Modeling of hysteresis in nanocrystalline VO2 thin films with random resistor networks

Abstract

The random resistor network (RRN) model is employed to simulate the thermal hysteretic behavior in nanopolycrystalline structure of vanadium dioxide (VO2) thin films. In calculation, the system is modeled as a binary composite medium consisting of random distribution for semiconducting and metallic regions in nano-VO2 microcrystals. In our simulation, we propose the IR transmittance to represent the volume fraction of the microcrystals that are in semiconducting state. The hysteresis model has been checked against the experimental measurements. There is satisfactory agreement between the calculated resistance-temperature trajectories with the measured major hysteresis loops for temperature covering the whole range from the low-temperature semiconductor behavior to the high-temperature metallic state, which gives strong support to the present approach. On the discussion of physical mechanical in our simulation, the phase transition in nano-VO2 thin films is due to the competition of these two components in VO2 nanopolycrystalline with the temperature changing, and the hysteretic phenomenon of this material is argued to be originated mainly from the difference of volume fraction represented the semiconducting phase in cooling and heating branches.