Semiconductor–metal–semiconductor transition: valence band photoemission study of Ag/Si(1 1 1) surfaces

The 3×3, 21×21 and 6×6 phases of Ag/Si(1 1 1) have been studied by angle-resolved photoemission and low-energy electron diffraction. The Ag/Si(1 1 1) 3×3 surface has an intrinsic semiconducting character with two fully occupied, dispersing surface state bands. We find that only one of the additional surface bands on the 21×21 surface is metallic in contrast to the two metallic bands discussed in the literature. On the 6×6 surface, the partially occupied surface band of the 21×21 surface seems to be absent, resulting in a gap of about 0.2 eV with respect to the Fermi-level.