Comparison of VO 2 thin films prepared by inorganic sol-gel and IBED methods

VO2 thin films with semiconductor-to-metal phase-transition properties were prepared by inorganic sol-gel and IBED (ion-beam-enhanced deposition) methods on SiO2/Si substrate. The crystalline phase and the shape and width of the hysteresis curves of these VO2 films were significantly different. For sol-gel VO2 films, the transition started at close to 62 °C upon heating. The temperature interval needed to complete the phase transition was 8 °C, the ratio of resistance (R20 °C/R80 °C) reached three orders and the hysteresis width was 6 °C. However, the IBED film post-annealed in Ar at 700 °C underwent a phase transition from 45 °C to 80 °C, the ratio of resistance was more than two orders and the hysteresis width was 2 °C. In addition, the TCR (temperature coefficient of resistance) at 22 °C of the IBED film was 3.5%/K, much larger than the 0.7%/K TCR of the sol-gel film.