Laser annealing of SnO2 thin-film gas sensors in single chip packages

A Nd:YAG laser beam has been used to anneal thin-film SnO2 gas sensors mounted in TO-8 packages. Annealing temperatures up to 1000 °C for a few minutes significantly improved the sensor signal. In particular, signal drifts can be reduced. Furthermore, signal changes become very fast around an operating temperature of 3000 °C. Saturation and recovery times are within seconds for CO and CH4. Ca-implanted sensors show cross sensitivities towards CO2 and NO2.