Ammonia Sensing Properties of α-Fe2O3 thin Films During Post-Annealing Process

Over the past few years, hematite (α-Fe2O3) has attracted much attention due to its ability to detect of various gases and vapors. This paper reports the effect of post-annealing process on nanostructure and NH3 gas sensitivity of α-Fe2O3 thin films. Fe thin films of 100 nm thickness were deposited by e-beam evaporation technique on SiO2/Si substrates and then post-annealed at different temperatures (600 and 800°C) with a constant oxygen gas flow. The samples were characterized by X-Ray Diffraction (XRD) method. The electrical resistance of the films was measured in the air and at presence of NH3 (200 ppm) in the temperature range of 50-300°C. The results showed that Fe2O3 thin films prepared by post-annealing of Fe thin films are able to detect the ammonia gas and the best sensitivity was achieved for the sample post-annealed at temperature of 800°C and at operating temperature of 150°C.