Photoconductive characteristic in individual WO(3-x) nanowire.

Tungsten Oxide nanowires, with their natural excellent structure, possess unique physical and chemical properties. In this paper, photoconductivity of single tungsten trioxide nanowire (WO3 NW) and single tungsten suboxide nanowire (WO(3-x) NW) have been studied respectively on a photoconductivity testing system. Under 514 nm wavelength laser illumination, an unsaturated photocurrent and a slow photoconductive responsivity could be expressed in single WO3 NW device. In WO(3-x) NW device, photoconductive responsivity was determined by the illuminating position. About 100 nA photocurrent could be generated and a fast optoelectric responsivity with a recover time about 90 ms from the device was observed. Not only photoconductive effect but also the photovoltaic effect was obtained from individual WO(3-x) NW device. According to the results of X-ray photoelectron spectroscopy, the mechanisms of photoconductive and photovoltaic effects in these two kinds of devices have been discussed and the oxygen vacancy played an important role in the photoconductive phenomenon. All these effects could be of practical use in the design and fabrication of photodetectors based on single tungsten oxide nanowire.

Pressure-induced structural transition in WO3 nanowires.

Raman spectroscopic analysis is performed on WO(3) nanowires at room temperature at pressures from ambient conditions to 45 GPa. Linear dependence of the first-order Raman signal on various high-pressure (HP) sections is observed. Upon increasing the applied pressure, the WO(3) nanowires undergo four phase transitions at pressures around 1.7, 4.6, 21.5, and 26.2 GPa, which are all less than that reported for bulk WO(3). When the pressure is up to 42.5 GPa, a new high-pressure phase (HP5) appears. This phase has never been reported and is not reversible while unloading the pressure.