Structure of the diamond (111)-(2×1) surface revisited with ion scattering

We present a medium-energy ion scattering study of the reconstructed diamond (111)-(2 x 1) surface. Measured blocking patterns were compared with patterns calculated for a variety of structure models. We find that a p-bonded chain model featuring tilted chains best describes our data. The tilt explains the observed electronic band gap at the surface, but is at variance with the results of recent energy minimization calculations based on the local density approximation. Our results are in disagreement with a previous ion scattering study of the reconstructed diamond (111) surface.