K0．8 Fe1．7 SeS超导体内的畴区形貌及三维分布研究

本文利用高角环形暗场像（HAADF）和衍衬像研究了K0．8 Fe1．7 SeS超导样品的超导畴区形貌及三维分布。在[001]带轴下观察到两类形貌的超导畴区，一类畴区尺寸为1μm左右，另一类为由几十纳米大小的小畴区组成的阵列。选区电子衍射和电子能量损失谱结果表明母体区对应Fe空位有序，而超导畴区可能对应K空位有序。STEM-EDS元素Mapping表明超导畴区边缘处K元素含量较多，K0．8 Fe1．7 SeS超导样品中可能至少存在三个相，分别为：K空位有序超导相、畴区外部Fe空位有序基体相以及两种空位有序区的过渡相。在[100]带轴下观察到了超导畴区具有连通性，构建了K0．8 Fe1．7 SeS超导样品中超导畴区的三维分布图。

Morphology and three-dimensional distribution of domains in superconductor K0.8 Fe1.7 SeS

High-angle aunular dark-field （HAADF） imaging and dark-field imaging technologies were employed to study the superconducting domain morphology and its distribution in three dimensions. Two types of domain morphologes are idenfied along the [001] direction： one is the domain with size of about 1 μm; the other is the array of small domain with size of tens of nanometers. Selected area electron diffraction and electron energy-loss spectroscopy indicate that the parent regions correspond to the Fe-vaccany ordering while the superconduting domains may correspond to the K-vacancy ordering. STEM-EDX Mapping experiment shows a K-rich distribution near the boundary of the domains, indicating that there are at least three phases in K0.8 Fe1.7 SeS sample. In addition, observations along the [ 100] direction reveal that the domains are connected, providing the direct evidence for the connectivity of superconducting domains. At last, the shematic of the three-dimensional distribution of domains is established.