Photoemission study of a thallium induced Si(111)-(3×3) surface

We have investigated the surface electronic structure of the Tl induced Si(111)-(3×3) surface by using angle-resolved photoelectron spectroscopy. Three semiconducting surface states were observed in the gap of the bulk band projection. Of these three states, the one, whose binding energy is approximately 0.3 eV, hardly disperses. Regarding the two other states, we discuss their properties by comparing their dispersion behaviors with those of the surface states of the other group III metal (Al, Ga and In) induced (3×3) reconstructions. The split observed at the Γ¯ point and the smaller dispersion widths of these two states indicate that the origins of the surface states of the Tl induced (3×3) reconstruction are not the same as those of the Al, Ga and In induced (3×3) reconstructions. These results support the idea that the atomic structure of the Tl/Si(111)-(3×3) surface is different from that of the (3×3) reconstructions induced by other group III metals, which was proposed in the literature.