Surface electronic structure of two- and three-dimensional holmium silicide on Si(111)

The surface electronic structure of two- and three-dimensional Ho silicides grown on Si(111) has been studied with the techniques of metastable de-excitation spectroscopy (MDS) and ultraviolet photoemission spectroscopy. Electronic structure differences between the two cases are examined, and the extreme sensitivity of MDS to the surface density of states (DOS) allows a direct comparison between deconvolved spectra and ab initio density-functional theory calculations. This comparison shows a good agreement between the DOS calculated for the Si (111) -1×1-Ho structure and MDS data obtained from an almost-complete layer of two-dimensional Ho silicide. The dominant role of the topmost silicon bilayer in determining the surface electronic properties is revealed.