Mechanistic insights into the formation of dislocation-related pits on diamond surface under plasma etching treatment: A combined simulation and experimental approach

Abstract

Reactive ion etching (RIE) is a widely applied technique for high-precision machining of demanding diamond devices. However, the persistent challenge of widely distributed dislocation-related etch pits on processed surfaces remains poorly understood. In this study, the material removal and pit formation during the etching of the dislocation region by hydrogen and oxygen were investigated by reactive force-field (ReaxFF) molecular dynamics simulation combined with experimental verification. The results unveiled the pivotal role of crystal structure disruption and symmetrically distributed stress, induced by dislocations, in promoting bond-breaking processes and triggering the formation of etch pits. The etching parameter optimized simulations revealed that once the impact effect of oxygen atoms counterbalances the promotion of dislocation to the bond breaking, the formation of dislocation pits can be effectively avoided, which is convincingly validated by experimental results. Besides, our research further verified that pure hydrogen etching is an inefficient surface post-treatment process with a more significant pit-forming problem, and exists two distinct pit-forming mechanisms dependent on the incident energy. Additionally, substrate temperature variation has global but negligible influences on pits formation within the 400 K range. These findings carry significant implications for the optimization of processing parameters and the large-scale implementation of RIE in diamond processing, demonstrating the potential to address pit-forming issues with commonly used gases.