Title :
Large-area YBCO films for microwave applications
Author :
Talvacchio, J. ; Forrester, M.G. ; Gavaler, J.R. ; Braggins, T.T.
Author_Institution :
Westinghouse Sci. & Technol. Center, Pittsburgh, PA, USA
fDate :
3/1/1991 12:00:00 AM
Abstract :
The authors have developed techniques for the in situ deposition of epitaxial YBCO films on 2-in-diameter wafers of LaAlO3(001) or α-Al2O3(11¯02) with an Sr-doped La2CuO4(001) (LSCO) buffer layer. The inductively measured transition temperature varied within the values of 91.1±0.5 K across the surface of the LaAlO3 wafer and 90.7±0.4 K across the buffered sapphire wafer. The epitaxial LSCO buffer layer acted not only as a barrier to diffusion of Al into the YBCO films, but improved the YBCO(005) X-ray rocking curve widths from 4° for films grown on bare sapphire to 1.2° for films on the LSCO-buffered sapphire. The typical buffer-layer thickness was 40 nm, although layers as thin as 4 nm appeared to be equally effective. The transport critical density was greater than 106 A/cm2 at 77 K for films on buffered sapphire. At 8.8 GHz and 4.2 K, the RF surface resistance was lower than that of gold, indicating that the films on sapphire will be useful in large-area UHF applications
Keywords :
X-ray diffraction examination of materials; barium compounds; high-temperature superconductors; superconducting epitaxial layers; superconducting transition temperature; yttrium compounds; 8.8 GHz; 91.1 to 90.7 K; Al2O3; La2CuO4:Sr; LaAlO3; RF surface resistance; YBa2Cu3O7-δ; buffer layer; diffusion; epitaxial; high temperature superconductors; in situ deposition; large area films; large-area UHF applications; microwave applications; transition temperature; transport critical density; Buffer layers; Dielectric constant; Dielectric losses; Dielectric substrates; High temperature superconductors; Lattices; Superconducting films; Surface resistance; Temperature measurement; Yttrium barium copper oxide;
Journal_Title :
Magnetics, IEEE Transactions on
