Charge transfer and relative fermi energies in Pd based alloys

Abstract

The XPS binding energy shifts of a species A due to its incorporation into a metallic alloy AxB1−x, can be defined as: ΔBA=ΔEAF+ΔωA, where ΔEAF is the difference between the Fermi energies of pure A and the alloy, and ΔωA is the A‐atom valence electron contribution to the binding energy shift of species A. We will show that, for the case of Pd‐noble metal alloys, one can equate ΔEAF to the negative of the core level Auger energy shift and that, for these alloys, charge transfer to the noble metal atom is very small. These results suggest the possibility of probing the relative Fermi energy in a general random alloy by measuring the Auger shift of a noble metal impurity inserted into the alloy. Clearly, if this is valid, two noble metal impurities in the same alloy should show a constant difference in Auger energy shifts, independent of the alloy concentration. By presenting results for trimetallic alloys with two noble metal components, we demonstrate that this is true in at least two cases: AuxPdyCuz and...