Nanoscale imaging and control of resistance switching in VO2 at room temperature

We demonstrate controlled local phase switching of a VO2 film using a biased conducting atomic force microscope tip. After application of an initial, higher "training" voltage, the resistance transition is hysteretic with IV loops converging upon repeated voltage sweep. The threshold V_set to initiate the insulator-to-metal transition is on order ∼5 V at room temperature, and increases at low temperature. We image large variations in V_set from grain to grain. Our imaging technique opens up the possibility for an understanding of the microscopic mechanism of phase transition in VO2 as well as its potential relevance to solid state devices.