High resolution photoelectron spectroscopy using synchrotron radiation is used to probe indirectly the substrate electronic response of faceting of W(111) induced by adsorbed Pd and Pt monolayers. The W4f7/2 core level is measured in this study. For clean W(111), there are three components observed in W 4f7/2 photoemission due to surface, subsurface and bulk atoms, respectively; the core level shift between surface and bulk atoms is 430 meV. Upon adsorption of Pd or Pt at 300 K, only a bulk-like W 4f7/2 peak is observed. The interface peak associated with W atoms at the Pd-W or Pt-W interface of the W(111) face coincides with the W bulk peak. Upon annealing of the metal-covered W(111) above ∼750 K, the entire surface undergoes a transition from planar to faceted; the W 4f7/2 core level associated with Pd- and Pt-covered W(211) facets broadens and its centroid shifts to the lower binding energy side of the W bulk peak. The centroid shift and peak broadening are attributed to W atoms at the Pd-W or Pt-W(211) interface of the facets. The relation between the interfacial energy and the binding energy difference of the interface W 4f7/2 peak and the surface W 4f7/2 peak is discussed.
- Low index single crystal surfaces
- Metal-metal interfaces
- Soft x-ray photoelectron spectroscopy