Growth and electronic properties of Tb silicide layers on Si(111)

Abstract

The formation, atomic structure, and electronic properties of Tb silicide layers on the Si(111) surface were studied using scanning tunneling microscopy as well as core-level and angle-resolved photoelectron spectroscopy. For Tb exposures around one monolayer, the formation of a hexagonal TbSi2 monolayer was found, while higher coverages led to the formation of a hexagonal Tb3Si5 multilayer with a 3×3R30° superstructure in the bulk layers. For the monolayer silicide, Si-2p core level spectra show a Fermi level position very close to the conduction band minimum of the silicon substrate, while the Fermi level shifts toward midgap in the multilayer case. The electronic structure of the monolayer is characterized by a Fermi surface consisting of electronlike ellipses around the M¯ points and a holelike state around the Γ¯ point. The effective masses of the band around the M¯ points are strongly anisotropic, with values around 1.45 m0 in the long direction and 0.16 m0 in the short direction of the ellipses. In the case of the multilayer, the ellipses around the M¯ points are less eccentric, and there are indications for Umklapp processes due to the 3×3R30° superstructure in the silicide bulk layers. The overall behavior of Tb is found to be similar to that of other trivalent rare earths on Si(111).