Surface Morphology and Microstructure of Thick ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta}$ Films on Vicinal $r$-Cut Sapphire Buffered With ${\rm CeO}_{2}$

Abstract

Microcrack-free thick YBa2Cu3O7-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 Jc of the film.