1 out line introduction & purpose sample and experimental setup results and discussion...
TRANSCRIPT
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Out line•Introduction & Purpose•Sample and Experimental setup•Results and discussion
•Photo-induced carrier dynamics•Polarization memory
•SummarySupported by TATP and Welch Foundation
13aWF-7 単層カーボンナノチューブにおける単層カーボンナノチューブにおける
光誘起キャリア緩和ダイナミクスおよびその偏光特性光誘起キャリア緩和ダイナミクスおよびその偏光特性
Relaxation and polarization dynamics of photo-induced carriers in individually-suspended single-walled carbon nanotubes
Y. HashimotoA. B, A. SrivastavaB , J. KonoB, J. ShaverC, V.C. MooreC, R.H. HaugeC, R.E. SmalleyC
Graduate School of Chiba Univ.A, ECE Dept., Rice Univ.B, Chemistry Dept., Rice Univ.C
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Single-Walled Carbon Nanotubesphoto-induced carrier lifetimes
Hertel and Moos, Phys. Rev. Lett. 84, 5002 (2000)Chen et al., Appl. Phys. Lett. 81, 975 (2002)Han et al., Appl. Phys. Lett. 82, 1458 (2003)Lauret et al., Phys. Rev. Lett. 90, 057404 (2003)Korovyanko et al. Phys. Rev. Lett. 92, 017403 (2004)
< 1 ps Bundled SWNT
5 - 120 ps Isolated SWNT
G. N. Ostojic et al., Phys. Rev. Lett. 92, 117402 (2004)Y.-Z. Ma et al., J. Chem. Phys. 120, 3368 (2004)A. Hagen et al., Appl. Phys. A 78, 1137 (2004)F. Wang et al., Phys. Rev. Lett. 92, 177401 (2004)L. Huang et al., Phys. Rev. Lett. 93, 017403 (2004)
~ 20 ns Theoretical C. D. Spataru et al., cond-mat/0301220 v1 (2003)
~ ns Isolated SWNT This work
3
nmrs 5.1
PurposePhoto-induced carrier relaxation dynamics
in the low excitation limit
Relaxation Dynamics ofPhoto-excited Carriers in SWNTs
Radiative Non-radiative
radnonrad
111radradnon
radnon
~ ps ~ ns
Exciton-exciton interaction ?
What kind of the Non-radiative relaxation is taking place ?~640 e-h pairs
in 1 m SWNT PRL 92, 077402 (2004)
nmaB 5.2
1 e-h pair per 1 m SWNT
~1 mJ/cm2PRL 92, 011742 (2004)
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Absorption shows sharp peaks
SWNT is well isolated
Single-Walled Carbon Nanotube Samples
Absorption spectrum
2.2
2.0
1.8
1.6
1.4
1.2Ab
sorp
tion
[cm
-1]
1.81.61.41.2
Photon energy [eV]
SWNT
SDS micelle
SDS miscelled SWNT
Science VOL 297 593 (2002)
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Experimental Setup
/ 2
Pulse picker80 MHz 800kHz
Ti:S laser80MHz
Excitation fluence: 100 nJ/cm2
Pump : Probe = 10 : 1
Si detector
Lock in
2.42.0
1.6
1.2
Abs
orpt
ion
[cm
-1]
1.81.71.61.51.4
Photon Energy [eV]
Laser wavelength: 1.550 eV (E2H2)
Delay stage (2 ns) ApertureSWNT
6
Checking the Experimental Setup
GaAsPolarization of the pump and probe pulse
T
/T
3210-1-2Time delay [ps]
No difference
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Photo-Induced Carrier Dynamics in SWNTin Low Excitation Limit
Pump-probe signal exists even at 1 nano-second !!!
Room temperature
Repetition rate: 8 MHz
Polarization of the pump and probe:
Previous reports in high excitation
< 120 ps
10-5
2
4
10-4
2
4
10-3
2
4
T
/T
10005000Time delay [ps]
8
1.0x10-3
0.8
0.6
0.4
0.2
0.0
T/T
10005000Time delay [ps]
1: < 1 ps
2: ~ 1 ns
Decay Dynamics
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E
E1DOS
E2
H2
H1
Decay Dynamics
~ ns
E2H2 E1H1 intraband transition
5x10-3
4
3
2
1
0
T/T
10-1Time delay [ps]
E1H1 carrier recombination1.0x10
-3
0.8
0.6
0.4
0.2
0.0
T/T
10005000Time delay [ps]
< 1 ps
10
1.0
0.8
0.6
0.4
0.2
0.0P
10005000Time delay [ps]
10-6
10-5
10-4
10-3
T
/T
10005000Time delay [ps]
Parallel Perpendiculer
Polarization Memory
TTTT
Pll
ll
Polarization memory exists even at 1 ns !!!
In bundled SWNT, the polarization decay time ~ 10 psO. J. Korovyanko et al., Phys. Rev. Lett. 92 017403 (2004)
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Polarization Memory
n I pump cos2
2/
2/
22
2/
2/
4
sincos
cos
dIT
dIT
pump
pumpll
45.05.0
TT
TTP
ll
ll
Pump
Absorption is reduced No change
Pump
Pump pulse polarization
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Summary•The transient absorption of the isolated SWNTs in low excitation regime shows very fast (< 1 ps) E2H2 E1H1 intraband transition and very long (~ 1ns) E1H1 carrier recombination
Future workTwo color pump-probe in the isolated SWNT
in the low excitation limit
10-6
10-5
10-4
10-3
T/T
8004000Time delay [ps]
•The polarization memory in isolated SWNTs shows no decay even at 1 ns.
1.0
0.8
0.6
0.4
0.2
0.0
P10008006004002000
Time delay [ps]