A study on the microwave responses of YBCO and TBCCO thin films by coplanar resonator technique

摘要

YBa2CuaO7(YBCO) thin films have been prepped by thermal coevaporation on LaAlO3 (LAO) substrates, and Tl2Ba2CaCu2O8(TBCCO) thin films are synthesized by magnetron sputtering method on LAO substrates. The transition temperature Tc is 90 K for YBCO/LAO and 104K for TBCCO/LAO. Microwave responses of the films are studied systematically by coplanar resonator technique. Energu gaps of the films obtained are △0 = 1.04kBTc for YBCO films and △0 = 0.84kBTc for TBCCO films by analysing the temperature dependence of resonant frequencies of coplanar resonator. Penetration depth at 0K λ0 = 198 nm for YBCO films and λ0 = 200 nm for TBCCO films could also be obtained by using the weak coupling theory and two fluid theory. Results of penetration depth and energy gap confirm the weak coupling properties of the films. In addition, microwave surface resistances Rs of YBCO/LAO and TBCCO/LAO are also investigated by analysing the quality factor and insert loss of the coplanar resonator. Surface resistance of TBCCO/LAO is less than that of YBCO/LAO, so that TBCCO/LAO films may have more potential applications.