MgO基片上的YBCO高温超导薄膜生长研究

【作者】 邱旸；

【导师】 李言荣；

【作者基本信息】 电子科技大学 ， 材料物理与化学， 2007， 硕士

【摘要】 大面积双面YBCO高温超导薄膜具有优异的电学性能和微波性能,能够进一步提高微波无源器件的特性,因此受到了科学与工业界的广泛重视。MgO基片具有各向同性的介电常数,而且介质损耗很低,非常适用于微波器件的制作。但是MgO与YBCO晶格失配度较大,并且MgO在空气中容易潮解,这为YBCO薄膜的外延生长带来了困难。本论文针对这些难点,对MgO基片上YBCO薄膜的生长展开了研究,具体工作内容如下:1.研究MgO基片上YBCO薄膜的溅射沉积工艺参数(如基片温度,沉积气氛等)对薄膜结构、形貌和性能的影响。通过对YBCO薄膜微观结构、表面形貌分析和性能分析得到生长YBCO薄膜所需的最优工艺参数为:基片温度为650℃,溅射电流为0.5A×2,溅射气氛为30Pa,氧氩比为1:2。2.试验和改进了多种制备方法,采用YBCO自外延生长和在基片表面增加MgO同质外延层提高了YBCO薄膜的电性能。与常规的沉积方法相比,上述方法制得的YBCO薄膜临界电流密度有一定提高。3、研究基片的高温退火处理工艺对生长的YBCO薄膜的面内外取向和Jc大小的影响。在经过预退火处理的基片上制备的YBCO薄膜性能有显著提高,临界电流密度Jc达2.3MA/cm2,微波表面电阻Rs降低到0.16m?,满足高性能高温超导微波器件对薄膜材料的要求。4、初步探讨了潮湿和干燥空气,以及外加磁场等不同环境中YBCO薄膜的稳定性问题,为微波超导器件的存放环境提供了参考。更多还原

【Abstract】 Large-area double-sided YBCO high temperature superconductor (HTS) thin films with excellent electrical and microwave properties, which can improve the performance of the microwave passive devices, have been paid intensive attention. MgO substrate with isotropic dielectric constant and very low dielectric loss is very suitable for the application of the microwave devices. It is difficult to prepare YBCO film on MgO substrate because of the large lattice mismatch between MgO and YBCO, and the deliquescency of MgO in the air. The growth of YBCO thin film on MgO substrate aiming at these difficult issues was studied in this thesis. The content in detail is as follows:1. The influence of the substrate temperature, and sputtering pressure, etc. on the film structure, surface state and performance has been studied. By analyzing the microstructure, orientation and surface state, optimum process parameters were obtained: substrate temperature being 650℃, sputtering power being 0.5(×2)A, sputtering pressure being 30Pa, and PO2:PAr being 1:2.2. YBCO self-epitaxy method and MgO homogenous epitaxy method were adopted to improve its properties. The critical current density (Jc) of YBCO film was relatively higher than that of YBCO thin film prepared by common sputtering method.3. The improvement of Jc and in-plain and out-of-plain grain orientation of YBCO film had been realised by pre-annealing of MgO substrates. The properties of YBCO films deposited on the annealed substrates were greatly improved, with Jc=2.3MA/cm2, and Rs(microwave resistance)≈0.16m?, which met the requirement of high performance microwave device.4. The stability of YBCO film in different environments was discussed and further suggestion has been given for preserving the films.更多还原