Metal–Si bonding in Cu/Si(111)‘‘5×5’’ using angle-resolved ultraviolet photoemission spectroscopy and band structure calculations

Abstract

Photoemission spectra from reacted submonolayer deposits of noble metals on Si both reflect the surface atomic configuration and measure metal–Si bonding behavior. We have studied the ‘‘5×5’’ structure of annealed Cu on Si(111) with angle-resolved ultraviolet photoemission spectroscopy, varying polarization and photon energy (14–25 eV) to examine the symmetries and atomic origins of observed features. Experimental results are compared in detail with ab initio computations of band structure for model structures using the pseudofunction method. The results indicate that most Cu atoms reside at highly symmetric sites, and bonds between coplanar atoms dominate the Cu d structure. The energy levels suggest a model with threefold rather than sixfold Cu–Si coordination. The Cu d states appear to obey dispersion determined by an expanded overlayer rather than by the substrate lattice.