Photoemission study of Pd thin films on Ru(0001) surface

At monolayer coverage of Pd on Ru(0001) surface, the core-level spectra of Pd 3d shows a positive core-level shift of X-ray photoelectron spectroscopy (XPS) while the d-band center of valence band spectra moves away from Fermi level in comparison of bulk Pd(111). The modification of electronic structures, displayed in core-level and valence band XPS spectra can be explained with substrate-induced charge polarization effect in Pd layer, resulting in lowering average potential around atom.

► Ultrathin Pd films on Ru(0001) surface is investigated with XPS.
► Pd 3d shows a positive core-level shift while d-band center moves away from Fermi level.
► The charge polarization effect of Pd adlayer is estimated from XPS analysis.