Vanadium dioxide films with good electrical switching property

Abstract

A novel method is described for preparing high-quality thin films which exhibit an abrupt resistivity change of 4 - 5 orders of magnitude at about ; this is the best result among those so far prepared on non-crystal substrates. To show the difference from the ordinary sol - gel method which uses vanadium alkoxide as precursor, this method has been called (by the authors) the inorganic sol - gel method, for it uses powder as precursor. This newly developed method shows some advantages in that it produces high-quality thin films (adherent, crack-free, and with good switching properties) in a cheap, simple, and reproducible way. The method consists of four processes: quenching, coating, drying and vacuum heat treatment. These processes show strong effects on the properties of the final films. In this paper, the effects of the drying process on the film blistering and the effects of film thickness, quenching temperature, and heat treatment time on the resistivity switching property were studied, and DSC, XRD, ESCA, and SEM were utilized to study the drying process and characterize the films. It was found that when the drying temperature was and heating rate was in the drying process, the final films would be blister-free and crack-free (on non-crystal substrates). It was also found that the magnitude of resistivity change at the phase transition of the samples treated at for 10 h under a pressure of 0.8 Pa increased with increasing thickness (in the thickness range 0.4 to ). When the film thickness was about , the magnitude of resistivity change of the samples treated under the same conditions was found to decrease with increasing quenching temperature. In a certain range of treatment time the magnitude of resistivity change of the samples treated at under a pressure of 0.8 Pa was found to increase with increasing heat treatment time.