First principles calculations of the adsorption and migration behaviors of N atoms on the H-terminated diamond (001) surface

In this paper, the adsorption and migration behaviors of nitrogen (N) atoms on the hydrogen - terminated diamond (0 0 1) surface [H-Ter-D (0 0 1) surface] were investigated. The adsorption energy, the electron charge and the magnetic moment were calculated through first principles methods. The investigation results show that on the fully H-Ter-D (0 0 1) surface, all surface C atoms have saturated bonds. However, the N atom can abstract the H atom from a surface carbon atom nearby or lead to the bond breaking of the dimer carbon atoms to form bonds with the surface carbon atoms. The maximum energy of adsorption reaches to 3.47 eV, corresponding to a stable configuration structure. The charge analysis and the density of state analysis further reveal that the N atom adsorbed has unpaired electrons, which provides the opportunity for adsorption of CH radicals. On the H-Ter-D (0 0 1) surface with one open radical site (1ORS) slab, the N atom can abstract the H atom from a surface carbon atom nearby and bond with the dimer carbon atoms. The adsorption energy rises to 4.85 eV. On the H-Ter-D (0 0 1) surface with the 2ORS slab, the activation energy for a N atom to migrate along the dimer chain to the next dimer is 1.31 eV. Moreover, the adsorption of the N atom on the 1ORS surface promotes the adsorption of a C atom nearby and improves the ability of C atom migration, which is beneficial for the growth of the diamond grains. According to the charge transform analysis, the electronegativity of N atoms plays an important role in their adsorption behaviors. In addition, when the N atom has been adsorbed on the H-Ter-D (0 0 1) surface, it could still be abstracted by the other deposited N atoms; this phenomenon may be the reason for a low deposition efficiency of N atoms in the N-doped diamond films.