Combined computational and spectroscopic structural characterization of oxygen-terminated diamond (110) surfaces

Diamond-based materials have unique properties that are exploited in electrochemical and quantum computing applications. When grown via chemical vapor deposition (CVD), the growth rate of the (110) face is typically much faster than the other two dominant crystallographic orientations, (111) and (100). Due to its fast growth rate, polished polycrystalline diamond predominantly exhibits (110)-texture, yet there are a lack of both experimental and theoretical studies on this surface. Whilst CVD growth confers hydrogen terminations on the diamond surface, many post-growth procedures such as polishing and lapping render the surface oxygen-terminated, which in turn impacts the surface properties of the material. In this study, we determine the oxygenation state of the (110) surface using a combination of density functional theory calculations and X-ray photoelectron spectroscopy experiments. We show that in the 0-1000 K temperature range, the phase diagram of the (110) surface is dominated by a highly stable phase of coexisting adjacent carbonyl and ether groups, while the stability of peroxide groups increases at low temperatures and high pressures. We propose a mechanism for the formation of the hybrid carbonyl-ether phase and rationalize its high stability. We further corroborate our findings by comparing simulated core-level binding energies with experimental X-ray photoelectron spectroscopy data.