Gas sensing properties of thin- and thick-film tin-oxide materials

Comparative gas detection measurements have been performed on thin-film (d∼50–300 nm) and thick-film (d∼15–80 μm) SnO2 devices. We find that at normal sensor operation temperatures of the order of 400°C thin-film devices mainly respond to oxidising gases such as O3 and NO2, whereas thick-film ones preferably respond to reducing species like CO and CH4. A significant response towards oxidising species, however, was observed upon reducing the operation temperature of the thick-film devices to about 100°C. We explain these effects in terms of a simple diffusion-reaction model taking into account the different architectures of thin- and thick-film gas sensing devices.