Properties of In2O3 films obtained by thermal oxidation of sprayed In2S3

In2S3 thin films were grown by the chemical spray pyrolysis (CSP) method using indium chloride and thiourea as precursors at a molar ratio of S:In=2.5. The deposition was carried out at 350 °C on quartz substrates. The film thickness is about 1 µm. The films were then annealed for 2 h at 550, 600, 650 and 700 °C in oxygen flow. This process allows the transformation of nanocrystal In2O3 from In2S3 and the reaction is complete at 600 °C. X-ray diffraction spectra show that In2O3 films are polycrystalline with a cubic phase and preferentially oriented towards (222). The film grain size increases from 19 to 25 nm and RMS values increase from 9 to 30 nm. In2O3 films exhibit transparency over 70-85% in the visible and infrared regions due to the thickness and crystalline properties of the films. The optical band gap is found to vary in the range 3.87-3.95 eV for direct transitions. Hall effect measurements at room temperature show that resistivity is decreased from 117 to 27 Ω cm. A carrier concentration of 1×1016 cm−3 and mobility of about 117 cm2 V−1 s−1 are obtained at 700 °C.