Preparation and characterization of room temperature operating NO2 gas sensor based on intermediate-sized porous silicon modified with WO3 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.