The structural phases and vibrational properties of Mo
 1−x
 W
 x
 Te
 2
 alloys

Oliver, Sean M.; Beams, Ryan; Krylyuk, Sergiy; Kalish, Irina; Singh, Arunima K.; Bruma, Alina; Tavazza, Francesca; Joshi, Jaydeep; Stone, Iris R.; Stranick, Stephan J.; Davydov, Albert V.; Vora, Patrick M.

doi:10.1088/2053-1583/aa7a32

Cited by 71 publications

(54 citation statements)

References 51 publications

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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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confidence: 99%

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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confidence: 99%

Dimensionality-driven orthorhombic MoTe2 at room temperature

Zhong

Kim

et al. 2018

Phys. Rev. B

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“…As previously discussed, investigations into the kinetics of phase transitions in monolayer MoTe 2 and other monolayer materials are nascent and much remains unknown. Experimental studies of thermal phase transitions in MoTe 2 have been reported to occur on timescales of several hours at high temperatures, 12,14 while other reports suggest that the kinetics can occur on timescales of minutes or less at ambient temperatures and below. 16,18 The large variability in these reports suggests that there is potential to engineer the kinetics of these phase transitions to achieve desired electronic or other device timescales.…”

Section: Discussionmentioning

confidence: 99%

“…4,5 The fast and reversible phase transition in Ge 2 Sb 2 Te 5 alloys can be achieved by Joule heating, 5 and this process can be employed in nonvolatile phase-change memory with lower programming voltages and higher memory densities than mainstream nonvolatile memory technologies. 2,3,6,7 Some layered and two-dimensional (2D) materials including MoTe 2 have been reported or predicted to exhibit structural phase changes during chemical processes, 8,9 temperature changes, [10][11][12][13][14] and tensile strains. 15,16 Some single layer transition metal dichalcogenide (TMD) monolayers, including monolayer MoTe 2 , can exist in a semiconducting trigonal prismatic state found in the bulk 2H structure, a semimetallic distorted octahedral state found in the bulk 1T′ monoclinic and orthorhombic (sometimes referred to as T d ) phases, and possibly other structures.…”

Section: Introductionmentioning

confidence: 99%

“…Experimental studies of thermal phase transitions in MoTe 2 have been reported to occur on timescales of several hours at high temperatures, 12,14 while other reports suggest that the kinetics can occur on timescales of minutes or less at ambient temperatures and below. 16,18 RESULTS Phase diagram of monolayer MoTe 2 under electrostatic gating Using the DFT-based approach developed in ref.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical potential for low energy consumption phase change memory utilizing electrostatically-induced structural phase transitions in 2D materials

Rehn

Pop

et al. 2018

npj Comput Mater

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Structural phase-change materials are of great importance for applications in information storage devices. Thermally driven structural phase transitions are employed in phase-change memory to achieve lower programming voltages and potentially lower energy consumption than mainstream nonvolatile memory technologies. However, the waste heat generated by such thermal mechanisms is often not optimized, and could present a limiting factor to widespread use. The potential for electrostatically driven structural phase transitions has recently been predicted and subsequently reported in some two-dimensional materials, providing an athermal mechanism to dynamically control properties of these materials in a nonvolatile fashion while achieving potentially lower energy consumption. In this work, we employ DFT-based calculations to make theoretical comparisons of the energy required to drive electrostatically-induced and thermally-induced phase transitions. Determining theoretical limits in monolayer MoTe 2 and thin films of Ge 2 Sb 2 Te 5 , we find that the energy consumption per unit volume of the electrostatically driven phase transition in monolayer MoTe 2 at room temperature is 9% of the adiabatic lower limit of the thermally driven phase transition in Ge 2 Sb 2 Te 5 . Furthermore, experimentally reported phase change energy consumption of Ge 2 Sb 2 Te 5 is 100-10,000 times larger than the adiabatic lower limit due to waste heat flow out of the material, leaving the possibility for energy consumption in monolayer MoTe 2 -based devices to be orders of magnitude smaller than Ge 2 Sb 2 Te 5 -based devices.

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“…Mo x W 1‐x Te 2 , the most attractive group‐6 TMD‐based Type‐II TWS by theoretical prediction, contains tunable topological surface states and is more stable than other TWS of the binary compounds, such as WTe 2 and MoTe 2 . The strength of the topological surface states of Mo x W 1‐x Te 2 depends directly on the length of Fermi arc, which can be tuned at the Brillouin zone by doping Mo (from 2 to 40%) into the WTe 2 system . Mo x W 1‐x Te 2 is a layered crystal, in which a single layer of W/Mo is sandwiched between two Te layers and stacked along the z‐axis via van der Waals interactions (Figure a).…”

Section: Introductionmentioning

confidence: 99%

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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The structural phases and vibrational properties of Mo _1−x W _x Te ₂ alloys

Cited by 71 publications

References 51 publications

Dimensionality-driven orthorhombic MoTe2 at room temperature

Dimensionality-driven orthorhombic MoTe2 at room temperature

Theoretical potential for low energy consumption phase change memory utilizing electrostatically-induced structural phase transitions in 2D materials

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

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The structural phases and vibrational properties of Mo 1−x W x Te 2 alloys

Cited by 71 publications

References 51 publications

Dimensionality-driven orthorhombic MoTe2 at room temperature

Dimensionality-driven orthorhombic MoTe2 at room temperature

Theoretical potential for low energy consumption phase change memory utilizing electrostatically-induced structural phase transitions in 2D materials

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

Contact Info

Product

Resources

About

The structural phases and vibrational properties of Mo _1−x W _x Te ₂ alloys

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