The atomic structure of the 7 x 7 reconstructed Si(111) surface was analysed by means of ultra-high vacuum transmission electron diffraction. A projected structure of the surface was deduced from the intensity distribution in transmission electron diffraction patterns of normal electron incidence and from Patterson and Fourier syntheses of the intensities. A 3-dimensional structure model, the dimer–adatom–stacking-fault model, was proposed. The model consisted of 12 adatoms arranged locally in the 2 x 2 structure, a stacking-fault layer and a layer with a vacancy at the corner and 9 dimers on the sides of each of the 2 triangular sub-cells of the 7 x 7 unit cell. The silicon layers in one sub-cell were stacked in the normal sequence, CcAaB + adatoms, while those in the other sub-cell were stacked in a faulted sequence, CcAa/C + adatoms. The model had only 19 dangling bonds; the smallest number among the models then proposed.

Structure Analysis of Si(111)-7 x 7 Reconstructed Surface by Transmission Electron Diffraction. K.Takayanagi, Y.Tanishiro, S.Takahashi, M.Takahashi: Surface Science, 1985, 164[2-3], 367-92