Auger Electron and X-Ray Photoelectron Spectroscopy Studies of Oxidation of Tin Using SnOx Thin Films Grown by Reactive Ion-Assisted Deposition

In order to accurately determine the oxidation state of tin and to investigate the chemical shifts between tin and its oxides, quantitative Auger electron spectroscopy and X-ray photoelectron spectroscopy studies were performed using Sn metal, stoichiometric SnO2 powder, and polycrystalline SnO x thin films. Films with different oxygen contents were grown using a reactive ion-assisted deposition technique. As the atomic ratio of tin to oxygen in the deposited films increased to the stoichiometric value of 2, the tin M 4 N 4,5 N 4,5 Auger transition and the corresponding Sn 3d 5/2 core-level photoelectron line gradually shifted to lower kinetic energy and higher binding energy by as much as 6±1 eV and 2.39±0.02 eV, respectively, relative to those of the tin metal. An explanation for the observed systematic difference between the chemical shifts of Auger and photoelectron lines is given. It is based on the difference in electronic polarization energy between the final two-hole state produced by the Auger electron emission and the final single-hole state produced by the photoelectron emission.