Experimental surface-state band structure of the Ba-induced Si(111) 3X1 surface

The surface-state band structure of the Ba-induced single-domain Si(111) 3 x 1 surface was studied in detail via angle-resolved photoelectron spectroscopy using synchrotron radiation. Applying different photon energies and experimental geometries, we obtained the experimental surface-state band structure, including information of the symmetry of the surface states. Our results indicate that the surface electronic state is undoubtedly semiconducting, in contrast to the prediction of previous band calculations. However, the dispersion feature of the three nonmetallic surface states is in almost perfect agreement with that calculated for the honeycomb-chained channel model. The inconsistency between our results and the theoretical calculation can be explained by the fact that the coverage of alkali-earth metal is not the same as that of alkali metal. Rather, the coverage of alkali-earth metal on the 3 x 1 surface is half that of alkali metal, i.e., 1/6 monolayer.