Strain Mapping of Two-Dimensional Heterostructures with Sub-Picometer Precision

Abstract

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.

References in corpus (6)

• The structure of suspended graphene sheets
• Grains and grain boundaries in highly crystalline monolayer molybdenum disulfide
• High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy
• Chemical assembly of atomically thin transistors and circuits in a large scale
• Sub-Nanometer Channels Embedded in Two-Dimensional Materials
• Coherent Atomically-Thin Superlattices with Engineered Strain

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• Very-High Dynamic Range, 10,000 frames/second Pixel Array Detector for Electron Microscopy
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• Rotational and Dilational Reconstruction in Transition Metal Dichalcogenide Moiré Bilayers
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• Fast Grain Mapping with Sub-Nanometer Resolution Using 4D-STEM with Grain Classification by Principal Component Analysis and Non-Negative Matrix Factorization
• Laser Annealing for Radiatively Broadened MoSe2 grown by Chemical Vapor Deposition
• Nanomechanical strain concentration on a 2D nanobridge within a large suspended bilayer graphene for molecular mass detection
• Defect contrast with 4D-STEM: Understanding crystalline order with virtual detectors and beam modification
• Reconstruction of the interatomic forces from dynamic Scanning Transmission Electron Microscopy data