Toward Moiré engineering in 2D materials via dislocation theory

Pochet, Pascal; McGuigan, Brian C.; Coraux, Johann; Johnson, Harley T.

doi:10.1016/j.apmt.2017.07.007

Cited by 49 publications

(38 citation statements)

References 38 publications

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“…The observed moiré defect is analogous in appearance to the point defects that interrupt the long-range periodicity in the atomic lattice. Similar point defect-like structure in moiré lattice was also previously observed in other graphitic systems by STM imaging ( 34 – 36 ). For graphene-based moiré lattices that are homogenous with van der Waals interactions primarily bonding the layers, we should view the point defects in the moiré lattice as a local change of the atomic registry between the graphene and hBN atoms, which thus affect the stacking order.…”

Section: Resultssupporting

confidence: 86%

Ultrahigh-resolution scanning microwave impedance microscopy of moiré lattices and superstructures

et al. 2020

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Two-dimensional heterostructures composed of layers with slightly different lattice vectors exhibit new periodic structure known as moiré lattices, which, in turn, can support novel correlated and topological phenomena. Moreover, moiré superstructures can emerge from multiple misaligned moiré lattices or inhomogeneous strain distributions, offering additional degrees of freedom in tailoring electronic structure. High-resolution imaging of the moiré lattices and superstructures is critical for understanding the emerging physics. Here, we report the imaging of moiré lattices and superstructures in graphene-based samples under ambient conditions using an ultrahigh-resolution implementation of scanning microwave impedance microscopy. Although the probe tip has a gross radius of ~100 nm, spatial resolution better than 5 nm is achieved, which allows direct visualization of the structural details in moiré lattices and the composite super-moiré. We also demonstrate artificial synthesis of novel superstructures, including the Kagome moiré arising from the interplay between different layers.

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Section: Resultssupporting

confidence: 86%

Ultrahigh-resolution scanning microwave impedance microscopy of moiré lattices and superstructures

et al. 2020

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“…The origin of the local minimum and saddle-point energy states can be traced to the incommensurability resulting in truncation of the moiré patterns at the edges, and can be conveniently described using a van der Waals dislocation model [22]. As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Rotational stability of twisted bilayer graphene

2020

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Moiré superlattices form in twisted graphene bilayers due to periodic regions of commensurability, but truncation of the moiré patterns affects the rotational stability of finitesized sheets. Here, we report the stepwise untwisting of nanometer-sized bilayer graphene flakes at elevated temperatures, each step corresponding to a potential energy barrier formed by changes to the commensurability between the moiré superlattice and flake size with twist angle. The number of locally-stable energy states and their barrier energies scale with the flake size, allowing twisted graphene flakes of several tens of nanometers to remain thermally stable even at chemical vapor deposition temperatures.

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“…These results aim to provide a thorough understanding of the mechanical response of 2D material interfaces to both in‐plane and out‐of‐plane deformations and ultimately offer direct guidelines for the optimal design of the strain engineering of 2D materials. The readers are also referred to detailed reviews on 2D material interfaces from different perspectives, such as of nanocomposites, tribology, and so on …”

Section: Mechanical Characterizations Of the 2d Material–substrate Inmentioning

confidence: 99%

“…For example, the interface in graphene bilayer and graphene–hBN heterostructure may rotate itself and cause strain in the 2D material lattice, driven by the vdW interaction . Overall, research about 2D material multilayers and heterostructures is still considered to be in its beginnings (as illustrated later) …”

Section: Mechanical Characterizations Of the 2d Material–substrate Inmentioning

confidence: 99%

“…Unconventional superconductivity in so‐called magic‐angle graphene has further excited studies of new physics in slightly twisted 2D multilayers and heterostructures . In these systems, the interface energy strongly couples the strain energy of the 2D material, leading to nanometer‐sized hexagonal domains termed Moiré patterns . The overall electronic and optoelectronic properties may hinge tightly on both the global strain in the layered structures (applied by the strain engineering techniques) and the local energy competition in the Moiré patterns (affected by the lattice mismatch, the twisting angle, and the type of materials) in a complex manner .…”

Section: Applications Challenges and Opportunitiesmentioning

confidence: 99%

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Strain Engineering of 2D Materials: Issues and Opportunities at the Interface

2019

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applications of 2D materials emerging at large strain levels. [8][9][10] Considering difficulties associated with building a microelectromechanical system for straining freestanding 2D materials, [11] 2D materials were often transferred onto a substrate such that the strain can be introduced to the 2D material by controlling the deformation of the bulk substrate. [12] Such fact has led to significant advances in the strategies for straining 2D materials with a film-substrate system, as well as in interface metrologies for the van der Waals (vdW) interaction between the 2D material and its substrate.Here, we first summarize recent experimental achievements on realizing mechanical strain to substrate-supported 2D materials by categorizing the deformation modes of the 2D material-substrate system. These deformation modes include in-plane modes caused by epitaxy, thermal-expansion mismatch, and stretching/compressing the substrate, as well as out-of-plane modes caused by wrinkling and buckling of 2D materials, bulging and poking 2D materials, and transferring 2D materials on a patterned substrate. We then review recent experimental characterizations of the mechanical response of 2D material-substrate interfaces to in-plane shear deformations and out-of-plane delamination. This is not meant to be an all-encompassing analysis of the broad-field topic of strain engineering, but instead, we point out how mechanical deformations are achieved into 2D materials within the film/ substrate system and how the mechanics of interfaces govern these deformation mechanisms. The goal is to deterministically apply both strain magnitude and strain distribution into these atomically thin films and ultimately achieve strain-coupled fundamental physics and chemistry, and exciting applications in a controllable manner. Considering the interdisciplinary nature of research in this field, we also refer the readers to comprehensive reviews from relevant perspectives, including synthesis of emerging 2D materials, characterizations of the strain in 2D materials (especially via the Raman spectroscopy), and applications of mechanically strained 2D materials. [6,13,14] 2D Materials

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Toward Moiré engineering in 2D materials via dislocation theory

Cited by 49 publications

References 38 publications

Ultrahigh-resolution scanning microwave impedance microscopy of moiré lattices and superstructures

Ultrahigh-resolution scanning microwave impedance microscopy of moiré lattices and superstructures

Rotational stability of twisted bilayer graphene

Strain Engineering of 2D Materials: Issues and Opportunities at the Interface

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