MICROSTRUCTURAL DEVELOPMENT DURING THE OXIDATION PROCESS IN SNO2 THIN-FILMS FOR GAS SENSORS

Polycrystalline SnO2 thin films with different thicknesses and microstructures have been produced by using the rheotaxial growth and thermal oxidation technique (RGTO), which allows one to obtain connected granular films. In this paper, we describe the basic mechanism of formation of a granular metallic film and the development of its microstructure during the oxidation process. Samples with different degrees of connection have been produced, starting from the same initial tin films, but changing the thermal treatment and the partial O2 pressure. SEM and XRD analysis are used to characterize the microstructures of the produced films. The functional properties of such sensors are tested by performing I-V and I-time measurements in dry air and in 1000 ppm of ethanol in air. A relation between the functional properties and the microstructure of the sensors has been established.