Probing the Charge Density Wave State in Bulk to Monolayer 2H-TaSe<sub>2</sub> by Raman Spectroscopy

ORAL

Abstract

Tantalum diselenide (TaSe2) is a metallic, layered transition metal dichalcogenide that can be cleaved into 2D layers. Bulk 2H-TaSe2 undergoes a structural phase transition to an incommensurate charge density wave state (CDW) at 122 K and a commensurate CDW state at 90 K. The CDW amplitude modes are Raman-active and well understood. Additionally, there are previously unanalyzed Raman peaks associated with the CDW that can be observed. We report the temperature and polarization dependence of all CDW modes and the undistorted-state Raman modes of TaSe2 for 633 nm, 515 nm, and 476 nm excitation. The intensity, frequency, and width of these peaks are monitored for samples from bulk down to monolayer thickness. We also track the transition temperature of the incommensurate and commensurate CDW states as a function of thickness. Finally, our DFT calculations provide insight into the nature and behavior of the CDW Raman modes.

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Presenters

  • Heather Hill

    • Engineering Physics, National Institute of Standards and Technology
    • National Institute of Standards and Technology
    • Physical Measurements Laboratory, National Institute of Standards and Technology
    • Physical Measurment Division, NIST
    • NIST -Natl Inst of Stds & Tech
    • NIST - National Institute of Standards and Technology

Authors

  • Heather Hill

    • Engineering Physics, National Institute of Standards and Technology
    • National Institute of Standards and Technology
    • Physical Measurements Laboratory, National Institute of Standards and Technology
    • Physical Measurment Division, NIST
    • NIST -Natl Inst of Stds & Tech
    • NIST - National Institute of Standards and Technology

  • Sugata Chowdhury

    • Physical Measurment Division, NIST
    • NIST -Natl Inst of Stds & Tech
    • NIST - National Institute of Standards and Technology

  • Jeffrey Simpson

    • Engineering Physics, National Institute of Standards and Technology
    • Physics, Towson University
    • Physics, Astronomy, and GeoSciences, Towson University
    • Towson University
    • Department of Physics, Astronomy, and Geosciences, Towson University
    • Physics, Astronomy, and Geosciences, Towson Univ and NIST

  • Albert Rigosi

    • NIST -Natl Inst of Stds & Tech
    • NIST - National Institute of Standards and Technology
    • National Institute of Standards and Technology

  • David Newell

    • NIST -Natl Inst of Stds & Tech
    • NIST - National Institute of Standards and Technology

  • Helmuth Berger

    • Crystal Growth Facility, Institute of Physics, École Polytechnique Fédéral de Lausanne
    • EPFL
    • Physics, Ecole Polytechnique Fédérale de Lausanne

  • Francesca Tavazza

    • Mechanical Measurment Division , NIST
    • NIST -Natl Inst of Stds & Tech
    • NIST - National Institute of Standards and Technology
    • Material Measurement Laboratory, National Institute of Standards and Technology

  • Angela Hight Walker

    • Engineering Physics, National Institute of Standards and Technology
    • National Institute of Standards and Technology
    • NIST - Natl Inst of Stds & Tech
    • Physical Measurements Laboratory, National Institute of Standards and Technology
    • Physical Measurment Division, NIST
    • NIST -Natl Inst of Stds & Tech
    • Physical Measurement Laboratory, National Institute of Standards and Technology
    • NIST - National Institute of Standards and Technology
    • National Institute of Standards and Technology (NIST)
    • National Institute of Standards & Technology