XPS study of the surface chemistry of Ag-covered L-CVD SnO2 thin films

In this paper, we present the results of X-ray photoelectron spectroscopy characterization of SnO2 thin films prepared by laser chemical vapour deposition (L-CVD) and subsequently covered by Ag atoms just after deposition and after long-term exposed to dry air, subsequent annealing in ultra high vacuum at 400 °C and dry air oxidation at 400 °C. Using the standard analytical procedure based on atomic sensitivity factors, the variation of surface chemistry defined in terms of the relative concentration of the main components of the films after the above-mentioned procedures has been determined. It was confirmed that after dry air exposure as well as dry air oxidation, the layers undergo an oxidation reaching almost SnO2 stoichiometry. Besides, during ultra high vacuum annealing, the films undergo reduction to almost SnO stoichiometry. At the same time, Ag atoms deposited at the top of layers diffuse into the subsurface layers. This was confirmed by X-ray photoelectron spectroscopy depth profiling analysis.