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- 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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- Sveningsson, M., et al.
(författare)
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Raman spectroscopy and field-emission properties of CVD-grown carbon-nanotube films
- 2001
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Ingår i: Applied Physics a-Materials Science & Processing. ; 73, s. 409-418
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Tidskriftsartikel (refereegranskat)abstract
- Carbon-nanotube films are very efficient cathodes for field-emission devices. This study presents a comprehensive comparison between structural, spectroscopic and field-emission properties of films of aligned and non-aligned multi-wall nanotubes (MWNTs) which are grown by thermal chemical vapour deposition. Three types of films are investigated: vertically aligned MWNTs with clean and coated nanotube side walls as well as non-aligned MWNT films. Raman spectra taken on the aligned MWNT films consist of many lines of first-, second- and third-order signals. Several lines are reported here far the first time for MWNTs. The presence of the surface coating leads to a decrease and broadening of the higher-order signals as well as an increase in the disorder-induced contributions in the first-order regime. The aligned MWNT films have excellent field-emission properties with very high emission current densities and low turn-on and threshold fields. The presence of a surface coating has no impact on the efficiency of the field-emission process. Films of non-aligned MWNTs show considerably reduced electron-emission current densities and larger critical fields.
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- Yao, Yiming, 1957, et al.
(författare)
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Synthesis of carbon nanotube films by thermal CVD in the presence of supported catalyst particles. Part I: The silicon substrate/nanotube film interface
- 2004
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Ingår i: Journal of Materials Science: Materials in Electronics. ; 15:8, s. 533-543
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The interface between the silicon substrate and a carbon nanotube film grown by thermal CVD with acetylene (C2H2) and hydrogen at 750 or 900 °C has been characterized by high resolution and analytical transmission electron microscopy, including electron spectroscopic imaging. Silicon (0 0 2) substrates coated with a thin (2.8 nm) iron film were heat treated in the CVD furnace at the deposition temperature in a mixture of flowing argon and hydrogen whereby nanosized particles of (Fe,Si)3O4 formed. These particles were reduced to catalytic iron silicides with the α–(Fe, Si), α2–Fe2Si and α1–Fe2Si structures during CVD at 900 °C, and multi-wall carbon nanotubes grew from supported particles via a base-growth mechanism. A limited number of intermediate iron carbides, hexagonal and orthorhombic Fe7C3, were also present on the substrate surface after CVD at 900 °C. The reduction of the preformed (Fe, Si)3O4 particles during thermal CVD at 750 °C was accompanied by disintegration leading to the formation of a number of smaller (
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