Atomistic Insights into Oxidation Mechanisms in Chemical–Mechanical Polishing of Diamond

Understanding the interfacial oxidation behavior during chemical–mechanical polishing (CMP) of diamond is important for controlling surface chemical modification and subsequent material removal. In this study, reactive force field molecular dynamics (ReaxFF MD) simulations were employed to comparatively investigate the atomistic evolution of interfacial oxidation, charge transfer, chemical species, and bond structures of single-crystal diamond in •OH- and H2O2-containing environments under different pressure conditions. The results show that oxidant chemistry and mechanical loading jointly regulate the kinetics and pathway selectivity of interfacial reactions. Elevated pressure promotes early-stage interfacial contact, surface activation, and oxidant consumption; however, the subsequent evolution of C–O bonds is also governed by oxidant-specific reaction kinetics and the availability of reactive species. In the •OH system, highly reactive radicals interact directly with mechanically activated carbon sites, whereas oxidation in the H2O2 system is additionally constrained by the stepwise decomposition of H2O2 and the generation of reactive intermediates, resulting in a comparatively moderated and decomposition-limited oxidation pathway. The interfacial reactions involve the formation and dynamic evolution of C–O, C–OH, and C–H structures, reflecting the competition between oxidation and hydrogenation. XPS measurements after H2O2-based CMP provide qualitative experimental evidence for the formation of oxygen-containing functional groups on the diamond surface, supporting the occurrence of interfacial oxidation. These findings provide atomistic insight into the coupled effects of oxidant chemistry and mechanical loading during diamond CMP and may assist in the rational design of oxidation-assisted polishing processes.