Direct measurement of lattice dynamics and optical phonon excitation in semiconductor nanocrystals using femtosecond stimulated raman spectroscopy

Daniel C. Hannah, Kristen E. Brown, Ryan M. Young, Michael R Wasielewski, George C Schatz, Dick T Co, Richard D Schaller

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14 Citations (Scopus)

Abstract

We report femtosecond stimulated Raman spectroscopy measurements of lattice dynamics in semiconductor nanocrystals and characterize longitudinal optical (LO) phonon production during confinement-enhanced, ultrafast intraband relaxation. Stimulated Raman signals from unexcited CdSe nanocrystals produce a spectral shape similar to spontaneous Raman signals. Upon photoexcitation, stimulated Raman amplitude decreases owing to experimentally resolved ultrafast phonon generation rates within the lattice. We find a ∼600 fs, particle-size-independent depletion time attributed to hole cooling, evidence of LO-to-acoustic down-conversion, and LO phonon mode softening.

Original languageEnglish
Article number107401
JournalPhysical Review Letters
Volume111
Issue number10
DOIs
Publication statusPublished - Sep 5 2013

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nanocrystals
Raman spectroscopy
photoexcitation
softening
excitation
depletion
cooling
acoustics

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

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abstract = "We report femtosecond stimulated Raman spectroscopy measurements of lattice dynamics in semiconductor nanocrystals and characterize longitudinal optical (LO) phonon production during confinement-enhanced, ultrafast intraband relaxation. Stimulated Raman signals from unexcited CdSe nanocrystals produce a spectral shape similar to spontaneous Raman signals. Upon photoexcitation, stimulated Raman amplitude decreases owing to experimentally resolved ultrafast phonon generation rates within the lattice. We find a ∼600 fs, particle-size-independent depletion time attributed to hole cooling, evidence of LO-to-acoustic down-conversion, and LO phonon mode softening.",
author = "Hannah, {Daniel C.} and Brown, {Kristen E.} and Young, {Ryan M.} and Wasielewski, {Michael R} and Schatz, {George C} and Co, {Dick T} and Schaller, {Richard D}",
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AU - Brown, Kristen E.

AU - Young, Ryan M.

AU - Wasielewski, Michael R

AU - Schatz, George C

AU - Co, Dick T

AU - Schaller, Richard D

PY - 2013/9/5

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AB - We report femtosecond stimulated Raman spectroscopy measurements of lattice dynamics in semiconductor nanocrystals and characterize longitudinal optical (LO) phonon production during confinement-enhanced, ultrafast intraband relaxation. Stimulated Raman signals from unexcited CdSe nanocrystals produce a spectral shape similar to spontaneous Raman signals. Upon photoexcitation, stimulated Raman amplitude decreases owing to experimentally resolved ultrafast phonon generation rates within the lattice. We find a ∼600 fs, particle-size-independent depletion time attributed to hole cooling, evidence of LO-to-acoustic down-conversion, and LO phonon mode softening.

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