Chen Jun, Wang Yanming, Xu Wenshuo, Wen Yi, Ryu Gyeong Hee, Grossman Jeffrey C, Warner Jamie H
Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, United Kingdom.
Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
ACS Nano. 2021 Oct 26;15(10):16748-16759. doi: 10.1021/acsnano.1c06736. Epub 2021 Oct 5.
Each 2D material has a distinct structure for its grain boundary and dislocation cores, which is dictated by both the crystal lattice geometry and the elements that participate in bonding. For the class of noble metal dichalcogenides, this has yet to be thoroughly investigated at the atomic scale. Here, we examine the atomic structure of the dislocations and grain boundaries (GBs) in two-dimensional PtSe, using atomic-resolution annular dark field scanning transmission electron microscopy, combined with density functional theory and empirical force field calculations. The PtSe we study adopts the 1T phase in large-area polycrystalline films with numerous planar tilt GB distinct dislocations, including 5|7 and 4|4|8 polygons, in tilt-angle monolayer GBs, with features sharply distinguished from those in 2H-phase TMDs. On the basis of dislocation cores, the GB structures are investigated in terms of pathways of dislocation chain arrangement, dislocation core distributions in different misorientation angles, and 2D strain fields induced. Based on the Frank-Bilby equation, the deduced Burgers vector magnitude is close to the lattice constant of 1T-PtSe, building the quantitative relationship of dislocation spacings and small GB angles. The 30° GBs are most frequently formed as a stitched interface between the armchair and zigzag lattices, constructed by a string of 5|7 dislocations asymmetrically with a small deviation angle. Another special angle GB, mirror twin 60° GB, is also mapped linearly by metal-condensed asymmetric or Se-rich symmetric dislocations. This report gives atomic-level insights into the GBs and dislocations in 1T-phase noble metal TMD PtSe, which is a promising material to underpin extending properties of 2D materials by local structure engineering.
每种二维材料的晶界和位错核心都有独特的结构，这由晶格几何结构和参与键合的元素共同决定。对于贵金属二硫属化物这类材料，尚未在原子尺度上对其进行深入研究。在此，我们使用原子分辨率环形暗场扫描透射电子显微镜，结合密度泛函理论和经验力场计算，研究二维PtSe中位错和晶界的原子结构。我们研究的PtSe在大面积多晶薄膜中采用1T相，具有许多平面倾斜晶界和独特的位错，包括倾斜角单层晶界中的5|7和4|4|8多边形，其特征与2H相过渡金属二硫属化物中的特征明显不同。基于位错核心，从位错链排列途径、不同取向差角度下的位错核心分布以及诱导的二维应变场等方面研究了晶界结构。基于弗兰克 - 比尔比方程，推导出的柏氏矢量大小接近1T - PtSe的晶格常数，建立了位错间距与小晶界角之间的定量关系。30°晶界最常形成为扶手椅型和锯齿型晶格之间的缝合界面，由一串具有小偏差角的不对称5|7位错构成。另一种特殊角度的晶界，即镜面对称孪晶60°晶界，也由金属凝聚不对称或富硒对称位错线性映射。本报告提供了关于1T相贵金属过渡金属二硫属化物PtSe中晶界和位错的原子级见解，PtSe是一种有前途的材料，有望通过局部结构工程扩展二维材料的性能。
