Effect of Ar ion irradiation on structural and optical properties of e-beam evaporated cadmium telluride thin films

CdTe thin films were prepared using e-beam evaporation technique. The prepared films were irradiated by Ar⁺ ions at different fluencies using multipurpose aluminum (Al) probe as in-situ. This could also be used in ion bombardment for cleaning the substrate prior to coating. The as grown and Ar⁺ ion irradiated films were confirmed to be of polycrystalline nature with X-ray technique. Ar⁺ ion irradiation enhances the growth of (1 1 1) oriented CdTe crystals and the Cd enrichment on the surface of CdTe thin films. Higher Ar⁺ ion flux helps to grow (2 2 0) oriented CdTe thin film. A considerable change in structural parameters like crystallite size, lattice parameter, internal strain, etc. could be observed as a result of high Ar⁺ ion flux. The applied in-plan stress in both as grown and irradiated film was identified to be of tensile nature. The applied stress was observed between 0.016 and 0.067 GPa for all Ar⁺ ion irradiated samples. As a result of the Ar⁺ ion irradiation, the in-plan stress varies between 1.38×10⁹ and 5.58×10⁹ dyn/cm². The observed bad gap was increased for higher Ar⁺ ion flux. It shows the effect of Ar⁺ ion irradiation on the modifications of optical properties. The observed results were encouraging on the use of simple multipurpose Al probe for Ar⁺ ion irradiation process as in-situ.