Plastic deformation mechanisms of ZnS and ZnTe under nanoindentation: molecular dynamics simulations

Zinc sulfide (ZnS) and (zinc telluride (ZnTe) are binary semiconductor compounds that exhibit excellent optical and electrical properties, and the mechanical behavior at the nanoscale level is crucial for their potential application. Nevertheless, experimental data are scarce regarding the mechanical characteristics of ZnS and ZnTe. For better applications of ZnS and ZnTe-based devices, it is crucial to understand, design, and control their mechanical properties. In this work, we have examined the indentation on (001), (110), and (111) planes of ZnS and ZnTe at the nanometric scale, along with an exploration of the associated plastic deformation utilizing molecular dynamics techniques. We compared and analyzed the loading curves, dislocation distribution evolutions, atomic displacement vectors, and stress distributions of the two materials under indentation.

The indentation simulations were performed in molecular dynamics software LAMMPS, using the Stillinger-Weber potential model. Visual analysis is done using OVITO software. A spherical indenter with a diameter of 12.0 nm moves down to the substrates for a depth of 5.0 nm at a steady speed of 0.01 nm/ps. Distinct anisotropic characteristics can be detected from the loading forces, dislocation distributions, atomic displacement vectors, and stress distributions. The dislocation distributions exhibit fourfold, twofold, and threefold symmetries in the case of (001), (110), and (111) planes. Results indicate that stress underneath the indenter should prompt the atoms to move, subsequently leading to the formation, propagation, and distribution of the dislocations. Another notable characteristic is the emergence of prismatic loops in ZnS. The findings offering valuable data for future utilization considerations.