Characterization of alpha-Fe2O3 thin films deposited by atmospheric pressure CVD onto alumina substrates

There has been considerable interest in recent years in thin film gas-sensing materials. In comparison with conventional sintered bulk gas sensors, thin film gas-sensing materials have good sensitivity, optimum operating temperature and selectivity. Therefore, it is attractive to prepare thin film gas sensors so as to improve the characteristics of commercialized sintered body gas sensors. In addition, sensors based on thin film gas-sensing materials are essential to the development and fabrication of 'integrated gas sensors'. Up to now, there seem to have been very few papers on the preparation and gas-sensing properties of alpha-Fe2O3 thin films. In this paper, an atmospheric pressure chemical vapor deposition (APCVD) technique is used to prepare gas-sensing alpha-Fe2O3 thin films. The ultrafine particle alpha-Fe2O3 films are deposited successfully onto alumina substrates. The films are characterized by X-ray diffraction and scanning electron microscopies(SEM), and the effects of process conditions on the average grain size are also investigated. Experiments show that the ultrafine particle alpha-Fe2O3 films made by APCVD exhibit a high sensitivity of 96% at 250 degrees C to grade 1 smoke and a good selectivity for detecting smoke in the presence of alcohol (C2H5OH), liquified petroleum gas (LPG), methane (CH4), and hydrogen (H-2).