Grain boundaries (GBs) are significant microstructures that dominate properties of polycrystalline two-dimensional (2D) materials. Low-symmetry rhenium disulfide monolayers provide an ideal platform to investigate diverse configurations of GBs and their orientation-dependent characteristics. Here, we utilize the preferential deposition of platinum-based nanoparticles on grain edges to rapidly locate nanoscale-wide overlapping GBs during microscopic-scale observation. Atomic-resolution investigations by aberration-corrected annular dark-field scanning transmission electron microscopy reveal diverse overlapping GBs constructed by parallel grains with transversal displacement. They prefer to align along several primary lattice directions with different interlayer atomic registries. Calculations show that the electronic band structures of overlapping GBs are strongly direction dependent, suggesting their potential in tunable electronic and photonic devices. Incommensurate overlapping GBs formed by quasi-parallel grains with ultrasmall twist angles are also observed. These results unveil the rich polymorphism of GBs and new opportunities to tailor properties of anisotropic 2D materials via GB engineering.

晶界（GBs）是支配多晶二维（2D）材料性能的重要微结构。低对称性的二硫化rh单分子膜为研究GBs的各种构型及其取向依赖性特性提供了理想的平台。在这里，我们利用在晶粒边缘的铂基纳米颗粒的优先沉积来在微观尺度观察过程中快速定位纳米范围的重叠GBs。通过像差校正环形暗场扫描透射电子显微镜进行的原子分辨率研究表明，由具有横向位移的平行晶粒构成的各种重叠GBs。他们更喜欢沿着几个主晶格方向与不同的层间原子注册表对齐。计算表明，重叠GB的电子能带结构与方向密切相关，表明它们在可调电子和光子器件中的潜力。还观察到由具有超小扭转角的准平行晶粒形成的不相称的重叠GB。这些结果揭示了GB的丰富多态性，以及通过GB工程定制各向异性2D材料属性的新机会。