1 research outputs found
Strain Mapping of Two-Dimensional Heterostructures with Subpicometer Precision
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 subpicometer precision and the ability 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 data sets contain the full spatially resolved lattice
information on the sample. By using this technique on tungsten disulfide
(WS<sub>2</sub>) and tungsten diselenide (WSe<sub>2</sub>) lateral
heterostructures, we have mapped lattice distortions with 0.3 pm precision
across multimicron fields of view and simultaneously observed the
dislocations and ripples responsible for strain relaxation in 2D laterally
epitaxial structures