Structural determination of Yb single-crystal films grown on W(110) using photoelectron diffraction

A quantitative analysis of the surface relaxation at the Yb(111) single-crystal films grown on W(110) has been undertaken applying energy-scan photoelectron diffraction technique using the two shifted components, i.e., surface and bulk of the lanthanide $4f$ core levels. Additional polar scans were recorded for a fixed photon energy along the crystal high-symmetry directions. The analysis of the data set following a trial and error fitting procedure confirmed a consistent fcc structure for all noncontaminated evaporated Yb films with the bulk lattice parameter corresponding to a value of $a=(5.44\mathrm{}\pm 0.05)\hspace{0.5em}\mathrm{\AA },$ about 1% contracted respect to the bulk fcc Yb metal. A refinement of the structural analysis indicates an inward surface relaxation of the interlayer spacing for the first two top layers with respect to the bulk lattice parameter.