亚皮米精度的二维异质结构应变测绘
Strain Mapping of Two-Dimensional Heterostructures with Sub-Picometer Precision
摘要：
下一代原子级薄的器件需要平面内的一维异质结来电连接不同的二维（2D）材料。然而，大多数2D材料之间的晶格失配导致不可避免的应变、位错或波纹，这会强烈影响它们的机械、光学和电子特性。我们已经开发出一种方法来映射二维异质结晶格和应变分布与亚皮米精度，并确定位错和面外波纹。我们收集了衍射图案从一个聚焦电子束的每个真实空间的扫描位置与高速，高动态范围，动量分辨检测器-电子显微镜像素阵列检测器（EMPAD）。得到的四维（4D）相空间数据集包含样品的完整空间分辨晶格信息。通过在二硫化钨（WS 2）和二硒化钨（WSe 2）横向异质结构上使用这种技术，我们在多微米的视场中以0.3 pm的精度绘制了晶格畸变图，同时观察到了负责2D横向外延结构中应变弛豫的位错和波纹。
英文摘要：
Next-generation, atomically thin devices require in-plane, one-dimensional heterojunctions to electrically connect different two-dimensional (2D) materials. However, the lattice mismatch between most 2D materials leads to unavoidable strain, dislocations, or ripples, which can strongly affect their mechanical, optical, and electronic properties. We have developed an approach to map 2D heterojunction lattice and strain profiles with sub-picometer precision and to identify dislocations and out-of-plane ripples. We collected diffraction patterns from a focused electron beam for each real-space scan position with a high-speed, high dynamic range, momentum-resolved detector - the electron microscope pixel array detector (EMPAD). The resulting four-dimensional (4D) phase space datasets contain the full spatially resolved lattice information of the sample. By using this technique on tungsten disulfide (WS2) and tungsten diselenide (WSe2) lateral heterostructures, we have mapped lattice distortions with 0.3 pm precision across multi-micron fields of view and simultaneously observed the dislocations and ripples responsible for strain relaxation in 2D laterally-epitaxial structures.
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