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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. 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

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  1. Optical and Electronic Measurements of Individual Carbon Nanotubes Steve Cronin University of Southern California Electrical Engineering - Electrophysics

  2. 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.

  3. AFM of Carbon Nanotube and DNA Molecules Carbon Nanotube DNA Bockrath, et al., Nano Lett., 2, 187 (2002).

  4. 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)

  5. on off Vbias Vgate SiO2 NT doped silicon Gate 1mm metallic Nanotube Field Effect Transistor (NT-FET) semiconducting

  6. 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

  7. 1mm AFM tip Strain Nanotubes unstrained length =3.8mm strain = 20nm  0.53%  5.3GPa Stress

  8. 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).

  9. 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).

  10. 2mm 1mm AFM tip Thank You! 1mm

  11. 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)

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