Optical Spectroscopy of Carbon Nanotubes

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Optical Spectroscopy of Carbon Nanotubes

• Tony F. Heinz
• Depts. of Physics and Electrical Engineering
• Nanoscale Science and Engineering Center
• Columbia University
• tony.heinz_at_columbia.edu
• http//heinz.phys.columbia.edu

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Single-Walled Carbon Nanotubes
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Optical Properties of Nanotubes
(1) Spectroscopic signature of nanotube
structure and quality
PLE excitation spectra Weisman et al., Rice U.
(2) Optoelectronic applications
Fluorophores, LEDs, detectors, Transparent
conductive electr. NLO materials (opt.
limiters, saturable absorbers, )
Avouris et al., IBM Science 300, 783 (2003)
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Optical Properties of Nanotubes

• (3) Nature of the excited states and their
  dynamics in model 1-D system
• The position and character of excited electronic
  states.
• Rate and mechanisms of light emission
• Carrier-carrier interaction and consequences
• Nanotube environment interaction and consequences
  
• Phonons and electron- phonon interactions

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Single-Wall Carbon Nanotubes
Un-roll
Graphene nanoribbon
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Research Themes

• Electronic transitions in nanotubes
• The role of many-body effects
• Ultrafast dynamics in nanotubes
• Optical measurements of individual nanotubes

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Spectroscopy of Individual Nanotubes

• Well-defined nanotube structure
• Simplified spectra
• Well-defined nanotube environment
• Environmental effects on nanostructures
• Well-defined nanotube spatial location
• Combine different techniques

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Collaborations
Columbia University Nanotube Spectroscopy
Multiwall Nanotubes Philip Kim Byoung-Hee Hong
(Physics)
Optical Spectroscopy Louis Brus Gordana
Dukovic, Matt Sfeir (Chemistry) Tony Heinz Feng
Wang, Yang Wu, Janina Maultzsch, Christophe
Voisin, Sami Rosenblatt, Stephane Berciaud
(Physics, EE) Nanotube Growth Stephen OBrien
Limin Huang (Materials Science) Nanotube Sample
Prep, Mechanical, Electrical Characterization Jim
Hone Mingyuan Huang, Bhuphesh Chandra, Henry
Huang (Mech. Eng.)
Brookhaven National Lab TEM Diffraction Yimei
Zhu, Jim Misewich Toby Betz
Graphene collaborations Louis Brus (Chemistry)
- Raman George Flynn (Chemistry) STM Philip Kim
(Physics) Nanoribbon samples Jim Hone (Mech E)
Mechanical proper. Jim Misewich (Brookhaven
Lab ) - IR spectroscopy
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Rayleigh Scattering Spectroscopy
Light Source
Dark-field imaging
Spectrometer and CCD
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Suspended Carbon Nanotubes
Science 306,1540 (2004)
SEM
Supercontinuum source from femtosecond laser
In-situ CVD growth
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Spectroscopy and Spectroscopic Assignments
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Rayleigh Spectra from Individual Nanotubes
Semiconducting
(E33, E44)
Metallic (M11 or M22)
Science 312, 554 (2006)
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Independent Structural Determination on Same
Nanotube


TEM by Brookhaven National Lab.
Collaboration -- Yimei Zhu (Analogous work with
Raman spectroscopy Jean-Louis Sauvajol,
Montpellier with Stuttgart group)
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Comparison of Spectra as Function of Chiral
Struture Semiconducting Tubes
Chiral Angle Dependence
Diameter Dependence
E44
E44
E33
E33
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Persistence of Crystallographic Structure Change
of Chirality?
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Persistence of Nanotube Crystallographic Structure
40 ?m
substrate
Spacing of chirality changes 1 mm for our CVD
growth conditions
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Nanotube Chirality Changes
Junction Geometry
Metallic-Metallic
Semi-Metallic
Semi-Semi
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Environmental Interactions
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Nanotube-Nanotube Interactions
b
A Isolated SWNT AB SWNT A bundled
with SWNT B
SEM Image
c
Dielectric screening by adjacent
SWNT induces red-shift in bandgap
Rayleigh Scattering Spectrum
F. Wang and Columbia Coll. PRL 96, 167401 (2006).
Shift of 47 meV no change in width
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Deposition of Pyrene Molecules
Spectra vs. position along nanotube
Spectra vs amount of deposition
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Significant Pertubation of Electronic States by
External Dielectric Medium

• Interpretation of spectra
• Sensors
• 1-D Band-gap Engineering

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Optical Spectroscopy of Individual Single-Walled
Carbon Nanotubes

• (1) Optical techniques can access nanotubes at
  single nanotube level
• Method provides
• Precise spectroscopy and assignments
• Probe of environmental interactions
• Coupling to other probes (structural,
  mech., electrical, )
• Specific conclusions for single-walled
  nanotubes from our studies
• Materials Chiral structure can
  change, but typically preserved
• over mm in CVD
  nanotubes
• Theory predicts correct trends for
  nanotube spectral assignments
• Test of response to mechanical
  perturbations
• Strong perturbation of electronic
  states by external dielectric scr.