Effect of nitrogen annealing on the structural, optical and photoluminescence properties of In2O3 thin films

• Sprayed In2O3 thin films were annealed under nitrogen atmosphere.
• An enhancement of the crystallinity was observed after annealing.
• Optical transmission is enhanced after heat treatment followed by a large band gap.
• Many optical parameters are investigated using the envelope method.
• Photoluminescence properties show three main peaks centered at 485, 505 and 795 nm.

The effect of heat treatment under nitrogen atmosphere on the structural, optical and photoluminescence properties of In2O3 thin films was studied in this work. In2O3 thin layers were annealed at 250 and 450 °C during 1 and 2 h. All heated films are polycrystalline and crystallize in to the body centered cubic structure with (400) as preferred orientation. Optical properties reveal an enhancement of transmission T in the transparency zone for 250 °C during 2 h and 450 °C during 1 h (T is of about 75%). Transmission and reflection spectra of the films exhibit interferences fringes which is characteristics of thickness uniformity and surface homogeneity. The heated films show a large band gap energy Eg varying from 3.41 to 3.49 eV. The refractive index was investigated using the envelope method. The extinction coefficient k, dielectric constant εr, packing density p and porosity were also studied using the refractive index results. The single oscillator energy E0 and dispersion energy Ed were determined using Wemple oscillatory model based on the envelope method. The obtained results lead to conclude that annealed In2O3 thin films is a good candidate to be used in many optoelectronic devices and especially as optical window in modern solar cells.