Unveiling the impact of Cd and Zn substitutions on the structural, mechanical, electronic, and optical properties of SrS: A first principles analysis

Abstract

This study employs ab-initio calculations based on density functional theory (DFT) to comprehensively investigate the multifaceted effects of Cd and Zn substitutions on the structural stability, mechanical behavior, electronic characteristics, and optical properties of SrS alloy. Structural analysis unveils a marginal reduction in lattice parameters for both doped compounds, signifying a subtle influence on the crystalline structure. Mechanical evaluation reveals that SrS and Sr0.75Cd0.25S keep their intrinsic brittleness, whereas the inclusion of 25 % Zn imparts a subtle ductile nature. The conservation of rigidity is observed post-doping, albeit with anisotropic features and differing degrees of stiffness among the compounds. Investigating electronic properties, the band gap of Sr0.75Cd0.25S persists as an indirect transition between M and Γ points, mirroring SrS's behavior. In contrast, a remarkable transformation is noted with 25 % Zn doping, shifting SrS to a direct band gap semiconductor. Interestingly, Cd and Zn incorporation leads to a band gap reduction, suggesting potential avenues for tuning the material's electronic behavior. Dielectric constant analyses unravel intriguing phenomena. The binary compound exhibits Mie resonance across the visible-infrared spectrum, a feature that contracts to the infrared range after doping. This nuanced shift has direct implications on the material's interaction with incident light and its resulting optical properties. Evaluation of the refractive index, absorption coefficient, reflectivity, and optical conductivity demonstrates a striking resemblance in the optical behavior of Sr0.75Zn0.25S and Sr0.75Cd0.25S to the pristine SrS alloy.