HUMIDITY-SENSITIVE CHARACTERISTICS OF SNO2-FE2O3 THIN-FILMS PREPARED BY SPRAY-PYROLYSIS

The humidity sensitivity of mixed iron oxide-tin oxide films has been investigated. The films were deposited by spraying alcohol solution of SnCl4 and Fe(NH4) (SO4)2 or Fe2(C2O4)3 on to quartz substrates heated at 480-degrees-C with subsequent annealing in various ambients - oxygen or humid air. The films were investigated by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). The humidity-sensitivity characteristics are plotted in the range 0%-93% RH. It was established that the humidity sensitivity, the response and the recovery time depend on the type of solution used for deposition, the type of thermal treatment, and the film thickness. It was found that the nature of the iron salt, used for the preparation of the spraying solution, and its concentration are of great importance for the humidity-sensitive properties of the films. The SnCl4 and Fe2(C2O4), films, treated thermally in humid air at 900-degrees-C for 1 h, possessed a short response time and high sensitivity to moisture.