Oxidation state control of solution-processed vanadium oxide thin-films and resistive switching of VO2 thin-film in a metastable state

Abstract

The solution processing of crystalline VO2 thin films has been intensively investigated for both fundamental studies and various electronic applications. However, previous studies have reported that the inevitable oxidation of vanadium cations in conventional precursor solutions hinders facile and reliable fabrication of VO2 thin films. Here we develop a kinetically stabilized precursor solution for solution-based VO2 thin-film fabrication. The stabilized solution precursor showed increased resistance to uncontrolled vanadium oxidation compared to conventional precursors. The synthetic conditions necessary for reliable VO2 thin-film fabrication were investigated at various oxygen concentrations and various annealing atmospheres. The oxygen level of an ambient atmosphere controls which of the three vanadium oxidation states arise, including V3+, V4+, and V5+ at a given temperature. The unusual occurrence of V3+ can be obtained without any reducing reagents. Nano-crystalline VO2 thin films subjected to rapid thermal shock exhibit metal-to-insulator transition at 58.9°C and resistive switching in a metastable state at 53.5°C, which could be further applied to future electronic devices such as memristors, Mott transistors, and Mott memories.