Photoemission study of W(4f) core-level shifts on (1×1)Fe/W(110)

High-resolution photoemission spectra of W(4f(7/2)) on (1 x 1) Fe/W(110) have been obtained from submonolayer to 2.5 overlayers of Fe. It is observed that the second layer of tungsten is modified by Fe overlayer, as well as by the first tungsten layer, during bi-metallic epitaxy. The first-layer tungsten atoms exhibit incremental W(4f(7/2)) shifts to lower binding energies with increasing Fe-W coordination whereas the W(4f(7/2)) level for the second-layer tungsten atoms shifts in the opposite direction. A coordination number and lattice relaxation shifts are proposed to account for these opposing core-level shifts of the first and second layer W atoms, respectively.