The Electrical and Structural Features of Vanadium-oxide Films as Formed by the Thermal Decomposition of Vanadium Naphthenate

Abstract

Abstract Vanadium-oxide thin film, which was amorphous, brownish, and transparent, was prepared more conveniently by improving Sekiya-Matsushita’s method by, for instance, decomposing vanadium naphthenate thermally; that is, 10 wt% of a 1-butanol solution of vanadium naphthenate was dropped on slide glass, dried in air, decomposed at 600 °C for 20 min under 0.5 l/min of a N2 stream which was equilibrated with water at 21.5 °C, and then taken out rapidly into the air for cooling. The VO thin film thus prepared usually showed an abrupt change in electric conductivity from 2×10−5 to 1×10−4 Ω−1 at about 60 °C. The electrical feature was greatly affected by the addition of other metal oxides, such as Na2O, TiO2, Cr2O3, MoO3, and ZrO2. Both the conductivity and the gap tended to decrease in the cases of TiO2, Cr2O3, and MoO3, and to increase in ZrO2. On the addition of Na2O, however, the conductivity increased only at temperatures lower than the transition point; thus, the gap decreased greatly, almost disappearing. It was concluded from these facts that the electrical feature of the vanadium-oxide film must be controlled to a great extent by the addition of some compounds of vanadium oxide with the other metal oxides formed at the grain boundary of the VO2 amorphous particles. That is, the larger the conductivity of the compound in the boundary layer, the more clearly the intrinsic feature of the VO2 particles appears, and vice versa.