We have investigated the influence of the superconducting layer thickness, d, on the structural and transport properties of Co-doped BaFe2As2 films deposited on Fe-buffered MgO substrates by pulsed laser deposition. The superconducting transition temperature and the texture quality of Co-doped BaFe2As2 films improve with increasing d due to a gradual relief of the tensile strain. For d>90 nm an additional 110 textured component of Co-doped BaFe2As2 was observed, which leads to an upward shift in the angular dependent critical current density at H // c. These results indicate that the grain boundaries created by the 110 textured component may contribute to the c-axis pinning.
In the present work we study the growth by pulsed laser deposition of YBa$_2$Cu$_3$O$_{7-δ}$ (YBCO) films on the r-cut sapphire substrates. To improve the matching of the lattice parameters between the substrate and the film we use CeO$_{2}$ buffer layer, recrystallized prior to the deposition of YBCO. The optimal thickness and temperature of recrystallization of the buffer layer is first determined using atomic force microscopy (AFM) and X-ray diffraction. Next, we use the AFM to examine the dependence of YBCO film roughness on the film thickness, and we study the homogeneity of magnetic flux…
Most commercial high-temperature superconducting coated conductors based on ion beam assisted MgO deposited templates use $\mathrm{LaMnO_3}$ (LMO) films as the terminating buffer layer. In contrast, coated conductors based on inclined substrate deposition (ISD)-MgO technology are still produced with homoepitaxial (homoepi)-MgO as the cap layer. In this work we report on the deposition of LMO buffer layers on ISD-MgO/homoepi-MgO by electron beam physical vapor deposition. The growth parameters of textured LMO films were studied systematically and their properties were optimized regarding the cr…
We have grown untwinned YBa$_2$Cu$_3$O$_{7-δ}$ (YBCO) films on (110) MgO substrates that were pre-annealed at high temperature in oxygen atmosphere. The annealing results in surface reconstruction with shallow facets, which induce the suppression of the YBCO twinning domains, and the preferential alignment of the CuO chains along one of the in-plane directions of the substrate. Because of the large mismatch between the in-plane lattice parameters of film and substrate, the strain induced by the MgO into the YBCO layer is strong and very peculiar. The YBCO film is compressed, with respect to th…
The influence of the buffer layer architecture on transport properties for BaFe1.8Co0.2As2 films on technical substrates
在IBAD-MgO/Y $_2$ O $_3$缓冲技术衬底上制备的BaFe $_{1.8}$ Co $_{0.2}$ As $_2$ /Fe双层膜中，观察到正常态下的低电阻和几乎与温度无关的电阻，以及正常-超导转变中的反常峰效应。电阻器网络阵列充分再现了这种效果，假设随着缓冲层厚度的减小，带和膜之间的电导增加。基于此模型，我们评估了这种效应对临界电流密度的影响，并成功地重建了双层膜的超导转变。
Superconductivity in spinel oxide LiTi2O4 epitaxial thin films
LiTi 2 O 4是一种独特的材料，因为它是唯一已知的氧化物尖晶石超导体。虽然体材料研究已经表明超导性可以用Bardeen-Cooper-Schreiffer理论来描述，但是超导性的微观机制还没有完全解决。超导性能对尖晶石晶体结构的各种缺陷的敏感性提供了对这种机制的深入了解。在MgAl 2 O 4、MgO和SrTiO 3单晶衬底上的LiTi 2 O 4外延膜提供了系统地探索晶格应变和微结构无序的影响的模型系统。影响带宽的晶格应变引起超导和正常状态性质的有限变化。微结构无序如反相晶界引起的Ti网络无序可降低临界温度，但Ti网络无序与Mg互扩散相结合对超导态的影响更为显著。厚度相关的运输研究表明，超导体-绝缘体的转变作为膜厚度的函数，而不管晶格应变和微观结构。此外，表面敏感的X射线吸收光谱已确定Ti保留站点对称性和平均价的散装材料，而不管膜厚度。
