Evolution of Raman spectra in Mo${}_{1-x}$W${}_x$Te${}_2$ alloys

Abstract

The structural polymorphism in transition metal dichalcogenides (TMDs) provides exciting opportunities for developing advanced electronics. For example, MoTe${}_2$ crystallizes in the 2H semiconducting phase at ambient temperature and pressure, but transitions into the 1T${}^{\prime }$ semimetallic phase at high temperatures. Alloying MoTe${}_2$ with WTe${}_2$ reduces the energy barrier between these two phases, while also allowing access to the T${}_d$ Weyl semimetal phase. The MoWTe${}_2$ alloy system is therefore promising for developing phase change memory technology. However, achieving this goal necessitates a detailed understanding of the phase composition in the MoTe${}_2$-WTe${}_2$ system. We combine polarization-resolved Raman spectroscopy with X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) to study MoWTe${}_2$ alloys over the full compositional range x from 0 to 1. We identify Raman and XRD signatures characteristic of the 2H, 1T${}^{\prime }$, and T${}_d$ structural phases that agree with density-functional theory (DFT) calculations, and use them to identify phase fields in the MoTe${}_2$-WTe${}_2$ system, including single-phase 2H, 1T${}^{\prime }$, and T${}_d$ regions, as well as a two-phase 1T${}^{\prime }$ + T${}_d$ region. Disorder arising from compositional fluctuations in MoWTe${}_2$ alloys breaks inversion and translational symmetry, leading to the activation of an infrared 1T${}^{\prime }$-MoTe${}_2$ mode and the enhancement of a double-resonance Raman process in 2H-MoWTe${}_2$ alloys. Compositional fluctuations limit the phonon correlation length, which we estimate by fitting the observed asymmetric Raman lineshapes with a phonon confinement model. These observations reveal the important role of disorder in MoWTe${}_2$ alloys, clarify the structural phase boundaries, and provide a foundation for future explorations of phase transitions and electronic phenomena in this system.

18 pages, 5 figures, 1 table

References in corpus (10)

• Quantum Spin Hall Effect and Topological Field Effect Transistor in Two-Dimensional Transition Metal Dichalcogenides
• Spectroscopic evidence for type II Weyl semimetal state in MoTe2
• Fermi arcs and their topological character in the candidate type-II Weyl semimetal MoTe2
• Engineering the structural and electronic phases of MoTe2 through W substitution
• Activation of new Raman modes by inversion symmetry breaking in type II Weyl semimetal candidate T'-MoTe2
• Double resonance Raman modes in mono- and few-layer MoTe${}_2$
• Measuring Chern numbers above the Fermi level in the Type II Weyl semimetal Mo${}_x$W${}_{1-x}$Te${}_2$
• Raman scattering in transition metal dichalcogenides MTe2 (M = Mo, W)
• Critical enhancement of thermopower in a chemically tuned polar semimetal MoTe${}_2$
• Effect of aging-induced disorder on the quantum transport properties of atomically thin WTe${}_2$

Cited by in corpus (25)

• Layer-dependent spin-orbit torques generated by the centrosymmetric transition metal dichalcogenide $\beta$-MoTe${}_2$
• Guide to optical spectroscopy of layered semiconductors
• Dimensionality-driven orthorhombic MoTe2 at room temperature
• Mechanical control of crystal symmetry and superconductivity in Weyl semimetal MoTe${}_2$
• Reversible Electrochemical Phase Change in Monolayer to Bulk MoTe2 by Ionic Liquid Gating
• Tailoring the Phase Transition and Electron-Phonon Coupling in 1T'-MoTe2 by Charge Doping: A Raman Study
• Efficient method for calculating Raman spectra of solids with impurities and alloys and its application to two-dimensional transition metal dichalcogenides
• Enhancement of the superconducting transition temperature by Re doping in Weyl semimetal MoTe${}_2$
• T${}_d$ to 1T${}^{\prime }$ structural phase transition in WTe${}_2$ Weyl semimetal
• Origin of magnetoresistance suppression in thin $\gamma$-MoTe${}_2$
• Appearance of T${}_d^{\ast }$ phase across the T${}_d$-1T${}^{\prime }$ phase boundary in Weyl semimetal MoTe${}_2$
• Superconducting properties of MoTe${}_2$ from the $abinitio$ anisotropic Migdal-Eliashberg theory
• Pressure-induced creation and annihilation of Weyl points in Td- and 1T"-Mo0.5W0.5Te2
• Topological phase transition in MoTe${}_2$: A Review
• Evolution of the structural transition in Mo${}_{1-x}$W${}_x$Te${}_2$
• Raman spectrum of 1T'-WTe2 under tensile strain: A first-principles prediction
• Superconductivity in doped Weyl semimetal Mo${}_{0.9}$Ir${}_{0.1}$Te${}_2$ with broken inversion symmetry
• Large-area synthesis of continuous two-dimensional MoTexSe2-x alloy films by chemical vapor deposition
• Valley Phenomena in the Candidate Phase Change Material WSe${}_{2(1-x)}$Te${}_{2x}$
• Polarization-resolved broadband time-resolved optical spectroscopy for complex materials: application to the case of MoTe${}_2$ polytypes
• Extrinsic n-type semiconductor transition in ZrSe2 with the metallic character through hafnium substitution
• Quantum oscillation study of the large magnetoresistance in Mo substituted WTe${}_2$ single crystals
• Interface engineering of van der Waals heterostructures towards energy-efficient quantum devices operating at high temperatures
• Equilibrium Phase Diagrams of Isostructural and Heterostructural Two-Dimensional Alloys from First Principles
• Controlled synthesis of MoxW1-xTe2 atomic layers with emergent quantum states