Atomic removal mechanism of nano polishing for single-crystal AlN substrate via molecular dynamics

Abstract

Molecular dynamics simulations were performed to research the microscopic atomic removal mechanism of diamond abrasive with sliding, rolling, vibrating and rolling & vibrating movements towards single-crystal AlN substrate. The influence of the sliding depth, sliding velocity, rotation axis, rolling velocity, amplitude and frequency of oscillations on atomic detachment, stacking, force, crystal structure evaluation, stress, radial distribution function and atomic strain was revealed. The results show that stronger mechanical action normally gained more atomic detachment, stacking, amorphization and larger strains. The larger impact of abrasive on the AlN substrate can break more bonds and reduce the cutting force. However, the interaction times between the substrate and the abrasive is reduced due to the higher sliding velocity, which leads to the elastic recovery of the substrate atoms occur quickly. The elastic recovery of the substrate reduces the number of removed atoms, decreases the degree of amorphous structure, and relieves the stress concentration. The rolling movement in reverse y-axis obtains the largest number of atoms detached while in the y-axis obtains the smallest number of atoms stacked and damage. The vibrating movement creates the severest atomic disorder and damage, and highest the number of atoms detached and stacked than other forms of movement, and these characteristics also affected by amplitude and the frequency of oscillation. The rolling movement is beneficial to the release of residual stress and the reduction of substrate damages. The vibrating movement makes it easier for the atoms to leave the initial lattice structure. Therefore, the rolling & vibrating movement produces relatively more atomic removal, less atomic stacking and damage. The adsorbed atoms on the surface of the abrasive and moved synchronously with the abrasive, showing higher temperature. In this study, the atomic removal behavior of AlN under different action forms of abrasive was systematically analyzed on the atomic scale, which provided theoretical guidance for the high-efficiency and low-damage processing of AlN.