Nano-Design of Oxide Particles and Electrode Structure for High Sensitivity NO2 Sensor Using WO3 Thick Film

Abstract

ABSTRACTNovel sensor design for high sensitivity gas sensors has been proposed for the detection of dilute NO2 using WO3 film. First, concerning nano-design of oxide particles, the disk-shaped WO3 particles (300 nm in diameter, 20 nm in thickness) were deposited on Au comb-type microelectrode (line width: 5 μm, distance between lines: 5 μm) to be WO3 thick film sensor. This sensor showed the excellent sensing properties to dilute NO2 at optimized thickness. Second, the nano-gap electrode with various gap-sizes (110–1500 nm) was fabricated by means of MEMS techniques in order to investigate the effect of microelectrode. When the gap size was decreased less than 800 nm, the sensitivity to dilute NO2 increased with decreasing gap size. This was understood from the facts that the contribution of interface resistance between particle and electrode to total sensor resistance was increased and that the sensitivity at electrode-grain interface was much larger than that at grain boundary. It was found that the designs of not only nano-particles but also nano-electrode were important for the fabrication of high sensitivity gas sensor.