Effect of treatment time and radio frequency power on roughness and wettability of oxygen plasma-etched Cadmium Telluride thin films

•The impact of oxygen plasma etch on the roughness of the CdTe film surface was studied.•A universality class of the scaling exponents has been observed.•State transition from the Cassie state to the Wenzel state was observed after etching.•The wettability and hydrophilicity of the surface improved using plasma etching. The thermal evaporated Cadmium Telluride (CdTe) on Indium tin oxide substrates was etched using Oxygen plasma at various treatment times and radio frequency (RF) power. The roughness and wettability parameters were calculated using atomic force microscopy and contact angle (CA) analysis. The morphology evolution increases the interface width w and the lateral correlation length ξ with etching time and RF power. The local roughness exponent near-0.5 shows the self-affine of the surface during the etching process. The obtained experimental exponents in the present work introduce the universality class of the scaling exponents. The surface hydrophilicity of films was studied using the measurement of the two droplets CA on the film surface and the surface energy. The physical and chemical structure of the surface affected by oxygen plasma causes the surface to become more rough and hydroxyl group formation. Infra-Red spectra of the untreated and etched films using Fourier transform infrared spectroscopy confirmed the presence of the CdTe bond and a hydroxyl group. The wettability behavior of the etched films demonstrated the transition from the Cassie-Baxter state to the Wenzel state. Results show surface energy of the etched films increases, and theirs become hydrophilic.