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Nanoscale Vibrational Mapping of Single SiGe Quantum Dots in the Electron Microscope

ORAL

Abstract

Through the engineering of complex structures such as alloys, nanostructures, and superlattice interfaces, the propagation of phonons can be manipulated to suppress material thermal conductivity1. Due to the lack of spatial resolution of conventional optical methods, experimental study of phonon behavior at nanostructure interfaces has been impossible until now. Recent developments in electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) have made it possible to study phonons at nanometer resolution2. Here we demonstrate the two-dimensional nanoscale vibrational mapping of a single SiGe quantum dot (QD) using an atom-sized probe in the electron microscope. For the first time, we experimentally reveal an enhancement in the Si optical mode intensity below the abrupt interface of the QD suggesting increased phonon population due to phonon reflection. We have also developed a new technique to map the differential momentum and flux of optical phonon modes at the nanoscale to directly reveal the reflection of propagating Si optical modes.

[1] Biswas, Kanishka, et al. Nature 489.7416 (2012): 414.
[2] Krivanek, Ondrej L., et al. Nature 514.7521 (2014): 209.

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Presenters

  • Chaitanya Gadre

    Physics and Astronomy, University of California Irvine

Authors

  • Chaitanya Gadre

    Physics and Astronomy, University of California Irvine

  • Xingxu Yan

    Materials Science and Engineering, University of California Irvine

  • Qichen Song

    Mechanical Engineering, Massachusetts Institute of Technology

  • Jie Li

    Physics and Astronomy, University of California Irvine

  • Lei Guo

    Physics and Astronomy, University of California Irvine

  • Toshihiro Aoki

    Irvine Materials Research Institute, University of California Irvine

  • Sheng-Wei Lee

    Materials Science and Engineering, National Central University

  • Gang Chen

    Mechanical Engineering, Massachusetts Institute of Technology

  • Ruqian Wu

    Department of Physics and Astronomy, University of California, Irvine, Physics and Astronomy, University of California Irvine, University of California, Irvine

  • Xiaoqing Pan

    University of California, Irvine, Physics and Astronomy, University of California Irvine