高T_c超导薄膜微波表面电阻的测量  

THE MEASUREMENT OF THE SURFACE RESISTANCE OF HIGH T_c SUPERCONDUCTING THIN FILM

作　　者：伍瑞新[1] 钱珉[1] 吴培亨[1] 杨森祖[1] 孙志坚 郭大元[1] 

机构地区：[1]南京大学信息物理系

出　　处：《南京大学学报（自然科学版）》1994年第3期451-457,共7页Journal of Nanjing University（Natural Science）

基　　金：国家超导技术联合开发中心资助

摘　　要：根据电磁场理论，求解了在矩型波导中载有超导样品时反射系数和透射系数的严格表达式．在２ｃｍ波段上，用微波传输法测量了ＹＢＣＯ超导薄膜的微波表面电阻．测量结果表明：微波传输法是测量高温超导薄膜表面电阻的一种可行方案．文中还对测量结果及误差作了定性分析．Generally there are two approaches to microwave charaCterization of new materials:resonant methods and transmission methods. The resonant method extracts the surface resistance R3 and λK from the quality factor and resonant frequency of a resonating structure.On the other hand, the direct transmission method gives the complex conductivity c of the film from the transmission coefficient S21 through the structure. Microwavetransmission measurement provides a simple and direct diagnostic method for charactetizing and evaluating high Tc films.Based on the el6Ctromagnetic theory, the exact expression of the transmission coefficient S21 and reflection coefficient S11 and its approximation is studied in the paper when the film samples are put into a rectangular waveguide.In the 2cm wave band, the transmission property of the sample is measured by the HP8510 vector network analyzer. The sample is deposited on the LaAlO3 by means of magnetron sputtering method. The microwave surface resistance and penetrating depth of the sample is calculated from the parameter S21 measured. The sudden change of the S21 is observed in the vicinity of the temperature Tc. The cylinder cavity is also used to evaluate the Rs. Experiment results show that the Rs obtained by the transmission method is greater than that of the cavity methods. The results also show that the transmission method is suitable for the high Tc superconducting thin films.The effect of the measurement error of S21 to the Rs and λL is analyzed by the numerical method. It shows that the accuracy of the phase measurement of S21 is the most important factor. Since the measurement is carried out under lower temperatures, the calibration paramaters and the connectors of the system will affect the measurement of Rs and λL directly.

关 键 词：超导薄膜 表面电阻 微波传输法 

分 类 号：O484.5[理学—固体物理]