Tungsten as a substitutional dopant and its effect on ultrafast switching of vanadium dioxide

ORAL

Abstract

VO$_{2}$ undergoes a metal-insulator transition (MIT) at 340K accompanied by a structural change from monoclinic (M1) to tetragonal (R). We have grown W-doped VO$_{2}$ films on glass and epitaxially on sapphire substrates and have characterized them by SEM, white light transmission, RBS, XRD, and Z-STEM. These provide direct experimental evidence that W acts as a substitutional dopant in the VO$_{2}$ lattice in addition to lowering the transition temperature. From GGA+U, DFT-based simulations we have also calculated the formation energy of substitutional W in VO$_{2}$, and relative stability of M1 and R phases before and after doping. Ultrafast pump-probe measurements at 800nm with varying pump fluences show that doped VO$_{2}$ switches at substantially lower fluences than undoped VO$_{2}$, indicating that the W dopant provides additional conduction-band electrons, thus altering the photo-induced dynamics of the phase transition.

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Authors

  • Joyeeta Nag

    • Vanderbilt University

  • Kannatassen Appavoo

    • Vanderbilt University

  • Weidong Luo

    • Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory

  • Gerd Duscher

    • Univeristy of Tennessee, Knoxville and Oak Ridge National Laboratory

  • Sokrates Pantelides

    • Vanderbilt U./ORNL
    • Vanderbilt University
    • Vanderbilt University, Oak Ridge National Laboratory
    • Vanderbilt University and Oak Ridge National Laboratory

  • Richard Haglund

    • Vanderbilt University