LOCAL DENSITY OF UNOCCUPIED STATES IN ION-BEAM-MIXED PD-AG ALLOYS

X-ray absorption spectroscopy (XAS) measurements have been used to probe the electronic structure of ion-beam-mixed (IBM) Pd-Ag thin films with bulk alloys being studied for comparison. Pd {ital L}{sub 3} and Ag {ital L}{sub 3} absorption edges for pure Pd, Ag, and Pd{sub 1{minus}{ital x}}Ag{sub {ital x}} alloys are discussed. Structural information from both x-ray diffraction and the XAS fine structure oscillations are discussed. The observed decrease of the white-line feature strength, at the Pd {ital L}{sub 3} edge, indicates that the local density of unoccupied Pd 4{ital d} states declines upon alloying with Ag in a manner similar to that observed in previous bulk studies. However, while the Pd {ital d}-hole count decreases monotonically for bulk alloys, in the IBM alloys it saturates at higher levels in the Ag-rich materials. This disparity is interpreted on the basis of a modified charge transfer due to structural differences in the IBM alloys. The Ag {ital L}{sub 3} near-edge region is largely unchanged in these alloys, indicating that the charge transferred away from the Ag site is dominantly of {ital non}-{ital d} type. Our experimental results are discussed in the context of recent electronic structure calculations and of previous work on thismore » alloy system. {copyright} {ital 1996 The American Physical Society.}« less