Solid-state effects on Ag in dilute alloys revealed by Cooper-minimum photoemission.

Abstract

Synchrotron-radiation photoemission has been used to study the region of the Cooper minimum of the Ag 4d states in the random substitutional alloys ${\mathrm{Al}}_{95}$${\mathrm{Ag}}_{5}$ and ${\mathrm{Cd}}_{97}$${\mathrm{Ag}}_{3}$. We have developed an internally consistent analysis by relating the intensity of the Ag 4d states to the intensity of the step at the Fermi level. The results are compared with previously published theoretical calculations for atomic Ag and experimental data for atomic Ag and solid Ag, and for a submonolayer thickness of Ag deposited on a Si(111) substrate. The Ag 4d Cooper minimum is perturbed from its atomic values owing to hybridization of the Ag 4d wave function with that of the neighbor atoms. We use this to deduce details of how silver is bonded in these different systems. It is shown that the Ag in dilute Al-Ag is quite similar to atomic Ag while in Cd-Ag the Ag atoms are somewhat more perturbed than in metallic Ag. In the Cd-Ag alloy, the 4d cross section per atom for Ag is lower than for Cd throughout the photon-energy range of 40--170 eV.