Molecular Beam Epitaxy of Highly Crystalline MoSe<sub>2</sub> on Hexagonal Boron Nitride

Poh, Sock Mui; Zhao, Xiaoxu; Tan, Sherman Jun Rong; Fu, Deyi; Fei, Wenwen; Chu, Leiqiang; Dan, Jiadong; Zhou, Wu; Pennycook, Stephen J.; Neto, A. H. Castro; Loh, Kian Ping

doi:10.1021/acsnano.8b04037

Cited by 89 publications

(73 citation statements)

References 70 publications

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“…Large‐scale growth of single‐crystalline transition metal dichalcogenide (TMDC) films with a low density of defects is yet to be realized, posing a bottleneck for implementing 2D electronics in industrial applications. To date, most chemical vapor deposition (CVD) grown films are polycrystalline and contain multiple imperfections, such as point defects, line defects, grain boundaries (GBs), stacking faults, and rotational disorder, which limit the carrier mobility, generate carrier traps, and reduce coherence in light emission. The growth of single phase TMDC films is complicated by the intralayer sliding in each monolayer (resulting in polymorphs, as in 1T and 1H) and interlayer sliding in multilayer films (creating different stacking polytypes, for example, 2H and 3R) .…”

Section: Methodsmentioning

confidence: 99%

“…The transition from twisted domain to 2H domain is triggered by the migration of the TGB toward the twisted domain. However, unlike the highly symmetric MTB structure, the TGB consists of nonperiodic arrays of dislocation cores that are composed of 5|7, 4|6, or 6|8‐fold rings . Hence, tracking the TGB migration with atomic precision during the in situ annealing experiment is challenging for bilayer or multilayer films.…”

Section: Methodsmentioning

confidence: 99%

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Healing of Planar Defects in 2D Materials via Grain Boundary Sliding

Zhao

Chen

et al. 2019

Advanced Materials

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carrier traps, and reduce coherence in light emission. The growth of single phase TMDC films is complicated by the intralayer sliding in each monolayer (resulting in polymorphs, as in 1T and 1H) [9,10] and interlayer sliding in multilayer films (creating different stacking polytypes, for example, 2H and 3R). [7,11] The inherent threefold symmetry as well as fluctuations in chemical potential during growth, coupled with the small energy barriers for rotation and translation of the atomic layers, provides many possibilities for freezing-in dislocations and stacking faults.Among the different CVD approaches, van der Waals (vdW) epitaxy has emerged as the most promising approach to grow large-scale highly crystalline TMDC films, although the films are not free of stacking faults. [12] The key to the success of vdW epitaxy lies in the fact that the surface of 2D TMDC has no dangling bonds, thereby relaxing the lattice matching conditions between the two crystals. Nevertheless, our previous studies have shown that the interlayer vdW interaction between two atomic layers is sufficiently strong to align the grains so that stacking configurations with the lowest energy can be attained, [4,7] which has implications for the healing of planar defects.In polycrystalline TMDCs, GBs are intrinsic 1D topological defects which divide the film into a cellular network of Understanding the mechanisms and kinetics of defect annihilations, particularly at the atomic scale, is important for the preparation of highquality crystals for realizing the full potential of 2D transition metal dichalcogenides (TMDCs) in electronics and quantum photonics. Herein, by performing in situ annealing experiments in an atomic resolution scanning transmission electron microscope, it is found that stacking faults and rotational disorders in multilayered 2D crystals can be healed by grain boundary (GB) sliding, which works like a "wiper blade" to correct all metastable phases into thermodynamically stable phases along its trace. The driving force for GB sliding is the gain in interlayer binding energy as the more stable phase grows at the expanse of the metastable ones. Density functional theory calculations show that the correction of 2D stacking faults is triggered by the ejection of Mo atoms in mirror twin boundaries, followed by the collective migrations of 1D GB. The study highlights the role of the often-neglected interlayer interactions for defect repair in 2D materials and shows that exploiting these interactions has significant potential for obtaining large-scale defect-free 2D films. 2D MaterialsLarge-scale growth of single-crystalline transition metal dichalcogenide (TMDC) films with a low density of defects is yet to be realized, posing a bottleneck for implementing 2D electronics in industrial applications. To date, most chemical vapor deposition (CVD) grown films are polycrystalline and contain multiple imperfections, such as point defects, [1,2] line defects, [3] grain boundaries (GBs), [4,5] stacking faults, [6,7] and rotational disorder, ...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Healing of Planar Defects in 2D Materials via Grain Boundary Sliding

Zhao

Chen

et al. 2019

Advanced Materials

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“…In order to move TMD based devices from laboratory studies to industrial circuit-level applications, it is more imperative to develop a scalable synthesis method to achieve high-quality, wafer-scale and continuous film. Thus it is essential to develop reliable and controllable synthetic strategy such as chemical vapor deposition (CVD) [25][26][27][28], molecular beam epitaxy (MBE) [29][30][31], metal-organic CVD (MOCVD) [32,33], and atomic layer deposition (ALD) [34,35]. During the past decade, researchers have made great achievements in the preparation of large-scale and high-quality 2D-TMDs samples via the CVD method, which greatly accelerate their practical application.…”

Section: Introductionmentioning

confidence: 99%

Recent progress in devices and circuits based on wafer-scale transition metal dichalcogenides

Tang

Zhang

Chen

et al. 2019

Sci. China Inf. Sci.

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“…Compared to CVD and other methods, MBE offers great advantages for large‐area layer‐by‐layer growth of highly uniform TMDs by virtue of the precisely controlled molecular beam flux and growth temperature. Intriguingly, endowed by the high formation energy of the 1Tʹ phases and the small lattice mismatches between the superlattices of (4 × 4) MoS 2 and (5 × 5) hBN (+0.98%), (3 × 3) MoSe 2 and (4 × 4) hBN (−1.57%), (3 × 3) WSe 2 and (2 × 2) Al 2 O 3 (+3.84%), van der Waals MBE epitaxy growths of single‐crystal‐like 2H MoS 2 , MoSe 2 and WSe 2 monolayers were established on hBN and sapphire templates . Nevertheless, MoTe 2 is a strain‐sensitive phase change material .…”

mentioning

confidence: 99%

“…At sufficiently high T G , the migration, diffusion and alignment of adsorbed atoms becomes considerable, producing isotropic films with smooth surface. MoS 2 , MoSe 2 and WSe 2 are classic examples of thermodynamics‐limited fractal growth . The phase transformation of 2H → 1Tʹ is very challenging because the formation energy of the 1Tʹ phase is obviously higher than that of the 2H phase; therefore, the concept of two mobilities “low‐temperature nucleation + high‐temperature growth” is widely applied to suppress vertical nucleation and promote lateral growth in MoS 2 (750 + 900 °C) .…”

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confidence: 99%

Molecular Beam Epitaxy Scalable Growth of Wafer‐Scale Continuous Semiconducting Monolayer MoTe₂ on Inert Amorphous Dielectrics

et al. 2019

Advanced Materials

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Transition metal dichalcogenides (TMDs) (MX 2 , M = Mo or W, X = S, Se, or Te) have attracted intense interest for developing ultrascaled electronics and optoelectronics by virtue of their attractive 2D layered structures and unique physical properties that are absent in their bulk counterparts. [1][2][3][4][5] Monolayer semiconducting TMDs show sizable direct bandgaps, quantum confinement effects, large exciton binding energies and effective valley polarizations, which unveils widespread applications in field-effect transistors (FETs), photodetectors, light-emitting diodes, pumped lasers, solar cells, and valleytronic devices. [6][7][8][9][10] More excitingly, their 2D structures offer superior electrostatic controllability and exemptible short-channel effects, rendering TMDs promising candidates for future sub-10 nm complimentary metal-oxide-semiconductor (CMOS) devices. [5,11,12] The applications of exfoliated TMD flakes in building high-performance prototypes of electronics, photonics, and optoelectronics have already been demonstrated. [13][14][15][16] The exfoliated flakes, however, suffer from Monolayer MoTe 2 , with the narrowest direct bandgap of ≈1.1 eV among Mo-and W-based transition metal dichalcogenides, has attracted increasing attention as a promising candidate for applications in novel near-infrared electronics and optoelectronics. Realizing 2D lateral growth is an essential prerequisite for uniform thickness and property control over the large scale, while it is not successful yet. Here, layer-by-layer growth of 2 in. wafer-scale continuous monolayer 2H-MoTe 2 films on inert SiO 2 dielectrics by molecular beam epitaxy is reported. A single-step Mo-flux controlled nucleation and growth process is developed to suppress island growth. Atomically flat 2H-MoTe 2 with 100% monolayer coverage is successfully grown on inert 2 in. SiO 2 /Si wafer, which exhibits highly uniform in-plane structural continuity and excellent phonon-limited carrier transport behavior. The dynamics-controlled growth recipe is also extended to fabricate continuous monolayer 2H-MoTe 2 on atomic-layer-deposited Al 2 O 3 dielectric. With the breakthrough in growth of wafer-scale continuous 2H-MoTe 2 monolayers on device compatible dielectrics, batch fabrication of high-mobility monolayer 2H-MoTe 2 field-effect transistors and the three-level integration of vertically stacked monolayer 2H-MoTe 2 transistor arrays for 3D circuitry are successfully demonstrated. This work provides novel insights into the scalable synthesis of monolayer 2H-MoTe 2 films on universal substrates and paves the way for the ultimate miniaturization of electronics.

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Molecular Beam Epitaxy of Highly Crystalline MoSe₂ on Hexagonal Boron Nitride

Cited by 89 publications

References 70 publications

Healing of Planar Defects in 2D Materials via Grain Boundary Sliding

Healing of Planar Defects in 2D Materials via Grain Boundary Sliding

Recent progress in devices and circuits based on wafer-scale transition metal dichalcogenides

Molecular Beam Epitaxy Scalable Growth of Wafer‐Scale Continuous Semiconducting Monolayer MoTe₂ on Inert Amorphous Dielectrics

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Molecular Beam Epitaxy of Highly Crystalline MoSe2 on Hexagonal Boron Nitride

Cited by 89 publications

References 70 publications

Healing of Planar Defects in 2D Materials via Grain Boundary Sliding

Healing of Planar Defects in 2D Materials via Grain Boundary Sliding

Recent progress in devices and circuits based on wafer-scale transition metal dichalcogenides

Molecular Beam Epitaxy Scalable Growth of Wafer‐Scale Continuous Semiconducting Monolayer MoTe2 on Inert Amorphous Dielectrics

Contact Info

Product

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Molecular Beam Epitaxy of Highly Crystalline MoSe₂ on Hexagonal Boron Nitride

Molecular Beam Epitaxy Scalable Growth of Wafer‐Scale Continuous Semiconducting Monolayer MoTe₂ on Inert Amorphous Dielectrics