A low power MEMS gas sensor based on nanocrystalline ZnO thin films for sensing methane

Nanocrystalline ZnO based sensor using micromachined silicon substrate has been reported for efficient detection of methane as opposed to conventional SnO2 based micromachined sensors for its higher compatibility to silicon IC technology and greater response. A suitably designed nickel microheater has been fabricated on to the micromachined Si platform. The optimum temperature for highest response magnitude and lowest response time were found to be 250 °C although relatively high (76.6%) response is obtained even at as low as 150 °C. Our study showed quite high response magnitude (87.3%), appreciably fast response time (8.3 s) and recovery time (17.8 s) to 1.0% methane at 250 °C. The sensor showed appreciably fast response (14.3 s) and recovery time (28.7 s) at 150 °C. The power consumption at an operating temperature of 250 °C was 120 mW and at 150 °C is only ∼70 mW. Moreover, this type of sensor was found to give fairly appreciable response for lower methane concentrations (0.01%) also. For higher methane concentrations (>0.5%) response is detectable even at 100 °C where the power consumption is only ∼40 mW.