Stacking fault induced symmetry breaking in van der Waals nanowires
Sutter, Eli; Komsa, Hannu-Pekka; Puretzky, Alexander A.; Unocic, Raymond R.; Sutter, Peter (2022-11-22)
ACS Nano 2022, 16, 12, 21199–21207
This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano, copyright © 2022 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsnano.2c09172.
https://rightsstatements.org/vocab/InC/1.0/
https://urn.fi/URN:NBN:fi-fe2023032733274
Tiivistelmä
Abstract
While traditional ferroelectrics are based on polar crystals in bulk or thin film form, two-dimensional and layered materials can support mechanisms for symmetry breaking between centrosymmetric building blocks, e.g., by creating low-symmetry interfaces in van der Waals stacks. Here, we introduce an approach toward symmetry breaking in van der Waals crystals that relies on the spontaneous incorporation of stacking faults in a nonpolar bulk layer sequence. The concept is realized in nanowires consisting of Se-rich group IV monochalcogenide (GeSe1–xSₓ) alloys, obtained by vapor–liquid–solid growth. The single crystalline wires adopt a layered structure in which the nonpolar A-B bulk stacking along the nanowire axis is interrupted by single-layer stacking faults with local A-A′ stacking. Density functional theory explains this behavior by a reduced stacking fault formation energy in GeSe (or Se-rich GeSe1–xSₓ alloys). Computations demonstrate that, similar to monochalcogenide monolayers, the inserted A-layers should show a spontaneous electric polarization with a switching barrier consistent with a Curie temperature above room temperature. Second-harmonic generation signals are consistent with a variable density of stacking faults along the wires. Our results point to possible routes for designing ferroelectrics via the layer stacking in van der Waals crystals.
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