Vapor Phase Crystallization of Vanadium Oxide by Hydrolysis of Vanadium Oxychloride

Abstract

A new method of preparing single crystals of V₂O₅, VO₂, V₃O₅, V₂O₃, and VO has been presented, which is based on the chemical decomposition of VOCL₃ vapor with moisture in an inert or reducing atmosphere. In this method, V₂O₅ and VO₂ crystallized in a whisker shape, whereas V₃O₅ and V₂O₃ in a dendritic form composed of well-developed thin platelets. Thin films of VO single crystal were successfully grown by the epitaxial technique on the MgO substrate, and those of VO₂ on either TiO₂ or GeO₂. The observation on the surface structures and on the morphology of the crystals thus obtained has suggested that the mechanism of `layer growth' may apply to the case of V₂O₅ and VO₂ crystals. The growth of V₃O₅ and V₂O₃ has been interpreted in terms of two-step mechanism, in which the crystallization begins with dendritic growth and then proceeds to layer growth. The epitaxial growth is successful only when sufficient structural matching holds between the substrate and the growing crystals.