Influence of thermal boundary conditions on the current-driven resistive transition in VO₂ microbridges

We investigate the resistive switching behaviour of $\mathrm{VO_2}$ microbridges under current bias as a function of temperature and thermal coupling with the heat bath. Upon increasing the electrical current bias, the formation of the metallic phase can progress smoothly or through sharp jumps. The magnitude and threshold current values of these sharp resistance drops show random behaviour and are dramatically influenced by thermal dissipation conditions. Our results also evidence how the propagation of the metallic phase induced by electrical current in $\mathrm{VO_2}$, and thus the shape of the resulting high-conductivity path, are not predictable. We discuss the origin of the switching events through a simple electro-thermal model based on the domain structure of $\mathrm{VO_2}$ films that can be useful to improve the stability and controllability of future $\mathrm{VO_2}$-based devices.