Photothermoelectric Effects in Localized Photocurrent of Individual VO2 Nanowires

Photocurrent studies of individual and isolated VO2 nanowires (NWs) with Pt metal contacts were conducted by using a focused laser beam. With localized probing, the photoresponse arising from the NW−Pt contact junctions and the main body of the NW can be separately examined. Rapid photoresponse (with and without bias) toward visible and infrared laser irradiation was observed to arise primarily from the NW−Pt contacts. Experiments at elevated temperature (above the semiconductor−metal transition temperature of VO2) revealed a remarkable ∼500 fold enhancement in the photocurrent generated at the NW−Pt contact junctions at zero external bias. Photoinduced thermoelectric effect is proposed as the key carrier transport mechanism dictating the photocurrent generated at the NW-Pt interface.