Thickness-dependent oxygenation in c-axis oriented REBa2Cu3O7-delta thin films deposited on closely matched substrates

Epitaxial c-axis oriented thin REBa2Cu3O7-delta films were deposited on clo sely matched substrates: YBa2Cu3O7-delta on SrTiO3 and GdBa2Cu3O7-delta on NdGaO3. Kinetics of oxygen in-diffusion was studied by resistivity changes during corresponding isothermal annealing in a reduced oxygen atmosphere. T he rate of oxygen uptake was found to be dependent on film thickness, abrup tly increasing after some critical film thickness of about 40 nm. The incre ase continued over several orders of magnitude, as the film gets thicker, s aturating for a film thickness of about 500 nm. Atomic Force Microscopy (AF M) clearly illustrates the transition from a dislocation-free to dislocatio n-developed microstructure at around the critical film thickness. It is bel ieved that these dislocations serve as easy paths for c-axis diffusion. (C) 2000 Elsevier Science B.V. All rights reserved.