Characterization and room temperature sensing of ammonia and ethanol by thermally oxidized indium films

Indium oxide (In2O3) films have been prepared by thermal oxidation of vacuum deposited indium (In) films onto glass substrate kept at room temperature (35 °C). The structural, optical and gas sensing properties of films oxidized in air at 400 and 500 °C have been investigated. X-ray diffraction (XRD) measurements indicate that the In2O3 films oxidized at these temperatures exhibit a high degree of crystallographic orientation along (2 2 2) plane. Field emission scanning electron microscopy shows large and small grains scattered at the surface of In2O3 films. The optical and sensing studies show that In2O3 film oxidized at 500 °C exhibits comparatively higher optical band gap of 3.8 eV and large gas response of 92% when exposed to 1000 ppm of ammonia at room temperature. Also an increase in optical absorbance towards ammonia for different concentrations at room temperature has been observed.