Electronic structure of Ag-induced root 3X root 3 and root 21X root 21 superstructures on the Si(111) surface studied by angle-resolved photoemissionspectroscopy and scanning tunneling microscopy - art. no. 205316

Polarization-dependent angle-resolved photoemission spectroscopy was used t o analyze the electronic band structure of the Si(111)-root 21 X root 21(R +/- 10.89 degrees)-Ag surface induced by adding submonolayer Ag atoms on to p of the Si(111)-root3 X root3-Ag surface at 140 K, together with a refinem ent of the electronic states of the initial root3 X root3-Ag substrate itse lf. The surface-state band crossing the Fermi level on the the root3 X root 3-Ag surface was found to have similar dispersions in both <(<Gamma>)over b ar>-(K) over bar and <(<Gamma>)over bar>-(M) over bar directions around the <(<Gamma>)over bar> point of the root3 X root3 surface Brillouin zone, and consist mainly of components parallel to the surface with no measurable po larization dependence. The five intrinsic surface-state bands observed on t he root3 X root3-Ag surface basically remained in the root 21 X root 21-Ag structure, but shifted down in energy position from the Fermi level by abou t 0.4 eV. This is due to electron transfer from the Ag adatoms to the subst rate, suggesting that the Ag adatoms in the root 21 X root 21-Ag phase sit on a nearly unaltered root3 X root3-Ag substrate, and do not make any orbit al hybridization with the substrate. Only one parabolic band crossing the F ermi level was found on the root 21 X root 21-Ag surface, for which distrib ution in real space is observed by bias-dependent scanning tunneling micros copy, This result is in contrast to two metallic bands on the root 21 X roo t 21 phase induced by Au or Cu adatoms on the root3 X root3-Ag substrate re ported in previous papers.