Periodic density-functional study on oxidation of diamond (100) surfaces

The chemical reactions of the diamond surfaces with oxygen play important roles in the chemical-vapor deposition process, etching, and wear of the surface. In the present study, periodic density-functional calculations have been performed to clarify the oxidation mechanisms of the hydrogenated diamond (100) surfaces. The oxidation processes have been simulated in terms of the reaction heats. The ether, hydroxyl, and ketone structures are found to be stable on the diamond (100) surfaces. At the initial stage of the oxidation, the ether structures are priory formed at monohydride dimer bonds on the diamond (100) surfaces. The insertions of oxygen atoms into the lower layers are difficult to occur. As the coverage of oxygen atoms on the diamond surface is increased, the formation of ketone structures becomes easier. The stable structure of the oxygen monolayer sensitively depends on the lattice parameters. As the cell parameters are decreased, the bridge ether becomes more stable and the on-top ketone becomes more unstable.