  Electrically driven metal-insulator transition in vanadium dioxide (VO2) is
of interest in emerging memory devices, neural computation, and high speed
electronics. We report on the fabrication of out-of-plane VO2
metal-insulator-metal (MIM) structures and reproducible high-speed switching
measurements in these two-terminal devices. We have observed a clear
correlation between electrically-driven ON/OFF current ratio and
thermally-induced resistance change during metal-insulator transition. It is
also found that sharp metal-insulator transition could be triggered by external
voltage pulses within 2 ns at room temperature and the achieved ON/OFF ratio is
greater than two orders of magnitude with good endurance.
