Role of Oxygen Vacancies in the Electrical Properties of WO3?x Nano/Microrods with Identical Morphology

摘要

Tungsten oxide (WO_(3?x)) crystalline nano/microrods with identical morphology but different contents of oxygen vacancies were prepared by thermally evaporating fixed amount of WO_3 powder in reductive atmosphere from different amounts of S power at 1150°C in a vacuum tube furnace, in which both sources were loaded in separate ceramic boat.With increasing amount of S powder, a series of tungsten oxides,WO_3, WO_(2.90), W_(19)O_(55) (WO_(2.89)), and W_(18)O_(49) (WO_(2.72)), could be obtained. And devices were fabricated by screen-printing the obtained WO_(3?x) crystals on ceramic substrates withAg-Pd interdigital electrodes.With increasing content of oxygen vacancies, the devices fabricated with WO_(3?x) crystals present a negative to positive resistance response to relative humidity. Under dry atmosphere, for the devices with increasing x, the strong response to light changed from short to long wavelength; under light irradiation, the conducting ability of the devices was enhanced, due to the more efficient separation and transportation of the photogenerated carriers; and under simulated solar irradiation, the photocurrent intensity of the W_(18)O_(49) device was roughly 8 times, about 500 times, and even 1000 times larger than that of the W_(19)O_(55), WO_(2.90), and WO_3 one, respectively.With the versatile optoelectrochemical properties, the obtained WO_(3?x) crystals have the great potential to prepare various humidity sensors and optoelectrical devices.