Effect of electron beam improved dielectric function on optical properties of sol-gel derived CuIn_1-XGa_XSe₂ thin-film

Electron beam has been applied as a practical posttreatment process for the surface modification at the CuIn_1-XGa_XSe₂ thin film. The rise of the film thickness indicated the advantages of the modified surface-related properties (such as the optical parameters to develop an optimum optical model) via enriching the microstructure with the negative charged beta particles by using Sr-90 radioisotope. The effect of negatively charged beta particles on dielectric constants was examined at two different dose levels (3 and 9.1 Gy) by using Sr-90 radioisotope. The application of the electron beam to the thin film surface caused the slight changes in refractive index (n), extinction coefficient (k) and optical absorption coefficient. The increase of refractive index and the improvement of absorption coefficient provided to distinguish clearly the decrease in extinction coefficient and the decline in energy band gap as the result of the rise of the beta dose at the thin-film. The slight variations in dielectric constants were performed by encouraging more dense structure to form the optimum crystalline network at the thin film (applied beta dose). The application of beta dose favoured inventive variations in the refractive index. The applied two different beta dose levels were below ∼3.1 Gy and above ∼9 Gy. The beta dose level at ∼9 Gy was ∼3 times dose value of 3.1 Gy (applied as a security value for the utilization of this thin film at the extreme environments such as international space station orbit). The refractive index stated its importance specifying the rise of the bending of light in the thin film structure.