Migration behaviour of carbon atoms on clean diamond (0 0 1) surface: A first principle study

Abstract

The adsorption and migration energies of a single carbon atom and the configuration evolution energies of two carbon atoms on a clean diamond (001) surface were calculated using the first principle method based on density functional theory to investigate the formation of ultra-nanocrystalline diamond (UNCD) film. The activation energy of a single atom diffusing along a dimer row is 1.96eV, which is almost the same as that of a CH2 migrating along a dimer row under hydrogen-rich conditions. However, the activation energy of a single atom diffusing along a dimer chain is 2.66eV, which is approximately 1.55 times greater than that of a CH2 migrating along a dimer chain in a hydrogen-rich environment. The configuration evolution of the two carbon atoms is almost impossible at common diamond film deposition temperatures (700–900°C) because the activation energies reach 4.46 or 5.90eV. Therefore, the high-energy barrier could result in insufficient migration of adatoms, leading to the formation of amorphous in UNCD films in hydrogen-poor CVD environment.