Nanostructure-dependent metal-insulator transitions in vanadium-oxide nanowires

Single-crystal VO2 nanowires were synthesized using atmospheric-pressure and physical vapor deposition and outfitted with electrodes for current-voltage measurements. The Mott insulator-to-metal transition temperatures of several nanowires with varying lateral dimensions were determined by measuring the voltage values at which the sharp current step, signaling that the occurrence of the insulator-to-metal or the reverse transitions, had taken place. The observed Mott transition temperatures, which ranged between 62 and 70 degrees C for the nanowires measured, trended downward with decreasing nanowire width. We ascribe this to strong interactions between the nanowire and the underlying silica substrate. However, the scatter in the Mott-temperature versus nanowire width exceeded the experimental uncertainty in the values of the Mott temperature, indicating that other parameters also contribute to the precise value of the Mott transition temperature of nanostructured VO2.