Nano-crystalline Fe2O3 thin films for ppm level detection of H2S

We have investigated the chemiresistive gas sensing characteristics of Fe2O3 thin films for a host of gases (H2S, C2H5OH, CO, NH3, CH4, CO2, NO and Cl2). Fe2O3 films were prepared by thermal oxidation of Fe films, which were deposited on (0 0 0 1) Al2O3 substrate by electron-beam evaporation method. The results of scanning electron microscopy, atomic force microscopy and X-ray diffraction revealed that the grains of these films are composed of nano-crystallites (size ∼32 nm). We demonstrate that these Fe2O3 films show purely n-type conductivity, with high selectivity, moderate response and recovery for H2S in the concentration range of 1–50 ppm.