Enhanced sensing characteristics in MEMS-based formaldehyde gas sensors

This paper presents a novel micro fabrication for formaldehyde gas sensors to enhance sensitivity and detection resolution capabilities. Therefore, two different types of fabrication sequences of gas sensors were considered, different positions of micro heaters and sensing layers to compare the effects of different areas of the sensing layers contact with the surrounding gas. The MEMS-based formaldehyde gas sensor consists of a quartz substrate, a thin-film NiO/Al₂O₃ sensing layer, an integrated Pt micro-hotplate, and Pt inter-digitized electrodes (IDEs) to measure the resistance variation of sensing layers caused by formaldehyde oxidation at the oxide surface. This abstract offers comparisons of the characteristics of sensors in different areas of the sensing layers contacting the surrounding gas as well as those to decrease the thickness of the sensing layer and deposits of the sensing layer using co-sputtering technology with NiO/Al₂O₃ to improve the sensitivity limits of the sensors. The experimental data indicated that increasing the area of the sensing layer that contacts with the surrounding gas and decreasing the thickness of the sensing layer in the sputtering process and then co-sputtered NiO/Al₂O₃ sensing layers, significantly enhanced the sensing characteristics of the developed formaldehyde sensor.