Low‐Temperature Solution Synthesis of Few‐Layer 1T ′‐MoTe₂ Nanostructures Exhibiting Lattice Compression

Abstract

Molybdenum ditelluride, MoTe2 , is emerging as an important transition-metal dichalcogenide (TMD) material because of its favorable properties relative to other TMDs. The 1T ' polymorph of MoTe2 is particularly interesting because it is semimetallic with bands that overlap near the Fermi level, but semiconducting 2H-MoTe2 is more stable and therefore more accessible synthetically. Metastable 1T '-MoTe2 forms directly in solution at 300 °C as uniform colloidal nanostructures that consist of few-layer nanosheets, which appear to exhibit an approx. 1 % lateral lattice compression relative to the bulk analogue. Density functional theory calculations suggest that small grain sizes and polycrystallinity stabilize the 1T ' phase in the MoTe2 nanostructures and suppress its transformation back to the more stable 2H polymorph through grain boundary pinning. Raman spectra of the 1T '-MoTe2 nanostructures exhibit a laser energy dependence, which could be caused by electronic transitions.

Highly Active, Durable Ultrathin MoTe2 Layers for the Electroreduction of CO2 to CH4

“…Clearly, the typical thickness of a single MoTe 2 flake was ≈2.1 nm, with a size of several square micrometers (Figure c). From the cross‐sectional HRTEM image in Figure S1 (Supporting Information), the interlayer spacing was measured to be 0.69 nm, very close to the reported value (0.7 nm), indicating that ultrathin MoTe 2 flakes have three layers. By contrast, the typical thickness of bulk MoTe 2 was greater than 300 nm (Figure S2, Supporting Information).…”

“…First, ultrathin MoTe 2 layers were synthesized by chemical vapor deposition, followed by ultrasonic exfoliation ( Figure , for more details see Supporting Information) . Transmission electron microscopy (TEM) images were recorded to examine the morphology of the mechanically exfoliated MoTe 2 layers and Figure a shows a typical TEM image: Several aggregated ultrathin flakes were observed.…”

Characterization of Few-Layer 1T′ MoTe2 by Polarization-Resolved Second Harmonic Generation and Raman Scattering

“…The polarization dependence also revealed that the totally symmetric Raman mode at ≈260 cm −1 is comprised of at least two peaks, although some simulations predict additional peaks. 44,49 These measurements help to clarify a discrepancy in the literature concerning the Raman scattering from 1T′ MoTe 2 as well as illustrate the changes in the crystal symmetry with layer parity. Finally, we demonstrate the relationship between the crystal axes and Raman polarization dependence, thereby enabling the identification of crystal orientation from Raman measurements alone.…”

Atomic Insights into Phase Evolution in Ternary Transition‐Metal Dichalcogenides Nanostructures

“…The properties of TMDs are closely associated with the polymorphism in crystal symmetry . In MoTe 2 , the room‐temperature stable phase is hexagonal 2H ( Figure a), which displays a bandgap of ≈1 eV, appealing for flexible and transparent optoelectronics devices . Through controllable conversion from 2H to the other semimetallic phases Tʹ (monoclinic, Figure b) and T d (orthorhombic, Figure c), the semiconducting to metallic transition can be realized, which helps achieve ohmic contact in heterojunctions and make broad applications including memory and phase‐change devices .…”