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Simple Procedure for Precise Peak Maximum Estimation for Energy Calibration inAES andXPS
Author(s) -
Cumpson P. J.,
Seah M. P.,
Spencer S. J.
Publication year - 1996
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/(sici)1096-9918(19960930)24:10<687::aid-sia174>3.0.co;2-q
Subject(s) - calibration , energy (signal processing) , simple (philosophy) , spectrometer , algorithm , spectral line , computational physics , maxima , computer science , optics , mathematics , statistics , physics , philosophy , epistemology , art , astronomy , performance art , art history
We present a simple, easily‐reproducible method of locating the maxima of XPS and AES peaks, to an energy uncertainty of, typically, 2–10 meV, which is particularly useful in the energy calibration of instruments using spectra acquired from standard reference materials. This method is mathematically equivalent to performing a least‐squares fit of a parabola to the top of the peak, but the calculation described here is very simple, requires no computer and can easily be done by pocket calculator. Although parabolic fitting to give peak energies is not a new method, we present it here in a particularly simple tabular form, which makes it easy to perform even without a computer. The statistics known to apply to XPS and AES intensities then allow us to derive a new equation for estimating the precision of the peak energy. We use this to obtain simple rules which give the most efficient ‘trade‐off’ between calibration and time spent acquiring the spectra.The XPS calibration spectra from a VG Escalab II spectrometer are used to verify the efficacy of the method, although the same method is readily applicable to AES. Quantitative comparisons are made with previous (and rather more time‐consuming) peak location methods. Agreement is excellent, showing that the new method can be used as part of an energy calibration procedure with the confidence that no discontinuity will be introduced into the calibration history of a spectrometer when switching to the new method.Precise energy calibration becomes increasingly important with the use of numerical methods such as linear least‐squares fitting principal component analysis and factor analysis.