Thermal-oxidative growth of aligned W_(18)O_(49) nanowire arrays for high performance gas sensor

摘要

Gas sensors based on aligned arrays of W_(18)O_(49) nanowires were formed directly via a novel route of in situ thermal oxidation of sputtered W film on the substrate attached patterned Pt electrodes. The well-developed nanowires have diameter of 10-20 nm and show roughly aligned morphology. It is found that the duration of oxygen exposure during thermal annealing plays a crucial role to harvest a pure phase of W_(18)C_(49) nanowire with desired length. The roughly aligned W_(18)O_(49) nanowires show favourable microstructure for gas adsorption and rapid gas diffusion. The NO_2 -sensing properties of aligned W_(18)O_(49) nanowires sensor were evaluated at 50℃ up to 200℃ over NO_2 concentration ranging from 250 ppb to 2.5 ppm. The results indicate that the W_(18)O_(49) nanowire arrays sensor exhibits good NO_2-sensing performances at its optimal operating temperature of 150 ℃, especially perfect stability and fast response-recovery characteristics. The reliable interface performance and fast gas adsorption-desorption properties of the directly assembled vertically aligned nanowire array attribute to the superior stability and quick response/recovery. The growth mechanism of aligned W_(18)O_(49) nanowires is proposed based on the direct SEM observations on the intermediate products, and meanwhile the sensing mechanism of the corresponding sensor is analyzed.