超导Tl2Ba2CaCu2O8+x 薄膜的太赫兹复电导率的提取

采用低温太赫兹时域光谱系统, 测试了高温超导 Tl2Ba2CaCu2O8+x 薄膜的太赫兹透射谱, 并提取了它在不同温度下的太赫兹电导率. 研究过程中发现提取后的参数存在电导率随频率波动大、与理论值偏差较大等问题.通过对基片厚度和太赫兹波入射角度的误差对高温超导薄膜电导率的影响进行了分析, 结果表明导致数据波动大是由于基片厚度的偏差引起的. 针对厚度差的影响, 一种矫正方法被提出, 通过对厚度的修正, 提高了数据提取的质量.     

Erratum to“Fabrication of Tl2Ba2CaCu2O8 superconducting films without thallium pellets

The rocking curve of Tl-2212 thin films in Fig.2 of our original paper[1]should be replaced with the following new one.Accordingly,in the fifth paragraph of Section 3 of the original paper,the statement“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.24°”should be“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.42°”.     

Fabrication of Tl_2Ba_2CaCu_2O_8 superconducting films without thallium pellets

A new improved two-step method in fabricating Tl_2Ba_2 CaCu_2O_8(Tl-2212) thin films is presented in this paper. In the first process of dc magnetron sputtering, the thallium content in the precursor film is largely increased by adjusting the ratio of thallium in the sputtering targets. After the second annealing process in the absence of additional thallium pellets or powder source, high-quality Tl-2212 thin films can be obtained. The proper content of thallium in the precursor film provides a relatively stable atmosphere to guarantee the growth of Tl-2212 film. This method avoids the repeated production of the thallium pellets in the post-annealing process, the repeatability and controllability of the experiment are greatly improved. X-ray diffraction(XRD) scans show that all of the sharp peaks of the sample films can be assigned to the(00 l) peaks of Tl-2212 phase. The highest superconducting critical temperature(Tc) of the films is 105 K and the critical current density(Jc) can achieve 1.93 MA/cm2 in zero magnetic field at 77 K for a 600 nm film.     

Growth of TlBa_2Ca_2Cu_3O_9 Epitaxial Thin Films by Two-Step Method in Argon

TlBa_2 Ca_2 Cu_3 O_9(Tl-1223) films have promising applications due to their high critical temperature and strong magnetic flux pinning. Nevertheless, the preparation of pure phase Tl-1223 film is still a challenge. We successfully fabricate Tl-1223 thin films on LaAlO_3(001) substrates using dc magnetic sputtering and a post annealing two-step method in argon atmosphere. The crystallization temperature of Tl-1223 films in argon is reduced by 100℃ compared to that in oxygen. This greatly reduces the volatilization of Tl and improves the surface morphology of films. The lower annealing temperature can effectively improve the repeatability of the Tl-1223 film preparation. In addition, pure Tl-1223 phase can be obtained in a broad temperature zone,from 790℃ to 830℃. In our study, the films show homogenous and dense surface morphology using the presented method. The best critical temperature of Tl-1223 films is characterized to be 110 K, and the critical current J_c(77 K, 0 T) is up to 2.13 × 106 A/cm~2.