XPS studies of superconducting Mo–Ru–Rh–Pd alloy

Superconducting quaternary alloys, Mo25Ru50Rh12.5Pd12.5, Mo30Ru45Rh12.5Pd12.5, Mo40Ru40Rh10Pd10 and Mo50Ru20Rh15Pd15 have been prepared using an arc melting furnace. X-ray photoelectron spectroscopic (XPS) measurements indicate that the binding energies of Pd 3d3/2 and 3d5/2 peaks increased by 0.5–0.9 eV. XPS measurements for several binary alloys, Pd1−xMox, Pd1−xRux, Pd1−xRhx and Pd1−xAgx (x=0.25, 0.5, 0.75 and 1.0) were also carried out to study the origin of the binding energy shifts of Pd 3d3/2 and 3d5/2 peaks. The binding energy shifts are found to be irrespective of the electronegativity of the constituent elements in the quaternary alloys, but rather closely related to the final state effects.