The role of crystal orientation in atomic-scale material removal mechanisms in single crystal aluminum nitride

This study investigates the crystal plane-dependent material removal mechanisms in single crystal aluminum nitride (AlN) using molecular dynamics (MD) simulation. The results reveal that the deformation and removal behaviors in AIN vary significantly with crystal orientation and scratch depth, as evidenced by analyses of scratch force, contact area, and pressure. Material removal, dominated by plastic deformation, is highly dependent on crystal orientation. Critical scratch depths for atomic removal initiation were identified as 4 Å on the a-plane, 6 Å on the m-plane, and 12 Å on the c-plane. The minimum removal depths corresponded to a monolayer of atoms for the a-plane (1.6 Å) and bilayers for the m-plane (5.4 Å) and c-plane (5.1 Å). The simulation demonstrated that tangential forces play a dominant role in material removal within the plastic regime. A removal model that incorporates the influence of crystal plane was developed to predict the elastic-plastic transition. This model was validated across multiple scales. The findings emphasize the critical influence of crystal plane on the thresholds and mechanisms of material removal, providing valuable insights for advancing ultra-precision machining of single crystal AlN.