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

Abstract Epitaxial c -axis oriented thin REBa 2 Cu 3 O 7− δ films were deposited on closely matched substrates: YBa 2 Cu 3 O 7− δ on SrTiO 3 and GdBa 2 Cu 3 O 7− δ on NdGaO 3 . Kinetics of oxygen in-diffusion was studied by resistivity changes during corresponding isothermal annealing in a reduced oxygen atmosphere. The rate of oxygen uptake was found to be dependent on film thickness, abruptly increasing after some critical film thickness of about 40 nm. The increase continued over several orders of magnitude, as the film gets thicker, saturating for a film thickness of about 500 nm. Atomic Force Microscopy (AFM) clearly illustrates the transition from a dislocation-free to dislocation-developed microstructure at around the critical film thickness. It is believed that these dislocations serve as easy paths for c -axis diffusion.