Energy surfaces of rare-earth silicide films on Si(111)

We report on angle-resolved photoelectron spectroscopy results of thin dysprosium-silicide layers formed on Si(1 1 1), taken with a toroidal analyzer allowing to image the energy surfaces in k(parallel to)-space. At monolayer dysprosium coverages, where hexagonal DySi2 grows with a 1 x 1 superstructure, electron pockets are observed at the (M) over bar points with highly anisotropic effective masses, and around a hole pocket at the (Gamma) over bar point also an anisotropic dispersion is found. The band filling of these two bands amounts to one, indicating an even number of electrons assigned to the surface unit cell. Similar features are found for multilayer coverages, where hexagonal Dy3Si5 layers are formed with a root 3 x root 3R30 degrees superstructure. the influence of zone folding effects due to the root 3 x root 3R30 degrees reconstructed layers in the bulk silicide, is only weak because of the high surface sensitivity of the experiments. (C) 2009 Elsevier B.V. All rights reserved.