Relaxation effects on the structural and piezoelectric properties of wurtzite ZnS and CdS thin films under in-plane strain

Abstract

Through first-principles investigations, we examine variations in the atomic crystal structure, thermal stability, electronic structure, and piezoelectric properties of wurtzite ZnS and CdS under in-plane strain. We specifically aim to elucidate the distinct effects arising from two relaxation modes: elastic and non-elastic. Our analyses reveal that the in-plane strain-induced deformation behaviors and performance changes in these sulfides are remarkably similar, attributable to the similar atomic arrangements, anionic sulfur elements, and analogous cation electronic configurations. However, following non-elastic relaxation, enhanced robustness emerges in the lattice volume and chemical bonding, alongside stronger thermal stability and attenuated modifications in the piezoelectric coefficient. We posit that these marked discrepancies from elastic relaxation may originate from subtle differences in the electronegativities and d-orbital electron configurations between the Zn²⁺ and Cd²⁺ cations. By offering fundamental new insights into the atomic-scale relaxation phenomena in wurtzite binaries, this work significantly furthers the fundamental understanding of structure-property relationships in these materials. Moreover, delineating the precise impacts of elastic versus non-elastic relaxation serves as an effective tuning methodology to engineer the piezoelectric and electronic traits of sulfide compounds for cutting-edge applications.