Transient local resistivity maximum during temperature-dependent oxygen diffusion in YBa2Cu3O7-delta thin films

We have investigated the oxygen diffusion behavior by means of electric res istivity measurements on epitaxial, c-axis-oriented YBa2Cu3O7-delta thin fi lms in the temperature regime up to 800 K, A pronounced transient local res istivity maximum (TRM) was observed at about T = 600 K during the first pos t-deposition heat treatment of the films in 900 mbar pure oxygen atmosphere . In the subsequent heating procedures this distinct maximum was not observ ed anymore. This temperature- and time-dependent effect appears to be assoc iated with the dissociation of molecular oxygen on the sample surface repre senting an important step in the in-diffusion of oxygen. Changes in the sur face microstructure and roughness during the first post-deposition heat tre atment in molecular oxygen atmosphere appear to strongly facilitate the oxy gen 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 molecula r oxygen, film thickness, microstructure of off-axis pulsed laser deposited and hollow-cathode magnetron sputtered YBa2Cu3O7-delta films, surface roug hness, and passivation by means of a Si-C-H-O-N overlay film. (C) 1999 Publ ished by Elsevier Science B.V. All rights reserved.