PROTOTYPE STRUCTURE FOR SYSTEMATIC INVESTIGATIONS OF THIN-FILM GAS SENSORS

We have developed thin-film prototype structures for electronic conductivity and impedance sensors with integrated heater, temperature sensor and interdigital electrodes. These structures serve as substrates for subsequent deposition of chemically sensitive materials. The structures are based upon platinum and sapphire, they are stable even at high temperatures (T ∼- 1073 K) under oxidizing and reducing conditions, and they have suitable dimensions for surface spectroscopic techniques to be applied as well. The last is important for optimizing sensors by characterizing their electronic and chemical structures such as stoichiometries, impurities, dopants or interdiffusion profiles of the sensitive layers. We use these structures to fabricate prototype NO2 sensors based upon SnO2, which show surprisingly low cross-sensitivities against CO and H2O. © 1990.