XPS study of the L-CVD deposited SnO2 thin films exposed to oxygen and hydrogen

In this paper, the XPS study of SnO2 thin films deposited by the L-CVD technique are presented. The influence of exposition of the as-deposited samples to oxygen O2 and hydrogen H2 on their stoichiometry was determined. Moreover, on the basis of detailed shape analysis of the Sn3d5/2 and O1s XPS peaks, the chemical shift of binding energy corresponding to the change of sample stoichiometry was separated from a shift of the binding energy corresponding to the change of interface Fermi level position EF–Ev in the band gap, using a new procedure of deconvolution of the core level XPS peaks. The shift of the Sn3d5/2 peak by approximately 0.5 eV towards the lower binding energy after highest H2 exposure was interpreted as a true chemical shift due to an increase of Sn2+ component, whereas the shift of Sn3d5/2 peak and O1s peak after highest O2 exposure by approximately 0.5 eV towards the lower binding energy was interpreted as a result of the shift of the interface Fermi level position in the band gap towards the top of valence band at the surface, which corresponds to a deep accumulation layer typical for SnO2 thin films.