Imaging domains and defects in the stacking of few-layer and twisted CrI<sub>3</sub>
ORAL
Abstract
Different lateral shifts of the stacked monolayers in CrI3 lead to different magnetic ground states, with a rhombohedral-symmetry stacking resulting in ferromagnetic layer ordering, and a monoclinic-symmetry stacking leading to antiferromagnetic layer ordering. Here we explore the structural arrangements found as the CrI3 thickness is systematically reduced to the monolayer limit using 4D-STEM electron diffraction and atomic resolution imaging. We find that CrI3 flakes from bilayer to 50 nanometer thickness remain in a monoclinic stacking when cooled to 95 K. However, the monoclinic group allows for multiple variants -- arising from 120 degree stacking rotations both in-layer and between neighboring CrI3 layers -- and we observe a rich assortment of stacking orders and domains, as well as moirés. We show that these stacking rotations can change as a function of temperature. The observed vertical superposition of monoclinic variants in few-layer to bulk CrI3 flakes may present as an overall three-fold symmetry to macroscopic-averaged measurement, but can be recognized by atomic resolution imaging.
*Research supported by PARADIM DMR-1539918, AFOSR MURI FA9550-18-1-0480, CCMR DMR-1719875.
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Presenters
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Ariana Ray
- School of Applied and Engineering Physics, Cornell University
- Physics, Cornell University