Use of angle-resolved photoemission and density functional theory for surface structural analysis of YSi2

The atomic structure of two-dimensional yttrium silicide epitaxially grown on Si(1 1 1) was investigated by means of density functional theory calculations and angle-resolved photoemission experiments. The obtained accuracy of the calculations allowed to discriminate different surface arrangements in a quantitative way via comparing their theoretical band structure to the experimental result. Theoretically we find significant changes in the dispersion of a surface localized band upon varying the thickness of the topmost silicon bilayer. For a thickness of 0.4 Å of the topmost silicon bilayer a strong asymmetry of the surface localized band with respect to Γ is found, while a thickness of 0.8 Å yields a more symmetric dispersion of the band. By comparison with the experimental photoemission results, which show a rather symmetric band around Γ, we can conclude that the topmost bilayer has a thickness of 0.8 Å.