Effect of Indenter Geometry on the Mechanical Response of Different Crystal Planes of InP in Nanoindentation: A Molecular Dynamics Study

The nanoindentation behavior of sphalerite indium phosphide (B3-InP) was investigated using a molecular dynamics (MD) simulation to explore the effects of different crystal orientations and indenter geometry. The evolution of atomic motions at the surface and subsurface, strain distribution, dislocation propagation, and the amorphous phase transition on each crystal plane of InP during indentation were analyzed in detail. It was found that the indenter geometry significantly influences the elastic-plastic transformation of the material: the Vickers indenter reduces the critical load for the “pop-in” event due to stress concentration, which delays the onset of plastic deformation. The InP(100) crystal plane deforms more elastically and less plastically under the spherical indenter, while the other two surfaces exhibit similar elastic deformation behavior, with comparable plastic deformation capacities. During nanoindentation, microcracks formed on the InP surface, with the most pronounced crack patterns observed on the (110) crystal plane, where cracks primarily extended along four specific crystal orientations. The InP(111) crystal plane showed excellent resistance to plastic deformation, characterized by the delayed occurrence of the “pop-in” event and a narrow distribution of atomic strains. Plastic deformation on the (100) crystal plane was dominated by the accumulation of local defects, while dislocation motion predominantly governed the deformation on the (110) and (111) crystal planes. This study elucidates the correlation between mechanical anisotropy and processing damage in InP wafers, providing a theoretical foundation for selecting abrasives in the ultraprecision machining of InP wafers.