Determination of the lattice relaxation at the Yb(111) surface using chemical-shift photoelectron diffraction

A quantitative analysis of the surface relaxation of thick Yb(111) single-crystal films grown on W(110) has been performed by photoelectron diffraction technique using high-energy resolution photoemission spectra of the surface core-level shift of Yb 4f. Our results demonstrate that Yb grows epitaxially in a fee structure without surface reconstruction. The surface atoms present an inward relaxation of the first and second layers by (3.6+/-0.3)% and (1.9+/-0.2)% of the bulk interlayer spacing, respectively. The appearance of the d-like surface-state at Yb(111) is assumed to be responsible for the inward surface relaxation.