Giant persistent photoconductivity of VO2 device by single-pulse femtosecond laser

Abstract

The manifestation of giant persistent photoconductivity (GPPC) is demonstrated with a fs (femtosecond) Ti:sapphire laser pulse that has a duration of 40 fs and a central wavelength of 400 nm. The femtosecond laser pulse was irradiated on a two-terminal VO2 device fabricated on a corning glass substrate. Under the applied voltages of 9–12 V, the GPPC takes place within 8.6–15 μs after the laser irradiation. The photocurrent from the GPPC in the VO2 device remains stable with the current decreasing slope of ∼0.003%/minute. With one-dimensional thermal model, the temperature (TIR) of the irradiated area is estimated as a function of time, indicating that TIR is above the insulation-to-metal transition temperature of VO2 thin film prior to the onset of GPPC. The ultrafast onset of GPPC of VO2 device can be utilized for ultrafast optoelectronic switch and memory device.