STRUCTURAL-PROPERTIES OF ZN-SUBSTITUTED EPITAXIAL YBA2CU3O7-DELTA

We optimized the deposition of YBa2(Cu1-xZnx)(3)O-7-delta thin-films u sing inverted cylindrical magnetron sputtering and report here a detai led structural study, especially in relation to crystal growth, associ ated surface morphology, Y2O3 precipitation and other secondary phases important for flux pinning. We find that the epitaxial quality of the Zn-substituted YBa2Cu3O7-delta films is decreased compared with high- quality pure YBa2Cu3O7-delta films prepared under identical conditions . The pure films have smoother surfaces, while those of Zn-substituted films contain pinholes and outgrowths. Secondary phases and a-axis gr ains were observed in the Zn-substituted films. Y2O3 precipitates with typical dimensions of 50-100 Angstrom have been found in both pure an d Zn-substituted samples. However, their density of about 10(23) m(-3) , observed in the pure films, is significantly reduced in the Zn-subst ituted films when increasing the Zn concentration up to 4%.