期刊
ACS NANO
卷 16, 期 12, 页码 21199-21207出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.2c09172
关键词
Layered crystals; germanium selenide; germanium sulfide; alloy; planar defects; electron microscopy; van der Waals stacking
类别
资金
- National Science Foundation, Division of Materials Research, Solid State and Materials Chemistry Program [2025298]
- National Science Foundation under Award ECCS
- [DMR-1904843]
- Div Of Electrical, Commun & Cyber Sys
- Directorate For Engineering [2025298] Funding Source: National Science Foundation
Breaking symmetry in van der Waals crystals through layer stacking offers a promising approach for designing new ferroelectric materials.
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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