Song Kepeng, Liu Jiakai, Lu Ning, Qi Dongqing, Qin Wei
School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China.
Suzhou Research Institute, Shandong University, Suzhou 215113, China.
Phys Chem Chem Phys. 2022 Mar 16;24(11):6393-6397. doi: 10.1039/d2cp00183g.
Topological defects such as dislocations in crystalline materials usually have major impacts on materials' mechanical, chemical and physical properties. Detailed knowledge of dislocation core structures is essential to understand their impacts on materials' properties. However, compared with imaging of core structures of edge dislocations, direct imaging of a screw dislocation core is challenging from the traditional edge-on direction because the atomic displacements are parallel to the screw dislocation line. Here, a screw dislocation with a Burgers vector 1/2[110] in orthorhombic CsPbBr nanocrystals is directly imaged at the atomic scale with the incident electron beam perpendicular to the dislocation line using aberration-corrected scanning transmission electron microscopy (STEM). The dislocation core is characterized by helical atomic planes along the dislocation line. Quantitative assessments of the change rate of the screw displacements reveal the dislocation line locate at a plane containing Cs and Br atoms. This study reveals the atomic structure of screw dislocation cores in CsPbBr and provides useful information for the understanding of structure-property relations of halide perovskites.
晶体材料中的拓扑缺陷（如位错）通常会对材料的力学、化学和物理性质产生重大影响。对位错核心结构的详细了解对于理解它们对材料性质的影响至关重要。然而，与刃位错核心结构的成像相比，从传统的侧视方向直接成像螺位错核心具有挑战性，因为原子位移与螺位错线平行。在此，使用像差校正扫描透射电子显微镜（STEM），以垂直于位错线的入射电子束在原子尺度上直接成像了正交晶系CsPbBr纳米晶体中具有柏氏矢量1/2[110]的螺位错。位错核心的特征是沿位错线的螺旋原子平面。对螺位错位移变化率的定量评估表明，位错线位于包含Cs和Br原子的平面上。这项研究揭示了CsPbBr中螺位错核心的原子结构，并为理解卤化物钙钛矿的结构-性质关系提供了有用信息。
