A system of epitaxial buffer layers on (100) SrTiO3 substrates for the preparation of bi-epitaxial grain boundaries in YBa2Cu3Ox for magnetometers

Abstract

With a combination of special buffer layers, bi-epitaxial grain boundaries in YBa2Cu3Ox (YBCO) used as Josephson junctions can be fabricated. On SrTiO3 substrates MgO and CeO2 buffer layers were used. For the production of these grain boundaries the epitaxial growth of MgO, CeO2 and MgO/CeO2 on SrTiO3 was 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 substrate 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).