OXYGEN DIFFUSION IN YBA2CU3O7-DELTA FILMS WITH DIFFERENT MICROSTRUCTURES

We have investigated the oxygen out- and in-diffusion in epitaxial c-a xis oriented YBa2Cu3O7-delta films from isothermal four-point electric resistivity measurements, The films were grown by two different depos ition methods: off-axis pulsed laser deposition (PLD) and hollow-catho de magnetron sputtering (HCMS). Chemical diffusion relaxation times ha ve been determined for the out- and in-diffusion of oxygen at temperat ures from 500 K up to 800 K. Both types of films yielded the same acti vation energy of about E-A = 1.1 eV for the diffusion processes. Howev er, at the same temperature, differences in the diffusion relaxation t imes were observed, This difference results from the different morphol ogies and microstructures we have studied with scanning electron micro scopy (SEM), Additionally, these results are compared to sputtered YBa 2Cu3O7-delta films passivated by amorphous Si-C-H-O-N overlay films. T he activation energy in these films was about 1 eV, and the diffusion relaxation times were much larger than in the samples without the over lay. (C) 1998 Elsevier Science B.V, All rights reserved.