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 $\mathrm{Si}\left(001\right)-(2\times 1)$ 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 $\overline{\Gamma }$ 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.