Effects of two-step heat treatment on properties of In sub(2) O sub(3):Zr thin film epitaxially grown on c-face sapphire substrate

A two-step heat treatment was carried out on a zirconium-doped indium oxide thin film epitaxially grown on a c-face sapphire substrate by a radio-frequency magnetron sputtering method. First, the as-grown film was heat-treated to improve its crystallinity. Air was selected as the heat-treatment atmosphere to avoid the precipitation of indium that occurs at high temperatures, and the crystallinity of the as-grown film was successfully improved by adopting this first-step heat treatment. The film with crystallinity improved by the first-step treatment was then heat-treated in N sub(2) to lower its resistivity. The resistivity of the film could be lowered about three orders of magnitude compared with that of the as-grown film after the second-step heat treatment under conditions at which the optical transmittance of the film remained sufficiently high in the wavelength region from 350 to 2000 nm.