Am. Salvia et Je. Castle, THE INTRINSIC ASYMMETRY OF PHOTOELECTRON PEAKS - DEPENDENCE ON CHEMICAL-STATE AND ROLE IN CURVE-FITTING, Journal of electron spectroscopy and related phenomena, 95(1), 1998, pp. 45-56
Correct estimation of peak and background in XP-spectra is necessary f
or quantitative analysis. The problem is made difficult because neithe
r the peak nor the background have a known shape and their separation
requires the photoemission process to be treated as a sequence of well
separated events. Background removal can be undertaken using the Toug
aard method which is based on a careful analysis of the electron trans
port taking place in a solid bur this procedure is designed to remove
only the extrinsic component. There is a further component of the back
ground which is intrinsic to the peak and associated with the photoemi
ssion event at the atomic/molecular level. In this paper we build on p
revious papers, which were concerned with metallic elements, to assess
the importance of oxidation on the intrinsic asymmetric shape of the
peak and thus make this available for curve fitting. This was done, us
ing a programme, Tryfit, based on the Shirley type algorithm modified
by Proctor to quote separately the peak and background intensity in XP
-spectra. The programme allows the shape parameter, kappa, to be extra
cted which helps in defining the 'intrinsic' shape of a photoelectron
peak. The shape parameter, kappa, is found to be independent of instru
mental effects and intrinsically related to atomic number and, as now
shown in this paper, to a certain extent to chemical state. It is demo
nstrated in this paper that its use can help in quantifying individual
peak contributions to a multicomponent XPS spectrum. (C) 1998 Elsevie
r Science B.V. All rights reserved.