A SYSTEM OF EPITAXIAL BUFFER LAYERS ON (100)SRTIO3 SUBSTRATES FOR THEPREPARATION OF BI-EPITAXIAL GRAIN-BOUNDARIES IN YBA2CU3OX FOR MAGNETOMETERS

With a combination of special buffer layers, bi-epitaxial grain bounda ries in YBa2Cu3Ox (YBCO) used as Josephson junctions can be fabricated . On SrTiO3 substrates MgO and CeO2 buffer layers were used. For the p roduction 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. Th e crystallinity was examined by x-ray diffraction, x-ray pole figure m easurement and RBS (Rutherford backscattering)-ion channelling. The fa brication of these bi-epitaxial grain boundaries requires an ion-etchi ng process, which damages the substrate surface. Therefore, an anneali ng process was necessary after the etching step. The quality of the ed ge and of the layers after the annealing process was studied by scanni ng electron microscopy (SEM) and RBS-ion channelling. Such bi-epitaxia l grain boundaries were used to realize SQUIDS (superconducting quantu m interference devices).