物理学报2018，Vol.67Issue(3)：207-215,9.DOI:10.7498/aps.67.20170822
低能离子对高温超导YBa2Cu3O7-δ薄膜的表面改性和机理
Low-energy ion beam mo dified surface property and mechanism of high temperature superconductor YBa2Cu3O7?δ thin film
摘要
Abstract
The interaction between ion beam and solid target is widely used in material modification. For the high tempera-ture superconducting thin film modification, however, earlier experiments show that the samples are accompanied by the degradation in superconducting properties due to the structural damage of materials. In order to improve surface morphologies and superconducting properties of YBa2Cu3O7?δ (YBCO) thin films, we introduce a new ion beam structure modification (ISM) method. Although the ion bombardment time parameter effect is not clear, the related mechanism should be clarified. In this paper, the bombardment processes with duration times of 8 min, 10 min and 12 min are investigated in a vacuum chamber with an Ar+ Kaufman ion source, and the direction between the incident ion beam and the normal of sample is fixed at a certain angle. Surface morphologies and the microstructures of YBCO samples are characterized by scanning electron micrographs and X-ray diffraction patterns, respectively. In the respect of supercon-ducting properties, the critical current density Jc is measured by Jc-scanning test. The results indicate that the needle-like a-axis grains and pores disappear gradually with the increase of the ion bombardment time. In order to characterize the effects of ion beam bombardment time on the internal strain in YBCO thin films, the relationship between the full width at half maximum and the Bragg diffraction angle of YBCO (00l) peak is studied by the William-Hall equation. The results show that the internal strain in YBCO thin film increases with increasing the ion beam bombardment time. At the same time, the critical current density Jc value of the sample after ISM processing increases, which is more than 2.2 times higher than that of the initial sample. The main reason for the increases of critical current density Jc in YBCO thin film is due to the drastic shrink of Cu—O bond caused by the increasing internal strain. Based on the bond contraction pair theory, the shrink of Cu—O bond improves the energy to break Cooper-pairs, and then increases the current carrying capacity of high temperature superconducting YBCO thin film, especially in copper-oxygen (CuO2) plane. The ISM process might be a useful method of markedly improving the surface morphology, meanwhile, the critical current density Jc value also increases in high temperature superconducting YBCO thin film.关键词
钇钡铜氧/离子束表面改性/临界电流密度/化学键收缩配对模型Key words
YBa2Cu3O7−δ/ion beam surface modification/critical current density/bond contraction pair model引用本文复制引用
王三胜,李方,吴晗,张竺立,蒋雯,赵鹏..低能离子对高温超导YBa2Cu3O7-δ薄膜的表面改性和机理[J].物理学报,2018,67(3):207-215,9.基金项目
国家自然科学基金(批准号:61473023)、国家高技术研究发展计划(批准号:2014AA032703)和航天科技创新基金(批准号:10300002012117002)资助的课题.Project supported by the National Natural Science Foundation of China(Grant No. 61473023), the National High Technology Research and Development Program of China(Grant No. 2014AA032703), and the Aerospace Science and Technology Innovation Fund of CASC(Grant No. 10300002012117002). （批准号:61473023）
