n型有序多孔硅基氧化钨室温气敏性能研究

Gas-sensing properties at room temperature for the sensors based on tungsten oxide thin films sputtered on n-type ordered porous silicon

利用电化学腐蚀方法制备了n型有序多孔硅,并以此为基底用直流磁控溅射法在其表面溅射不同厚度的氧化钨薄膜.利用X射线和扫描电子显微镜表征了材料的成分和结构,结果表明,多孔硅的孔呈柱形有序分布,溅射10min的WO3薄膜是多晶结构,比较松散地覆盖在整个多孔硅的表面.分别测试了多孔硅和多孔硅基氧化钨在室温条件下对二氧化氮的气敏性能,结果表明,相对于多孔硅,多孔硅基氧化钨薄膜对二氧化氮的气敏性能显著提高.对多孔硅基氧化钨复合结构的气敏机理分析认为,多孔硅和氧化钨薄膜复合形成的异质结对良好的气敏性能起到主要作用,氧化钨薄膜表面出现了反型层引起了气敏响应时电阻的异常变化.

n-type porous silicons are prepared by the electrochemical corrosion method, on which tungsten oxide thin films with different thickness values are sputtered using DC reactive magnetron sputtering. The structures of ordered porous silicons and tungsten oxide thin films are characterized using field emission scanning electron microscope, which show that the pores are pillared and ordered and the thin films cover the porous layer loosely with many pores open to ambient air. The X-ray diffraction characterization indicates that the lattice structure of tungsten oxide thin film is mainly triclinic polycrystalline. The gas-sensing properties at room temperature for both ordered porous silicon and composite structure are studied, which indicate that the latter is much more sensitive to nitrogen dioxide than the former. And there is a critical spurting time of WO3 thin film, which in our case is 10 min. The sensing mechanism of composite structure is discussed and the probable explanation for the improvement of sensitivity to NO2 is the formation of hetero- junctions between the ordered porous silicon layer and the WO3 thin film. In addition, there exists an inversion layer on the surface of the WO3 thin film, which causes the anomalous resistance to change during the gas sensing measurements.