Transient local resistivity maximum during temperature-dependent oxygen diffusion in YBa sub(2)Cu sub(3)O sub(7- delta ) thin films

We have investigated the oxygen diffusion behavior by means of electric resistivity measurements on epitaxial, c-axis-oriented YBa sub(2)Cu sub(3)O sub(7- delta ) thin films in the temperature regime up to 800 K. A pronounced transient local resistivity maximum (TRM) was observed at about T identical with 600 K during the first post-deposition heat treatment of the films in 900 mbar pure oxygen atmosphere. In the subsequent heating procedures this distinct maximum was not observed anymore. This temperature- and time-dependent effect appears to be associated with the dissociation of molecular oxygen on the sample surface representing an important step in the in-diffusion of oxygen. Changes in the surface microstructure and roughness during the first post-deposition heat treatment in molecular oxygen atmosphere appear to strongly facilitate the oxygen dissociation and to produce proper catalytic centers for this process. This model is supported by detailed experimental TRM studies investigating the influence of the following parameters: partial pressure of the molecular oxygen, film thickness, microstructure of off-axis pulsed laser deposited and hollow-cathode magnetron sputtered YBa sub(2)Cu sub(3)O sub(7- delta ) films, surface roughness, and passivation by means of a Si-C-H-O-N overlay film.