Physical Review B

Effect of Ag on the surface barrier for depletion of oxygen from polycrystalline YBa2Cu3O7 oxides

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We have investigated the effect of evaporated Ag on the depletion of oxygen from polycrystalline YBa2Cu3O7- in a He ambient atmosphere by in situ resistivity experiments and surface spectroscopies. Our data indicate an increase in the rate of out-diffusion of oxygen due to the presence of the Ag, which lowers the surface barrier for the out-diffusion of oxygen by 0.20.03 eV. We have performed x-ray photoelectron spectroscopy (XPS) analysis of the in situ fractured surfaces to indicate the presence of Ag at the internal surfaces in the oxide. XPS data from Ag-free in situ scraped samples show oxygen accumulation in the near-surface region upon vacuum annealing. This effect is prevented by evaporation of a few monolayers of Ag. 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. © 1989 The American Physical Society.


01 Feb 1989


Physical Review B