Epitaxial CeO2 buffer layer on deliberately miscut sapphire for microcrack-free thick YBa2Cu3O7−δ films

CeO2 buffer layers were grown on deliberately miscut Al2O3(11¯02) surfaces by pulsed laser deposition. Atomic force microscopy observations revealed that their morphology was very smooth. High lattice perfection of the CeO2 layer was shown by X-ray diffraction. Thick YBa2Cu3O7−δ (YBCO) films have been grown on such vicinal surfaces by laser ablation. The resultant YBCO films were stoichiometric and microcrack-free with a porous morphology (confirmed by scanning electron microscopy), consisting of interconnected islands and deep holes (pores). The porous feature is considered as one of the sources contributing to the strain-relieving mechanism responsible for the increase in film thickness without microcracking. Microcrack-free thick YBCO films revealed Tc=90.5±0.5K, Jc(77.3K,0T)=1.5-3.0×106A/cm2, and a substantial enhancement of Jc×t(77.3K,0T) up to 246 A/cm.