Energy loss functions derived by Monte Carlo simulation from the Au 4f XPS spectrum

doi:10.1016/0039-6028(92)90252-2

Surface Science

Volume 261, Issues 1–3, 15 January 1992, Pages 403-411

https://doi.org/10.1016/0039-6028(92)90252-2 Get rights and content

Abstract

We have used conventional deconvolution methods to obtain the original no-loss XPS spectrum, the so-called source function, by using loss functions derived from optical constant measurements and high-energy electron transmission experiments. However, the source functions derived are far from the Lorentzian type expected theoretically, because these loss functions do not precisely describe the actual energy loss processes of photoelectrons of low energies ranging from 100 eV to 1000 eV, where surface excitations, for example, play an important role. We have, therefore, attempted to derive a more reasonable loss function for Au4f X-ray photoelectrons by Monte Carlo simulation of the escape processes of signal electrons, in which both the elastic and inelastic scattering are included. The result indicates that the present Monte Carlo simulation reproduces the XPS spectrum very well, leading to the derivation of a more realistic loss function of wider practical use.

References (20)

V.M. Dwyer et al.
Surf. Sci.
(1988)
J.C. Ingram et al.
Appl. Surf. Sci.
(1990)
J.C.H. Spence
Ultramicroscopy
(1979)
M.E. Twigg
Ultramicroscopy
(1982)
R.F. Reilman et al.
J. Electron Spectrosc. Relat. Phenom.
(1976)
Z.-J. Ding et al.
Surf. Sci.
(1989)
S. Tougaard
Surf. Sci.
(1989)
D.A. Shirley
Phys. Rev.
(1972)
S. Tougaard
Surf. Interface Anal.
(1988)
S. Tougaard et al.
Phys. Rev.
(1982)

There are more references available in the full text version of this article.

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Energy loss functions derived by Monte Carlo simulation from the Au 4f XPS spectrum

Abstract

Surf. Sci.

Appl. Surf. Sci.

Ultramicroscopy

Ultramicroscopy

J. Electron Spectrosc. Relat. Phenom.

Surf. Sci.

Surf. Sci.

Phys. Rev.

Surf. Interface Anal.

Phys. Rev.