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Richard Schaller
Department of Chemistry
Northwestern University
Argonne National Laboratory
*Lattice and Carrier Dynamics in Quantum-Confined Materials on *
*Ultrafast Timescales*
*Thursday, April 3, 2014*
*RLE Conference Room - 36-428 *
*3:00 - 4:00pm *
*Abstract*:
Excess carrier energy, which many aim to utilize for advanced energy
conversion technologies, rapidly dissipates from electrons and holes in
both bulk and quantum confined semiconductors despite expectation of slowed
cooling in the latter. We aim to characterize dissipation channels
available to carriers via time-resolved optical spectroscopies. We utilize
both femtosecond stimulated Raman spectroscopy (FSRS) and time-resolved
photoluminescence in order to gain insights as to rates and modes of
dissipation. Using FSRS, we characterize longitudinal optical (LO) phonon
production and dissipation throughout the process of confinement-enhanced,
ultrafast intraband carrier relaxation. Upon excitation, we observe a
decrease in stimulated Raman amplitude and note a size-independent LO
phonon formation time. Mode softening is observed along with evidence of
phonon down-conversion processes. Furthermore, spectrally and temporally
resolved photoluminescence suggest evidence of acoustic phonon dissipation
times that follow diffusive transport, which we can manipulate.
*Bio*
*Richard D. Schaller* is a Staff Member at Argonne National Lab in the
Center for Nanoscale Materials and is also an Assistant Professor in the
Department of Chemistry at Northwestern University. He received his PhD
with Prof. Rich Saykally from University of California Berkeley in 2002 in
the area of nonlinear optical microscopy and near-field optics.
Subsequently he was selected as a Reines Distinguished Postdoctoral Fellow
and became a Permanent Technical Staff Member at Los Alamos National Lab
for a combined total of 8 years under the advising of Dr. Victor Klimov.
In 2012, he was selected as a Kavli Fellow by the National Academy of
Sciences. He has worked on the electronic and optical properties of
semiconductor nanocrystals for more than a decade, has published 75
publications, has delivered more than 40 invited presentations, and holds 3
patents.
Light refreshments will be served
*The Center for Excitonics is an Energy Frontier Research Center funded by
the U.S. Department of Energy, Office of Science and Office of Basic Energy
Sciences*
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