A study on the microwave responses of YBCO and TBCCO thin films by coplanar resonator technique
A study on the microwave responses of YBCO and TBCCO thin films by coplanar resonator technique
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DOI：
10.1088/1009-1963/16/10/036
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发表时间：
2007-10
期刊：
影响因子：
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通讯作者：
Li-Bin Shi;Yun-Fei Wang;Yu-Yang Ke;Guo-Hua Zhang;Luo Sheng;Xue-Qiang Zhang;Chun-Guang Li;L. Hong;Yu-Sheng He
中科院分区：
文献类型：
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作者：
Li-Bin Shi;Yun-Fei Wang;Yu-Yang Ke;Guo-Hua Zhang;Luo Sheng;Xue-Qiang Zhang;Chun-Guang Li;L. Hong;Yu-Sheng He
在LaAlO3（LAO）衬底上采用热共蒸发法制备了YBa2Cu3O7（YBCO）薄膜，在LAO衬底上采用磁控溅射法制备了Tl2Ba2CaCu2O8（TBCCO）薄膜。YBCO/LAO的转变温度为90k， TBCCO/LAO的转变温度为104k。利用共面谐振腔技术对薄膜的微波响应进行了系统的研究。通过分析共面谐振腔谐振频率的温度依赖性，得到YBCO薄膜的能隙为Δ0 = 1.04kBTc， TBCCO薄膜的能隙为Δ0 = 0.84kBTc。利用弱耦合理论和双流体理论还可以得到YBCO膜在0 K时的穿透深度λ0 = 198 nm， TBCCO膜在0 K时的穿透深度λ0 = 200 nm。穿透深度和能隙的结果证实了膜的弱耦合特性。此外，通过分析共面谐振腔的质量因数和插入损耗，研究了YBCO/LAO和TBCCO/LAO的微波表面电阻Rs。TBCCO/LAO的表面电阻小于YBCO/LAO，因此TBCCO/LAO薄膜具有更大的应用潜力。
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 is90 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 Δ0 = 1.04kBTc for YBCO films and Δ0 = 0.84kBTc for TBCCO films by analysing the temperature dependence of resonant frequencies of coplanar resonator. Penetration depth at 0 K 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.