Quantum Transport and Dynamics in Nanostructures
The 4th Windsor Summer School on Condensed Matter Theory
6-18 August 2007, Great Park Windsor (UK)
Physics of Nanotubes, Graphite and
Graphene
Mildred Dresselhaus
Massachusetts Institute of Technology, Cambridge, MA
Physics of Nanotubes, Graphite
and Graphene
Outline of Lecture 1 - Nanotubes
•
•
•
•
•
Brief overview of carbon nanotubes
Review of Photophysics of Nanotubes
Phonon assisted Photoluminescence
Double wall carbon nanotubes
Nano-Metrology
Carbon Nanotube researchstill a growing field
•
•
1991 nanotube observation by Sumio Iijima (NEC) opening field
number of publications is still growing exponentially
6000
5000
4000
3000
2000
1000
0
1991
1996
2001
2006
number of publications containing “Carbon Nanotube” vs. time
Iijima, S., Helical Microtubules of Graphitic Carbon. Nature, 1991. 354(6348): p. 56-58.
Carbon Nanotubes
(5,5)
Armchair Nanotube
(9,0)
Zigzag Nanotube
(6,5)
Chiral Nanotube
(n,m) notation focuses on symmetry of cylinder edge
Carbon materials
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Diamond
Graphite (hexagonal, rhombohedral)
HOPG (highly oriented pyrolytic graphite)
Pyrolytic graphite
Turbostratic graphite
Kish graphite
Liquid carbon
Amorphous carbon
Carbon and graphitic foams
Carbon fibers
Fullerenes
Nanotubes
Nanohorns
Graphene fibers and scrolls
Graphene
Graphene ribbons
3D, 2D, 1D Carbon Materials
Diamond
sp3
(3D) 1332
cm-1
Graphite
Chain
sp2 (2D) 1582 cm-1
sp1 (1D) 1855 cm-1
All are Raman active with characteristic frequencies
Unique Properties of Carbon
Nanotubes within the Nanoworld
graphene sheet
armchair
SWNT
• Size: Nanostructures with dimensions
of ~1 nm diameter (~10 atoms around
the cylinder)
• Electronic Properties: Can be either
metallic or semiconducting depending on
diameter and orientation of the hexagons
zigzag
• Mechanical: Very high strength,
modulus, and resiliency. Good
properties on both compression and
extension.
chiral
• Physics: 1D density of electronic states
• Single molecule Raman spectroscopy
and luminescence.
• Single molecule transport properties.
• Heat pipe, electromagnetic waveguide.
One Dimensional Systems:
• High aspect ratio
• Enhanced density of states
• Single wall carbon nanotubes SWNT:Nanowire
Chirality and diameter-dependent properties
E
3D
Bulk Semiconductor
D. O. S.
D. O. S.
D. O. S.
D. O. S.
Nanotube
E
2D
Quantum Well
E
E
1D
Quantum Wire
0D
Quantum Dot
Nanotube Structure in a Nutshell
(4,2)
Graphene Sheet
SWNT
Rolled-up graphene layer
Large unit cell.
G
G
G
C h = na1 + ma 2 ≡ ( n , m )
L a
⎧
2
2
d
n
nm
m
=
=
+
+
t
⎪⎪
π π
⎨
3m
⎪θ = tan − 1
⎪⎩
2n + m
Each (n,m) nanotube is a unique molecule
R.Saito et al, Imperial College Press, 1998
Electronic structure of a carbon nanotube
Rolling up 2D graphene sheet
Confinement of 1D electronic states
1D van Hove singularities high density of electronic
states (DOS) at well defined
energies
Graphene ribbons resemble nanotubes in some ways
Metal or Semiconductor ?
R. Saito et al., Appl. Phys. Lett. 60, 2204 (1992)
• Density of States
• Depending on Chirality, Diameter
metal
⎧ 3p
n−m = ⎨
⎩3 p ± 1 semiconductor
Each (n,m) nanotube is a unique molecule
Armchair graphene ribbons can be M or S
Egap ∝ 1/ dt
Physics of Nanotubes, Graphite
and Graphene
Outline of Lecture 1 - Nanotubes
•
•
•
•
•
Brief overview of carbon nanotubes
Review of Photophysics of Nanotubes
Phonon assisted Photoluminescence
Double wall carbon nanotubes
Nano-Metrology
Resonance Raman Spectroscopy (RRS)
A.M. Rao et al., Science 275 (1997) 187
RRS: R.C.C. Leite & S.P.S. Porto, PRL 17, 10-12 (1966)
Raman spectra from SWNT bundles
• Enhanced Signal
9 Optical Absorption
9 e-DOS peaks
E = 0.94eV
= 1.17eV
π
π∗
= 1.58eV
= 1.92eV
diameter-selective resonance process
ωRBM = α / dt
= 2.41eV
Resonant Raman Spectra of Carbon Nanotube Bundles
M. A. Pimenta (UFMG) et al., Phys. Rev. B 58, R16016 (1998)
G-band resonant Raman spectra
laser energy
G-band
dt = 1.37 ± 0.18 nm
Diameter dependence of
the Van-Hove singularities
Single Nanotube Spectroscopy yields Eii, (n,m)
Resonant Raman spectra for isolated single-wall carbon
nanotubes grown on Si/SiO2 substrate by the CVD method
RBM
A. Jorio (UFMG) et al., Phys. Rev. Lett. 86, 1118 (2001)
Metallic
'
Semiconducting
Each nanotube has a
unique DOS because of
trigonal warping effects
R. Saito et al.,
Phys. Rev. B 61, 2981
(2000)
Raman signal from one
SWNT indicates a strong
resonance process
(ωRBM, Eii) Æ
(n,m)
Raman Spectra of SWNT Bundles
Metallic G-band
G-band
G+
G-
Raman Intensity
G+
o
G+
GRBM: ωRBM∝ 1/dt
G′-band
D-band
Raman Shift (cm−1)
•RBM gives tube diameter and diameter distribution
•Raman D-band characterizes structural disorder
•G- band distinguished M, S tubes and G+ relates to charge transfer
•G’ band (2nd order of D-band) provides connection of phonon to its wave vector
Water, 1.1 g/cm3
SDS
Band Gap Fluorescence
1.0 g/cm3
1.2 g/cm3
SDS=Sodium Dodecyl Sulfate
2
Energy [eV]
c2
Excitation (nm)
M. J. O’Connell et al., Science 297 (2002) 593
S. M. Bachilo et al., Science 298 (2002) 2361.
Peaks only
c1
0
fluorescence
absorption
v1
v2
–2 0
Density of Electronic States
e-DOS of (n, m) = (10,5)
Emission (nm)
Initially (n,m) assignments were made by
empirical excitation-emission pattern
PHOTOLUMINESCENCE
SDS-wrapped HiPco nanotubes in solution
S. M. Bachilo et al., Science 298, 2361 (2002)
™2n+m=constant family patterns are observed in the PL excitation-emission spectra
™Identification of ratio problem
™Showed value of mapping optical transitions
Perhaps this technique can be applied to study graphene ribbons
Raman Mapping of a Nanotube
G-band @ 1600cm-1
4
40
Silicon @ 520cm-1
RBM @ 173cm-1
4
x 10
40
x 10
9
40
4
2.5
8
20
20
2
2
2
-2
800
-20
-2
600
0
(µm)
1.5
7
0
0
(µm)
0
(µm)
2
0
0
-20
20
1000
6
-20
5
-2
4
-40
-40
-4
1
-40
-4
400
-60
-60
-6
0.5
-4
3
-60
-6
200
-80
2
-6
-80
1
-80
-8
-2
-10
-100
-20
-8
0
0
0
20
2 (µm)
0
-100
-20
-2
-10
0
0
20
2 (µm)
H. Son et al. unpublished (2006)
-8
-100
-20
-2
-10
0
0
20
0
2 (µm)
Resonance Raman Spectroscopy
on the same sample used for PL
E33S
E11M
E22S
RRS
2n+m = constant
family behavior is
observed
E33S
Fantini (UFMG) et al.
PRL (2004) showed
RRS and PL give
the same Eii
Family effects are
mainly due to
trigonal warping
E11M
E22S
simple tight binding (sTB)
sTB
γ0=2.9eV
The simple TB does not
describe Eii correctly!
EXTENDED TIGHT BINDING MODEL
Kataura plot is calculated within the
extended tight-binding approximation
using Popov/Porezag approach:
Transition Energy (eV)
™ curvature effects (ssσ, spσ, ppσ, ppπ)
™ long-range interactions (up to ~4Å)
™ geometrical structure optimization
The extended tight-binding
calculations show family behavior
(differentiation between S1 & S2
and strong chirality dependence)
similar to that of the PL empirical fit
Inverse Diameter (1/nm)
M 2n+m=3p
S1 2n+m=3p+1
S2 2n+m=3p+2
Family behavior is strongly influenced
by the trigonal warping effect
Ge.G. Samsonidze et al., APL 85, 5703 (2004)
N.V. Popov et al Nano Lett. 4, 1795 (2004) & New J. Phys. 6, 17 (2004)
2n+m families in SWNTs
R. Saito et al., Phys. Rev. B, 72, 153413 (2005)
Brillouin zone (BZ)
2D graphene BZ
SWNT BZ
K
K’
type I
type II
Family
0 : metal
mod (2n+m, 3) = 1 : type I SC
2 : type II SC
2n+m = const family
type I – type II separation
(example)
(8,0), (7,2), (6,4)
→
2n+m = 16 type I family
Physics of Nanotubes, Graphite
and Graphene
Outline of Lecture 1 - Nanotubes
•
•
•
•
•
Brief overview of carbon nanotubes
Review of Photophysics of Nanotubes
Phonon assisted Photoluminescence
Double wall carbon nanotubes
Nano-Metrology
DNA wrapping of SWNTs
DNA Wrapping:
Æ provides good separation of
CoMoCAT SWNT sample
Subsequent fractionation:
Æ results in sample strongly
enriched in (6,5) species
M. Zheng, et al. Science 302, 1546 (2003)
Average DNA helical
pitch ~ 11nm,
height ~ 1.08nm.
DNA-Assisted SEPARATION
M. Zheng et al., Science, 302,1546 (2003).
load
sample
add
eluant
Ion-exchange chromatography
(IEC)
Hybrid DNA-SWNTs:
• M-SWNT different surface charge density,
higher polarizability, elute before S-CNTs
column
containing
stationary
phase
RBM Spectra Taken at E laser = 2.18eV
collect
samples
Raman characterization shows
that
•DNA wrapping removes metallic
(M) SWNTs
•Chromatography further removes
M SWNTs preferentially
(6,5)
M
CoMoCAT CNT
S
(No DNA)
DNA-CNT
Fractionated DNA-CNT
150
200
250
300
Raman Shift (cm -1 )
350
400
Nanotube PL Spectroscopy
•
Most Measurements
•
- excitation at E22,
emission at E11
- measured with Xe lamp
- (2n+m) family patterns
provide (n, m)
identifications.
Our Measurements
– (6,5) enriched sample
– Intense light source
(laser)
– Allows observation of
phonon assisted
processes
PL map of SDS- dispersed HiPco CNTs
Maruyama et al. NJP (2003)
Maruyama’s work suggests study of detailed phonon-assisted
excitonic relaxation processes for different phonon branches.
PL Spectra of (6,5) Nanotubes
1.64
8
Excitation Energy (eV)
1.6
7.5
7
1.56
6.5
1.52
6
1.48
5.5
5
1.44
1.05
1.1
1.15
1.2
1.25
Emission Energy (eV)
1.3
Phonon-assisted transitions on an expanded scale
Chou, et al PRL 94, 127402 (2005)
E11 = 1.26eV
E22 = 2.18eV
Excitons in Carbon Nanotubes
Experimental Justification for excitons
2-photon excitation to a 2A+ symmetry exciton (2p)
and 1-photon emission from a 1A− exciton (1s)
cannot be explained by the free electron model
2A+
BAND-EDGE
ABSORPTION (a.u.)
1A−
E11 (1s)
1.2
1.4
1.6
1.8
2.0
2-PHOTON EXCITATION ENERGY
The observation that excitation and emission are
at different frequencies supports exciton model
1.4
EMISSION ENERGY
1A−
E11 (1s)
E11 (2p)
(9,1)
(8,3)
1.3
(6,5)
(7,5)
1.2`
1.2
1.4
1.6
1.8
2-PHOTON EXCITATION ENERGY
Wang et al. Science 308, 838 (2005)
The exciton-phonon sidebands
further support exciton model
HiPco + SDS solution
E22S - E11S
Sideband
F. Plentz Filho (UFMG) et al,
PRL 95, 247401 (2005)
E11S - E11S
Perebeinos, Tersoff and Avouris,
PRL 94, 027402 (2005)
Emission Identified with
One and Two Phonon Processes:
Phonon dispersion relations
of graphite
2 iLO/iTO near Γ
2 iTO near K (G’ band)
2 iLO/iLA near K
2 oTO near Γ(M-band)
1iLO/iTO near Γ (G-band)
Chou et al., PRL 94, 127402 (2005)
Two phonon
process
One phonon
process
Non-degenerate Pump-probe
Frequency domain
S. G. Chou et al. PRL 94 127402 (2005)
Epump = 1.57±0.01eV, ~E11(6,5)+2ħωD
Eprobe = around E11of (6,5) nanotube
(Instrument resolution ~250fs)
Eprobe =E11(6,5)
EPump ~E11(6,5)+ 2ħωph, D
Fast optics, Time domain
Intraband
relaxation
Pump
Probe
Interband
relaxation
S. G. Chou et al. Phys. Rev. B (2005)
Pump Probe Studies at Special Epump
• Epump = 1.57±0.01eV≈E111A-(6,5)+2ħωD
• Eprobe = around E111A-of (6,5) nanotube
Pump
Intraband
relaxation
Probe at
band edge
K
Exciton population at E111A-(6,5):
• Quick rise (within 200fs)
• Three decay components:
• τfast~680fs (dominant process)
• τint~2-3ps (dominant process)
• τslow~50ps (weak during first
20ps).
Probing at Different Energies:
-Pump at 1.57±0.01 eV
Eiij
1.27eV (8,3)
1.25eV(6,5)
E111A-(8,3)+2hwD
E111A-(6,5)+2hwD
u
E111A-(7,5)+2hwD
1.22eV
o5
1.20eV(7,5)
o4
o3
o2
o1
1.16eV
z
Exp.
O5
O4
O2
(n,m)
(8,3)
(6,5)
(7,5)
EProbe
1.27eV
1.25eV
1.20eV
FluenceJ/m2
0.3
0.3
0.1
fast
900fs
700fs
800fs
%
70
45
90
Int
Several ps
3ps
N/A
0
E111A-(8.3)
E111A-(6,5)
E111A-(7,5)
K
%
Traces mixed
45
N/A
Slow
30ps
50ps
40ps
%
30
10
10
More on Excitons
• Why?
– Large binding energy (0.5eV)
• Even at room temperature, excitons
exist.
– Exciton specific phenomena
• dark excitons, two photon, environment
• What can we know or imagine?
2+
1-
A11
– Near cancellation by self energy
• ETB + many body effects reproduce Eii
– Localized exciton wave function
• enhancement of optical process
• Length dependence.
Wang et al. Science
308, 838 (2005)
A11 (2p)
(1s)
Exciton exists only in the 3M-triangle
E55S
E11S
E22S
E33S
E44S
Energy minima for the π∗ band exist only in 3MΔ.
Cutting lines occur around K-point.
Symmetry considerations
J. Jiang et al. Phys. Rev. B75 035405 (2007)
Centre of mass motion
:Good quantum number
Relative motion
Bright and dark excitons
A-: bright exciton
A+, E and E*: dark excitons
A symmetry excitons
K
K
K Γ
K’
e h
K Γ
C2
e
h
e
K’
A±
h
K
Γ
E symmetry exciton and its dispersion
K
E exciton
h
e
K’
K’
E* exciton
K
K
Bright and dark excitons
A- : bright exciton
A+, E, E*: dark excitons
Dispersion for (6,5) NT
K’
K
h
e K
Dark state has the lowest energy
J. Jiang et al. Phys. Rev. B75 035405 (2007)
A- : bright exciton
A- : bright exciton
A+, E and E*: dark excitons
11
11
11
11
Lowest energy but not symmetry allowed
Physics of Nanotubes, Graphite
and Graphene
Outline of Lecture 1 - Nanotubes
•
•
•
•
•
Brief overview of carbon nanotubes
Review of Photophysics of Nanotubes
Phonon assisted Photoluminescence
Double wall carbon nanotubes
Nano-Metrology
Raman Spectra of SWNT Bundles
Metallic G-band
G-band
G-
Raman Intensity
G+
o
G+
GRBM: ωRBM∝ 1/dt
G’-band
D-band
Raman Shift (cm−1)
Photophysics of SWNTs is now at an advanced stage
Photophysics of MWNTs (DWNTs) is at an early stage
Motivation for studying DWNTs
• Applications
– world shows much interest
• Synthesis
– world has made major progress
• Promising for fundamental physics
• Study of the interface between DWNTs
and bilayer graphene should enrich
both areas
Approaches to DWNTs
• simplest assumption
+
=
Suggests using Kataura plots for SWNTs as first
approximation for DWNTs, but E(k) of monolayer and
bilayer graphene say more detail is needed
Br2-doped double-wall nanotubes
Pristine DWNTs
(a)
Br2-DWNTs
(b)
TEM images
Highly pure
samples
(99% of DWNTs +
1% of SWNTs +
catalysts
particles)
5 nm
5 nm
(c)
(d)
SEM images
100nm
100nm
Endo et al. Nanolett.
4,1451 (2004)
Kataura plot: undoped vs. doped SWNTs
using Extended Tight Binding Model
Inner tubes
Outer tubes
2.4
2.0
1.6
dt (nm)
1.2
Doped
(+0.04 e-/C)
0.8
18
26
17
Undoped
2.5
29
21
20
32
24
Eii (eV)
35
2.0
27
38
30
S
E33
1.5
33
36
23
16
26
19
29
39
22
25
M
E11
28
S
1.0
100
• Different
configurations
for outer/inner
nanotubes
depending on
laser energy
S
E11
31
E22
150
200
250 −1
Frequency (cm )
300
350
Semiconducting outer/Metallic inner configuration
M
RBM properties at Elaser=2.33 eV
• Breathing mode spectrum
from the Br2 dopant
• Resonance with Bromine
electronic transitions
• Can identify individual
(n,m) inner tubes from
Kataura plot
(b)
(8,5)
(12,3)
(11,5)
2
(7,7)
(9,3)
(9,6)
100
Br -doped
Br2 doped
Elaser = 2.33 eV
Pristine
ELaser= 2.33 eV
150
Raman Intensity (arb. units)
1.4
(a)
Raman Intensity (arb. units)
1.0
S
200
250
-1
Frequency (cm)
300
26
29
21
32
24
35
38
100
150
200
250
-1
Frequency (cm )
A.Souza-Filho. et al PRB (2006)
300
350
150
27
22
200
23
250 −1
Frequency (cm )
350
Metallic outer/Semiconducting inner configuration
M
S
• Intensity enhancement after
bromine doping
RBM properties at Elaser=1.58 eV • Doping changing relative
intensities of (n,m) tubes
1.0
E
= 1.58 eV
(a)
pristine
• The Kataura plot for SWNTs
1.0
(11,0)
gives identification for inner
wall tubes and shows doping effect
(10,2)
*
(9,4)
1.4
(b)
240
250
260
270
-1
Frequency (cm )
280
*
(9,1)
100
150
200
250
-1
Frequency (cm )
33
3
36
300
22
25
28
S
E11
31
E22
150
200
Br2 doped
250 −1
Frequency (cm )
(11,0)
(10,2)
*
350
29
39
S
Elaser = 1.58 eV
1.4
Raman Intensity (arb. units)
Raman Intensity (arb. units)
laser
(9,4)
240
250
260
270
-1
280
Frequency (cm )
*
100
150
200
250
-1
Frequency (cm )
300
350
Metallic shielding effects
Metallic outer/semiconducting inner wall
D and G band (DWNTs)
Elaser=1.58 eV
Raman Intensity
S
1500
1550
1600
-1
Frequency (cm )
1301
D band
1200
1300
1650
Br2-doped
1554
1400
1500
M
Pristine
1600
1700
Frequency (cm-1)
• The G-band is predominantly from semiconducting
Nanotubes (based on diameter dependence)
• No shift in the G-band for semiconducting inner tubes
• The inner tubes are shielded by the metallic outer tubes
Charge transfer effects
Semiconducting outer/metallic inner
D and G band (DWNTs)
Elaser=2.33 eV
M
1581
Br2-doped
1599
1570
Raman Intensity
S
1545
D band
1341
1450
1500
1550
1600
1650
-1
Frequency (cm )
1592
1575
Pristine
1562
1537
x0.5
1200
1485
1400
1600
-1
Frequency (cm )
1450
1519
1500
1550
1600
-1
1650
Frequency (cm )
• The G-band profile is a mixing of semiconducting and metallic profiles;
• Shift in the G-band from semiconducting outer tubes indicates charge
transfer to the Br2 molecules
• The BWF (Breit Wigner Fano) decreases after doping.
• The decrease in the overall intensity indicates depletion of states
(a)
Elaser
M
2.33 eV
S
G band Raman spectra of
Br2 doped DWNTs.
Br2 doped
Pristine
(b)
x0.3
1450
1500
1550
1600
-1
Frequency (cm )
Raman Intensity
Raman Intensity
Charge transfer and screening
effects
S
1650
Metallic inner tubes highly
affected by doping
Semiconducting inner tubes
is not affected when shielded by
metallic tubes
Elaser
1450
1500
1.58 eV
M
1550
Frequency (cm
1600
-1
)
1650
Calculated electronic charge density
difference (ρdoped - ρundoped) of DWNTs
Calculation supports experimental observations about charge transfer
A.G. Souza Filho et al Nano Letters (2007)
Undoping experiments on
bromine doped DWNTs
Br2-adsorbed DWNTs
Outer tubes
Br2
Elaser=2.33 eV
Inner tubes
Raman Intensity
Br2
Energy
needed
for removing
Br2
is ~ 25 meV
o
heating
21 C
o
cooling
600 C
o
21 C
100
200
300
400
Frequency (cm-1)
500
• The dopant is completely removed after heat treatment
Souza Filho et al, PRB (2006)
Spectrum for RBM for pristine and
H2SO4doped DWNTs
Outer Walls
Inner Walls
M
H2SO4 doped
Elaser=2.052 eV
Raman Intensity
Pristine
S
150
200
250
300
350
400
-1
Frequency (cm )
•Outer walls strongly affected by doping
•Inner semiconducting (S) tubes weakly interact with dopant
•Inner metallic (M) tubes more strongly interact with dopant
E. Barros et al, PRB (2007)
What we learned from
intercalation studies of DWNTs
• The Kataura plot from SWNTs provides a
semi-quantitive interpretation of frequencies
for inner wall tubes for DWNTs
S
• The M/S configuration shields inner
semiconducting tubes from the effect of the
dopant
• The S/M configuration allows charge transfer
to inner metallic tubes
M
M
S
This work potentially relates to bilayer graphene
Laser Energy Dependence of G′-band Spectra
The SWNT G’ band corresponds to peak 3 of DWNTs
4
3
2
1
2650
-1
Frequency (cm )
2700
2600
2.186 eV
2550
2500
outer
inner
SWNTs
2400
2600
2800
-1
Frequency (cm )
2450
The ~2450 cm-1 peak (TO+LA) in
DWNTs is downshifted relative to
the corresponding peak in SWNTs
0
1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6
Excitation Energy (eV)
Some resemblance to bilayer graphene
E. B. Barros et al., PRB in press (2007)
Physics of Nanotubes, Graphite
and Graphene
Outline of Lecture 1 - Nanotubes
•
•
•
•
•
Brief overview of carbon nanotubes
Review of Photophysics of Nanotubes
Phonon assisted Photoluminescence
Double wall carbon nanotubes
Nano-Metrology
The problem of Nano-metrology
Why do we need metrology for nanotechnology?
Why do we need reference standards?
What is new about metrology at the nano-scale?
What does nanoscience have to do with metrology?
World wide production of Carbon Nanotubes
MWNTs 270 tons/yr (2.45× 105 kg/year)
SWNTs 7 tons/yr (6.35 × 103 kg/year)
8K US$ / kg to 5.0 × 105 US$ / kg
(R. Blackmon, http://www.wtec.org/cnm/)
Metrology is guided by applications
Potential Applications of Carbon Nanotubes
by M. Endo, M. S. Strano, P. M. Ajayan @ Springer TAP111
Large Volume Applications
Limited Volume Applications
(Mostly based on Engineered
Nanotube Structures)
Present
- Battery Electrode Additives (MWNT)
- Composites (sporting goods; MWNT)
- Composites (ESD* applications; MWNT)
*ESD – Electrical Shielding Device
- Scanning Probe Tips (MWNT)
- Specialized Medical Appliances
(catheters) (MWNT)
Near Term
(less than ten
years)
- Battery and Super-capacitor Electrodes
- Multifunctional Composites
- Fuel Cell Electrodes (catalyst support)
- Transparent Conducting Films
- Field Emission Displays / Lighting
- CNT based Inks for Printing
- Single Tip Electron Guns
- Multi-Tip Array X-ray Sources
- Probe Array Test Systems
- CNT Brush Contacts
- CNT Sensor Devices
- Electro-mechanical Memory Device
- Thermal Management Systems
Long Term
(beyond ten
years)
- Power Transmission Cables
- Structural Composites (aerospace and
automobile etc.)
- CNT in Photovoltaic Devices
- Nano-electronics (FET,Interconnects)
- Flexible Electronics
- CNT based bio-sensors
- CNT Fitration/Separation
Membranes
- Drug-delivery Systems
Quantity
What should we measure? At which scale?
vs.
“Quality”
Thermogravimetric analysis (TGA)
Quartz cyrstal microbalance (QCM)
QCM shows SWNTs are non-homogeneous already at the μg scale
TGA (375 °C)
100
~mg
90
massMassremaining
(%)
Remaining, %
Remaining, %
massMass
remaining
(%)
Statistical Comparison
77.90 %
80
70
60
50
40
30
20
10
QCM (375 °C)
100
~µg
90
75.88 %
80
70
60
50
40
30
20
10
0
0
1
1
5
9
13
17
experiment
number
Experiment Number
21
25
25
1
1
5
9
13
17
Experiment Number
experiment
number
21
25
Can we trust the measurements?
What do we use for measuring nanomaterials properties?
4-PROBES TRANSPORT
R14 ≠ R12+R23+R34
SCANNING
PROBES
ELECTRON
MICROSCOPY
1
2
3
4
Purewal et al.,PRL 98,186808 (2007)
IBM Website
LIGHT: Raman and photoluminescence
LOCALIZED LIGHT EMISSON
50nm
From Achim Hartschuh
From Hubert - FEI
Can we trust the measurements?
What is the ideal environment?
Encapsuled by micelles
Sitting on a substrate
Suspended in air
Within a forest
Nano-metrology is a wide open area for development requiring collaboration
between metrology and nanoscience experts