EVIDENCE FOR TILTED CHAINS ON THE DIAMOND(111)-(2X1) SURFACE

We present the first X-ray diffraction structure analysis of the recon structed diamond (111) surface. The atomic geometry is obtained from t he distribution of diffracted intensities along integer-order rods of Bragg scattering perpendicular to the surface. Of all the geometries c onsidered, an atomic arrangement featuring tilted chains of pi-bonded surface atoms with distortions in subsurface layers is found to provid e the best agreement between the calculated and measured structure fac tors. The tilted-chain topology explains the origin of the observed su rface band gap, but it is at variance with recent theoretical predicti ons base on the local density approximation. (C) 1998 Elsevier Science B.V.