A quantitative analysis of the (2 x 1) reconstruction of the diamond (111) surface by low-energy electron diffraction was presented. Spot intensity versus energy data, I(E), were collected for normal incidence up to electron energies of 500eV and analysed using the tensor low-energy electron diffraction perturbation method. A close fit between experimental and calculated data (according to a Pendry R-factor R = 0.19) confirmed the model of π-bonded chains at the very surface, wherein neighbouring chains were at different heights equivalent to a considerable surface corrugation (0.68Å). It was found that the chains were practically untilted, i.e. the buckling within the chains was negligible (≤0.01Å). The possible dimerization of the chains was also very small (relative bond-length difference d = 0.7%), though the respective limits of error would allow values up to about 7%. For the sub-surface structure It was found that the surface reconstruction extends rather deep into the surface according to the considerable buckling amplitudes within sub-layers down to the fourth bilayer. All structural parameters retrieved, including the negligible tilt and dimerization of chains as well as the extension of the surface reconstruction to deeper layers, were in excellent quantitative agreement with the results of ab initio calculations.

Geometry of the (2 x 1) Reconstruction of Diamond (111). S.Walter, J.Bernhardt, U.Starke, K.Heinz, F.Maier, J.Ristein, L.Ley: Journal of Physics - Condensed Matter, 2002, 14[12], 3085-92