Surface segregation and core-level shift of a PdRh alloy studied by XPS

The surface core-level shift and surface segregation of a Pd93Rh7 alloy have been considered in the light of X-ray photoemission spectroscopy. A core-level shift of the Pd3d line to a lower binding energy as far as the surface atoms are concerned has been observed, which can be expected on the basis of the Z + 1 approximation. Also, surface segregation of Pd atoms has been found by using different take-off angles between the momentum of the escaping photoelectron and the surface of the PdRh alloy. This effect has been discussed in terms of the surface density of electronic states and the d-band occupancy of an alloy.