Annealing effect on the methane sensing performance of Pt–SnO2/ZnO double layer sensor

Abstract

Low power consumption is a new emerged requirement for methane sensors long-term working in a gas supervisorycontrolsystem. Great challenges remain in development of heat free methane sensors based on metal oxide semiconductors (MOS). In this work, Pt-doped SnO2 (Pt-SnO2) grow on well aligned ZnO nanorod-array to form an inter-staggered double-layer structure on AZO glass by a two-step hydrothermal method, with the annealing temperature being systematically studied. The optimized processing parameters are 1 at% Pt doping content and 700 °C annealing temperature, offering the best sensing response of 3.36 to 800 ppm CH4 at room temperature. SnO2/ZnO without Pt doping shows linear I-V relationship, while the Pt-SnO2/ZnO shows a Schottky-like I-V curve with the Schottky barrier height decreases as increasing the CH4 concentration. The activation energy (ΔEa) for CH4 dissociation decreases with increasing the annealing temperature, and the ΔEa of the optimized Pt-SnO2/ZnO sample is only one-third of that in the SnO2/ZnO. In addition to the piezoelectric polarization electric field in ZnO, the build up Schottky-like barrier and the reduced activation energy via Pt doping and annealing are demonstrated to be efficient for enhancing the methane sensing performance at low operation temperature.