Gas sensing properties of multiple networked GaN/WO3 core-shell nanowire sensors

Abstract GaN nanowires and GaN-core/WO 3 -shell nanowires were synthesized by the thermal evaporation of GaN powders followed by the sputter-deposition of WO 3 and their gas sensing properties were examined. The multiple networked pristine GaN nanowire sensors showed responses of approximately 125%, 140%, 146%, 159%, and 183% to 1, 2, 3, 4, and 5 ppm NO 2 gases, respectively. These responses are comparable to those obtained previously using metal oxide semiconductor one-dimensional nanostructure sensors. The responses of the nanowires to 1, 2, 3, 4, and 5 ppm NO 2 gases were improved 1.3, 1.4, 1.6, 1.7 and 1.8 fold, respectively, further through the encapsulation of GaN nanowires with a WO 3 thin film. The improvement in the response of GaN nanowires to NO 2 gas by encapsulation is attributed to the modulation of electron transport at GaN–WO 3 heterojunction. The electron transport in the core-shell nanowires is modulated by the heterojunction with an adjustable energy barrier height, resulting in an enhanced sensing property of the core-shell nanostructures.