LASER-ABLATED YBCO THIN-FILMS - RELATIONS BETWEEN STRUCTURAL AND ELECTRICAL-PROPERTIES

YBCO thin films were prepared by laser ablation with a KrF-excimer las er (248 nm) on (100) SrTiO3-substrates. The aim of this work was to ge t smooth YBCO films with good superconducting properties for use in si ngle-layer or multilayer Josephson elements. To study the relations be tween electrical and structural properties the influence of ablation p arameters like oxygen partial pressure (P(O2)), substrate temperature (T(s)) and target to substrate distance (d) were investigated. To anal yse the films X-ray diffraction, Rutherford backscattering (RBS) and S canning electron microscopy (SEM) were used.We found a strong reproduc ible correlation between the position of the samples in the p(O2)-T(s) -diagram and their structural and electrical properties like c-axis or ientation (FWHM of best samples < 0, 15-degrees), c-axis length, outgr owth density, critical temperature (T(Coff), for R=0) and current dens ity at 77 K. The surface morphology strong correlates to the investiga ted parameters. In a parameter region of p(O2) approximately 70 Pa, T( s) approximately 720-degrees-C and d=4 cm we found outgrowth free smoo th films with good superconducting properties. The results on single f ilms were used to produce multilayer systems of YBCO-SrTiO3-YBCO on (1 00) SrTiO3-substrates.