Shuangyun Ma

Preparation and characterization of room temperature operating NO 2 gas sensor based on intermediate-sized porous silicon modified with WO 3 thin films

In this paper, intermediate-sized porous silicon (PS) sensing material was prepared via galvanostatic electrochemical anodization technique in a Teflon double-tank cell configuration. Then, tungsten oxide (WO3) thin films were deposited onto the PS surface by using DC reactive magnetron sputtering method. The morphology of PS and WO3/PS were observed by field emission scanning electron microscope (FESEM), respectively. Subsequently, the NO2-sensing performances of PS and WO3/PS sensors were studied at room temperature (RT, 25°C) up to 100°C. The results indicated both sensors had the same optimal operating temperature of RT. Moreover, it is found that pure PS showed a typical n-type semiconductor behavior. However, after depositing the WO3 thin films, the WO3/PS behaved as a p-type semiconductor.

Synthesis of tungsten oxide nanowires/porous silicon composite and its sensing properties for NO 2

A novel composite structure of WO3 nanowires/porous silicon has been successfully synthesized via a convenient thermal evaporation method without using any catalysts. The diameters and lengths of nanowires are 40-60 nm and 20-30 μm, respectively, and the aspect ratio (length/diameter) of nanowires could be in range of 500-750. The obtained products were investigated by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The response to NO2 of WO3 nanowires/porous silicon composite was investigated. It was found that the composite sensor had a good response to NO2 at 50 °C. The lowest concentration of NO2 detected was 1ppm and the response could be up to 6.17 at NO2 concentration of 6 ppm. The novel composite structure improved sensing properties which are significant for future applications.