Surface structures and electron affinities of bare and hydrogenated diamond C(100) surfaces

The structure and electronic properties of bare and H-terminated C(100)-2×{}1 surfaces have been studied by ab initio molecular dynamics. Stable 2×{}1 structures were found for both clean and monohydride-terminated surfaces. The 1×{}1 dihydride phase is energetically unstable relative to H₂ desorption, although a local minimum, consisting of canted dihydride pairs, was found. The bare diamond (100)-2×{}1 surface has a positive electron affinity, while a negative electron affinity is obtained for both the 2×{}1:H and 1×{}1:2H surfaces. The existence of negative electron affinity for the diamond (100)-2×{}1:H surface is in good agreement with recent experimental data.