Semiconductor to metal transition in MoTe2

Vellinga, M.B.; Jonge, Robert de; Haas, C.

doi:10.1016/0022-4596(70)90085-x

Cited by 112 publications

(94 citation statements)

References 14 publications

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“…• C from the α-phase diamagnetic semiconductor to the β-phase paramagnetic metal 8,9 . MoTe 2 has the smallest direct energy band gap (∼ 1.1 eV) at the K point (hexagonal corner) in the Brillouin zone (BZ) among all semiconducting TMDs, the band gap is similar to the indirect gap (∼ 1.1 eV) of silicon 10,11 .…”

Section: Introductionmentioning

confidence: 99%

Double resonance Raman modes in monolayer and few-layerMoTe2

et al. 2015

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We study the second-order Raman process of mono-and few-layer MoTe2, by combining ab initio density functional perturbation calculations with experimental Raman spectroscopy using 532, 633 and 785 nm excitation lasers. The calculated electronic band structure and the density of states show that the resonance Raman process occurs at the M point in the Brillouin zone, where a strong optical absorption occurs due to a logarithmic Van-Hove singularity of electronic density of states. Double resonance Raman process with inter-valley electron-phonon coupling connects two of the three inequivalent M points in the Brillouin zone, giving rise to second-order Raman peaks due to the M point phonons. The calculated vibrational frequencies of the second-order Raman spectra agree with the observed laser-energy dependent Raman shifts in the experiment.

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Section: Introductionmentioning

confidence: 99%

Double resonance Raman modes in monolayer and few-layerMoTe2

et al. 2015

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“…MoTe2 is an exfoliable transition metal dichalcogenide (TMD) which crystallizes in three symmetries; the semiconducting trigonal-prismatic 2H−phase, the semimetallic 1T ′ monoclinic phase, and the semimetallic orthorhombic T d structure [1][2][3][4] . The 2H−phase displays a band gap of ∼ 1 eV 5 making it appealing for flexible and transparent optoelectronics.…”

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Engineering the Structural and Electronic Phases of MoTe₂ through W Substitution

et al. 2017

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MoTe2 is an exfoliable transition metal dichalcogenide (TMD) which crystallizes in three symmetries; the semiconducting trigonal-prismatic 2H−phase, the semimetallic 1T ′ monoclinic phase, and the semimetallic orthorhombic T d structure 1-4 . The 2H−phase displays a band gap of ∼ 1 eV 5 making it appealing for flexible and transparent optoelectronics. The T d−phase is predicted to possess unique topological properties 6-9 which might lead to topologically protected non-dissipative transport channels 9 . Recently, it was argued that it is possible to locally induce phasetransformations in TMDs 3,10,11,14 , through chemical doping 12 , local heating 13 , or electric-field 14,15 to achieve ohmic contacts or to induce useful functionalities such as electronic phase-change memory elements 11 . The combination of semiconducting and topological elements based upon the same compound, might produce a new generation of high performance, low dissipation optoelectronic elements. Here, we show that it is possible to engineer the phases of MoTe2 through W substitution by unveiling the phase-diagram of the Mo1−xWxTe2 solid solution which displays a semiconducting to semimetallic transition as a function of x. We find that only ∼ 8 % of W stabilizes the T d−phase at room temperature. Photoemission spectroscopy, indicates that this phase possesses a Fermi surface akin to that of WTe2 16 .The properties of semiconducting and of semimetallic MoTe 2 are of fundamental interest in their own right, but are also for their potential technological relevance. In the mono-or few-layer limit it is a direct-gap semiconductor, while the bulk has an indirect bandgap 5,17,18 of ∼ 1 eV. The size of the gap is similar to that of Si, making 2H−MoTe 2 particularly appealing for both purely electronic devices 19,20 and optoelectronic applications 21 . Moreover, the existence of different phases opens up the possibility for many novel devices and architectures. For example, controlled conversion of the 1T ′ −MoTe 2 phase to the 2H−phase, as recently reported 22 , could

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“…MoTe2 is one of the few TMDCs in that it stabilizes both semiconducting and metallic polytypes, transitions between which can be further controlled by temperature, alloying, strain, and electrostatic gating [4][5][6][7][8][9][10]. 1T-MoTe2 is unstable, however-distortion of in-plane bonds gives rise to an enlarged monoclinic unit cell ( or 1T' phase) at room temperature [11].…”

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Dimensionality-driven orthorhombic MoTe2 at room temperature

Zhong

Kim

et al. 2018

Phys. Rev. B

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Abstract:We use a combination of Raman spectroscopy and transport measurements to study thin flakes of the type-II Weyl semimetal candidate MoTe2 protected from oxidation. In contrast to bulk crystals, which undergo a phase transition from monoclinic to the inversion symmetry breaking, orthorhombic phase below ~250 K, we find that in moderately thin samples below ~12 nm, a single orthorhombic phase exists up to and beyond room temperature. This could be due to the effect of c-axis confinement, which lowers the energy of an out-of-plane hole band and stabilizes the orthorhombic structure. Our results suggest that Weyl nodes, predicated upon inversion symmetry breaking, may be observed in thin MoTe2 at room temperature. Main text:

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Semiconductor to metal transition in MoTe2

Cited by 112 publications

References 14 publications

Double resonance Raman modes in monolayer and few-layerMoTe2

Double resonance Raman modes in monolayer and few-layerMoTe2

Engineering the Structural and Electronic Phases of MoTe₂ through W Substitution

Dimensionality-driven orthorhombic MoTe2 at room temperature

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Semiconductor to metal transition in MoTe2

Cited by 112 publications

References 14 publications

Double resonance Raman modes in monolayer and few-layerMoTe2

Double resonance Raman modes in monolayer and few-layerMoTe2

Engineering the Structural and Electronic Phases of MoTe2 through W Substitution

Dimensionality-driven orthorhombic MoTe2 at room temperature

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Engineering the Structural and Electronic Phases of MoTe₂ through W Substitution