration.The instrument is then adjusted or subsequent BE measure-ments are corrected. For a routine check of the instrumentalcalibration, either one or two measurements are made each ofthe same core levels of co
38、pper and gold. Fig. 1 is a flow chartthat summarizes the steps of the calibration procedure; refer-ences are given to relevant sections of this standard. Anoptional procedure is provided for determining the averageenergy of the X rays from a monochromated Al X-ray source,using a measured position of
39、 a copper Auger peak in order todetermine modified Auger parameters.5. Significance and Use5.1 X-ray photoelectron spectroscopy is used extensivelyfor the surface analysis of materials. Elements (with theexception of hydrogen and helium) are identified from com-parisons of the binding energies deter
40、mined from photoelec-tron spectra with tabulated values. Information on chemicalstate can be derived from the chemical shifts of measuredphotoelectron andAuger-electron features with respect to thosemeasured for elemental solids.5.2 Calibrations of the BE scales of XPS instruments arerequired for fo
41、ur principal reasons. First, meaningful compari-son of BE measurements from two or more XPS instrumentsrequires that the BE scales be calibrated, often with anuncertainty of about 0.1 to 0.2 eV. Second, identification ofchemical state is based on measurement of chemical shifts ofphotoelectron and Au
42、ger-electron features, again with anuncertainty of typically about 0.1 to 0.2 eV; individual mea-surements, therefore, should be made and literature sourcesneed to be available with comparable or better accuracies.Third, the availability of databases (3) of measured BEs forreliable identification of
43、 elements and determination of chemi-cal states by computer software requires that published dataand local measurements be made with uncertainties of about0.1 to 0.2 eV. Finally, the growing adoption of qualitymanagement systems, such as, ISO 9001, in many analyticallaboratories has led to requireme
44、nts that the measuring and testequipment be calibrated and that the relevant measurementuncertainties be known.5.3 The actual uncertainty of a BE measurement depends oninstrument properties and stability, measurement conditions,and the method of data analysis. This practice makes use oftolerance lim
45、its 6d (chosen, for example, at the 95 % confi-dence level) that represent the maximum likely uncertainty ofa BE measurement, associated with the instrument in aspecified time interval following a calibration (ISO 15472). Auser should select a value of d based on the needs of theanalytical work to b
46、e undertaken, the likely measurement anddata-analysis conditions, the stability of the instrument, and thecost of calibrations. This practice gives information on thevarious sources of uncertainty in BE measurements and onmeasurements of instrumental stability. The analyst shouldinitially choose som
47、e desired value for d and then make tests,as described in 8.14 to determine from subsequent checks ofthe calibration whether BE measurements are made within thelimits 6d. Information is given in Appendix X1 on how toevaluate the uncertainty of a binding-energy measurement fora material of interest t
48、hat is associated with the uncertainty ofthe calibration procedure. This information is provided for fourcommon analytical situations. It is important to note that someBE measurements may have uncertainties larger than d as aresult of poor counting statistics, large peak widths, uncertain-ties assoc
49、iated with peak synthesis, and effects of surfacecharging.5.4 Instrument settings typically selected for analysis shouldbe used with this practice. Separate calibrations should bemade if key operating conditions, such as choices of analyzerpass energy, aperture sizes, or X-ray source, are varied.Settings not specified in this practice are at the discretion of theuser, but these same settings should be recorded and consis-tently used whenever this practice is repeated in order that thecurrent results will be directly comparable to the previousresults.5.5 All of the operations
