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Title: Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires

Similar to electron waves, the phonon states in semiconductors can undergo changes induced by external boundaries. However, despite strong scientific and practical importance, conclusive experimental evidence of confined acoustic phonon polarization branches in individual free-standing nanostructures is lacking. Here we report results of Brillouin-Mandelstam light scattering spectroscopy, which reveal multiple (up to ten) confined acoustic phonon polarization branches in GaAs nanowires with a diameter as large as 128 nm, at a length scale that exceeds the grey phonon mean-free path in this material by almost an order-of-magnitude. The dispersion modification and energy scaling with diameter in individual nanowires are in excellent agreement with theory. The phonon confinement effects result in a decrease in the phonon group velocity along the nanowire axis and changes in the phonon density of states. Furthermore, the obtained results can lead to more efficient nanoscale control of acoustic phonons, with benefits for nanoelectronic, thermoelectric and spintronic devices.
Authors:
ORCiD logo [1] ;  [1] ;  [2] ;  [3] ; ORCiD logo [2] ;  [4] ;  [1] ;  [1]
  1. Univ. of California - Riverside, Riverside, CA (United States)
  2. Aalto Univ., Aalto (Finland)
  3. Aalto Univ., Aalto (Finland); Univ. of Eastern Finland, Joensuu (Finland)
  4. Univ. of California - Riverside, Riverside, CA (United States); Moldova State Univ., Chisinau (Republic of Moldova)
Publication Date:
Grant/Contract Number:
SC0012670
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Univ. of California - Riverside, Riverside, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; nanowires
OSTI Identifier:
1361532

Kargar, Fariborz, Debnath, Bishwajit, Kakko, Joona -Pekko, Säynätjoki, Antti, Lipsanen, Harri, Nika, Denis L., Lake, Roger K., and Balandin, Alexander A.. Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires. United States: N. p., Web. doi:10.1038/ncomms13400.
Kargar, Fariborz, Debnath, Bishwajit, Kakko, Joona -Pekko, Säynätjoki, Antti, Lipsanen, Harri, Nika, Denis L., Lake, Roger K., & Balandin, Alexander A.. Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires. United States. doi:10.1038/ncomms13400.
Kargar, Fariborz, Debnath, Bishwajit, Kakko, Joona -Pekko, Säynätjoki, Antti, Lipsanen, Harri, Nika, Denis L., Lake, Roger K., and Balandin, Alexander A.. 2016. "Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires". United States. doi:10.1038/ncomms13400. https://www.osti.gov/servlets/purl/1361532.
@article{osti_1361532,
title = {Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires},
author = {Kargar, Fariborz and Debnath, Bishwajit and Kakko, Joona -Pekko and Säynätjoki, Antti and Lipsanen, Harri and Nika, Denis L. and Lake, Roger K. and Balandin, Alexander A.},
abstractNote = {Similar to electron waves, the phonon states in semiconductors can undergo changes induced by external boundaries. However, despite strong scientific and practical importance, conclusive experimental evidence of confined acoustic phonon polarization branches in individual free-standing nanostructures is lacking. Here we report results of Brillouin-Mandelstam light scattering spectroscopy, which reveal multiple (up to ten) confined acoustic phonon polarization branches in GaAs nanowires with a diameter as large as 128 nm, at a length scale that exceeds the grey phonon mean-free path in this material by almost an order-of-magnitude. The dispersion modification and energy scaling with diameter in individual nanowires are in excellent agreement with theory. The phonon confinement effects result in a decrease in the phonon group velocity along the nanowire axis and changes in the phonon density of states. Furthermore, the obtained results can lead to more efficient nanoscale control of acoustic phonons, with benefits for nanoelectronic, thermoelectric and spintronic devices.},
doi = {10.1038/ncomms13400},
journal = {Nature Communications},
number = ,
volume = 7,
place = {United States},
year = {2016},
month = {11}
}