Structural studies of Si (111) 2 × 1 surfaces using low-energy electron diffraction

The structure of the Si(111)2×{}1 surface is studied using dynamic low-energy electron diffraction analysis at three different off-normal electron incidence angles, with emphasis on the π-bond chain model. The optimum π-bond chain geometry has a buckling of 0.35 {} between the two chain atoms and a large distortion in the subsurface layer. The bond length of surface chains is determined to be 2.25±{}0.02 {} by detailed analysis. We compare our results with those of other authors.