SENSITIVE, SELECTIVE AND STABLE CH4 DETECTION USING SEMICONDUCTING GA2O3 THIN-FILMS

Due to the large operating temperature range of Ga2O3 thin films, a temperature programmed setting of the gas sensitivity is possible. In the temperature range between 500 and 650 degrees C the sensors may be operated as sensitive sensors for reducing gases (e.g., CO, H-2) based on chemisorption mechanisms. Increasing the temperature causes a strong decrease in the sensitivity to these gases and a strong increase in the sensitivity to CH4. At an operating temperature of 740-780 degrees C no significant sensitivity of the sensor to H-2 or CO in wet air is observed but there is a sensitivity conductance increase by about a factor of 80 as a response to 0.5 vol.% CH4. In the case of a further temperature increase, the effect of H-2 and CO is inverted to a conductivity decrease, whereas the CH4 sensitivity remains almost unchanged. A similar behaviour is observed in the case of binary gas mixtures. At a tuned operating temperature, there is no significant effect resulting from the coadsorption of other reducing gases or humidity on the CH4 sensor characteristics. Resistance values at this temperature have proven to be stable over several hundreds of hours even in the case of continuous exposure to CH4.