Publication
Applied Physics Letters
Paper

Surface segregation of Ba in polycrystalline YBa2Cu 3O7 oxides: The effect of silver

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Abstract

We have investigated the effect of annealing polycrystalline YBa 2Cu3O7-δ samples in a He ambient and in vacuum, on the composition of their internal surfaces. X-ray photoelectron spectroscopy (XPS) data indicate a decrease in the amount of BaCO3 but a higher proportion of Ba at the near-surface region upon low-temperature annealing in He or vacuum. The latter effect seems to derive from the presence of a surface barrier for oxygen outdiffusion, and can be prevented by diffusing Ag into the polycrystalline sample. Changes in the cutoff energies of the ultraviolet photoelectron spectra indicate that a submonolayer coverage of Ag is sufficient to produce a change in the work function of 0.3 eV, corresponding to the lowering of the surface barrier.

Date

01 Dec 1989

Publication

Applied Physics Letters

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