Anomalous Raman Spectra and Thickness Dependent Electronic properties of WSe2

Abstract

Typical Raman spectra of transition metal dichalcogenides (TMDs) display two prominent peaks, E2g and A1g, that are well separated from each other. We find that these modes are degenerate in bulk WSe2 yielding one single Raman peak. As the dimensionality is lowered, the observed peak splits in two as a result of broken degeneracy. In contrast to our experimental findings, our phonon dispersion calculations reveal that these modes remain degenerate independent of the number of layers. Interestingly, for minuscule biaxial strain the degeneracy is preserved but once the crystal symmetry is broken by uniaxial strain, the degeneracy is lifted. Our calculated phonon dispersion for uniaxially strained WSe2 shows a perfect match to the measured Raman spectrum which suggests that uniaxial strain exists in WSe2 flakes possibly induced during the sample preparation and/or as a result of interaction between WSe2 and the substrate. Furthermore, we find that WSe2 undergoes an indirect to direct bandgap transition from bulk to monolayers which is ubiquitous for semiconducting TMDs. These results not only allow us to understand the vibrational properties of WSe2 but also provides detailed insight to their physical properties.

arXiv commenthttp://link.aps.org/doi/10.1103/PhysRevB.87.165409

References in corpus (11)

• Electric Field Effect in Atomically Thin Carbon Films
• Atomically thin MoS2: A new direct-gap semiconductor
• The Raman Fingerprint of Graphene
• Phonons and related properties of extended systems from density-functional perturbation theory
• Observation of tightly bound trions in monolayer MoS2
• Evolution of Electronic Structure in Atomically Thin Sheets of WS2 and WSe2
• High Performance Single Layered WSe2 p-FETs with Chemically Doped Contacts
• Two-dimensional transition metal dichalcogenides under electron irradiation: defect production and doping
• High Efficiency Graphene Solar Cells by Chemical Doping
• Phonon Softening and Direct to Indirect Bandgap Crossover in Strained Single Layer MoSe2
• Phonons in potassium doped graphene: the effects of electron-phonon interactions, dimensionality and ad-atom ordering

Cited by in corpus (77)

• Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Lattice dynamics in mono- and few-layer sheets of WS2 and WSe2
• Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers
• Origin of indirect optical transitions in few-layer MoS2, WS2 and WSe2
• Halide-Assisted Atmospheric Pressure Growth of Large WSe2 and WS2 Monolayer Crystals
• Broadband Photovoltaic Detectors based on an Atomically Thin Heterostructure
• Thermal conductivity of monolayer MoS2, MoSe2, and WS2: Interplay of mass effect, interatomic bonding and anharmonicity
• Tuning of the electronic and optical properties of single layer black phosphorus by strain
• Measurement of high exciton binding energy in the monolayer transition-metal dichalcogenides WS2 and WSe2
• Biaxial strain tuning of the optical properties of single-layer transition metal dichalcogenides
• Electronic properties of single-layer and multilayer transition metal dichalcogenides $M{X}_2$ ($M=$ Mo, W and $X=$ S, Se)
• Probing critical point energies of transition metal dichalcogenides: surprising indirect gap of single layer $SL-WS{e}_2$
• Precise and reversible band gap tuning in single-layer MoSe2 by uniaxial strain
• Generation and evolution of spin-, valley- and layer-polarized excited carriers in inversion-symmetric WSe2
• Achieving Large, Tunable Strain in Monolayer Transition-Metal Dichalcogenides
• Interlayer electronic hybridization leads to exceptional thickness-dependent vibrational properties in few-layer black phosphorus
• Mechanics of freely-suspended ultrathin layered materials
• Screw-Dislocation-Driven Growth of Two-Dimensional Few-Layer and Pyramid-Like WSe2 by Sulfur-Assisted Chemical Vapor Deposition
• Hexagonal AlN: Dimensional-Crossover-Driven Bandgap Transition
• Enhanced Optoelectronic Response in Bilayer Lateral Heterostructures of Transition Metal Dichalcogenides
• Double resonance Raman modes in mono- and few-layer MoTe${}_2$
• A WSe2 vertical field emission transistor
• Largely tunable band structures of few-layer InSe by uniaxial strain
• Momentum-Resolved View of Electron-Phonon Coupling in Multilayer WSe${}_2$
• The role of momentum-dark excitons in the elementary optical response of bilayer WSe${}_2$
• Zone-center phonons of bulk, few-layer, and monolayer 1T-TaS${}_2$: Detection of the commensurate charge density wave phase through Raman scattering
• Nano-imaging of intersubband transitions in van der Waals quantum wells
• Electronic and Vibrational Properties of PbI 2 : From Bulk to Monolayer
• Double resonant Raman scattering and valley coherence generation in monolayer WSe2
• Environmental effects on the electrical characteristics of back-gated WSe2 field effect transistors
• Bilayer SnS${}_2$: Easy-tunable Stacking Sequence by Charging and Loading Pressure
• Exciton dynamics in WSe2 bilayers
• Enhanced electron-phonon interaction in multi-valley materials
• Strain Mapping In Single-Layer 2D Crystals Via Raman Activity
• Thermal conductivity and phonon hydrodynamics in transition metal dichalcogenides from first-principles
• Narrow-band anisotropic electronic structure of ReS${}_2$
• Distinctive signatures of the spin- and momentum-forbidden dark exciton states in the photo-luminescences of strained WSe${}_2$ monolayers under thermalization
• Thermoelectric Transport Coefficients in Mono-layer MoS2 and WSe2 Role of Substrate, Interface Phonons, Plasmon, and Dynamic Screening
• Adaptive tip-enhanced nano-spectroscopy
• Superior valley polarization and coherence of 2s excitons in monolayer WSe2
• Quantum plasmonic hot-electron injection in lateral WSe2/MoSe2 heterostructures
• Thickness mapping and layer number identification of exfoliated van der Waals materials by Fourier imaging micro-ellipsometry
• Stacking-dependent exciton multiplicity in WSe${}_2$ bilayers
• Gold on WSe2 Single Crystal Film as a Substrate for Surface Enhanced Raman Scattering (SERS) Sensing
• Valley Polarization-Electric Dipole Interference and Nonlinear Chiral Selection Rules in Monolayer WSe${}_2$
• $h$-AlN-Mg(OH)${}_2$ vdW Bilayer Heterostructure: Tuning the excitonic characteristics
• Phonon-assisted exciton and trion conversion efficiency in transition metal Dichalcogenides
• Quantum transport through MoS${}_2$ constrictions defined by photodoping
• New insights in the lattice dynamics of monolayers, bilayers, and trilayers of WSe2 and unambiguous determination of few-layer-flakes' thickness
• Interplay of Excitonic Complexes in $p$-Doped WSe${}_2$ Monolayers
• Ag and Au Atoms Intercalated in Bilayer Heterostructures of Transition Metal Dichalcogenides and Graphene
• Impact of Pauli-blocking effect on optical limiting properties of WSe2 thin films
• Experimental demonstration of the suppression of optical phonon splitting in 2D materials by Raman spectroscopy
• Hole spin relaxation in bilayer WSe${}_2$
• Hematite at its thinnest limit
• Stable Monolayer alpha-Phase of CdTe: Strain-Dependent Properties
• Raman spectrum of 1T'-WTe2 under tensile strain: A first-principles prediction
• Dry transfer of CVD graphene using MoS${}_2$-based stamps
• Spin diffusion in p-type bilayer WSe${}_2$
• Substrate Effects on the Speed Limiting Factor of WSe${}_2$ Photodetectors
• Group Theory analysis of phonons in two-dimensional Transition Metal Dichalcogenides
• Tuning of Interlayer Coupling in Large-Area Graphene/WSe2 van der Waals Heterostructure via Ion Irradiation: Optical Evidences and Photonic Applications
• Bio-realistic and versatile artificial dendrites made of anti-ambipolar transistors
• Two-Dimensional Transition Metal Dichalcogenides-Based Counter Electrodes for Dye-Sensitized Solar Cells
• Evidence of Mott Insulator with Thermally Induced Melting Behavior in Kagome Compound Nb3Cl8
• Electron density control in tungsten diselenide monolayers via photochlorination
• Characterization of WSe${}_2$ films using reflection Kikuchi diffraction in the scanning electron microscope and multivariate statistical analyses
• A combined experimental and theoretical study of the electronic and vibrational properties of bulk and few-layer Td-WTe2
• Layered semiconductors integrated with polyimide thin films for high-quality valleytronic and quantum-photonic systems
• Moire-Engineered Excitonic Landscape and Phonon-Mediated Recombination in Twisted WSe2 Bilayers
• Measurements of absolute bandgap deformation-potentials of optically-bright bilayer WSe${}_2$
• Exchange-Correlation Functionals in 2D Materials: Applications, Challenges, and Limitations
• Ellipticity-Controlled Bright-Dark Coherence Transition in Monolayer WSe2
• Band Gap Estimation of Multilayer 2D Semiconductor Channels Using Thin Graphite Contact
• Impact of Electrical Contacts on Transition Metal Dichalcogenides-Based Acoustoelectric and Acousto-Photoelectric Devices
• Non-Linear behavior of Raman Linewidth of 1-3 Layer WSe2