Distinct Acoustic and Optical Phonon Dependences on Particle Size, Oxidation, and Temperature in Silicon Nanocrystals

Shuonan Chen; Devin Coleman; Douglas L. Abernathy; Arnab Banerjee; Lorenzo Mangolini; Chen Li

doi:10.1021/acs.jpcc.2c04246

Distinct Acoustic and Optical Phonon Dependences on Particle Size, Oxidation, and Temperature in Silicon Nanocrystals

Shuonan Chen, Devin Coleman, Douglas L. Abernathy, Arnab Banerjee, Lorenzo Mangolini, Chen Li

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Abstract

Phonon, as a momentum carrier, may play an important role in the photoluminescence of silicon nanocrystals. However, a systematic experimental study on phonon dynamics in spatially confined silicon systems remains limited. We used inelastic neutron scattering to investigate particle size, oxidation, and temperature effects on phonon dynamics of silicon nanocrystals by measuring phonon density of states of 12 and 50 nm silicon nanocrystals with several oxidation levels at different temperatures. We showed that the lattice vibrations of large silicon nanocrystals and bulk silicon are substantially different. We found that transverse acoustic phonon modes have much stronger dependences on particle size, oxidation, and temperature than optical phonon modes. We showed that the changes in phonon dynamics have the largest effect on vibrational entropy and free energy of silicon nanocrystals at intermediate temperatures. Our results shed light on phonon dynamics of silicon-based functional nanomaterials and will facilitate further investigations of electron-phonon interactions in spatially confined silicon systems.

Original language	English
Pages (from-to)	12704-12711
Number of pages	8
Journal	Journal of Physical Chemistry C
Volume	126
Issue number	30
DOIs	https://doi.org/10.1021/acs.jpcc.2c04246
State	Published - Aug 4 2022

Funding

This material is based upon work supported by the National Science Foundation under Grant No. 1750786. C.L. and S.C. acknowledge the support of the University of California, Riverside via Initial Complement. S.C. expresses sincere gratitude to Bin Wei, Qiyang Sun Qingan Cai, Songrui Hou, Yaokun Su, and Matthew Dickson for meaningful discussions. L.M. and D.C. acknowledge the support of the National Science Foundation via award No. 1351386 (Career). This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This material is based upon work supported by the National Science Foundation under Grant No. 1750786. C.L. and S.C. acknowledge the support of the University of California, Riverside via Initial Complement. S.C. expresses sincere gratitude to Bin Wei, Qiyang Sun, Qingan Cai, Songrui Hou, Yaokun Su, and Matthew Dickson for meaningful discussions. L.M. and D.C. acknowledge the support of the National Science Foundation via award No. 1351386 (Career). This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

Funders	Funder number
National Science Foundation	1750786
Office of Science
Oak Ridge National Laboratory
University of California, Riverside	1351386

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10.1021/acs.jpcc.2c04246

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title = "Distinct Acoustic and Optical Phonon Dependences on Particle Size, Oxidation, and Temperature in Silicon Nanocrystals",

abstract = "Phonon, as a momentum carrier, may play an important role in the photoluminescence of silicon nanocrystals. However, a systematic experimental study on phonon dynamics in spatially confined silicon systems remains limited. We used inelastic neutron scattering to investigate particle size, oxidation, and temperature effects on phonon dynamics of silicon nanocrystals by measuring phonon density of states of 12 and 50 nm silicon nanocrystals with several oxidation levels at different temperatures. We showed that the lattice vibrations of large silicon nanocrystals and bulk silicon are substantially different. We found that transverse acoustic phonon modes have much stronger dependences on particle size, oxidation, and temperature than optical phonon modes. We showed that the changes in phonon dynamics have the largest effect on vibrational entropy and free energy of silicon nanocrystals at intermediate temperatures. Our results shed light on phonon dynamics of silicon-based functional nanomaterials and will facilitate further investigations of electron-phonon interactions in spatially confined silicon systems.",

author = "Shuonan Chen and Devin Coleman and Abernathy, {Douglas L.} and Arnab Banerjee and Lorenzo Mangolini and Chen Li",

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T1 - Distinct Acoustic and Optical Phonon Dependences on Particle Size, Oxidation, and Temperature in Silicon Nanocrystals

AU - Chen, Shuonan

AU - Coleman, Devin

AU - Abernathy, Douglas L.

AU - Banerjee, Arnab

AU - Mangolini, Lorenzo

AU - Li, Chen

PY - 2022/8/4

Y1 - 2022/8/4

N2 - Phonon, as a momentum carrier, may play an important role in the photoluminescence of silicon nanocrystals. However, a systematic experimental study on phonon dynamics in spatially confined silicon systems remains limited. We used inelastic neutron scattering to investigate particle size, oxidation, and temperature effects on phonon dynamics of silicon nanocrystals by measuring phonon density of states of 12 and 50 nm silicon nanocrystals with several oxidation levels at different temperatures. We showed that the lattice vibrations of large silicon nanocrystals and bulk silicon are substantially different. We found that transverse acoustic phonon modes have much stronger dependences on particle size, oxidation, and temperature than optical phonon modes. We showed that the changes in phonon dynamics have the largest effect on vibrational entropy and free energy of silicon nanocrystals at intermediate temperatures. Our results shed light on phonon dynamics of silicon-based functional nanomaterials and will facilitate further investigations of electron-phonon interactions in spatially confined silicon systems.

AB - Phonon, as a momentum carrier, may play an important role in the photoluminescence of silicon nanocrystals. However, a systematic experimental study on phonon dynamics in spatially confined silicon systems remains limited. We used inelastic neutron scattering to investigate particle size, oxidation, and temperature effects on phonon dynamics of silicon nanocrystals by measuring phonon density of states of 12 and 50 nm silicon nanocrystals with several oxidation levels at different temperatures. We showed that the lattice vibrations of large silicon nanocrystals and bulk silicon are substantially different. We found that transverse acoustic phonon modes have much stronger dependences on particle size, oxidation, and temperature than optical phonon modes. We showed that the changes in phonon dynamics have the largest effect on vibrational entropy and free energy of silicon nanocrystals at intermediate temperatures. Our results shed light on phonon dynamics of silicon-based functional nanomaterials and will facilitate further investigations of electron-phonon interactions in spatially confined silicon systems.

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JO - Journal of Physical Chemistry C

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Distinct Acoustic and Optical Phonon Dependences on Particle Size, Oxidation, and Temperature in Silicon Nanocrystals

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