Comparison Study between the Effect of (He-Ne) Laser Irradiation and Heat Treatment on the Optical Properties of Dichromium Trioxide Thin Film

In this study, we investigate the effect of (He-Ne) laser irradiation for half hour and heat treatment (annealing) at 450°C for 2 hours on the optical properties of dichromium trioxide Cr2O3 thin films, p repared on glass slides by chemical spray pyrolysis at 400°C with sp raying rate (1 ml /min) and (0.19±0.05) μm thickness. The optical characteristics of the prepared thin films have been investigated by UV/VIS sp ectrophotometer in the wavelength range (300– 900)nm. Op tical properties such as absorption coefficient (α), optical band gap (Eg), extinction coefficient (k), refractive index (n), and complex dielectric constants (€1 €2) were evaluated from the absorp tance and transmittance sp ectra. All the films were found to exhibit allowed electronic transition(α 10^4 cm^-1). The absorption edge shifted toward the longer wavelength (red shift) after irradiation, leading to decrease the optical band gap (Eg) from 3.13 eV for untreated film to 2.97eV for the irradiated film, while Eg was increased to 3.22 eV for the annealed film, indicating (blue shift). It was realized that localized states width (Et) for untreated film was increased from 0.47 eV to 0.56 eV after irradiation, and decreased to 0.41 eV after annealing.