TL2BA2CACU2O8 FILMS WITH VERY LOW MICROWAVE SURFACE-RESISTANCE UP TO 95 K

Very low surface resistance Tl2Ba2CaCu2O8 films of thickness 1.0-mu-m on (100) LaAlO3 were fabricated and characterized. The films are highly c-axis oriented (x-ray diffraction rocking curve full width half maximum of 0.68-degrees) with good in-plane epitaxy with respect to the substrate. The T(c) of the films was 107.6 +/- 0.5 K as measured by ac magnetic susceptibility. The surface resistance at 10 GHz was measured with the parallel plate resonator technique and found to be 23 +/- 5-mu-OMEGA at 4.2 K, 130 +/- 20-mu-OMEGA at 77 K, and 300 +/- 60-mu-OMEGA at 95 K. Using a 20 GHz TE011 end-wall replacement copper cavity, the surface resistance was found to be comparable to that of copper, about 18 m-OMEGA, at 104 +/- 1 K. The surface resistance of the films is significantly lower than that of all films reported to date at temperatures above 70 K and only slightly higher than the best high-temperature superconductor films reported to date at 4.2 K.