MEMS-based formaldehyde gas sensor integrated with a micro-hotplate. Microsystem Technol

A novel micro formaldehyde gas sensor with a sputtered NiO thin film integrated with a micro hotplate was fabricated and this thin-film sensor had a sensitivity of 10 Ωppm-1 at 300oC and a detection limit below.1.0 ppm. A microfabricated formaldehyde gas sensor is developed which uses a silica substrate with Pt micro heaters as the micro hotplate and a thin-film NiO layer as a conductivity-sensitive material. The substrate is deposited with NiO thin film as sensing elements, Pt resistors as heaters, and Au as interdigitated electrodes for resistance measurement. As voltages were applied to Pt heaters, temperature of micro hotplates increased. Thus, at 300oC, when formaldehyde was present in the atmosphere, it was adsorbed and as a result the electrical conductivity of NiO films was increased. The measured resistance between the interdigitated electrodes was changed. The formaldehyde gas sensor was integrated with a Pt resistor as a micro heater for the enhancement of sensitivity. The sensitivity was shown to be 10 Ωppm-1 and the detection limit was 1.0 ppm. 1