Origin of variation in switching voltages in threshold-switching phenomena of VO2 thin films

We investigated the origin of the variation in switching voltages in threshold-switching of VO2 thin films. When a triangular-waveform voltage signal was applied, the current changed abruptly at two switching voltages, i.e., V-ON (insulator-to-metal) and V-OFF (metal-to-insulator). V-ON and V-OFF were measured by changing the period of the voltage signal, the temperature of the environment, and the load resistance. We observed that either V-ON or V-OFF varied significantly and had different dependences with respect to the external parameters. Based on the mechanism of the metal-insulator transition induced by Joule heating, numerical simulations were performed, which quantitatively reproduced all of the experimental results. From the simulation analysis, the variation in the switching voltages for threshold-switching was determined to be thermal in origin. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4790842]