Large‐Area and High‐Quality 2D Transition Metal Telluride

Zhou, Jiadong; Liu, Fucai; Lin, Junhao; Huang, Xiangwei; Xia, Juan; Zhang, Bowei; Zeng, Qingsheng; Wang, Hong; Zhu, Chao; Niu, Lin; Wang, Xuewen; Fu, Wei; Yu, Peng; Chang, Tay Rong; Hsu, Chuang‐Han; Wu, Di; Jeng, Horng Tay; Huang, Yizhong; Lin, Hsin; Shen, Zexiang; Yang, Ciqiu; Lu, Li Syuan; Suenaga, Kazu; Zhou, Wu; Pantelides, Sokrates T.; Liu, Guangtong; Liu, Zheng

doi:10.1002/adma.201603471

Cited by 210 publications

(235 citation statements)

References 38 publications

(68 reference statements)

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“…In Figure b, Raman spectra of the CVD‐synthesized T d ‐ & 2H‐ Mo 0.32 W 0.67 Te 2.01 (blue trace) and T d ‐Mo 0.29 W 0.72 Te 1.99 (red trace) nanosheets together with the CVT‐grown T d ‐Mo 0.29 W 0.71 Te 2.0 bulk crystal (black trace) were compared to characterize their alloy features and phase identifications. For T d ‐Mo 0.29 W 0.71 Te 2.0 bulk crystal (black trace),

A_{1}^{2}

at 74.4 cm −1 (

A_{1}^{2}

), 106.3 cm −1 (

A_{1}^{3}

), 126.3/129.7/132.4 cm −1 (

A_{1}^{4}

), 159.8 cm −1 (

A_{1}^{7}

), 209.1 cm −1 (

A_{1}^{9}

), and 266.4 cm −1 (

A_{1}^{10}

), of which the spectral assignments consist with the earlier reports . Notably, the vibrational pattern of T d ‐Mo 0.29 W 0.72 Te 1.99 nanosheets (red trace) is similar, but has a slight blue shift, to that of T d ‐Mo 0.29 W 0.71 Te 2.0 bulk crystal (black spectra); this blue shift is attributed to the screening of long‐range Coulomb forces in the few‐layered nanosheets .…”

Section: Resultssupporting

confidence: 76%

Phase‐Engineered Weyl Semi‐Metallic Mo_xW_1‐xTe₂ Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

et al. 2019

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The emerging Weyl semi‐metals with robust topological surface states are very promising candidates to rationally develop new‐generation electrocatalysts for dye‐sensitized solar cells (DSSCs). In this study, a chemical vapor deposition (CVD) method to synthesize highly crystalline Weyl semi‐metallic MoxW1‐xTe2 nanocrystals, which are applied for the counter electrode (CE) of DSSCs for the first time, are employed. By controlling the temperature‐dependent phase‐engineered synthesis, the nanocrystal grown at 760 °C exhibits the mixed phases of semiconducting Td‐ & 2H‐Mo0.32W0.67Te2.01 with charge carrier density of (1.20 ± 0.02) × 1019 cm−3; whereas, the nanocrystal synthesized at 820 °C shows a single phase of semi‐metallic Td‐Mo0.29W0.72Te1.99 with much higher carrier density of (1.59 ± 0.04) × 1020 cm−3. In the cyclic voltammetry (CV) analysis over 200 cycles, the MoxW1‐xTe2‐based electrodes show better stability in the I−/I3− electrolyte than a Pt electrode. In DSSC tests, a Td‐Mo0.29W0.72Te1.99‐decorated CE achieves the efficiency (η) of 8.85%, better than those CEs fabricated with Td‐ & 2H‐Mo0.32W0.67Te2.01 (7.81%) and sputtered Pt (8.01%). The electrochemical impedance spectra reveal that the Td‐Mo0.29W0.72Te1.99 electrode possesses low charge‐transfer resistance in electrocatalytic reactions. These exceptional properties make Weyl semi‐metallic Td‐MoxW1‐xTe2 a potential electrode material for a wide variety of electrocatalytic applications.

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A_{1}^{2}

at 74.4 cm −1 (

A_{1}^{2}

), 106.3 cm −1 (

A_{1}^{3}

), 126.3/129.7/132.4 cm −1 (

A_{1}^{4}

), 159.8 cm −1 (

A_{1}^{7}

), 209.1 cm −1 (

A_{1}^{9}

), and 266.4 cm −1 (

A_{1}^{10}

Section: Resultssupporting

confidence: 76%

Phase‐Engineered Weyl Semi‐Metallic Mo_xW_1‐xTe₂ Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

et al. 2019

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“…This has important implications for the band structure of 3D MTe 2 : nearly compensated electron and hole pockets emerge, which encircle Dirac fermions with small masses; these pockets are characterized by a rotating pseudospin with consequences for circular dichroism. Recent progress in the fabrication of few-layer WTe 2 has enabled magnetoresistance measurements that support our theory of electron-hole compensation [94,95]. Our predicted dichroism has not been verified, but should now be possible to observe.…”

Section: Discussionmentioning

confidence: 67%

Topological Nonsymmorphic Metals from Band Inversion

et al. 2016

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We expand the phase diagram of two-dimensional, nonsymmorphic crystals at integer fillings that do not guarantee gaplessness. In addition to the trivial, gapped phase that is expected, we find that band inversion leads to a class of topological, gapless phases. These topological phases are exemplified by the monolayers of MTe 2 (M ¼ W; Mo) if spin-orbit coupling is neglected. We characterize the Dirac band touching of these topological metals by the Wilson loop of the non-Abelian Berry gauge field. Furthermore, we develop a criterion for the proximity of these topological metals to 2D and 3D Z 2 topological insulators when spinorbit coupling is included; our criterion is based on nonsymmorphic symmetry eigenvalues, and may be used to identify topological materials without inversion symmetry. An additional feature of the Dirac cone in monolayer MTe 2 is that it tilts over in a Lifshitz transition to produce electron and hole pockets-a type-II Dirac cone. These pockets, together with the pseudospin structure of the Dirac electrons, suggest a unified, topological explanation for the recently reported, nonsaturating magnetoresistance in WTe 2 , as well as its circular dichroism in photoemission. We complement our analysis and first-principles band structure calculations with an ab-initio-derived tight-binding model for the WTe 2 monolayer.

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“…This was followed with a study on the absorption dichroism in monolayer 1T’-MoTe 2 [27]. Recently a group has shown that growth of 1T’-WTe 2 in monolayer form is possible by CVD [28] but there remains a need for careful investigation of the properties of monolayer flakes as well as a deeper understanding of the process of degradation under ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

Large-area synthesis of high-quality monolayer 1T’-WTe ₂ flakes

et al. 2017

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Large-area growth of monolayer films of the transition metal dichalcogenides is of the utmost importance in this rapidly advancing research area. The mechanical exfoliation method offers high quality monolayer material but it is a problematic approach when applied to materials that are not air stable. One important example is 1T’-WTe2, which in multilayer form is reported to possess a large non saturating magnetoresistance, pressure induced superconductivity, and a weak antilocalization effect, but electrical data for the monolayer is yet to be reported due to its rapid degradation in air. Here we report a reliable and reproducible large-area growth process for obtaining many monolayer 1T’-WTe2 flakes. We confirmed the composition and structure of monolayer 1T’-WTe2 flakes using x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, Raman spectroscopy and aberration corrected transmission electron microscopy. We studied the time dependent degradation of monolayer 1T’-WTe2 under ambient conditions, and we used first-principles calculations to identify reaction with oxygen as the degradation mechanism. Finally we investigated the electrical properties of monolayer 1T’-WTe2 and found metallic conduction at low temperature along with a weak antilocalization effect that is evidence for strong spin–orbit coupling.

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Large‐Area and High‐Quality 2D Transition Metal Telluride

Cited by 210 publications

References 38 publications

Phase‐Engineered Weyl Semi‐Metallic Mo_xW_1‐xTe₂ Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

Phase‐Engineered Weyl Semi‐Metallic Mo_xW_1‐xTe₂ Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

Topological Nonsymmorphic Metals from Band Inversion

Large-area synthesis of high-quality monolayer 1T’-WTe ₂ flakes

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Large‐Area and High‐Quality 2D Transition Metal Telluride

Cited by 210 publications

References 38 publications

Phase‐Engineered Weyl Semi‐Metallic MoxW1‐xTe2 Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

Phase‐Engineered Weyl Semi‐Metallic MoxW1‐xTe2 Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

Topological Nonsymmorphic Metals from Band Inversion

Large-area synthesis of high-quality monolayer 1T’-WTe 2 flakes

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Product

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Phase‐Engineered Weyl Semi‐Metallic Mo_xW_1‐xTe₂ Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

Phase‐Engineered Weyl Semi‐Metallic Mo_xW_1‐xTe₂ Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

Large-area synthesis of high-quality monolayer 1T’-WTe ₂ flakes