NO2 gas sensing properties of Pd/WO3 films prepared by glancing angle deposition

The fabrication procedure of gas sensing films deposited by physical vapor deposition is more compatible with the micro-electro-mechanical system (MEMS) process. However, low sensitivity and high working temperature of gas sensing films limit their application. In this work, tungsten trioxide (WO 3 ) films were deposited on silicon oxide by glancing angle deposition (GLAD), and palladium (Pd) was deposited onto the WO 3 layer. Then, the morphology, structure, and nitrogen dioxide (NO 2 ) gas sensing properties of the Pd/WO 3 films were studied. The results show that the Pd/WO 3 films may comprise discrete Pd islands and columnar WO 3 nanorods. The nanostructure can detect 0.5 ppm NO 2 at 150 °C with a sensitivity of 1.85 and possesses good selectivity, which can be mainly attributed to large specific surface area of nanorods, catalysis of Pd, and Schottky barrier between Pd and WO 3 . Therefore, the Pd/WO 3 nanostructure prepared by GLAD has great potential in the field of NO 2 MEMS sensors.