Figure 1

(a) Resistance-temperature curve of a VO${}_2$ single crystal. The red and blue lines denote increasing and decreasing temperatures, respectively. (b) Thermal cycle dependence of MIT temperature at a fixed temperature ramp rate of 0.1 °C/min.Reuse & Permissions

Figure 2

Images of optical microscope during the onset of MIT near T = 66.8 °C (heating) and T = 61.2 °C (cooling) taken within ∼1 sec, respectively. The boundary of metal-insulator phase propagates along the rutile $c$ axis of a VO${}_2$ crystal.Reuse & Permissions

Figure 3

Laue patterns from x-ray diffraction as a function of temperature. (a) and (b) At T = 25 °C (I), the insulating M2 phase is present. As the temperature increases to 50∼52.5 °C (II, III, and IV), the coexistence of phases M1 and M2 can be seen. The M1 phase remains up to the MIT, which occurs at 68 °C (V). The R phase shows immediately after the MIT at 68.2 °C (VI). After undergoing a MIT in the cooling process (VII and VIII), the coexistence of M1 and R phases are shown when the temperature is set to 66.2 °C, accompanied by a decrease in resistivity. Letter S inside the figures represents diffraction peak from the sapphire wafer used for sample mounting. (Inset) Spontaneous MIT of VO${}_2$ was stopped in the middle of the transition. The state remained quasistable with temperature variation (±0.3 °C) for 30 minutes. Then this quasistable insulating state made a transition to metallic state. M1 and M1′ denote two twin domains of the M1 phase.Reuse & Permissions