Photoemission studies of the W(110)/Ag interface

We have taken normal emission photoelectron spectra using tunable synchrotron radiation from Ag overlayers grown epitaxially on W(110). One ordered monolayer (ML) exhibits four Ag-induced essentially d-like states at initial energies between 4 and 7 eV below E-F. Analysis of their intensity versus photon energy gives an interpretation in terms of d-like quantum well states at E-i=(-4.2+/-0.1)eV, (-4.6+/-0.1)eV and (-5.0+/-0.1)eV and a state at E-i=(-6.2+/-0.2)eV which couples strongly to a substrate bulk band. Quantum well states showing s-like character are identified at E-i=(-3.1+/-0.1)eV, related to an Ag thickness of 2 ML, and at E-i=(-2.4+/-0.1)eV, identified with the 3 ML film. Moreover, a d-like interface state is clearly identified at E-i =(-1.4+/-0.1)eV. Besides overlayer-induced attenuation, the substrate emission appears unchanged. All photoemission features observed in our study can be uniquely identified, and this gives a solid starting point for future adsorbate studies on W(110) covered with 1 or 2 ML Ag. (C) 2000 Elsevier Science B.V. All rights reserved.