A system of epitaxial buffer layers on (100) srtio₃infstrates for the preparation of bi-epitaxial grain boundaries in yba₂cu₃o_xfor magnetometers

With a combination of special buffer layers, bi-epitaxial grain boundaries in YBa₂Cu₃O_x(YBCO) used as Josephson junctions can be fabricated. On SrTiO₃infstrates MgO and CeO₂buffer layers were used. For the production of these grain boundaries the epitaxial growth of MgO, CeO₂and MgO/CeO₂on SrTiO₃was studied. The crystal quality of the buffer layers was optimized by variation of several deposition parameters. The crystallinity was examined by X-ray diffraction, X-ray pole figure measurement and RBS (Rutherford backscattering)-ion channelling. The fabrication of these bi-epitaxial grain boundaries requires an ion-etching process, which damages the infstrate surface. Therefore, an annealing process was necessary after the etching step. The quality of the edge and of the layers after the annealing process was studied by scanning electron microscopy (SEM) and RBS-ion channelling. Such bi-epitaxial grain boundaries were used to realize SQUIDs (superconducting quantum interference devices).