Van der Waals heterostructures form a unique class of layered artificial solids in which physical properties can be manipulated through controlled composition, order and relative rotation of adjacent atomic planes. Here we use atomic-resolution transmission electron microscopy to reveal the lattice reconstruction in twisted bilayers of the transition metal dichalcogenides, MoS₂ and WS₂. For twisted 3R bilayers, a tessellated pattern of mirror-reflected triangular 3R domains emerges, separated by a network of partial dislocations for twist angles θ < 2°. The electronic properties of these 3R domains, featuring layer-polarized conduction-band states caused by lack of both inversion and mirror symmetry, appear to be qualitatively different from those of 2H transition metal dichalcogenides. For twisted 2H bilayers, stable 2H domains dominate, with nuclei of a second metastable phase. This appears as a kagome-like pattern at θ ≈ 2°, transitioning at θ → 0 to a hexagonal array of screw dislocations separating large-area 2H domains. Tunnelling measurements show that such reconstruction creates strong piezoelectric textures, opening a new avenue for engineering of 2D material properties.

范德华异质结构形成一类独特的分层人造固体，其中可以通过控制相邻原子平面的组成，顺序和相对旋转来操纵其物理性质。在这里，我们使用原子分辨率的透射电子显微镜揭示了过渡金属二卤化物MoS ₂和WS _2的扭曲双层中的晶格重构。对于扭曲的3R双层，出现了镜面反射的三角形3R域的棋盘格化图案，被扭曲角θ的部分位错网络分隔 <2°。这些3R域的电子性质，由于缺乏反型和镜像对称性而具有层极化的导带状态，在质量上似乎与2H过渡金属二卤化物的电子性质不同。对于扭曲的2H双层，稳定的2H结构域占主导地位，其核具有第二个亚稳相。这表现为在一个戈薇状图案θ 听，说：2°，在过渡θ  →交通0到螺旋位错分离大面积2H域的六边形阵列。隧道测量表明，这种重建会产生强大的压电纹理，从而为2D材料属性的工程设计开辟了新途径。