Effect of heat treatment on the current induced dynamic mixed metal-insulator phase in needle-like VO2 single crystals

Abstract

The Insulator-Metal-Transition adjoined by a structural transition of VO2 is induced above room temperature (340 K) by heating or self-heating. A steep resistance-jump of up to five orders of magnitude occurs at this transition in high quality, unstrained single crystals. Insulating domains sliding in the sense of the electric current within the metallic background were found so far exclusively in the current induced mixed metal-insulator phase of VO2 single crystals; it is known for a long time that their uniformity and speed as function of current density are very sensitive to crystal quality. The high energetical cost of domain emission is the focus of our present investigations. In this Communication we report on the surprising behavior of a needle-like VO2 single crystal. Several I-V closed loops traced at room temperature concurrently with video recording of the crystal under the microscope, were followed by R(T) measurements during three slow heating-cooling cycles between room temperature and above 340 K, followed in their turn by an additional set of I-V measurements and video recordings. The results show that the slow cycling through the transition using external heat had a healing effect on the reproducibility of R(T) while increasing the activation energy of conduction in the insulating state and in reducing the damping term in the domains' sliding velocity. The intriguing result of this set of measurements was that the energy cost of the domain emission, was higher after healing than prior to it.