Fine-tuning the structure of cubic indium oxide and their ethanol-sensing properties

Fine-tuning the structure of cubic indium oxide (In2O3) was carried out with different calcination temperatures and atmospheres. The structural properties of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, electron paramagnetic resonance spectroscopy (EPR) and X-ray photoelectron spectroscopy (XPS). Ethanol-sensing performance of the products was investigated, and the depletion layer theory was used to explain the sensing mechanism. The experimental results indicated that the ethanol-sensing responses of In2O3 increased with the increasing intensity of chemisorbed oxygen, and decreased with the increasing intensity of donor defects. The In2O3 annealed at 300 °C or in oxygen had higher responses because of more chemisorbed oxygen. However, the In2O3 annealed at 600 °C or in nitrogen had lower responses due to more donor defects (Vo and Ini). In situ diffuse reflectance infrared spectroscopy (DRIFTS) study revealed that surface reduction and reconstruction of In2O3 happened at room temperature upon ethanol adsorption, which may lead our results contradicted previous reports.