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We report herein a facile electrochemical approach to synthesizing various layered composite films of nanomaterials and conducting polymers, called nanoveneers. Layered structures of polypyrrole film with single-walled carbon nanotubes (SWNTs), graphene, and Au nanoparticles have been obtained by electropolymerization of pyrrole molecules on a heavily doped silicon wafer preloaded with target conductive nanomaterials. A free-standing, transparent, and highly conductive composite film was achieved after peeling off from a silicon wafer. Different from traditional homogeneous composite materials, such kinds of nanoveneers combined to the best extent the structural continuity and processability of conducting polymers with the high conductivity and functionality of discontinuous SWNTs, graphene, and other nanomaterials. The layered electrochemical deposition provides a great freedom for constructing various nanostructures with well-controlled geometry and thus physicochemical properties, as demonstrated by SWNT/polypyrrole nanoveneers. These nanoveneers are particularly attractive in areas of chemical sensors, labels, transparent electronics, and optoelectronics.

We present a general selective positioning and integration technique for fabricating single-walled carbon nanotube (SWNT) circuits with preselected individual SWNTs as building blocks by utilizing poly(methyl methacrylate) (PMMA) thin film as a macroscopically handlable mediator. The transparency and marker-replicating capability of PMMA mediator allow the selective placement of chirality-specific nanotubes onto predesigned patterned surfaces with a resolution of ca. 1 mum. This technique is compatible with multiple operations and p-n conversion by chemical doping, which enables the construction of complex and logic circuits. As demonstrations of building SWNTs circuits, we fabricated a field effect inverter, a 2 x 2 all-SWNT crossbar field effect transistor (FET), and flexible FETs on plastic with this technique. This selective positioning approach can also be extended to construct purpose-directed architecture with various nanoscale building blocks.

In the present study, individual suspended single-walled carbon nanotubes (SWNTs) were prepared and the temperature coefficients of Raman frequency of 13 SWNTs were measured. It is found that the t...

By using the specifically designed multigap nanoelectrodes, we demonstrated an effective approach for the simultaneous dielectrophoretic separation and assembly of metallic and semiconducting single-walled carbon nanotubes (SWNTs). An approximate metallic-semiconducting-metallic multiarray structure was created by an inward-propagative sequential assembly of SWNTs under ac electric field. Such kinds of SWNT multiarray structures exhibited ultra-low-power consumption and excellent thermal sensing performances with the sensitivity being dependent on the number of gaps: the more gaps, the higher sensitivity. The effective separation of metallic and semiconducting tubes in different gaps is believed to be responsible for the improved sensitivity to temperature.

This paper describes a negative nanoimprint lithography (N-NIL) technique for fabricating metallic nanostructures via combining conventional nanoimprint lithography (NIL) with wet chemical etching. Various metallic nanostructures such as gold grating, gold/chromium alternate bimetallic grating and gold nanoelectrode arrays, which are negative replications of the stamp pattern, have been fabricated with N-NIL. This method has demonstrated its advantages on varying the feature size of obtained metallic nanostructures with a single stamp as well as on fabricating bimetallic nanostructures. In addition, it offers a unique path to fabricate micro?nano complex structures in a single imprint process, which compensates the limitation of conventional nanoimprint lithography and maintains the advantages of conventional nanoimprint lithography such as high throughput, low cost and sub-100?nm resolution.

We report a novel electric-field-enhanced chemical assembly approach for fabricating highly aligned SWNT arrays on a solid surface with remarkably improved efficiency and packing density, which is very important for the real applications of carbon nanotube arrays. With the enhancement of the electric field, the assembling kinetics of SWNTs is remarkably speeded up to effectively decrease the assembling time, and the packing density can even exceed the saturated density of conventional assembly method by four times within only half an hour. The molecular dynamics simulation results illustrated the alignment of SWNTs with their long axes along the electric flux in solution, leading to the increase of packing density and efficiency through overcoming the steric hindrance of the "giant" carbon nanotubes.

Single-walled carbon nanotubes (SWNTs) are promising building blocks for nanoelectronics. However, because of the mixture of metallic and semiconducting single-walled carbon nanotubes (m-SWNTs and s-SWNTs), it is necessary to identify them for nanodevice integerations. In this work, we have observed obvious electrodeposition differences of ultralong m-SWNTs and s-SWNTs. Using high-resolution atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM), particle densities along different carbon nanotubes were examined. Interestingly, m-SWNTs and s-SWNTs showed obviously different deposition behaviors, i.e., exponential decay of particle densities with different decay coefficients. This electrochemical approach can be used for a simple identification of m-SWNTs and s-SWNTs.

We presented a controllable yet simple approach for fabricating an air-stable single-walled carbon nanotube (SWNT) diode with the atomic force microscopy (AFM) manipulation technique. The AFM tip w...

In this work, we have demonstrated that the local deformation at the crossed carbon nanotube (CNT) junctions can introduce significant tunable local gate effect under ambient environment. Atomic force microscope (AFM) manipulation of the local deformation yielded a variation in transconductance that was retained after removing the AFM tip. Application of a large source-drain voltage and pressing the CNT junction above a threshold pressure can respectively erase and recover the transconductance modulation reversibly. The local gate effect is found to be independent of the length of the crossed CNT and attributed to the charges residing at the deformed junctions due to formation of localized states. The number of localized charges is estimated to be in the range of 10(2) to 10(3). These results may find potential applications in electromechanical sensors and could have important implications for designing nonvolatile devices based on crossed CNT junctions.

We demonstrate herein that organic metal tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) can serve as an ideal material for source and drain electrodes to build unipolar p-type single-walled carbon nanotube (SWNTs) field-effect transistors (FETs). SWNTs were synthesized by the chemical vapor deposition (CVD) method on silicon wafer and then TTF-TCNQ was deposited by thermal evaporation through a shadow mask to form the source and drain contacts. An SiO2 layer served as the gate dielectric and Si was used as the backgate. Transfer characteristics show that these TTF-TCNQ contacted devices are Schottky barrier transistors just like conventional metal contacted SWNT-FETs. The most interesting characteristic of these SWNT transistors is that all devices demonstrate the unipolar p-type transport behavior. This behavior originates from the unique crystal structure and physical properties of TTF-TCNQ and this device may have potential applications in carbon nanotube electronics.

We demonstrated the controllable interconnection of single-walled carbon nanotubes (SWNTs) under alternating current (ac) electric field. The interconnected carbon nanotubes were found to be parallel with the electric flux and increased abruptly with deposition time following a self-accelerating process. Theoretical simulation indicates that the alignment and the interconnection of carbon nanotubes were induced by the dielectrophoresis force and the electric field redistribution at the nanotube apexes.

By fabricating a PMMA control strip at the SWNTs-electrode contact area to screen off the water gate effect, metallic and semiconducting SWNTs were easily identified during the conventional electropolymerization process.

We demonstrated a prototype of nanoelectromechanical switch which was fabricated with single-walled carbon nanotubes (SWCNTs). An alternating current electric field was utilized to assemble interconnected SWCNTs suspended over the focused ion beam lithography fabricated trenches on the electrode surface. By controlling the electromechanical coupling between the electrostatic and elastostatic forces acting on the SWCNTs, we realized the on and off states of the SWCNT switches. Both two-terminal and three-terminal measurements have been conducted and indicated repeatable switch effects.

An electrochemical technique for fabricating nanogaps is proposed, which utilizes an in situ gap-impedance-tuning mechanism to realize precise control of gap separation. Nanogap electrodes with gap separation from tens of nanometer to sub 10 nm have been fabricated by combining conventional photolithography and this controlled electrodeposition technique. The gap separation can be tuned by changing monitoring parameters based on a homemade electrochemical setup, which provides high sensitivity and reproducibility. In addition, a possible mechanism for controlling gap separation at tens of nanometer level at present conditions was discussed.