High‐Precision Twist‐Controlled Bilayer and Trilayer Graphene

Chen, Xudong; Wei, Xin; Jiang, Wenshuai; Liu, Zhibo; Chen, Yongsheng; Tian, Jianguo

doi:10.1002/adma.201505129

Cited by 96 publications

(105 citation statements)

References 34 publications

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“…Recently, the TBG with a precise rotation angle of 30 • was experimentally realized and its spectrum measured in epitaxially grown samples on top of SiC surface 16 . In addition, similar TBGs have been realized on top of Ni surface 17,18 and also by a transfer method 19 . Moreover, another 30 • -rotated stack of atomic layers have also been realized in graphene on top of BN layer 20 as well as MoSe 2 bilayer system 21 .…”

Section: Introductionmentioning

confidence: 99%

Quasicrystalline electronic states in 30∘ rotated twisted bilayer graphene

2019

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The recently realized bilayer graphene system with a twist angle of 30 • offers a new type of quasicrystal which unites the dodecagonal quasicrystalline nature and graphene's relativistic properties.Here, we introduce a concise theoretical framework that fully respects both the dodecagonal rotational symmetry and the massless Dirac nature, to describe the electronic states of the system. We find that the electronic spectrum consists of resonant states labeled by 12-fold quantized angular momentum, together with the extended relativistic states. The resulting quasi-band structure is composed of the nearly flat bands with spiky peaks in the density of states, where the wave functions exhibit characteristic patterns which fit to the fractal inflations of the quasicrystal tiling. We also demonstrate that the 12-fold resonant states appear as spatially-localized states in a finite-size geometry, which is another hallmark of quasicrystal. The theoretical method introduced here is applicable to a broad class of "extrinsic quasicrystals" composed of a pair of two-dimensional crystals overlaid on top of the other with incommensurate configurations. arXiv:1901.04701v2 [cond-mat.mes-hall]

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Section: Introductionmentioning

confidence: 99%

Quasicrystalline electronic states in 30∘ rotated twisted bilayer graphene

2019

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“…The nonlinear ionizations are almost independent on the initial defects of the target materials. Hence, femtosecond laser ablation is deterministic and reproducible 7 , and almost any material can be machined using a femtosecond laser, including metals 8 , 9 , 10 , semiconductors 11 , 12 , dielectrics 13 , 14 , polymers 15 , two-dimensional materials 16 , 17 , 18 , 19 , 20 , ultrahard materials 21 and biological tissues 22 , 23 . In addition, ionization mechanism can be adjusted by changing femtosecond laser energy and its temporal/spatial distribution to control laser-material interactions 24 .…”

Section: Introductionmentioning

confidence: 99%

Electrons dynamics control by shaping femtosecond laser pulses in micro/nanofabrication: modeling, method, measurement and application

et al. 2017

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During femtosecond laser fabrication, photons are mainly absorbed by electrons, and the subsequent energy transfer from electrons to ions is of picosecond order. Hence, lattice motion is negligible within the femtosecond pulse duration, whereas femtosecond photon-electron interactions dominate the entire fabrication process. Therefore, femtosecond laser fabrication must be improved by controlling localized transient electron dynamics, which poses a challenge for measuring and controlling at the electron level during fabrication processes. Pump-probe spectroscopy presents a viable solution, which can be used to observe electron dynamics during a chemical reaction. In fact, femtosecond pulse durations are shorter than many physical/chemical characteristic times, which permits manipulating, adjusting, or interfering with electron dynamics. Hence, we proposed to control localized transient electron dynamics by temporally or spatially shaping femtosecond pulses, and further to modify localized transient materials properties, and then to adjust material phase change, and eventually to implement a novel fabrication method. This review covers our progresses over the past decade regarding electrons dynamics control (EDC) by shaping femtosecond laser pulses in micro/nanomanufacturing: (1) Theoretical models were developed to prove EDC feasibility and reveal its mechanisms; (2) on the basis of the theoretical predictions, many experiments are conducted to validate our EDC-based femtosecond laser fabrication method. Seven examples are reported, which proves that the proposed method can significantly improve fabrication precision, quality, throughput and repeatability and effectively control micro/nanoscale structures; (3) a multiscale measurement system was proposed and developed to study the fundamentals of EDC from the femtosecond scale to the nanosecond scale and to the millisecond scale; and (4) As an example of practical applications, our method was employed to fabricate some key structures in one of the 16 Chinese National S&T Major Projects, for which electron dynamics were measured using our multiscale measurement system.

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“…This assumption was not unreasonable because AB stacking (interplanar spacing 3.35 Å) is the minimum energy configuration for planar graphene layers and the less stable AA stacking (interplanar spacing 3.53 Å) is not present in pure crystalline graphite2. With the progress in fabricating mono- and multilayer graphene3, unique Moiré patterns45678 are revealed arising from the atomic-resolution transmission electron microscopy (TEM) morphology with rotating angles between graphene planes (i.e., disorderly stacked), and are proved as the signature of disordered graphite. Recently, we have shown that AA’ stacking of graphene planes (where each graphene plane is shifted by 1/2 hexagon from zigzag AA stacking or by 1/4 hexagon from armchair AB stacking) exists, and may be the structure of multi-wall carbon nanotubes (MWNTs) (i.e., helically grown AA’ graphite)910.…”

mentioning

confidence: 99%

The Nature of Metastable AA’ Graphite: Low Dimensional Nano- and Single-Crystalline Forms

Lee

Kim

Hembram

et al. 2016

Sci Rep

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Over the history of carbon, it is generally acknowledged that Bernal AB stacking of the sp2 carbon layers is the unique crystalline form of graphite. The universal graphite structure is synthesized at 2,600~3,000 °C and exhibits a micro-polycrystalline feature. In this paper, we provide evidence for a metastable form of graphite with an AA’ structure. The non-Bernal AA’ allotrope of graphite is synthesized by the thermal- and plasma-treatment of graphene nanopowders at ~1,500 °C. The formation of AA’ bilayer graphene nuclei facilitates the preferred texture growth and results in single-crystal AA’ graphite in the form of nanoribbons (1D) or microplates (2D) of a few nm in thickness. Kinetically controlled AA’ graphite exhibits unique nano- and single-crystalline feature and shows quasi-linear behavior near the K-point of the electronic band structure resulting in anomalous optical and acoustic phonon behavior.

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High‐Precision Twist‐Controlled Bilayer and Trilayer Graphene

Cited by 96 publications

References 34 publications

Quasicrystalline electronic states in 30∘ rotated twisted bilayer graphene

Quasicrystalline electronic states in 30∘ rotated twisted bilayer graphene

Electrons dynamics control by shaping femtosecond laser pulses in micro/nanofabrication: modeling, method, measurement and application

The Nature of Metastable AA’ Graphite: Low Dimensional Nano- and Single-Crystalline Forms

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