The stability of a de-protonated site on the hydrogenated (111) surface of diamond, under chemical vapor deposition conditions, was studied by using  ab initio  and semi-empirical molecular orbital methods. This sort of anionic vacant site was expected to form when a surface H atom was removed, and the resultant radical site captured an electron. This yielded a closed shell structure for the anionic C atom. The effects of model cluster size, as well as basis set selection, in molecular orbital studies were also examined. The stabilization energy approached about 1.5 to 1.9eV, and this surface-localized state lay within the band-gap of diamond; as expected. The spatial distribution of the highest occupied molecular orbital confirmed that the captured electron was localized around the anionic vacant site. It was suggested that the latter, which formed on the hydrogenated (111) surface of diamond, should be taken into account when studying the chemical vapor deposition growth mechanism of diamond.

S.Komatsu: Journal of Applied Physics, 1996, 80[6], 3319-26