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Electrical and field-emission properties of chemically anchored single-walled carbon nanotube patterns

Well-defined and high-density single-walled carbon nanotube (SWNT) patterns were fabricated using a combination of photolithographic and chemical assembling processes. Unlike the patterned SWNT arrays reported thus far, these SWNT patterned layers have high-density multilayer structures and excellent surface adhesion due to their direct chemical bonding to their substrates, which results in high electrical conductivity. We found that the high-density multilayer SWNT patterns emit electrons under an applied electrical field. The electrical resistivities of the SWNT layers were found to be 5–10Ωcm, with a turn-on electric field of about 3V∕μm at an emission current density of 10μA∕cm2. This technique for fabricating SWNT patterns can be used in the production of field-emission displays and in future device integration requiring carbon nanotubes (CNTs), because it provides large-area patterning of SWNTs with high stability and uniformity.

Vertical Alignment of Carbon Nanotubes Using the Magneto-Evaporation Method

We developed a novel method of vertical alignment of SWNTs using a single-step process for the simultaneous vertical alignment of the SWNTs by a magnetic field and the fixation of their alignment by means of the direct evaporation of the films. We fabricated Fe-oxide/SWNT samples that are reacted by iron-oleate complex, oleic acid and cut SWNTs in 1-octadecene. The Fe-oxide/SWNT samples are dispersed in N,N-dimethylformamide and the resulting solution was deposited on an ITO glass substrate using the spraying method with magnetic field. After evaporation of the SWNT solution in the presence of a magnetic field, we transferred the nanotubes to the vacuum-evaporator chamber, and titanium is evaporated by e-beam evaporation to hold the vertical alignment of the SWNTs. The resulting SWNTs exhibit the formation of a high degree of vertically aligned SNWTs over a large area. We showed that the degree of orientation of the SWNTs is strongly influenced by the field strength, film thickness of the evaporating molecules and evaporating rates. This technique takes significant advantages of the alignment of SWNTs with high aspect ratio at room temperature, without any organic binders and without the need for further alignment procedures. Moreover, this method might be applicable to other anisotropic materials with high aspect ratio.

Carbon nanotube conducting arrays by consecutive amidation reactionsElectronic Supplementary Information (ESI) available: fabrication method and characterization data for micropatterned SWNT conducting arrays. See http://www.rsc.org/suppdata/cc/b3/b315348g/

Carbon nanotube conducting arrays were constructed via consecutive amidation reactions with the aid of a linker molecule and a condensation agent on a patterned amine-terminated glass substrate. The electrical resistivity of the nanotube films was sensitive to the degree of coverage for the substrate, making it possible to tailor nanotube multilayers suitable for use in micro- or nanoscale electronic devices and circuits.

Surface alignment and control of a dendritic liquid crystal in ultrathin films

Surface alignment and control of hexagonal molecular cylinders from an asymmetric supramolecular liquid crystal was established. Transmission electron microscopy images show that the cylinders are strongly affected by the substrate and film thickness. The cylinders align perpendicular to a hydrophobic substrate, while planar alignment takes place on hydrophilic surfaces. Different morphologies are encountered depending on the film thickness. Thick films of such a material exhibit a highly ordered hexagonal structure where the cylinders are oriented either parallel or perpendicular depending on the substrate. For thin films whose thickness is 10 nm < t < 20 nm, they spontaneously form holes with straight edges aligned with hexagonal symmetry of the (10) orientation of the underlying molecular lattice. Thinner films lead to a liquid-like disordered in-plane structure. Unlike the behaviour of thin films of a typical block copolymer, where the natural period of the block copolymer is manifested through the formation of hole, the hole structures from these types of asymmetric dendrimers can be attributed to the low surface energy planes, revealed by the faceting of discontinuous films.

Fabrication of well-aligned SWNT arrays using colloidal self-assembly

A novel method to fabrication of well-aligned SWNT arrays on SAM-modified ITO glass substrates, using a well dispersed ef-SWNT solution, a supporting frame consisting of a monolayer of monodisperse silica beads, and the appropriate electric fields, has been developed. The use of the colloidal monolayer as a supporting frame enables the vertical alignment of the SWNTs on the ITO substrate. This method has the following advantages over the previously reported ones: low CNT consumption, mild temperature conditions, and large area deposition.