Auger Heating and Thermal Dissipation in Zero-Dimensional CdSe Nanocrystals Examined Using Femtosecond Stimulated Raman Spectroscopy
Journal Article
·
· Journal of Physical Chemistry Letters
- Northwestern Univ., Evanston, IL (United States)
- Northwestern Univ., Evanston, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
In this paper, we report femtosecond stimulated Raman spectroscopy (FSRS) measurements on dispersions of CdSe semiconductor nanocrystals (NCs) as a function of particle size and pump fluence. Upon photoexcitation we observe depletion of stimulated Raman gain corresponding to generation of longitudinal optical (LO) phonons followed by recovery on picosecond timescales. At higher fluences, production of multiple excitons slows recovery of FSRS signals, which we attribute to sustained increases of LO phonon populations due to multiexcitonic Auger heating. Additionally, owing to discretized electronic structure of these NCs, such heating cannot be readily monitored via electronic spectroscopic analysis of high energy band tails as has been performed for higher-dimensionality materials. Notably, recovery timescales exceed those of the biexcitonic Auger recombination process and as such reveal overall thermalization timescales likely owing to an acoustic phonon thermalization bottleneck that dictates the cooling timescale.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
- Grant/Contract Number:
- AC02-06CH11357; FG02-99ER14999
- OSTI ID:
- 1491813
- Journal Information:
- Journal of Physical Chemistry Letters, Journal Name: Journal of Physical Chemistry Letters Journal Issue: 16 Vol. 9; ISSN 1948-7185
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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