Oxygen pressure manipulations on the metal-insulator transition characteristics of highly (0 1 1)-oriented vanadium dioxide films grown by magnetron sputtering

The metal-insulator transition behaviour of vanadium dioxide (VO2) films grown at different oxygen pressures is investigated. With the aid of temperature-dependent electrical and infrared transmittance experiments, it is found that the transition temperature in the heating process goes up with increasing argon-oxygen ratio, whereas the one in the cooling process shows an inverse variation trend. It is found that the hysteresis width of the phase transition is narrowed at a lower argon-oxygen ratio because the defects introduced by excess oxygen lower the energy requirement of transformation. Furthermore, the defects reduce the forbidden gap of the VO2 system due to the generation of a V⁵⁺ ion. The present results are valuable for the achievement of VO2-based optoelectronic devices.