A micro hot-wire sensors for gas sensing applications

Many works to improve the stability and sensitivity of metal-oxide based gas sensors have been carried out during last several decades. As one of stability problems, we can present an example that the resistance alters to some extent when the devices are exposed to the normal air, which becomes an obstacle to its practical use. In this paper, we proposed a new type of micro gas sensor with single electrode for improving stability and sensitivity. Generally, metal-oxide gas sensors have two electrodes for heating and sensing. But this new type sensor has only a single electrode by depositing a sensing metal-oxide material onto the heating electrode. Owing to this structure, the sensor output signal in ambient condition could be very stable unlikely to metal-oxide gas sensor. As a result of CO gas sensing characteristics, this sensor shows 80 mV voltage output for 1000 ppm and linearity for ranges (0–250 ppm) of gas concentrations. The deviation of sensor resistance is about 1% for 3 months and a little influence for humidity upto 90% RH.