Ellipsometry and x-ray photoelectron spectroscopy study of SnO2 reduction at the interface with sputtered <i>a</i>-Si:H

Abstract

Very thin layers of hydrogenated and unhydrogenated amorphous silicon have been deposited on tin oxide substrates under different temperatures and H2 partial pressures by dc magnetron sputtering. The deposition processes are monitored by real time in situ ellipsometry. We observe the reduction reaction of the SnO2 exposed to a H- or Si-containing deposition flux in the early stages of film growth by real time ellipsometry. The chemical states of Sn at the a-Si:H (or a-Si)/SnO2 interface have been studied by x-ray photoelectron spectroscopy (XPS). XPS confirms that a Si flux alone can reduce SnO2 to elemental Sn, and that this reaction is temperature dependent. However, the contribution of Si is secondary to that of H atoms in the reduction reaction.