Surface resistance of large-area Tl2Ba2CaCu2O8 thin films at microwave and millimeter wave frequencies measured by three noncavity techniques

The surface resistanceR_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_swas found to exhibit a quadratic dependence on frequencyf at 77 K:R_sf^2.0±0.1. The highest-quality films yieldR_s=145±15 at 10 GHz and 77 K. Scanning confocal resonator mapping ofR_sacross a 2-inch (5.1 cm) diameter wafer yielded a base value forR_sof 16±1 m at 77 K and 94.1 GHz (equivalent to 180±10 at 10 GHz) and good uniformity inR_sacross the wafer. HTS-sapphire resonator measurements ofR_sfor fifteen 1.2 cm square parts cut from a 3-inch diameter wafer yieldedR_svalues scaled to 10 GHz of 196±10 at 80 K. Similar values were measured for Tl₂Ba₂CaCu₂O₈ films prepared on both sides of a 2-inch diameter wafer.Rs values at 10 GHz and 80 K of 147–214 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 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.