STABILITY OF HALOGEN-TERMINATED DIAMOND(111) SURFACES

The adsorption of the different species X and CX(3) on an X-terminated diamond (111) surface (X = H, F,Cl, Br) has been investigated structu rally and energetically, using a cluster approach and two different ty pes of quantum mechanical methods: the ab initio molecular orbital (MO ) method and the first-principle density functional theory (DPT) metho d, respectively. The halogen species F and Cl, as well as hydrogen H, were all shown to be able to sustain the sp(3) structural configuratio n of the surface carbon atoms. Furthermore,the adsorption energies wer e much larger for the H and F species than for other species like Cl a nd Br, indicating that H and F species stabilize the diamond(lll) surf ace better than the Cl and Br species do. For Br large sterical hindra nces are induced, and the diamond (111) surface cannot be stabilized. The adsorption of CH3 or CF3 to a radical carbon on a H- or F-terminat ed diamond (111) surface stabilizes also the sp(3) structural configur ation of the radical carbon atom. The large difference in adsorption e nergy of the species CH3 and CF3 indicates that the probability for di amond growth, based on the CF3 species as a dominant growth species on a F-terminated diamond (111) surface, is much lower than for growth b ased on the CF3 species as a dominant growth species on a H-terminated surface. There is no tendency for the gaseous species CCl3 and CBr3 t o adsorb on a Cl- or Br-terminated diamond (111) surface.