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

Abstract

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.