SURFACE-MORPHOLOGY AND CRYSTALLINITY OF SINGLE-DOMAIN YBCO CRYSTAL

Large single domain YBa2Cu3O7-x (YBCO) crystals were fabricated by the modified pulling method (SRL-CP method). The crystal growth from a sh arpened YBCO seed crystal, which was cut into the shape of a reversed pyramid, was carried olt for the purpose of obtaining a single domain crystal. The typical grown crystal was 13 mm(2) in size and 10 mm in l ength and the growth direction was the c-axis. In the nb plane of the as-grown crystal, a large spiral step was clearly observed. Morphology of this surface was investigated by atomic force microscopy (AFM). Bo th micro- and macro-steps were simultaneously observed with four-fold symmetry. This large concentric step in whole area indicate the single domain crystal has grown. The vertical height of the micro-step was l ess than 2 nm and almost equal to the c-axis unit cell height of the Y BCO crystal. The spiral growth model explains the growth mechanism of YBCO crystals. The appearance of the macro-step was explained by the p erturbation of the supersaturation. Furthermore, the crystallinity of YBCO single crystals was investigated by X-ray diffraction (XRD). The full width of half maximum (FWHM) of the X-ray rocking curve spectrum was about 0.11-0.12 degrees and X-ray topographs also show the single domain crystal has grown. However, the dislocation hollow core was lef t in the central part along the growth direction. (C) 1998 Published b y Elsevier Science Ltd. All rights reserved.