Structure analysis of two-dimensional Holmium silicide by low energy electron diffraction

The Ho/Si(1 1 1)-1×1 and H–Ho/Si(1 1 1)-1×1 surfaces have been investigated by low energy electron diffraction I–V curve analysis. Several structural models have been tried and the optimum structure has been obtained using a combination of search methods. In the case of the Ho/Si(1 1 1) surface, Ho atoms sit on T4 sites of the Si(1 1 1) near bulk-like layer and are located underneath a Si bilayer which is rotated 180° with respect to the substrate Si layers. This is the same structure as proposed by medium-energy ion scattering. In the case of the H–Ho/Si(1 1 1)-1×1 surface, Si atoms in the surface bilayer have normal stacking and are located above the same lateral position as the topmost bulk layer.