Topology–chemistry coupling governs universal cooperative polishing in β-BN and C-doped β-BN

This study develops a mechanism-based cooperative polishing framework to elucidate nanoscale material removal behavior in β-BN and C-doped β-BN wafers under multi-motion chemical mechanical polishing (CMP) conditions using large-scale molecular dynamics simulations. The effects of sliding, rolling, vibration, and coupled rolling–vibration motions on material removal rate (MRR), surface morphology, energy dissipation, and atomic-scale deformation mechanisms are systematically investigated. The results demonstrate that multi-motion polishing significantly outperforms conventional sliding-dominated CMP by simultaneously enhancing MRR and improving surface integrity. Among all motion modes, counterclockwise rolling yields the highest MRR, while rolling–vibration coupling provides the most favorable balance between material removal efficiency and surface smoothing. In addition, multi-edge abrasive topologies promote more uniform stress distribution and increased contact multiplicity, leading to enhanced polishing stability and efficiency compared with sole-sharpness abrasives. At the atomic scale, two distinct removal mechanisms are identified. Pristine β-BN exhibits an atom-by-atom removal process governed by its rigid covalent B-N network, whereas C-doped β-BN shows a cooperative chain-type removal mechanism involving collective detachment of B-N-C atomic sequences due to locally weakened and heterogeneous bonding configurations. Carbon incorporation introduces bond heterogeneity and spatially varying cohesive resistance, which significantly alters the energy landscape for bond rupture and facilitates more efficient material removal under dynamic loading conditions. More importantly, the study reveals that polishing behavior is governed by the coupled interaction between abrasive topology and material bonding heterogeneity. The synergy between these two factors controls the transition from localized deformation to distributed cooperative removal. When the coupling effect becomes sufficiently strong under specific motion conditions, the system enters a synchronized cooperative regime in which material removal simultaneously enhances surface smoothing and spatial surface reorganization. Based on these findings, a mechanism-based cooperative polishing framework is proposed to unify geometry-driven and chemistry-modulated polishing behaviors within a single physically interpretable description for BN-based systems. The proposed framework provides atomistic insight into how abrasive kinematics, contact topology, and bonding heterogeneity jointly govern CMP performance in layered ceramic materials.