COMPARISON OF THE SURFACE-MORPHOLOGY AND MICROSTRUCTURE OF IN-SITU AND EX-SITU DERIVED YBA2CU3O7-X THIN-FILMS

The surface morphology and microstructure of in situ and ex situ deriv ed YBa2Cu3O7-x (YBCO) thin films have been investigated. In situ films were deposited by single-target off-axis sputtering and three-target co-sputtering. Ex situ films were derived by metalorganic deposition ( MOD) of trifluoroacetate precursors. Surface defects resulting from mi xed a-axis and c-axis orientation as well as secondary phases have bee n identified in these films. Despite these defects, films with excelle nt electrical properties have been formed. However, defects interfere with film patterning and the fabrication of multi-layered structures. Several secondary phase precipitates have been identified, including C uO, Y2O3, Cu-Ba-O, and YCu2O5. Secondary phases resulting from a lack of stoichiometry can be eliminated by direct composition control in th e MOD and three-target sputtering techniques, and by composition contr ol through the application of an externally applied magnetic field in single-target off-axis sputtering. Secondary phases caused by contamin ation were also identified: Cr-Ba-O in off-axis sputtering, resulting from contamination by the oxidized heater block; and BaSO4 in MOD, res ulting from gas phase impurities. These results suggest that cation co mposition control is not sufficient to prevent the formation of second ary phases and that small levels of contamination may prevent phase-pu re material from being formed.