| 41. |
- Lassesson, Andreas, 1976, et al.
(författare)
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A femtosecond laser study of the endoral fullerenes Li@C60 and La@C82
- 2005
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Ingår i: Eur. Phys. J. D. - : Springer Science and Business Media LLC. - 1434-6060. ; 34, s. 205-209
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Tidskriftsartikel (refereegranskat)abstract
- The endohedral fullerenes La@C82 and Li@C60 have been studied in the gas phase with femtosecond laser excitation. The two molecules show qualitatively the same behaviour with respect to ion yield vs. pulse energy, but markedly different fragmentation patterns, with La@C82 fragmenting via the shrink-wrap mechanism and Li@C60 predominantly losing the metal atom in the first fragmentation step. The ion yields and electron energy distributions of La@C82 agree well with a recently developed model for fs laser ionisation of C60.
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| 42. |
- Lassesson, Andreas, 1976, et al.
(författare)
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Formation of small lanthanum-carbide ions from laser induced fragmentation of La@C-82
- 2003
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 119:11, s. 5591-5600
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Tidskriftsartikel (refereegranskat)abstract
- The fragmentation behavior of the endohedral metallofullerene La@C-82 was studied using gas phase time-of-flight mass spectrometry. The results were compared with the fragmentation of C-60. When the metallofullerene was excited by a 337 nm ns laser, small lanthanum-carbide fragments LaCn+, n=0-6, were detected. A simple statistical maximum entropy model was used to simulate the excitation energy dependence of the loss of the LaCn+ molecules as well as C-2 evaporation to form smaller metallofullerenes. By comparing experimental ion intensities with the model, the appearance energies of LaCn+, n=0-6, were found to lie above 65 eV. The lanthanum-carbide fragments ejected from La@C-82 decrease in size with increasing internal energy. The ejection of La+ and LaC2+ is preferred at the expense of larger fragments such as LaC4+ and metallofullerenes at the higher excitation. (C) 2003 American Institute of Physics.
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| 43. |
- Lassesson, Andreas, 1976, et al.
(författare)
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Investigations into the fragmentation and ionization of highly excited La@C-82
- 2002
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 117:21, s. 9811-9817
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Tidskriftsartikel (refereegranskat)abstract
- We report the first measurements of delayed ionization of the metallofullerene La@C-82. When highly excited in laser desorption, La@C-82 was found to ionize over several microseconds. The rate of delayed ionization of La@C-82 was compared to C-60 under the same extraction conditions, and found to be significantly different. A theoretical model was used for the fitting of the ion signal of the two fullerenes. The metallofullerene results can be fitted well over a time window
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| 44. |
- Lee, DongSu, et al.
(författare)
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Extraction of semiconducting carbon nanotubes by repeated dielectrophoretic filtering
- 2005
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 80, s. 5-8
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Tidskriftsartikel (refereegranskat)abstract
- We have separated semiconducting carbon nanotubes from as-grown batch material (HiPco production). A special configuration of electrodes which generates a 3-dimensional electric field gradient was used to filter out and deposit metallic carbon nanotubes by the dielectrophoretic method, leaving the remaining dispersion enriched in semiconducting nanotubes. The efficiency of filtering was determined by Raman spectroscopy. Using repeated deposition cycles, the ratio of semiconducting to metallic tubes was increased. After seven cycles, the proportion of semiconducting tubes in the remaining dispersion reached 94%.
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| 45. |
- Lee, DongSu, et al.
(författare)
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Fabrication of crossed junctions of semiconducting and metallic carbon nanotubes: A CNT-gated CNT-FET
- 2006
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Ingår i: Journal of nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 0000-0000. ; 6, s. 1325-1330
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a method to fabricate crossed junctions between semiconducting (s) and metallic (m) carbon nanotubes (CNTs) combining electric field directed chemical vapor deposition growth and dielectrophoretic alignment. By separating the s- and m-CNTs with a thin dielectric an ultrasmall field effect transistor (FET) was fabricated. By using the m-CNT as a gate it was possible to modulate the source-drain current through the s-CNT FET channel. We have also used the m-CNT as an electrical lead. An off-state current lowering was observed when the m-CNT lead was used as a drain electrode.
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| 46. |
- Lee, SangWook, et al.
(författare)
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A three-terminal carbon nanorelay
- 2004
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Ingår i: Nano letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 4:10, s. 2027-2030
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Tidskriftsartikel (refereegranskat)abstract
- Three-terminal nanorelay structures were fabricated with multiwall carbon nanotubes (MWNTs). The nanotube relays were deflected by applying a gate voltage until contact (mechanical and/or electrical) was made with a drain electrode, thus closing the circuit. It was possible to achieve multiple switching cycles, showing that carbon nanotubes are suitable and practical systems for developing nanoelectromechanical devices of this kind.
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| 47. |
- Lee, SangWook, et al.
(författare)
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Fabrication and mechanical properties of suspended one-dimensional polymer nanostructures: polypyrrole nanotube and helical polyacetylene nanofibre
- 2006
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 17, s. 992-996
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Tidskriftsartikel (refereegranskat)abstract
- Mechanical properties of suspended quasi-one-dimensional polymer nanostructures were investigated using atomic force microscopy (AFM). A recently developed new acid-free etch method combined with electron beam lithography was used to fabricate suspended polypyrrole (PPy) nanotubes and helical polyacetylene (HPA) nanofibres. The elastic modulus of each suspended structure was obtained by AFM force–distance measurements. The estimated modulus value of the PPy nanotube (HPA nanofibre) was 0.96 GPa (0.5 GPa). Using this acid-free method, all-organic flexible NEMS devices can be fabricated in the future.
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| 48. |
- Lee, SangWook, et al.
(författare)
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In situ Raman measurements of suspended individual single-walled carbon nanotubes under strain
- 2007
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 7, s. 2590-2595
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Tidskriftsartikel (refereegranskat)abstract
- We present a technique for in situ Raman measurements of suspended individual single-walled carbon nanotubes (SWNTs) under strain. We observe a strong change in the radial breathing mode intensity with increasing strain as the nanotube moves out of (or into) resonance, and for strain greater than 2%, there is a clear irreversible upshift in the G-mode frequencies accompanied by an increase in intensity of a broad peak at a position associated with the D mode. For lower strain, the G-mode peaks (A1, E1, and E2) do not change significantly in position but change in relative intensity.
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| 49. |
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| 50. |
- Lindahl, Niklas, 1981, et al.
(författare)
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Determination of the Bending Rigidity of Graphene via Electrostatic Actuation of Buckled Membranes
- 2012
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 12:7, s. 3526-3531
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Tidskriftsartikel (refereegranskat)abstract
- Classical continuum mechanics is used extensively to predict the properties of nanoscale materials such as graphene. The bending rigidity, kappa, is an important parameter that is used, for example, to predict the performance of graphene nanoelectromechanical devices and also ripple formation. Despite its importance, there is a large spread in the theoretical predictions of kappa for few-layer graphene. We have used the snap-through behavior of convex buckled graphene membranes under the application of electrostatic pressure to determine experimentally values of kappa for double-layer graphene membranes. We demonstrate how to prepare convex-buckled suspended graphene ribbons and fully clamped suspended membranes and show how the determination of the curvature of the membranes and the critical snap-through voltage, using AFM, allows us to extract kappa. The bending rigidity of bilayer graphene membranes under ambient conditions was determined to be 35.5(-15.0)(+20.0) eV. Monolayers are shown to have significantly lower kappa than bilayers.
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