Electronic structure of the Si(111) √3×√3R30°-B surface from theory and photoemission spectroscopy

The Si(111) Sqrt 3 × Sqrt 3R30°-B [Si(111)-B] surface has evolved into a particularly interesting surface in the context of on-surface molecular self-assembly. Photoemission spectroscopy is a powerful tool to understand the interaction between the surface and the adsorbates. Previous studies of Si(111)-B contain many inconsistencies with regard to the Si 2p core level and valence-band dispersion. Here we employ synchrotron-based core-level and angle-resolved photoemission spectroscopy measurements in combination with density functional theory (DFT) calculations to address these issues. DFT calculations of the Si 2p core-level spectra accurately identify contributions from one bulk and five surface components, which allows us to obtain a comprehensive understand- ing of the spectra recorded at different photon energies. As an archetypal example, this refined decomposition is employed to understand the changes in Si 2p spectra upon the adsorption of cobalt phthalocyanine molecules. Regarding the valence-band dispersion of the clean Si(111)-B surface, our comprehensive DFT and photoemis- sion investigations are able to reconcile the inconsistencies appearing in previous studies and reveal several yet unreported surface states. Furthermore, we are able to theoretically and experimentally resolve the distribution of these surface states in constant energy plots.