Atomic-Resolution Mapping of Localized Phonon Modes at Grain Boundaries

Benedikt Haas; Tara M. Boland; Christian Elsässer; Arunima K. Singh; Katia March; Juri Barthel; Christoph T. Koch; Peter Rez

doi:10.1021/acs.nanolett.3c01089

Atomic-Resolution Mapping of Localized Phonon Modes at Grain Boundaries

Benedikt Haas, Tara M. Boland, Christian Elsässer, Arunima K. Singh, Katia March, Juri Barthel, Christoph T. Koch, Peter Rez

Physics

Research output: Contribution to journal › Article › peer-review

1 Scopus citations

Abstract

Phonon scattering at grain boundaries (GBs) is significant in controlling the nanoscale device thermal conductivity. However, GBs could also act as waveguides for selected modes. To measure localized GB phonon modes, milli-electron volt (meV) energy resolution is needed with subnanometer spatial resolution. Using monochromated electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) we have mapped the 60 meV optic mode across GBs in silicon at atomic resolution and compared it to calculated phonon densities of states (DOS). The intensity is strongly reduced at GBs characterized by the presence of 5- and 7-fold rings where bond angles differ from the bulk. The excellent agreement between theory and experiment strongly supports the existence of localized phonon modes and thus of GBs acting as waveguides.

Original language	English (US)
Pages (from-to)	5975-5980
Number of pages	6
Journal	Nano Letters
Volume	23
Issue number	13
DOIs	https://doi.org/10.1021/acs.nanolett.3c01089
State	Published - Jul 12 2023

Keywords

density functional theory
electron energy loss spectroscopy
grain boundaries
phonons
scanning transmission electron microscopy
semiconductors

ASJC Scopus subject areas

Bioengineering
General Chemistry
General Materials Science
Condensed Matter Physics
Mechanical Engineering

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10.1021/acs.nanolett.3c01089

Cite this

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title = "Atomic-Resolution Mapping of Localized Phonon Modes at Grain Boundaries",

abstract = "Phonon scattering at grain boundaries (GBs) is significant in controlling the nanoscale device thermal conductivity. However, GBs could also act as waveguides for selected modes. To measure localized GB phonon modes, milli-electron volt (meV) energy resolution is needed with subnanometer spatial resolution. Using monochromated electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) we have mapped the 60 meV optic mode across GBs in silicon at atomic resolution and compared it to calculated phonon densities of states (DOS). The intensity is strongly reduced at GBs characterized by the presence of 5- and 7-fold rings where bond angles differ from the bulk. The excellent agreement between theory and experiment strongly supports the existence of localized phonon modes and thus of GBs acting as waveguides.",

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AU - Haas, Benedikt

AU - Boland, Tara M.

AU - Elsässer, Christian

AU - Singh, Arunima K.

AU - March, Katia

AU - Barthel, Juri

AU - Koch, Christoph T.

AU - Rez, Peter

PY - 2023/7/12

Y1 - 2023/7/12

N2 - Phonon scattering at grain boundaries (GBs) is significant in controlling the nanoscale device thermal conductivity. However, GBs could also act as waveguides for selected modes. To measure localized GB phonon modes, milli-electron volt (meV) energy resolution is needed with subnanometer spatial resolution. Using monochromated electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) we have mapped the 60 meV optic mode across GBs in silicon at atomic resolution and compared it to calculated phonon densities of states (DOS). The intensity is strongly reduced at GBs characterized by the presence of 5- and 7-fold rings where bond angles differ from the bulk. The excellent agreement between theory and experiment strongly supports the existence of localized phonon modes and thus of GBs acting as waveguides.

AB - Phonon scattering at grain boundaries (GBs) is significant in controlling the nanoscale device thermal conductivity. However, GBs could also act as waveguides for selected modes. To measure localized GB phonon modes, milli-electron volt (meV) energy resolution is needed with subnanometer spatial resolution. Using monochromated electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) we have mapped the 60 meV optic mode across GBs in silicon at atomic resolution and compared it to calculated phonon densities of states (DOS). The intensity is strongly reduced at GBs characterized by the presence of 5- and 7-fold rings where bond angles differ from the bulk. The excellent agreement between theory and experiment strongly supports the existence of localized phonon modes and thus of GBs acting as waveguides.

KW - density functional theory

KW - electron energy loss spectroscopy

KW - grain boundaries

KW - phonons

KW - scanning transmission electron microscopy

KW - semiconductors

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Atomic-Resolution Mapping of Localized Phonon Modes at Grain Boundaries

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Keywords

ASJC Scopus subject areas

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