A Study of the Phase Change Material Mo<sub>1-x</sub>W<sub>x</sub>Te<sub>2</sub>

ORAL

Abstract

Structural polymorphism in the transition metal dichalcogenide (TMD) MoTe2 is ideal for enabling ultrathin phase change memories. Under ambient conditions, MoTe2 crystallizes in the 2H semiconducting phase, but can be grown in the 1T’ semimetallic phase that transitions into the Td phase below ~250 K. Alloying MoTe2 with WTe2 is theorized to reduce the barrier between the 2H and 1T’ phases, which may improve the efficiency of TMD-based memories and provide on-demand topological phase transitions. Contradictory reports of the Mo1-xWxTe2 phase diagram [1,2] demonstrate the need for new investigations of this alloy system. Here, we combine Raman spectroscopy, x-ray diffraction, scanning transmission electron microscopy, and density-functional theory to explore the phase boundaries of bulk Mo1-xWxTe2 alloys. Our work confirms the existence of 2H, 1T’, and Td regions, as well as a two-phase 1T’-Td region in the MoTe2-WTe2 system [3]. We extract the phonon correlation length through the phonon confinement model, identify disorder-enhanced two-phonon scattering, and observe disorder-activation of infrared modes. These results provide a foundation for future applications of the Mo1-xWxTe2 alloys.

[1] Rhodes et al. Nano Lett. 2017 [2] Lv et al. Sci. Rep. 2017 [3] Oliver et al. 2D Mat. 2017

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Presenters

  • Sean Oliver

    • Physics and Astronomy, George Mason University

Authors

  • Sean Oliver

    • Physics and Astronomy, George Mason University

  • Ryan Beams

    • Material Measurement Laboratory, National Institute of Standards and Technology

  • Sergiy Krylyuk

    • Material Measurement Laboratory, National Institute of Standards and Technology

  • Irina Kalish

    • Material Measurement Laboratory, National Institute of Standards and Technology

  • Arunima Singh

    • Material Measurement Laboratory, National Institute of Standards and Technology

  • Alina Bruma

    • Material Measurement Laboratory, National Institute of Standards and Technology

  • 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

  • Jaydeep Joshi

    • Departments of Physics and Astronomy, George Mason University
    • Physics and Astronomy, George Mason University

  • Iris Stone

    • Physics and Astronomy, George Mason University

  • Stephan Stranick

    • Material Measurement Laboratory, National Institute of Standards and Technology

  • Albert Davydov

    • Material Measurement Laboratory, National Institute of Standards and Technology
    • NIST

  • Patrick Vora

    • George Mason University
    • Departments of Physics and Astronomy, George Mason University
    • Physics and Astronomy, George Mason University