AVS 46th International Symposium
    Applied Surface Science Division Wednesday Sessions
       Session AS-WeM

Paper AS-WeM7
Straightforward Methods for Accurate Estimation of Attenuation Length and Similar Quantities in XPS and AES

Wednesday, October 27, 1999, 10:20 am, Room 6A

Session: Gaede-Langmuir Award Address and Quantitative Surface Analysis
Presenter: P.J. Cumpson, National Physical Laboratory, UK
Authors: P.J. Cumpson, National Physical Laboratory, UK
M.P. Seah, National Physical Laboratory, UK
I.S. Gilmore, National Physical Laboratory, UK
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The surface-sensitivity of X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) is due to strong inelastic scattering of electrons. Elastic scattering also takes place, and modifies@footnote 1@ the absolute intensities, the sensitivity factors, the intensities from layers, and (in the case of XPS) the asymmetry parameter @beta@, all of which feed-in to quantitative analysis of spectra. The modification is a multiplicative factor of between 3% and 30% depending on the kinetic energy and material. The behaviour of the asymmetry parameter is particularly important for those using monochromated XPS instruments. Elastic scattering affects these quantities in a straightforward way. This leads to some simple recommendations on analysis geometry, and estimation of Attenuation Lengths to optimise the accuracy of quantifications without increasing complexity. One can measure surface composition and layer thicknesses to known, acceptable accuracy,@footnote 2@ provided one can estimate the Attenuation Length of signal electrons in the sample being analysed. In particular, Attenuation Lengths for organic materials are important in defining polymer, lubricant or contamination surface layers by Angle-Resolved XPS. We therefore pay particular attention to how to estimate Attenuation Length values for an arbitrary organic material. These estimates are in excellent agreement with Monte Carlo calculations. @FootnoteText@ @footnote 1@ A Jablonski, Surf. Sci. 364 (1996) 380. @footnote 2@ P J Cumpson and M P Seah, Surf. Interface Anal. 25 (1997) 430.