One-dimensional delocalized adsorbate bloch states on a semiconductor surface: C₂H₄/Si(001)-(2×1)

We report the observation of a 1D molecular adsorbate band structure caused by direct adsorbate-adsorbate interactions on a semiconductor.For ethylene chemisorbed on Si(001)-(2×1) two adsorbate-derived electronic states, 1b_3u and 1b_2g, are found to delocalize along the Si-Si dimer rows.The corresponding bands can be followed in reciprocal space from the Γ^¯ point into the third surface Brillouin zone.Density functional calculations for ethylene adsorbed on a silicon slab reproduce the experimental 1D band structure and allow us to identify the origin of the lateral interactions.