Influence of the growth mechanism on the grain boundary structure in YBa2Cu3O7 thin film bicrystals

Abstract The growth control of thin YBa 2 Cu 3 O 7 (YBCO) film bicrystals determines the quality of Josephson junctions and weak links. Previous TEM experiments on various thin film bicrystals showed grain boundary oscillations that were not clearly explained. We combined AFM, SEM, conventional TEM and HRTEM in order to perform a complete characterization of both substrate and YBa 2 Cu 3 O 7 thin film bicrystals. Our results clearly show that the grain boundary oscillations are due to the YBCO growth mechanisms leading to a conflictual crystallographic situation at the grain boundary. The resulting crystallographic structure of the grain boundary may affect the interpretation of several recent experiments purporting to determine the nature of the HTC superconductivity.