Structural and superconducting characteristics of YBa2Cu3O7 films grown by fluorine-free metal-organic deposition route
Structural and superconducting characteristics of YBa2Cu3O7 films grown by fluorine-free metal-organic deposition route
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DOI：
10.1016/j.actamat.2017.11.050
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发表时间：
2018-02
期刊：
影响因子：
9.4
通讯作者：
Yue Zhao;Jingyuan Chu;T. Qureishy;Wei Wu;Zhiwei Zhang;P. Mikheenko;T. Johansen;J. Grivel
中科院分区：
文献类型：
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作者：
Yue Zhao;Jingyuan Chu;T. Qureishy;Wei Wu;Zhiwei Zhang;P. Mikheenko;T. Johansen;J. Grivel
利用x射线互反空间映射（RSM）、透射电子显微镜（TEM）和磁光成像（MO）等手段研究了无氟金属有机沉积（FF-MOD）技术在laalo3单晶（LAO）衬底上沉积的YBa2Cu3O7（YBCO）薄膜的微观结构和超导性能。结合x射线衍射和TEM截面分析，发现FF-MOD YBCO薄膜的主要缺陷是层错，即YBa2Cu4Oxintergrowths和ab-plane孪晶。由于与瞬态液相相关的高度外延生长机制，在FF-YBCO薄膜中也继承了LAO孪晶衬底结构。含有平行于c轴位错的低密度平面缺陷导致MO图像中观察到条纹图案。相比之下，低氟（LF） MOD薄膜在平面上呈现纹理马赛克分布，并且受下方LAO孪晶的影响很小，这意味着严重的结构紊乱很可能与大量小角度晶界有关。此外，通过XRDθ−2θ扫描在LF-MOD薄膜中检测到更高密度的层错。在层错与YBCO基体交界处形成的部分位错作为强的线状（或点状）钉住中心。这些结构特征与低氟mod薄膜具有较好的超导性能，特别是在77 K外磁场下的超导性能是一致的。这项工作为深入了解MOD YBCO薄膜的微观结构与超导性之间的关系提供了一个深入的见解。
Microstructure and superconducting performance of YBa2Cu3O7(YBCO) films deposited on LaAlO3single crystal (LAO) substrates by a fluorine-free metal-organic deposition (FF-MOD) technique, have been studied by means of X-ray reciprocal space mapping (RSM), cross-sectional transmission electron microscopy (TEM) and magneto-optical (MO) imaging. Combining the X-ray diffraction and the TEM cross-sectional analysis, it is revealed that stacking faults, i.e. YBa2Cu4Oxintergrowths, andab-plane twins are main defects in the FF-MOD YBCO films. Due to the highly epitaxial growth mechanism related to transient liquid phase, the LAO twinned substrate structure is also inherited in the FF-YBCO films. The low-density planar defects containing dislocations parallel toc-axis result in stripy patterns observed in the MO images. For comparison, the low-fluorine (LF) MOD film show a texture mosaic spread in theabplane and is little influenced by the LAO twinning underneath, implying the severe structural disorder most likely associated with the large amount of small-angle grain boundaries. Moreover, the higher density of stacking faults was also detected by XRDθ−2θscan in the LF-MOD film. It is suggested that associated partial dislocations formed at the boundary between the stacking faults and YBCO matrix act as strong linear (or dot) pinning centers. These structural characteristics are well in line with the better superconducting performance of the low fluorine-MOD film, in particular under external magnetic field at 77 K. This work offers an in-depth insight into the correlation between the microstructure and superconductivity in the MOD YBCO films.