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 EF. Analysis of their intensity versus photon energy gives an interpretation in terms of d-like quantum well states at Ei=(−4.2±0.1) eV, (−4.6±0.1) eV and (−5.0±0.1) eV and a state at Ei=(−6.2±0.2) eV which couples strongly to a substrate bulk band. Quantum well states showing s-like character are identified at Ei=(−3.1±0.1) eV, related to an Ag thickness of 2 ML, and at Ei=(−2.4±0.1) eV, identified with the 3 ML film. Moreover, a d-like interface state is clearly identified at Ei=(−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.