Dendritic composite array of silicon nanowires/WO3 nanowires for sensitive detection of NO2 at room temperature

Dendritic composite array of silicon nanowires (SiNWs)/WO3 nanowires was prepared for highly sensitive gas sensor application. WO3 nanowires were grown directly on the top section of SiNWs fabricated by metal-assisted chemical etching (MACE), through thermal annealing of pre-deposited W film to obtain dendritic SiNWs/WO3 nanowires array. At room temperature (RT), the composite sensor shows obviously enhanced sensing response to NO2 in comparison to pure SiNWs sensor. The response value upon 5 ppm NO2 exposure is more than four folds of that from SiNWs. Meanwhile, good selectivity as well as perfect dynamic characteristic, especially ultrafast response (response time <1 s to 0.5-5 ppm NO2) is achieved for the composite sensor. The underlying sensing mechanism of the composite sensor is analyzed in detail.