A study on the microwave responses of YBCO and TBCCO thin films by coplanar resonator technique
Shi Li-Bin(史力斌)a)b), Wang Yun-Fei(王云飞)a), Ke Yu-Yang(柯于洋)a), Zhang Guo-Hua(张国华)a), Luo Sheng(罗胜)a)†, Zhang Xue-Qiang(张雪强)c), Li Chun-Guang(李春光)c), Li Hong(黎红)c), and He Yu-Sheng(何豫生) c)
a Department of Physics, University of Science and Technology Beijing, Beijing 100083, China; b Department of Physics, Bohai University, Jinzhou 121000, China; c Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
Abstract YBa2Cu3O7(YBCO) thin films have been prepared 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 104 K for TBCCO/LAO. Microwave responses of the films are studied systematically by coplanar resonator technique. Energy gaps of the films obtained are ${\it\Delta}_0=1.04k_{\rm B}T_{\rm c} $ for YBCO films and ${\it\Delta}_0=0.84k_{\rm B}T_{\rm c} $ for TBCCO films by analysing the temperature dependence of resonant frequencies of coplanar resonator. Penetration depth at 0 K $\lambda _0 =198$ nm for YBCO films and $\lambda _0 =200$ 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.
Received: 05 December 2006
Revised: 11 April 2007
Accepted manuscript online:
Fund: Project supported by the
National Natural Science Foundation of China (Grant No
10474121).
Cite this article:
Shi Li-Bin(史力斌), Wang Yun-Fei(王云飞), Ke Yu-Yang(柯于洋), Zhang Guo-Hua(张国华), Luo Sheng(罗胜), Zhang Xue-Qiang(张雪强), Li Chun-Guang(李春光), Li Hong(黎红), and He Yu-Sheng(何豫生) A study on the microwave responses of YBCO and TBCCO thin films by coplanar resonator technique 2007 Chinese Physics 16 3036
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