Femtosecond electron imaging of defect-modulated phonon dynamics

Precise manipulation and control of coherent lattice oscillations via nanostructuring and phonon-wave interference has the potential to significantly impact a broad array of technologies and research areas. Resolving the dynamics of individual phonons in defect-laden materials presents an enormous c...

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Bibliographic Details
Published in:Nature communications 2016-04, Vol.7 (1), p.11230-11230, Article 11230
Main Authors: Cremons, Daniel R., Plemmons, Dayne A., Flannigan, David J.
Format: Article
Language:English
Subjects:
639/301/930/2735
639/624/1111/1115
Acoustics
Crystal defects
Defects
Electron imaging
Energy
Humanities and Social Sciences
Localization
multidisciplinary
Nucleation
Oscillations
Phase transitions
Phonons
Propagation
Science
Science (multidisciplinary)
Sound propagation
Symmetry
Velocity
Wave fronts
Wave propagation
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Summary:Precise manipulation and control of coherent lattice oscillations via nanostructuring and phonon-wave interference has the potential to significantly impact a broad array of technologies and research areas. Resolving the dynamics of individual phonons in defect-laden materials presents an enormous challenge, however, owing to the interdependent nanoscale and ultrafast spatiotemporal scales. Here we report direct, real-space imaging of the emergence and evolution of acoustic phonons at individual defects in crystalline WSe 2 and Ge. Via bright-field imaging with an ultrafast electron microscope, we are able to image the sub-picosecond nucleation and the launch of wavefronts at step edges and resolve dispersion behaviours during propagation and scattering. We discover that the appearance of speed-of-sound (for example, 6 nm ps −1 ) wavefronts are influenced by spatially varying nanoscale strain fields, taking on the appearance of static bend contours during propagation. These observations provide unprecedented insight into the roles played by individual atomic and nanoscale features on acoustic-phonon dynamics. Phonons—crystal lattice vibrations—interact with crystal defects on the nanometre spatial scale and femtosecond timescale. Here, the authors demonstrate direct, real-space imaging of the nucleation, emergence and dispersion of single-phonon wavefronts at individual atomic-scale defects in semiconductors.
ISSN:2041-1723
2041-1723
DOI:10.1038/ncomms11230