Direct observation of vortex structure in a high T-c YBa2Cu3O7-y thin filmby bitter decoration method

The Bitter decoration technique is one of the most powerful techniques to s tudy the vortex structure of superconductor. We report the observation of v ortex: structure in a high T-c YBa2 Cu-3 O7-y (YBCO) thin film by Bitter de coration method. The image of vortex structure was monitored by SEM, AFM an d high resolution optical microscope. For magnetic field about 4-6mT,a vort ex structure is seen. The vortex image varied with changing magnetic field. As compared with the vortex image of a Bi2Sr2CaCu2O8+y Single crystal, the observed image appeared to be more randomly distributed.