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 ${\mathrm{H}}_2$ 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.