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

Microcrack-free thick YBa
₂
Cu
₃
O
_7-delta
(YBCO) films were successfully fabricated by pulsed laser deposition on deliberately miscut AI
₂
O
₃
(1102) (5.22deg off towards [1102
_]
) buffered with CeO
₂
. 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 AI
₂
O
₃
[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 / CeO
₂
interface, indicating the importance of the microstructure of the CeO
₂
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.