Preparation and room temperature NO2-sensing performances of n-porous silicon/n-WO3 nanowires heterojunction

• A novel composite of n-porous silicon/n-WO3 nanowires (PS/WO3 NWs) was prepared.
• WO3 NWs were obtained by a two-step heating process of as-sputtered W film on PS.
• PS/WO3 NWs showed excellent sensing properties to low concentration NO2 at 25 °C.
• N-PS/n-WO3 showed a p-type semiconductor behavior to NO2 due to the heterojunction.

In this paper, n-porous silicon/n-WO3 nanowires composite was prepared by a two-step heating process of as-sputtered W film on the nano-porous silicon (PS), and the effect toward sensing response characteristics of NO2 gas was studied. The morphology and crystal structure of samples were investigated by means of FESEM, TEM and XRD. The gas sensing properties of PS/WO3 nanowires were investigated toward NO2 gas of 0.5–2 ppm at 25 °C up to 125 °C. The composite exhibited an anomalistic p-type semiconductor behavior due to the strong effect of the heterojunction. In addition, the composite showed an excellent response, great selectivity and stability for efficient detection of ppm even ppb level NO2 at 25 °C. We proposed a qualitative explanation to discuss the gas sensing mechanism. These results were significant from the standpoint of applications requiring great room temperature gas sensing.

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