SURFACE-RESISTANCE OF LARGE-AREA TL2BA2CACU2O8 THIN-FILMS AT MICROWAVE AND MILLIMETER-WAVE FREQUENCIES MEASURED BY 3 NONCAVITY TECHNIQUES

The surface resistance R(s) of Tl2Ba2CaCu2O8 films fabricated on LaAlO3 wafers up to 3 inches (7.6 cm) in diameter through a post-deposition anneal process was measured over the frequency range 5.55-94.1 GHz by the following techniques: 5.55 and 27.5 GHz high-temperature superconductor (HTS) sapphire resonators, 10 GHz parallel plate resonator, and 94.1 GHz scanning confocal resonator. R(s) was found to exhibit a quadratic dependence on frequency f at 77 K: R(s) is-proportional-to f2.0+/-0.1. The highest-quality films yield R(s) = 145 +/- 15 muOMEGA at 10 GHz and 77 K. Scanning confocal resonator mapping of R(s) across a 2-inch (5.1 cm) diameter wafer yielded a base value for R(s) of 16 +/- 1 mOMEGA at 77 K and 94.1 GHz (equivalent to 180 +/- 10 muOMEGA at 10 GHz) and good uniformity in R(s) across the wafer. HTS-sapphire resonator measurements of R(s) for fifteen 1.2 cm square parts cut from a 3-inch diameter wafer yielded R(s) values scaled to 10 GHz of 196 +/- 10 muOMEGA at 80 K. Similar values were measured for Tl2Ba2CaCu2O8 films prepared on both sides of a 2-inch diameter wafer. R(s) values at 10 GHz and 80 K of 147-214 muOMEGA were maintained over the course of 40 independent and successive deposition runs and corresponding anneals under nominally identical film fabrication conditions. Surface resistance at 5.55 GHz remained below 80 muOMEGA for maximum rf magnetic fields up to 85 Oe at 4.2 K and 7 Oe at 80 K, respectively. Results are compared with predictions of the two-fluid model. The relative advantages and disadvantages of the different techniques for measuring surface resistance are discussed.