Role of grain boundaries in the insulator-to-metal transition in VO₂

Vanadium dioxide (VO₂) undergoes an insulator-to-metal transition (IMT) at 340K that can be triggered by Joule heating from applied voltage. The large change in resistivity of up to five orders of magnitude and high-speed switching time make VO₂ an attractive material for nanoelectronics. In the voltage-triggered IMT, grain boundaries in a polycrystalline VO₂ film can affect the IMT properties at the nanoscale. Here we use COMSOL Multiphysics, a finite element analysis software, to simulate the temperature and IV-characteristics of a range of polycrystalline films with different grain boundary characteristics. We determine how the voltage required to trigger the IMT and temperature distribution depend on grain size, grain boundary thickness, and grain boundary conductivity. We find that tuning the properties of grain boundaries can reduce the IMT voltage by up to 50%.