Photoemission study of the electronic and chemical structure of amorphous CuxY100-x films

Valence band and core level photoelectron spectra are reported for clean Cu_xY_100-x amorphous thin films grown in situ by sputtering of targets with different stoichiometry. The density of occupied states of these amorphous metallic alloys is shown not to be a simple linear superposition of the constituent densities of states. Experimental evidence shows overlap of Cu and Y d bands with significant electron transfer from Y to Cu atoms which induce large bonding shifts, narrowing and intensity modifications of the valence band. The same conclusion is reached from the Cu core level shift and asymmetry. An estimation of the effective Coulomb interaction on Cu sites from Auger results is attempted.