Surface morphology and crystallinity of single domain YBCO crystal

Abstract

Large single domain YBa 2 Cu 3 O 7−x (YBCO) crystals were fabricated by the modified pulling method (SRL-CP method). The crystal growth from a sharpened YBCO seed crystal, which was cut into the shape of a reversed pyramid, was carried out for the purpose of obtaining a single domain crystal. The typical grown crystal was 13 mm 2 in size and 10 mm in length and the growth direction was the c -axis. In the ab plane of the as-grown crystal, a large spiral step was clearly observed. Morphology of this surface was investigated by atomic force microscopy (AFM). Both 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 less than 2 nm and almost equal to the c -axis unit cell height of the YBCO crystal. The spiral growth model explains the growth mechanism of YBCO crystals. The appearance of the macro-step was explained by the perturbation 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° and X-ray topographs also show the single domain crystal has grown. However, the dislocation hollow core was left in the central part along the growth direction.