Photo-assisted bistable switching using Mott transition in two-terminal VO2 device

In order to investigate bistable switching characteristics of planar junction devices based on vanadium dioxide (VO2) thin films, we have measured the optical power dependence of the threshold voltage of the device, at which a current jump, regarded as the Mott metal-insulator transition (MIT), happened, by using an infrared laser with a wavelength of ∼1.55 μm, illuminated onto the VO2 film. In a test closed loop circuit connecting a DC voltage source, a standard resistor, and a VO2 thin film device in series, the bistability of the voltage across the device (VD) was examined with respect to a variety of illumination powers (PLs). By triggering the forward or reverse phase transition (Mott MIT) of the VO2 film with “SET” or “RESET” optical pulse, respectively, the photo-assisted bistable switching of VD in the test circuit properly DC biased could be realized at an intermediate PL chosen between optical powers of “SET” and “RESET” pulses. In particular, the transient response of VD showed not only bistable states of VD but also their switching speed.