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Optical and Electronic Measurements of Individual Carbon Nanotubes. Steve Cronin University of Southern California Electrical Engineering - Electrophysics. What is a Carbon Nanotube?. Chirality (n,m) :. C h = 4a 1 + 2a 2 = (4,2).

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steve cronin university of southern california electrical engineering electrophysics

Optical and Electronic Measurements of Individual Carbon Nanotubes

Steve Cronin

University of Southern California

Electrical Engineering - Electrophysics

slide3

What is a Carbon Nanotube?

Chirality (n,m):

Ch = 4a1 + 2a2= (4,2)

  • Imagine rolling a sheet of graphite into a seamless cylindrical tube

Honeycomb Graphite

Sheet

  • Two integers (n,m) determine all the properties of a carbon nanotube.
  • Nanotubes can have metallic or semiconducting electronic structure, if (n-m)/3.
afm of carbon nanotube and dna molecules
AFM of Carbon Nanotube and DNA Molecules

Carbon Nanotube

DNA

Bockrath, et al., Nano Lett., 2, 187 (2002).

why study carbon nanotubes
Why Study Carbon Nanotubes?
  • 1nm in diameter, up to 1cm in length, aspect ratio of 107
  • 1 defect in 1012 C atoms => ballistic conduction
  • High melting point ~3800oC
  • High young’s modulus 1TPa (103 times diamond)
  • High electronic current carrying capacity (109A/cm2) ~103 times higher than that of the noble metals
  • Thermal conductivity 6600W/mK at room temperature is twice the maximum known bulk thermal conductor, isotropically pure diamond = 3320W/mK

Despite 18,000 publications, no large scale commercial applications of nanotubes

Li , Yu, Rutherglen, Burke, Nano Lett., 4 2003 (2004)

Fan, Goldsmith, Collins, Nature Materials, 4, 906 (2005)

slide6

on

off

Vbias

Vgate

SiO2

NT

doped

silicon

Gate

1mm

metallic

Nanotube Field Effect Transistor (NT-FET)

semiconducting

slide7

Single Nanotube Raman Spectroscopy

Metallic

Semiconducting

G-band

RBM

Jorio, et al., PRL, 86, 1118 (2001)

Eii

Despite the extremely small geometric cross-section the Raman signal from a single isolated nanotube can be observed.

  • 105 enhancement in scattering cross-section due to singularities in the DOS
  • Resonance occurs when Elaser=Eii
  • Only observe nanotubes that are resonant with Elaser
slide8

1mm

AFM tip

Strain Nanotubes

unstrained length =3.8mm

strain = 20nm  0.53%

 5.3GPa Stress

slide9

Raman Spectra of Strained NT

1mm

AFM tip

unstrained length =3.8mm

strain = 20nm  0.53%

 5.3GPa Stress

  • D, G, G’ bands are downshifted by 16.1, 14.8 and 27.7cm-1 (5 times bulk)
  • Lower phonon frequencies as C-C bond length increases

Cronin, et al., PRL, 93, 167401 (2004).

slide10

Raman Spectra of Broken NT

strain=1.65%

broken

  • D, G and G’ downshift by 27, 14 and 40cm-1
  • Broken tube resumes original D, G and G’ values.
  • Strain deformations are elastic

Cronin, et al., PRL, 93, 167401 (2004).

slide11

2mm

1mm

AFM tip

Thank You!

1mm

slide12

2mm

1mm

Grants:

1mm

  • NIRT ECS-0210752
  • NSF Grant Nos. DMR-01-16042 and DMR-02-44441
  • NSEC Grant No. PHY-01-17795
  • Dupont-MIT alliance

AFM tip

Thank You!

People:

Rajay Kumar, Hao Zhou, Adam Bushmaker (USC)

A. Stolyarov, Prof. M. Tinkham (Harvard)

R. Barnett, E. Demler (Harvard)

Y. Yin, A. Walsh, Prof. A.K. Swan, Prof. B.B. Goldberg (BU)

Prof. M.S. Dresselhaus (MIT)