Preparation of epitaxial V2O3 films on C-, A- and R-planes of α-Al2O3 substrates by coating-pyrolysis process

Epitaxial films of vanadium(III) oxide V2O3 were prepared on the C-, A-, and R-planes of alpha-Al2O3 substrates by a coating-pyrolysis process. The final heat treatment was carried out at 1000 degrees C in a precisely controlled gas how of a CO-CO2 mixture (pCO/pCO(2) = 10(-1)) at ambient pressure. This condition corresponds to an oxygen partial pressure of similar to 10(-12) atm. The X-ray diffraction theta-2 theta scanning and pole-figure analysis showed that the 0.5-mu m-thick V2O3 films chiefly comprise the grains grown epitaxially to the substrate surfaces and a small amount of uniaxially oriented crystallites with the c-axis perpendicular to the substrate surfaces. In the films grown on the C- and A-planes of alpha-Al2O3, epitaxial grains grown 60 degrees-rotated in the basal plane relative to the substrates (or 180 degrees domains) were also present. The occurrence of the uniaxially c-axis-oriented and 180 degrees domains may be attributed to the crystallization from the film surf;ice accompanying the reduction of the precursors, which contain higher-valence vanadium ions, by the GO-CO: mixed gas, whereas the epitaxial grains grow from the film/substrate interface. (C) 2000 Elsevier Science S.A. All rights reserved.