Phase accumulation model analysis of quantum well resonances formed in ultra-thin Ag, Au films on W(110)

Series of quantum well states (QWS's) have been observed in photoemission spectra for the Ag/W(110) and Ag/Au/W(110) systems in a binding energy region lying outside of the substrate energy gap that is needed for full confinement of electronic waves in the adlayer. It is shown that the observed features can be described as the quantum well resonance states. An extended phase accumulation model has been applied for analysis of these states and their energy positions. It has been shown that a good correlation with experimental results can be reached. when a phase shift is introduced into the model which is related to partial scattering of confined waves on the electronic states in region of QWS formation outside of the substrate energy gap. The resulting total phase shift obtained on the base of this approach correlates nicely with the experimental one for both investigated systems. (C) 2001 Elsevier Science B.V. All rights reserved.