Figure 3
The electronic structure of VO2 on TiO2 and c-Al2O3 as well as studies of the photoelectric properties of VO2 on TiO2. (a) Schematic band diagram of the hole transfer mechanism for VO2 on TiO2 and c-Al2O3 where the photon energy is demonstrated for the VO2 on TiO2 as being sufficient to excite carriers in the TiO2 layer and insufficient in the case of VO2 on c-Al2O3. Where the hole transfer is designated by the segmented line and the carrier movement is designated by the solid lines6,19. (b) Reflectivity measurements with a 405 nm diode laser illuminating VO2 deposited on TiO2(001) as the sample underwent a thermally induced IMT via heating and subsequent cooling where the dashed line indicated transition temperature. (c) The photocurrent switching of VO2 on TiO2(001) upon solely 405 nm illumination as the laser power was varied. The light was held on for 40 seconds post switching. (d) The same photocurrent switching measurement of VO2 on c-Al2O3(0001) where the 405 nm laser power was varied. The light was held on for 40 seconds post switching. (e) The photocurrent switching cycle for VO2 on TiO2(001) upon 405 nm illumination switching over 10 cycles. (f) External quantum efficiency measurement for VO2 on TiO2 as varied with laser power. (g) The average photocurrent and optical response of VO2 on TiO2(001) as the sample was thermally ramped through the optical transition where the 405 nm laser power was 1 mW through the thermal ramping where the dashed line indicates transition temperature.
