Effect of oxygen content on the electrical properties of sputter deposited vanadium oxide thin-films

In this article, different oxidation states of vanadium in vanadium oxide (VO) thin-films, deposited on Si(100) at room temperature by reactive rf-sputtering of a pure metallic vanadium target at different Ar/O2 ratios, have been identified. A qualitative assessment of the XPS spectra reveals that vanadium exists in the V5+ and V4+ oxidation states in the oxide thin-films. The highest content of V5+ oxidation state is present in the oxide film deposited at highest O2 ratio (Ar:O2 = 1:4). Vanadium oxide deposited at highest O2 ratio shows insulator-to-metal (IM) transition whereas the devices, deposited at other oxygen ratios do not show any appreciable change. This transition has been ascribed to a voltage-induced joule heating effect which in turn results in formation of metallic conduction channel across the device. Thus, the ratios of Ar and O2 in the reactive plasma play a critical role in determining the IM transition properties of vanadium oxide thin-films.