An Energetic Examination of Oxygen on Diamond (100) Surfaces

Abstract

The chemical termination of the diamond (100) surface plays a critical role in determining the performance of near-surface nitrogen-vacancy (NV) centers, which are promising platforms for emerging quantum sensing and computing technology. Oxygen-termination of the diamond (100) surface produces favorable conditions for NV center applications. On this surface, carbonyl (C=O) and (C–O–C) terminations coexist. The carbonyl termination likely introduces magnetic noise and is an undesirable termination. These two states’ relative stability at finite temperatures and near defects remains unclear. In this work, molecular dynamics (MD) simulations with enhanced sampling techniques, including on-the-fly probability enhanced sampling (OPES), are used to construct free-energy surfaces for monolayer coverage of oxygen on diamond (100). For ideal surfaces, ether is favored at low temperatures, with carbonyl becoming increasingly stable as temperature rises. Free-energy differences between states predict approximately 90% ether coverage at 300 K, consistent with prior studies. In contrast, substitution defects locally favor carbonyl at 600 K and perturb oxygen bonding environments over distances exceeding 12 ˚A.