Atomic scale DFT based investigation of tuning and quantum modulation of zinc blende ZnS bandgap for next-generation materials

This study reveals the electric-field-induced tuning and modulation of electronic bandgap of zinc blende ZnS as potential prospect for the next generation optoelectronics. By employing Generalized Gradient Approximation (GGA) with a Plane-Wave basis set based on the Quantum espresso package, the correlation between electronic bandgap engineering, tuning/switchable modulations with the varying applied electric field strength is established. We unveiled dynamical switching in range from 2.37 eV to 0 eV (at critical field) under the positive field strength of 0.01 V Å^-1 to 0.5 V Å^-1, and from 2.41 eV to 1.52 eV under the negative fields strength from -0.01 V Å^-1 to -0.5 V Å^-1 along the out-of-plane <i>z</i>-axis. The valence and conduction bands overlap at a critical field (0.5 V Å^-1) is attributed due to the Mott transition, where electron-electron interactions persuade a transition in behavior from semiconductor to conductor. The partial (PDOS) and total density of states (TDOS) display electric-field-tailored dynamically switching of the sp³ hybridization into the Zn-3d, Zn-2s and S-2p states. The modulation of local density of states (LDOS), charge density and variation in charge transfer (between Zn and S) further confirm electric-field-induced redistribution of charges between Zn and S atoms. Optical parameters, comprising refractive index (<i>n</i>(<i>ω</i>)), absorption coefficient (<i>α</i>(<i>ω</i>)), reflectivity (<i>R</i>(<i>ω</i>)), extinction co-efficient (<i>k</i>(<i>ω</i>)), real (<i>ε</i> ₁(<i>ω</i>)) and imaginary (<i>ε</i> ₂ <i>ω</i>)) dielectric function and electron energy loss (ELS)) display field-dependent behavior, signifying the potential of ZnS as a tunable optoelectronic material. These findings validate the feasibility of electric-field-controlled engineering of ZnS properties, paving the way for exciting advancements in the controlled functionalities in semiconductors to design innovative next-generation optoelectronic and photonic devices.