An optical study of the electrically driven insulator-metal transition in V${}_2$O${}_3$

The strongly correlated oxide V${}_2$O${}_3$ undergoes an insulator-metal transition (IMT) from a low-temperature antiferromagnetic insulating phase to a paramagnetic metallic phase at around 160 K, resulting in a several orders-of-magnitude change in resistivity. We investigated the electrical breakdown of a V${}_2$O${}_3$ thin film, grown by rf-sputtering on a r-cut sapphire substrate, by concomitantly measuring the electrical properties as well as the spatially resolved optical reflectivity. At temperatures near the IMT, the current voltage characteristics show jumps to lower voltages, indicating electrical breakdown of the insulating phase. Whether this electrically driven IMT is electric-field induced or caused by the creation of electro-thermal domains through Joule heating is in focus of recent research. The reflectivity measurement reveals that the breakdown is accompanied by a change in reflectivity, which can be attributed to the formation of spatially confined metallic filaments.