Influence of ambient atmosphere on metal-insulator transition of strained vanadium dioxide ultrathin films

Abstract

The effect of ambient atmosphere on metal-to-insulator transition (MIT) in strained vanadium dioxide (VO2) ultrathin films (7–8nm) grown epitaxially on TiO2 (001) single crystal substrate by pulsed laser deposition was investigated by varying the ambient oxygen pressure and substrate temperature with the intention being to control arbitrarily the MIT events of strained VO2 ultrathin films, including the MIT temperature and the resistivity change. When reducing the ambient oxygen pressure, the MIT temperature remained almost constant, whereas the change of resistivity during MIT tended to be smaller. Contrary, varying the substrate temperature resulted in the variation of the MIT temperature with keeping the abruptness of transition. The lower the substrate temperature, the lower the MIT temperature, and in addition the MIT temperature ∼290K with keeping the abrupt change of resistivity is found to be the lowest compared with previously reported values. The reduction of the MIT temperature was found to correlate with shortening c-axis length when decreasing the substrate temperature, indicating the significant strain effects. Thus these results highlight that controlling appropriately the ambient atmosphere enables us to modulate arbitrarily the MIT events of strained VO2 thin films near room temperature.