| 1. |
- Liu, Bingbing, et al.
(författare)
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Electric resistance of single-walled carbon nanotubes under hydrostatic pressure
- 2001
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Ingår i: Solid State Communications. - : Elsevier B.V.. - 0038-1098 .- 1879-2766. ; 118:1, s. 31-36
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Tidskriftsartikel (refereegranskat)abstract
- The electric resistance of single-walled nanotube mats has been studied systematically under both ambient and high hydrostatic pressures up to 1.5 GPa. Both the temperature dependence of the resistance and the magnetoresistance indicate that electrical transport occurs by variable range hopping, apparently in 2D. We suggest that this unexpected dimensionality arises from a fractal network of tubes and bundles. Under hydrostatic pressure (HP) the resistance still shows 2D variable range hopping and decreases with increasing HP. An irreversible increase in localization length and DOS is induced below 0.5 GPa. The behavior is reversible and due to strong interaction of tubes from 0.5 GPa up to 1.05 GPa. These results indicate that 2D variable range hopping occurs within bundles.
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| 2. |
- Liu, Bingbing, et al.
(författare)
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Raman study of bromine-doped single-walled carbon nanotubes under high pressure
- 2002
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Ingår i: Journal of Physics: Condensed Matter vol. 14 issue no. 44. - Bristol : Institute of Physics. ; , s. 11255-11259
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Konferensbidrag (refereegranskat)abstract
- Raman results for different single-walled carbon nanotube bundles doped withBr2 were studied both at ambient pressure and under high pressure up to 6 GPa.Our study indicates that bromine resides in the interstitial channel of nanotubebundles as a form of polymer.
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| 3. |
- Liu, Bingbing, et al.
(författare)
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Resistivity and fractal structure in carbon nanotube networks
- 2002
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Ingår i: Journal of Physics Condensed Matter vol. 14 issue 44. - Bristol : Institute of Physics. ; , s. 11125-11129
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Konferensbidrag (refereegranskat)abstract
- We have measured the temperature and magnetic field dependence of the resistance for bulk samples of single-walled nanotubes treated in different ways. Hydrostatic pressure-treated samples and as-grown samples show a two-dimensional variable-range hopping behaviour while samples treated in non-hydrostatic pressure or in acid for a long time show a three-dimensional transport behaviour. We suggest that the observed two-dimensional behaviour arises from a network structure with a fractal dimension lower than three.
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| 4. |
- Liu, Bingbing, et al.
(författare)
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Synthesis and characterization of single-walled nanotubes produced with Ce as catalyst
- 2000
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Ingår i: Molecular Materials: Molecular Crystals and Liquid Crystals Section C, vol. 13. - : Overseas Publishers Association N.V.. ; , s. 75-80
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Konferensbidrag (refereegranskat)abstract
- We have studied the effect of using rare-earth elements C (typically +4 oxide state) and Eu (typically +2 oxide state) together with nanometer Ni as catalysts to synthesize SWNT in high yield by arc evaporation. A black collar deposit containing mainly SWNT was formed in the presence of Ce/Ni while only nanometer carbon particles were formed using Eu/Ni, as identified by SEM, TEM and Raman spectra. The Raman spectra of our SWNT mats show difference from spectra shown in the literature in a low frequency range, indicating that our mats contain chiral tubes. The temperature dependent resistance of SWNT mats was also measured. A semiconducting behaviour was observed with a negative dR/dT and no resistance minimum from 2 to 350 K. The resistance follows a 2D variable range hopping behaviour.
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| 5. |
- Liu, Bingbing, et al.
(författare)
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Synthesis and characterization of single-walled nanotubes produced with Ce/Ni as catalysts.
- 2000
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Ingår i: Chemical Physics Letters. - : Elsevier B.V.. - 0009-2614 .- 1873-4448. ; 320:3-4, s. 365-372
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Tidskriftsartikel (refereegranskat)abstract
- SWNTs were synthesized in high yield in the presence of Ce/Ni as catalyst. Raman and SEM results show that a fraction of the tubes are chiral and have small diameters (the smallest one is 0.79 nm), indicating that Ce plays an important role in the formation. Acid treatment is effective in eliminating impurities but changes the morphology and the electric resistance of mats with increasing treatment time. The resistance of as-grown and short time acid-treated mats follow a 2D VRH behaviour while mats treated for a long time follow a 3D model. The results indicate that hopping conduction occurs on bundles or on tubes and that there are intrinsic links between tubes in as-grown mats.
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| 6. |
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| 7. |
- Liu, Bingbing, et al.
(författare)
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Transport properties of single-walled nanotube mats under hydrostatic pressure
- 2000
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Ingår i: Electronic Properties of Novel Materials: Science and Technology of Molecular nanostructures. - Melville : American Institute of Physics (AIP). - 1563969734 ; , s. 344-348
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Konferensbidrag (refereegranskat)abstract
- The study of electrical transport properties of bulk single-walled carbon nanotube (SWNT) materials attracts a lot of attention. However, the transport results differ from sample to sample[l]. Some results show semiconducting behavior with different laws and whether the behavior is dominated by on-tube or on-bundle effects or by interbundle contacts is still unknown. Therefore, further investigation is still meaningful. The effect of hydrostatic pressure(HP), which is expected to significantly change the interaction between tubes or bundles, gives us a further possibility to understand the characteristic properties. Under HP, Raman spectra and electric resistance show pronounced changes at 1.5GPa[2]. In this study, we systematically studied the electric resistance up to 1.5 GPa, giving a different image of the transport behavior.
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| 8. |
- Yu, Miao, et al.
(författare)
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SERS study of single-walled carbon nanotubes on silver films deposited on different substrates
- 2003
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Ingår i: Chemical Journal of Chinese Universities / Gao Deng Xue Xiao Hua Xue Xue Bao. - : Chinese Electronic Periodical Services. - 0251-0790. ; 24:6, s. 1285-1288
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Tidskriftsartikel (refereegranskat)abstract
- Surface-enhanced Raman scattering of single-walled carbon nanotubes (SWNTs) on silver films deposited on various substrates, including sapphire, quartz and glass, has been studied systematically. The characteristic features of G-band and D-band have been analyzed and compared with arc discharged and laser ablation samples. D-band is much more sensitive than G-band. The position and the intensity of the G-band in SERS spectra depend on substrates. The peak shift and absolute intensity of G-band on sapphire is obviously larger than that on glass. The contribution of high frequency vibrations to the D-band is also deendent on substrates. Compared to the SWNTs samples with a high semiconducting tube concentration, the sample with high metallic tube concentration has a stronger interaction with silver films.
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