Hydrogen plasma interactions with tin oxide surfaces

We have exposed films of various conductive transparent oxides (CTOs) such as SnO 2 and indium tin oxide to hydrogen plasmas in d.c. and r.f. discharges and have measured the white light optical transmission, the room air work function and the sheet resistances before and after the exposure as a function of the discharge parameters, the sample temperature and the exposure time. In addition, we have determined the surface composition of unexposed and exposed samples by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy and the depth of plasma interactions by AES profiling. Interactions with positive hydrogen ions in the plasma lead to a chemical reduction at the CTO surface. As the main consequence, the optical transmission is decreased by the formation of an absorbing oxygen-depleted surface layer.