Dispersions of surface states on diamond (100) and (111)

We present angle-resolved photoelectron spectra and surface state dispersions for the clean, 2×{}1 reconstructed (111) and (100) surfaces of diamond. For the (100) surface a surface state is found in the gap of the projected bulk band structure around Y-bar, which has a binding energy of 2.7 eV at Y-bar (relative to the Fermi level) and a dispersion in the {Γ}-bar-Y-bar direction of 0.5 eV, consistent with theory. At {Γ}-bar a surface resonance is observed at 1.4 eV binding energy. No surface states were observed above the valence-band maximum. Our results on the (111) surface show a strongly dispersing surface state that reaches its maximum 0.5 eV below the Fermi level at K-bar. This result implies a gap of at least 0.5 eV in the surface electronic structure, which has consequences for the surface reconstruction in terms of a {π}-bonded chain model.