Temperature dependence of the first-order metal-insulator transition in VO2 and programmable critical temperature sensor

For VO2-based two-terminal devices, the first- order metal-insulator transition (MIT, jump) is controlled by an applied voltage and temperature, and an intermediate monoclinic metal phase between the MIT and the structural phase transition (SPT) is observed. The conductivity of this phase linearly increases with increasing temperature up to T-SPT approximate to 68 degrees C and becomes maximum at T-SPT. Optical microscopic observation reveals the absence of a local current path in the metal phase. The current uniformly flows throughout the surface of the VO2 film when the MIT occurs. This device can be used as a programmable critical temperature sensor where the applied voltage is controlled by a program. (c) 2007 American Institute of Physics.