TwistAngle-Dependent Atomic Reconstruction and MoiréPatterns in Transition Metal Dichalcogenide Heterostructures
Figshare documentation (Figshare (United Kingdom))(2020)
摘要
Van der Waals layered
materials, such as transition metal dichalcogenides
(TMDs), are an exciting class of materials with weak interlayer bonding,
which enables one to create so-called van der Waals heterostructures
(vdWH). One promising attribute of vdWH is the ability to rotate the
layers at arbitrary azimuthal angles relative to one another. Recent
work has shown that control of the twist angle between layers can
have a dramatic effect on TMD vdWH properties, but the twist angle
has been treated solely through the use of rigid-lattice moire
patterns. No atomic reconstruction, that is, any rearrangement of
atoms within the individual layers, has been reported experimentally
to date. Here, we demonstrate that vdWH of MoSe2/WSe2 and MoS2/WS2 at twist angles ≤1°
undergo significant atomic level reconstruction leading to discrete
commensurate domains divided by narrow domain walls, rather than a
smoothly varying rigid-lattice moire pattern as has been assumed
in prior experimental work. Using conductive atomic force microscopy
(CAFM), we show that TMD vdWH at small twist angles exhibit large
domains of constant conductivity. The domains in samples with R-type
stacking are triangular, whereas the domains in samples with H-type
stacking are hexagonal. Transmission electron microscopy provides
additional evidence of atomic reconstruction in MoSe2/WSe2 structures and demonstrates the transition between a rigid-lattice
moire pattern for large angles and atomic reconstruction for
small angles. We use density functional theory to calculate the band
structures of the commensurate reconstructed domains and find that
the modulation of the relative electronic band edges is consistent
with the CAFM results and photoluminescence spectra. The presence
of atomic reconstruction in TMD heterostructures and the observed
impact on nanometer-scale electronic properties provide fundamental
insight into the behavior of this important class of heterostructures.
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关键词
twistangle-dependent
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