Transcript Document

Longer than 1 nano-second !!!
Long-Lived Dilute Photocarriers in Individualy-suspended
Single-Walled Carbon Nanotubes
Y. Hashimoto, A. Srivastava, J. Shaver, G. N. Ostojic, S. Zaric, V.
C. Moore, R. H. Hauge, R. E. Smalley, and J. Kono
Rice University
Out line
•Introduction & Purpose
•Sample and Experimental setup
•Results and discussion
•Photo-induced carrier dynamics
•Polarization memory
•Summary
Supported by TATP and Welch Foundation
Introduction to Single-Walled Carbon Nanotube
Diameter: 1 nano-meter
Length: < 1 inch
ultimate quantum wire
Each peak corresponds
to particular (n,m)
Single Walled Carbon Nanotubes
photo-induced carrier life time
< 1 ps Bundled SWNT
5 - 50 ps Isolated SWNT
~ ns Isolated SWNT
~ 20 ns Theoretical
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)
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)
This work
C. D. Spataru et al., cond-mat/0301220 v1 (2003)
The relaxation dynamics of the
photo-excited carriers in SWNTs
radiative Non-radiative
1


1
 rad
~ ps

1
 non rad
~ ns
 non rad   rad
   nonrad
What kind of the Non-radiative relaxation is taken place ?
~640 e-h pairs
rs  1.5nm rex  2.5nm
~1mJ/cm2
in
In the previous study with a high-peak power OPA laser
PRL. 92, 077402 (2004)
1 mm SWNT < 20 ps
Exciton-exciton interaction ?
Purpose
Photo-induced carrier relaxation dynamics
in the low excitation limit
1 e-h pair per 1 mm SWNT
Single Walled Carbon Nanotube Sample
Absorption spectrum
-1
Absorption [cm ]
SDS miscelled SWNT
SWNT
2.2
2.0
1.8
1.6
1.4
1.2
1.2
1.4
1.6
Photon energy [eV]
1.8
Absorption shows sharp peaks
SDS micelle
Science VOL 297 593 (2002)
SWNT is well isolated
Experimental setup
-1
Absorption [cm ]
Pulse picker
80 MHz – 800 kHz
Laser wavelength: 1.550 eV (E2H2)
Ti:s laser
80MHz
2.4
2.0
1.6
1.2
1.4 1.5 1.6 1.7 1.8
Photon Energy [eV]
Si detector
Delay stage (2 ns)
l/2
Excitation fluence: 100 nJ/cm2
Pump : Probe = 10 : 1
SWNT
Aperture
Lock in
Photo-induced carrier dynamics in SWNT
in low excitation limit
Room temperature
T/T
10
10
10
10
-3
Repetition rate: 8 MHz
-4
Polarization of the
pump and probe:
-5
-6
0
400
Time delay [ps]
800
Previous report
in high excitation
 ~ 20 ps
Photo-induced carrier dynamics shows very long decay !!!
Pump and probe signal persist even at 1 nano-second
Decay dynamics
1.0x10
-3
1:  < 1 ps
T/T
0.8
0.6
2:  ~ 1 ns
0.4
0.2
0.0
0
500
Time delay [ps]
1000
Decay dynamics
E2H2  E1H1 intraband transition
E
5x10
-3
4
T/T
3
2
1
< 1 ps
E2
0
-1
E1
~ ns
DOS
E1H1 carrier recombination
H1
1.0x10
-3
0.8
T/T
H2
0
1
Time delay [ps]
0.6
0.4
0.2
0.0
0
500
1000
Time delay [ps]
Polarization memory
Polarization of the
pump and probe pulses
1.0
10
Tll  T
P
TllTll  TT
0.8
P
0.6
-4
P
T/T
10
Parallel
Perpendicular
-3
0.4
10
Tll  T
-5
0.2
0
400
800
Time delay [ps]
0.0
0
200 400 600 800 1000
Time delay [ps]
Polarization memory persist even at 1 ns !!!
In bundled SWNT, the polarization decay time ~ 10 ps
O. J. Korovyanko et al., Phys. Rev. Lett. 92 017403 (2004)
Summary
T/T
10
10
10
10
-3
-4
-5
-6
0
400
Time delay [ps]
800
•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
1.0
0.6
P
•The polarization memory in
isolated SWNTs shows no
decay even at 1 ns.
0.8
0.4
0.2
0.0
0
200 400 600 800
Time delay [ps]
1000
Future work
Two color pump-probe in the isolated SWNT
in the low excitation limit
Excited SWNT
(12,1)L : 797 nm
(11,3)L : 792 nm
(10,5)l : 786 nm
(9,7)l : 790 nm
Raman spectrum
G mode ~200meV
Intensity
Caused by the graphite structure
Depend on the chirality
RBM mode ~30meV
Depend on the diameter of the CNT
0
500
1000
1500
-1
Raman shift [cm ]
How to estimate the carrier concentration
Density of the SWNT:
9.7 x 1011mm/cm2
(in the 1mm path length cuvette)
Density of the SWNT in solution:
~20 x 10-6g/cm3
Mass density of SWNT (11. 0):
2.06 x 10-18 g/mm
Excitation intensity:
Absorption:
6.2 x 1015 photon/cm2
Excitation intensity:
1 mJ/cm2
Photon energy:
1 eV
10% (per 1 mm)
6.2 1015 photon/ cm2 10%
2

6
.
4

10
photon/ mm
11
2
9.7 10 mm / cm
Longer than 1 nano-second !!!
Long-Lived Dilute Photocarriers in Individualy-suspended
Single-Walled Carbon Nanotubes
Y. Hashimoto, A. Srivastava, J. Shaver, G. N. Ostojic, S. Zaric, V.
C. Moore, R. H. Hauge, R. E. Smalley, and J. Kono
Rice University
Out line
•Introduction & Purpose
•Sample and Experimental setup
•Results and discussion
•Photo-induced carrier dynamics
•Polarization memory
•Summary
Supported by TATP and Welch Foundation
Introduction to Single-Walled Carbon Nanotube
Diameter: 1 nano-meter
Length: < 1 inch
ultimate quantum wire
Single Walled Carbon Nanotubes
photo-induced carrier life time
< 1 ps Bundled SWNT
5 - 50 ps Isolated SWNT
~ ns Isolated SWNT
~ 20 ns Theoretical
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)
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)
This work
C. D. Spataru et al., cond-mat/0301220 v1 (2003)
The relaxation dynamics of the
photo-excited carriers in SWNTs
radiative Non-radiative
1


1
 rad
~ ps

1
 non rad
~ ns
 non rad   rad
   nonrad
What kind of the Non-radiative relaxation is taken place ?
~640 e-h pairs
rs  1.5nm rex  2.5nm
~1mJ/cm2
in
In the previous study with a high-peak power OPA laser
PRL. 92, 077402 (2004)
1 mm SWNT < 20 ps
Exciton-exciton interaction ?
Purpose
Photo-induced carrier relaxation dynamics
in the low excitation limit
1 e-h pair per 1 mm SWNT
Single Walled Carbon Nanotube Sample
Absorption spectrum
-1
Absorption [cm ]
SDS miscelled SWNT
SWNT
2.2
2.0
1.8
1.6
1.4
1.2
1.2
1.4
1.6
Photon energy [eV]
1.8
Absorption shows sharp peaks
SDS micelle
Science VOL 297 593 (2002)
SWNT is well isolated
Experimental setup
-1
Absorption [cm ]
Pulse picker
80 MHz – 800 kHz
Laser wavelength: 1.550 eV (E2H2)
Ti:s laser
80MHz
2.4
2.0
1.6
1.2
1.4 1.5 1.6 1.7 1.8
Photon Energy [eV]
Si detector
Delay stage (2 ns)
l/2
Excitation fluence: 100 nJ/cm2
Pump : Probe = 10 : 1
SWNT
Aperture
Lock in
Photo-induced carrier dynamics in SWNT
in low excitation limit
Room temperature
T/T
10
10
10
10
-3
Repetition rate: 8 MHz
-4
Polarization of the
pump and probe:
-5
-6
0
400
Time delay [ps]
800
Previous report
in high excitation
 ~ 20 ps
Photo-induced carrier dynamics shows very long decay !!!
Pump and probe signal persist even at 1 nano-second
Decay dynamics
1.0x10
-3
1:  < 1 ps
T/T
0.8
0.6
2:  ~ 1 ns
0.4
0.2
0.0
0
500
Time delay [ps]
1000
Decay dynamics
E2H2  E1H1 intraband transition
E
5x10
-3
4
T/T
3
2
1
< 1 ps
E2
0
-1
E1
~ ns
DOS
E1H1 carrier recombination
H1
1.0x10
-3
0.8
T/T
H2
0
1
Time delay [ps]
0.6
0.4
0.2
0.0
0
500
1000
Time delay [ps]
Polarization memory
Polarization of the
pump and probe pulses
1.0
10
Tll  T
P
TllTll  TT
0.8
P
0.6
-4
P
T/T
10
Parallel
Perpendicular
-3
0.4
10
Tll  T
-5
0.2
0
400
800
Time delay [ps]
0.0
0
200 400 600 800 1000
Time delay [ps]
Polarization memory persist even at 1 ns !!!
In bundled SWNT, the polarization decay time ~ 10 ps
O. J. Korovyanko et al., Phys. Rev. Lett. 92 017403 (2004)
Summary
T/T
10
10
10
10
-3
-4
-5
-6
0
400
Time delay [ps]
800
•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
1.0
0.6
P
•The polarization memory in
isolated SWNTs shows no
decay even at 1 ns.
0.8
0.4
0.2
0.0
0
200 400 600 800
Time delay [ps]
1000
Future work
Two color pump-probe in the isolated SWNT
in the low excitation limit