Ellipsometry and X-Ray Photoeiectron Spectroscopy Study of SnO₂ Reduction at the Interface With Sputtered A-Si:H

Very thin layers of hydrogenated and unhydrogenated amorphous silicon have been deposited on tin oxide substrates under different temperatures and H₂partial pressures by dc magnetron sputtering. The deposition processes are monitored by real time in situ eilipsometry. 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 eilipsometry. The chemical states of Sn at the a-Si:H (or a-Si)/SnO₂ interface have been studied by x-ray photoeiectron 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.