摘要:
Two-dimensional (2D) materials are among the most promising candidates for next-generation electronics due to their atomic thinness, allowing for flexible transparent electronics and ultimate length scaling. While 2D materials achieve the thinnest possible devices, high-quality stitching over lateral dimensions is also necessary. We reported the direct synthesis of MoS2 channels embedded within WSe2 monolayers forming dislocation-free lateral hetero-interfaces. The electronic band structure of these channels offers the promise of carrier confinement in a direct-gap material and charge separation needed to access the ultimate length scales necessary for future electronic applications. To provide the lattice information of these lateral heterojunctions over a large field of view, we developed an approach by collecting diffraction patterns from a focused electron beam for each scan position with an electron microscope pixel array detector (EMPAD). The resulting 4D datasets contain the full spatially resolved lattice information of the sample. By using this technique on WS2 and 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.

Reference:
Y. Han*, M. Li*, G. Jung*, M. A. Marsalis, Z. Qin, M. J. Buehler, L. Li, D. A. Muller, “Sub-nanometer Channels Embedded in Two-Dimensional Materials,” Nature Materials, doi:10.1038/nmat5038 (2017)

Y. Han, S. Xie, K. Nguyen, M. Cao, M.W. Tate, P. Purohit, S. M. Grunner J. Park, D. A. Muller, “Picometer-Precision Strain Mapping of Two-Dimensional Heterostructures using an Electron Microscopy Pixel Array Detector (EMPAD),” Microscopy and Microanalysis, 23 (S1), 438-439 (2017)