Transmission electron microscopy investigation of SnO2 thin films for sensor devices

Tin oxide thin films, deposited on alumina or silicon, are commonly employed as sensors of pollutant gases in the atmosphere. The response of these materials in gas sensing applications depends on the microstructural and morphological characteristics of the film, which are dependent on the specific production process and deposition conditions. Sensor sensitivity and selectivity can be improved by doping the oxide layer with small quantities of Pt. Tin oxide films were deposited on polycrystalline alumina substrates by reactive r.f. magnetron sputtering at different values of the substrate temperature during the process. Transmission electron microscopy was employed to investigate the microstructure of the samples, before and after Pt doping. The TEM results are discussed in relation to the behavior of the films in sensing applications.