ZENG Chuanqing

(Institute of Systems Engineering, CAEP, Mianyang, Sichuan 621900)

Abstract: In this paper, a new type of solid-state hydrogen gas sensor that couples novel metal hydride thin films with a microelectro-machined mechanical system (MEMS) structure known as a micro-hotplate is described. Micro-hotplate structures are fabricated via surface silicon micromachining, resulting in a suspended platform with an embedded heater and thermally isolated from the substrate. A rare earth metal thin film, coated with a palladium capping layer, is deposited on this structure and serves as the active hydrogen-sensing layer. The change in electrical resistance of this bilayer when exposed to hydrogen gas is the sensor output. Sub-second response to 0.25% hydrogen in air and sensitivity to hydrogen concentration below 200ppm are measured. Rise and decay times of the response depend on the effective temperature of the microhotplate and decrease with increasing heater power. These results suggest that the device has the potential to meet the sensing requirements of trace hydrogen gas application.

Key words: MEMS, micro-hotplate, hydride metallic membrane, rare earth metallic membrane