Atomic stick-slip behaviors and anisotropic deformations on a rough surface during GaN wafer polishing: A simulation study

Abstract

This paper studies the process of a diamond abrasive that polishes on a GaN workpiece surface by using molecular dynamics simulation. The workpiece has an array of asperities to imitate the surface roughness. The effects of motion parameters, motion pathways, abrasive sizes, and orientations on the stress, structure change, surface morphology, temperature, and the number of removed atoms are analyzed. Notably, the stick-slip behavior occurs when the abrasive crosses the asperity system at 5.0 Å, causing the periodic marks of stress, structure change, and atomic strain on the surface. At 5.0 Å depth, compared to the sliding motion, the rolling motion shows a higher rate of removing the workpiece atoms. Along the asperity, moving through the asperity peak leads to greater deformation and material removal than in the valley. Moreover, the bigger abrasive causes more severe deformations than the smaller one. At 5.0 Å depth and a rough surface, changing the crystalline orientation does not induce adequate changes. This paper demonstrates the stick-slip behaviors through the asperity system model, the advantage of the rolling motion, the effects of the abrasive size, and the crystalline orientation on the surface morphology.