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 (WO3) films were deposited on silicon oxide by glancing angle deposition (GLAD), and palladium (Pd) was deposited onto the WO3 layer. Then, the morphology, structure, and nitrogen dioxide (NO2) gas sensing properties of the Pd/WO3 films were studied. The results show that the Pd/WO3 films may comprise discrete Pd islands and columnar WO3 nanorods. The nanostructure can detect 0.5 ppm NO2 at 150 degrees 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 WO3. Therefore, the Pd/WO3 nanostructure prepared by GLAD has great potential in the field of NO2 MEMS sensors.