Abstract
Ultrafast optical pump, X-ray diffraction probe experiments were performed on CdSe nanocrystal (NC) colloidal dispersions as functions of particle size, polytype, and pump fluence. Bragg peak shifts related to heating and peak amplitude reduction associated with lattice disordering are observed. For smaller NCs, melting initiates upon absorption of as few as ∼15 electron-hole pair excitations per NC on average (0.89 excitations/nm3 for a 1.5 nm radius) with roughly the same excitation density inducing melting for all examined NCs. Diffraction intensity recovery kinetics, attributable to recrystallization, occur over hundreds of picoseconds with slower recoveries for larger particles. Zincblende and wurtzite NCs revert to initial structures following intense photoexcitation suggesting melting occurs primarily at the surface, as supported by simulations. Electronic structure calculations relate significant band gap narrowing with decreased crystallinity. These findings reflect the need to consider the physical stability of nanomaterials and related electronic impacts in high intensity excitation applications such as lasing and solid-state lighting.
| Original language | English |
|---|---|
| Pages (from-to) | 5315-5320 |
| Number of pages | 6 |
| Journal | Nano Letters |
| Volume | 17 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - Sep 13 2017 |
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Keywords
- melting
- molecular dynamics
- multiexciton
- Nanocrystals
- phonon
- transient diffraction
ASJC Scopus subject areas
- Bioengineering
- Chemistry(all)
- Materials Science(all)
- Condensed Matter Physics
- Mechanical Engineering
Cite this
Transient Melting and Recrystallization of Semiconductor Nanocrystals under Multiple Electron-Hole Pair Excitation. / Kirschner, Matthew S.; Hannah, Daniel C.; Diroll, Benjamin T.; Zhang, Xiaoyi; Wagner, Michael J.; Hayes, Dugan; Chang, Angela Y.; Rowland, Clare E.; Lethiec, Clotilde M.; Schatz, George C; Chen, Lin X.; Schaller, Richard D.
In: Nano Letters, Vol. 17, No. 9, 13.09.2017, p. 5315-5320.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Transient Melting and Recrystallization of Semiconductor Nanocrystals under Multiple Electron-Hole Pair Excitation
AU - Kirschner, Matthew S.
AU - Hannah, Daniel C.
AU - Diroll, Benjamin T.
AU - Zhang, Xiaoyi
AU - Wagner, Michael J.
AU - Hayes, Dugan
AU - Chang, Angela Y.
AU - Rowland, Clare E.
AU - Lethiec, Clotilde M.
AU - Schatz, George C
AU - Chen, Lin X.
AU - Schaller, Richard D
PY - 2017/9/13
Y1 - 2017/9/13
N2 - Ultrafast optical pump, X-ray diffraction probe experiments were performed on CdSe nanocrystal (NC) colloidal dispersions as functions of particle size, polytype, and pump fluence. Bragg peak shifts related to heating and peak amplitude reduction associated with lattice disordering are observed. For smaller NCs, melting initiates upon absorption of as few as ∼15 electron-hole pair excitations per NC on average (0.89 excitations/nm3 for a 1.5 nm radius) with roughly the same excitation density inducing melting for all examined NCs. Diffraction intensity recovery kinetics, attributable to recrystallization, occur over hundreds of picoseconds with slower recoveries for larger particles. Zincblende and wurtzite NCs revert to initial structures following intense photoexcitation suggesting melting occurs primarily at the surface, as supported by simulations. Electronic structure calculations relate significant band gap narrowing with decreased crystallinity. These findings reflect the need to consider the physical stability of nanomaterials and related electronic impacts in high intensity excitation applications such as lasing and solid-state lighting.
AB - Ultrafast optical pump, X-ray diffraction probe experiments were performed on CdSe nanocrystal (NC) colloidal dispersions as functions of particle size, polytype, and pump fluence. Bragg peak shifts related to heating and peak amplitude reduction associated with lattice disordering are observed. For smaller NCs, melting initiates upon absorption of as few as ∼15 electron-hole pair excitations per NC on average (0.89 excitations/nm3 for a 1.5 nm radius) with roughly the same excitation density inducing melting for all examined NCs. Diffraction intensity recovery kinetics, attributable to recrystallization, occur over hundreds of picoseconds with slower recoveries for larger particles. Zincblende and wurtzite NCs revert to initial structures following intense photoexcitation suggesting melting occurs primarily at the surface, as supported by simulations. Electronic structure calculations relate significant band gap narrowing with decreased crystallinity. These findings reflect the need to consider the physical stability of nanomaterials and related electronic impacts in high intensity excitation applications such as lasing and solid-state lighting.
KW - melting
KW - molecular dynamics
KW - multiexciton
KW - Nanocrystals
KW - phonon
KW - transient diffraction
UR - http://www.scopus.com/inward/record.url?scp=85029355129&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85029355129&partnerID=8YFLogxK
U2 - 10.1021/acs.nanolett.7b01705
DO - 10.1021/acs.nanolett.7b01705
M3 - Article
VL - 17
SP - 5315
EP - 5320
JO - Nano Letters
JF - Nano Letters
SN - 1530-6984
IS - 9
ER -