Title :
Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ and YBa/sub 2/Cu/sub 3/O/sub 7/ films on large area MgO and sapphire substrates for high power microwave and rf applications
Author :
Face, D.W. ; Pellicone, F.M. ; Small, R.J. ; Bao, L. ; Warrington, M.S. ; Wilker, C.
Author_Institution :
DuPont Electron., Wilmington, DE, USA
fDate :
6/1/1999 12:00:00 AM
Abstract :
This paper describes recent work at DuPont to extend the high power microwave performance of YBa/sub 2/Cu/sub 3/O/sub 7/ and Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ high T/sub c/ superconducting (HTS) films on 2 inch diameter MgO and sapphire substrates. The YBa/sub 2/Cu/sub 3/O/sub 7/ films were produced by in-situ off-axis sputtering with radiant substrate heating. The Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films were produced by off-axis sputtering followed by annealing in oxygen and Tl/sub 2/O vapor. The microwave surface resistance and power handling of these films was measured over a wide range of temperature (20 K to 85 K) using an HTS-sapphire resonator technique. At 70 K, the surface resistance of YBa/sub 2/Cu/sub 3/O/sub 7/ films on sapphire remained below 250 /spl mu//spl Omega/ (@8.1 GHz) for microwave surface current densities up to 1.7/spl times/10/sup 6/ A/cm/sup 2/. At 70 K, the surface resistance of Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films on MgO remained below 230 /spl mu//spl Omega/ (@8.1 GHz) with microwave current densities up to 2/spl times/10/sup 6/ A/cm/sup 2/.
Keywords :
barium compounds; calcium compounds; critical current density (superconductivity); high-frequency effects; high-temperature superconductors; sputter deposition; sputtered coatings; superconducting microwave devices; superconducting thin films; surface conductivity; thallium compounds; yttrium compounds; 20 to 85 K; 8.1 GHz; Al/sub 2/O/sub 3/; HTS-sapphire resonator technique; HTSC films; MgO; RF applications; Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/; YBa/sub 2/Cu/sub 3/O/sub 7/; annealing; high power microwave applications; in-situ off-axis sputtering; large area MgO substrate; microwave current densities; microwave surface current densities; microwave surface resistance; power handling; radiant substrate heating; sapphire substrate; Annealing; Current density; Electrical resistance measurement; Electromagnetic heating; High temperature superconductors; Microwave theory and techniques; Sputtering; Superconducting films; Superconducting microwave devices; Surface resistance;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
