Microstructure and X-Ray Study of Preferentially Oriented SnO2 Thin Film Prepared by Pyrohydrolytic Decomposition

Preferentially oriented SnO2 thin films were prepared by pyrohydrolytic decomposition onto a glass substrate along the direction of flux flow. The obtained films were oriented in [200] and then [002] directions along the direction of flow. To reveal the orientation mechanism from the initial stage of growth, [200]-oriented SnO2 thin film was prepared on a chemically stable GaAs single crystal. The successive growth structure of the thin film on the substrate was accurately observed and characterized using HR-AEM (high-resolution analytical electron microscopy). A layer of nuclei about 50 Å in width was observed between the GaAs substrate and the oriented overgrown layer. It is suggested that such preferential nucleation occurs from an early stage of growth, and is strongly dependent on supersaturation of the flux flowing along the substrate.