CHARACTERIZATION OF THE B/SI SURFACE ELECTRONIC-STRUCTURES

High-resolution angle-resolved core-level and valence-band photoelectron spectroscopy have been used to characterize the electronic structures of the B/Si (111)-(square-root 3 X square-root 3) surfaces. The results have been compared with theoretic calculations and other group-III metals and Si-terminated Si (111) surfaces that share the same type of surface reconstruction. We have observed a structure evolution from B-T4 to B-S5 and finally to Si-T4 as deposited boron atoms diffuse into the substrate with increasing annealing temperature. The chemically shifted component appearing in the Si 2p core-level spectrum is attributed to charge transfer from the top layer Si and Si adatoms to the sublayer B-S5 atoms. For the Si/Si (111)-(square-root 3 X square-root 3) surface, a newly discovered chemically shifted component is associated with back bond formation between the Si adatoms and the underneath Si atoms. A new emission feature has been observed in the valence-band spectra unique to the B/Si (111)-(square-root 3 X square-root 3) surface with B-S5 configuration. Thin Ge layer growth on this structure has also been performed, and we found that no epitaxial growth could be achieved and the underneath structure was little disturbed.