Methane and hydrogen sensing properties of catalytic combustion type single-chip micro gas sensors with two different Pt film thicknesses for heaters

A catalytic combustible type single-chip micro gas sensor was fabricated by MEMS technology and responses with input powers and methane and hydrogen gas concentrations were characterized. The ranges of responses at Pt thickness of 450 nm and input power of 128 mW were 1.076–2.433 mV for methane concentrations of 2315–5787 ppm, and 0.965–2.514 mV for hydrogen concentrations of 282–706 ppm, respectively. The ranges of responses at Pt thickness of 150 nm and input power of 112 mW were 0.192–0.438 mV for methane concentrations of 2315–5787 ppm and 0.949 mV to 2.496 ppm for hydrogen concentrations of 282–706 ppm, respectively. The responses to H 2 concentration ratios were 3.65 mV/10 3 ppm for a micro gas sensor with a 450 nm thick heater and 3.81 mV/10 3 ppm for a micro gas sensor with a 150 nm thick heater. But in the case of methane gas response, the response to concentration ratios of the micro gas sensor using the 150 nm thick Pt heater was remarkably different from the case of the 450 nm thick Pt heater. The ratios for CH 4 were 3.51 mV/10 4 ppm for the micro gas sensor with a 450 nm thick heater and 0.6 mV/10 4 ppm for the micro gas sensor with a 150 nm thick heater, respectively. From these results, the micro gas sensor that has the thicker heater with a thickness of 450 nm showed higher sensitivity to methane gas than the micro gas sensor with a thinner heater with a thickness of 150 nm.