Surface Morphology and Microstructure of Thick YBa2Cu3O7−δ Films on Vicinal r-Cut Sapphire Buffered With CeO

Microcrack-free thick YBa₂Cu₃O_7-delta (YBCO) films were successfully fabricated by pulsed laser deposition on deliberately miscut AI₂O₃ (1102) (5.22deg off towards [1102_]) buffered with CeO₂. Characterization of the films revealed a porous morphology, consisting of interconnected islands and deep holes (pores). The microstructure of the YBCO films was further investigated by cross-section (cut along both AI₂O₃ [1101] and [1120] transmission electron microscopy (TEM). No apparent interface reaction is seen for all the TEM observations. A high density of linear defects aligned near c-axis are frequently observed. All the defects are initiated from the YBCO / CeO₂ interface, indicating the importance of the microstructure of the CeO₂ buffer layer and the sapphire substrate for the growth of YBCO. In addition, numerous small stacking faults lying in the alpha - b-plane of YBCO were produced by the linear defects. The high density of the growth-induced defects may act as strong pinning centers in YBCO films and therefore increase J_c of the film.