1、Designation: E 1217 05Standard 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 E 1217; the number immediately following the designation indi
2、cates 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes methods for deter
3、mining thespecimen area contributing to the detected signal in Augerelectron spectrometers and some types of X-ray photoelectronspectrometers when this area is defined by the electroncollection lens and aperture system of the electron energyanalyzer. The practice is applicable only to those X-raypho
4、toelectron spectrometers in which the specimen area ex-cited by the incident X-ray beam is larger than the specimenarea viewed by the analyzer, in which the photoelectrons travelin a field-free region from the specimen to the analyzerentrance, and in which an auxiliary electron gun can bemounted to
5、produce an electron beam of variable energy on thespecimen.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 imagin
6、g properties of the electron energy analyzer.1.3 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 to establish appro-priate safety and health practices and determine the applica-bility of regula
7、tory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 673 Terminology Relating to Surface AnalysisE 1016 Guide for Literature Describing Properties of Elec-trostatic Electron Spectrometers2.2 ISO Standards:ISO 18115:2001 Surface Chemical AnalysisVocabulary33. Terminology3.1 Defi
8、nitionsSee Terminology E 673 for terms used inAuger electron spectroscopy and X-ray photoelectron spectros-copy.4. Summary of Practice4.1 An electron beam with a selected energy is scannedacross the surface of a test specimen. The beam may bescanned once, that is, a line scan, or in a pattern, that
9、is,rastered. As the electron beam is deflected across the specimensurface, measurements are made of the intensities detected bythe electron energy analyzer as a function of the beam positionfor selected conditions of analyzer operation. The measuredintensities may be due to electrons elastically sca
10、ttered by thespecimen surface, to electrons inelastically scattered by thespecimen, or to Auger electrons emitted by the specimen. Theintensity distributions for a particular detected electron energycan be plotted as a function of beam position in several waysand can be utilized to obtain informatio
11、n on the specimen areacontributing to the detected signal and on analyzer perfor-mance for the particular conditions of operation. This informa-tion can be used to determine the analysis area (see Terminol-ogy E 673 or ISO 18115).5. Significance and Use5.1 Auger electron spectroscopy and X-ray photo
12、electronspectroscopy are used extensively for the surface analysis ofmaterials. This practice summarizes methods for determiningthe specimen area contributing to the detected signal forinstruments in which a focused electron beam can be scannedover a region with dimensions greater than the dimension
13、s ofthe specimen area viewed by the analyzer.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 area1This practice is under the jurisdiction of ASTM Committee E42 on SurfaceAnal
14、ysis and is the direct responsibility of Subcommittee E42.03 on Auger ElectronSpectroscopy and X-Ray Photoelectron Spectroscopy.Current edition approved Nov. 1, 2005. Published December 2005. Originallyapproved in 1987. Last previous edition approved in 2000 as E 1217 00.2For referenced ASTM standar
15、ds, 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.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, N
16、ew York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.depends on whether or not the electrons are retarded beforeenergy analysis, the analyzer pass energy or retarding ratio ifthe electrons are retarded before energy anal
17、ysis, the size ofselected slits or apertures, and the value of the electron energyto be measured. The observed specimen area depends 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
18、 the observed specimen area as afunction of measurement conditions, for example, electronenergy or analyzer pass energy, may need to be known if thespecimen materials in regular use have lateral inhomogeneitieswith dimensions comparable to the dimensions of the specimenarea viewed by the analyzer.5.
19、4 This practice can give useful information on the imagingproperties of the electron energy analyzer for particular con-ditions of operation. This information can be helpful incomparing analyzer performance with manufacturers specifi-cations.5.5 Examples of the application of the methods described i
20、nthis practice have been published (1-6).45.6 An ISO Technical Report provides guidance on deter-minations of lateral resolution, analysis area, and sample areaviewed by the analyzer in AES and XPS (7). Baer andEngelhard have used well-defined dots of a material on asubstrate to determine the area o
21、f a specimen contributing tothe measured signal of a small-area XPS measurement (8).This area could be as much as ten times the area estimatedsimply from the lateral resolution of the instrument. Theamount of intensity in fringe or tail regions could also behighly dependent on lens operation and the
22、 adequacy ofspecimen alignment. In scanningAuger microscopy, the area ofanalysis is determined more by the radial extent of backscat-tered electrons than by the radius of the primary beam (9, 10).6. Apparatus6.1 Test Specimen, preferably a conductor, is required and ismounted in the Auger electron o
23、r X-ray photoelectron spec-trometer in the usual position for surface analysis. It isrecommended that the test specimen 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
24、dimensions much less thanthe expected spatial resolution of the analyzer or the width ofthe incident beam on the specimen 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
25、 unaided eye (see 8.6). It isdesirable that the surface of the test specimen be cleaned by ionsputtering or other means 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 m
26、ust be available onthe spectrometer to provide a beam of electrons incident on thetest specimen surface with energy typically 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
27、 different regions ofthe 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 anddis
28、play the selected 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
29、 withselected 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
30、 be provided. 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 mad
31、e with two waveform generatorsor two programmable power supplies.7. Procedure7.1 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 and 2000 eV may
32、 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 be chosen to d
33、etermine 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 scan is a relativ
34、ely 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 allows convenien
35、t 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 plates.Line scans ca
36、n 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 0.5 kHz to 1 k
37、Hz. The4The boldface numbers in parentheses refer to the list of references at the end ofthis practice.E1217052waveforms are amplified and coupled through a transformer tothe deflection plates of the electron gun, one output beingdesignated for horizontal deflection and the other for verticaldeflect
38、ion. A resistive center-tap is connected across eachtransformer output with the midpoints 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
39、,that is, absence of any Lissajous figures. Select the gains of theamplifiers to deflect 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
40、 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 Programma
41、ble Power SuppliesProgram acomputer to control the output voltages of two programmablepower supplies. Connect the outputs of the power supplies tothe deflection plates of the electron gun. Make these connec-tions as in 7.2.2.1; connect center taps across each powersupply, also as in 7.2.2.1. At a gi
42、ven vertical position, step theelectron beam horizontally across the test specimen surface.The beam then can be stepped vertically prior to the nexthorizontal sweep, and so on. Make measurements for eachhorizontal sweep and for equally spaced horizontal lines withinthe vertical sweep range. The inte
43、rval between the positions ofthe electron beam on the specimen surface together with thewidth of the beam at the surface will determine the spatialresolution in the measurement of the specimen area contribut-ing to each detected signal.7.2.3 The maximum amount of deflection of the electronbeam on th
44、e test specimen should be less than that whichwould cause significant (5 %) reduction of incident electron-beam current, for example, reduction due to interception of thebeam by electrodes of the electron gun.7.3 The amount of deflection of the electron beam on thetest specimen can be determined fro
45、m electron intensitymeasurements with test objects, for example, grids or holes, ofknown dimensions (1). The test object is mounted on the testspecimen and features of known shape and size are located inthe recorded data (see 7.7). Alternatively, a feature can belocated in plots of absorbed current
46、(see 7.4) due to, forexample, specimen roughness or a specimen mounting clip (3).The specimen can then be moved a known amount using amanipulator and a new plot made of absorbed current. Thedifference in the positions of the selected feature on the twoplots corresponds to the displacement of the spe
47、cimen.7.4 It is recommended that measurements be made of thecurrent to the specimen (the absorbed current) as the electronbeam is scanned across the specimen surface. These measure-ments can give information about the topography of thespecimen surface and are useful for ensuring that any structurein
48、 the other intensity measurements (see 7.5) is not associatedwith specimen topography.7.5 Select the electron signals to be measured from theanalyzer.7.5.1 Elastic PeakThe electron energy analyzer can beadjusted to detect electrons elastically scattered by the speci-men surface, that is, at the ener
49、gy of the incident electronbeam. This choice is recommended for initial survey measure-ments since this signal is the strongest.Apossible disadvantageof this choice is that incorrect intensity measurements may bemade if, for energy analyzers with sufficiently high energyresolution, the instrument does not remain aligned on theelastic peak as the electron beam is deflected on the specimen(4); see also Guide E 1016.7.5.2 Inelastically Scattered ElectronsThe electron en-ergy analyzer can be adjusted to detect electrons inelasticallyscattered by the specimen surface. Th
