ARPES study of the surface states from Au/Ag(111): evolution with coverage and photon energy

The Shockley surface states formed on the (I 11) surfaces of noble metals have been extensively studied, but few reports exist on layered thin film systems. We present angle-resolved photoemission (ARPES) results, recorded at normal emission in the photon energy range from 21 to 49 eV, which describe the behavior of these sp-derived surface states for An layers epitaxially grown on Ag(l 11). Growth was performed at room and low temperatures. In both cases, the ARPES spectra are found to evolve from Ag(I I I)-like to Au(I I I)-like features as the thickness of the Au film increases. In particular, the surface-state binding energy shifts from the Ag(I 11) to the bulk Au(1 1 1) position, the shift being already evident at coverages lower than one monolayer. The origin of the changes observed in the surface-state peak as a function of An coverage and photon energy will be discussed. (C) 2002 Published by Elsevier Science B.V.