NO2-sensing properties based on the nanocomposite of n-WO3−x/n-porous silicon at room temperature

In this paper, the nanocomposite of n-WO3−x/n-PS was prepared through sputtering tungsten oxide films on the intermediate-PS substrate and the effect toward sensing response characteristics of NO2 gas was studied. The morphology, crystallographic structure, bond configuration and surface chemical composition of the nanocomposite were investigated by using field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD), Raman spectrum (RS) and X-ray photoelectron spectroscopy (XPS), respectively. The NO2-sensing performances of the sensor were measured at different temperatures ranging from room temperature (25 °C) to 100 °C. The sensor showed an anomalistic p-type semiconducting behavior, which probably owing to the strong amplification effect of the heterojunction. One kind of conceivable sensing mechanism explaining this behavior was introduced in detail. Besides, the sensor exhibited a strong response, fast response-recovery rate, excellent repeatability and good selectivity for efficient detection of ppb level NO2. The enhanced gas-sensing properties can be originated from the sensing materials with special nanostructures, including high specific surface area, large amounts of oxygen vacancies and stable gas diffusion channel.