EVALUATION OF CORRECTION PARAMETERS FOR ELASTIC-SCATTERING EFFECTS INX-RAY PHOTOELECTRON-SPECTROSCOPY AND AUGER-ELECTRON SPECTROSCOPY

We describe a relatively simple, reliable, and fast approach for quant itative surface analyses by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) that significantly improves the acc uracy of analyses of polycrystalline solids, The common formalism of X PS and AES is based on the assumption, now known to be incorrect, that elastic-electron-scattering effects are negligible. These effects can be taken into account by the use of correction parameters (two for XP S and one for AES) in a modified formalism. These correction parameter s can be conveniently expressed in terms of the ratio zeta of the tran sport mean free path to the inelastic mean free path for a particular material and electron energy, and we give an improved procedure for de termining this ratio for elemental solids and compounds at electron en ergies ranging from 50 to 2000 eV. We test the utility and validity of the derived correction parameters for XPS based on comparisons with p arameter values and photoelectron intensities derived from Monte Carlo simulations for some 400 photoelectron lines in 27 elements excited b y ME and Al characteristic x rays. It is pointed out that the systemat ic errors associated with the neglect of elastic-electron scattering i n XPS depend on the instrumental configuration, and range from -20% to 30% for two WS configurations investigated here. With the use of the modified XPS formalism and the two correction parameters, these errors were reduced to between -3% and 2% for most of the photoelectron line s, although with a few lines the errors were as large as -10%. Good pe rformance of the modified formalism for AES has been reported previous ly. We describe and discuss the application of this approach for surfa ce analyses of multi-component solids. The improved procedure for calc ulating the ratio zeta can also be used for estimation of the mean esc ape depth of photoelectrons and Auger electrons. (C) 1997 American Vac uum Society.