Preparation and characterization of microcrack-free thick YBa2CU3O7-δ films

High quality epitaxial YBa2Cu3O7-delta (YBCO) superconducting films were fabricated on (00l) LaAlO3 substrates using the direct-current sputtering method. The attainment of an unusually high film thickness (up to 2.0 mu m) without microcracking was attributed in part to the presence of pores correlated with yttrium-rich composition in the films. The influence of the film thickness on the microstructure was investigated by X-ray diffraction conventional scan (theta-2 theta, omega-scan, pole figure) and high-resolution reciprocal space mapping. The films were c-axis oriented with no a-axis-oriented grains up to the thickness of 2 mu m. The surface morphology and the critical current density (J(c)) strongly depended on the film thickness. Furthermore, the reasons for these thickness dependences were elucidated in detail.