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This paper presents a number of factors which have been found to be important to the growth of carbon nanotubes and nanofibres by plasma enhanced chemical vapour deposition. The effect of the electric field in a plasma discharge on nanotube growth is investigated and shown to be important in achieving nanotube alignment. The use of a plasma discharge also enables deposition to take place at lower temperatures, facilitating the use of substrates which would otherwise be damaged. The effect of varying the ratio of carbon feedstock gas to etchant gas is investigated and the ratio is shown to be important for controlling the shape of deposited nanostructures. The effects of varying plasma power are investigated, showing that greater plasma power results in a lower growth rate. Higher levels of plasma power are also shown to cause the sidewalls of deposited carbon nanotubes to be etched. Finally, the growth rate of carbon nanotubes and nanofibres is shown to depend upon the strength of the local electric field. It is proposed that a higher field causes greater ionization within the plasma, which results in a higher growth rate. This is borne out by comparing simulation results with experimental observations.

The ubiquitous static friction (stiction) and adhesion forces comprise a major obstacle in the manipulation of matter at the nanoscale (Falvo et al 1999 Nature 397 236; Urbakh M et al 2004 Nature 430 525). In this work it is shown that a surface coated with vertically aligned carbon nanotubes—a nanotube forest—acts as an effective non-stick workbench for the manipulation of micro-objects and fibres/wires with one or more dimensions in the nano-range. These include organic nanofibres (Balzer and Rubahn 2001 Appl. Phys. Lett. 79 3860) and microsized latex beads, which adhere strongly even to a conventional low surface-energy material like Teflon. Although organic nanofibres are attractive as device components due to their chemical adaptability, adhesion forces nearly always rule out manipulation as a route to assembly of prototype devices based on such materials, because organic materials are soft and fragile, and tend to stick to any surface. We demonstrate here that the nanotube forest due to its roughness not only exhibits very low stiction and dynamic friction; it also acts as a springy and mechanically compliant surface, making it possible to lift up and manipulate delicate nanostructures such as organic nanofibres in ways not possible on planar, rigid surfaces.

The controllable growth of vertically aligned ZnO nanowires using a simple vapour deposition method system is reported. The growth properties are studied as a function of the thickness of the Au catalyst layer, total pressure, deposition temperature and oxygen partial pressure. The experiments indicate the existence of five main zones of growth. The zone in which the aligned wires grow varies according to the pressure, temperature and oxygen partial pressure. A specific level of low supersaturation of Zn and oxygen vapour are both necessary to ensure the correct rate of growth, which then leads to having thin and densely aligned wires. The growth kinetics are discussed in terms of the interdependent variables. It was found that the diameter and density of the nanowires is controlled mostly by the growth temperature and pressure. The zone with the most aligned nanowires with the highest aspect ratio was found to be at 5?mbar in a temperature range of 860?800??C with a flow of 27?sccm of a N2/O2 mixture.

The role of plasma in plasma enhanced chemical vapour deposition of carbon nanotubes and nanofibres is investigated with both experimental and computational diagnostic techniques. A residual gas analysis (RGA) of a 12 mbar dc discharge with a C2H2/NH3 gas mixture is conducted near the Ni catalyst surface employed for carbon nanofibre growth. The results are corroborated with a 1D dc discharge model that solves for species densities, ion momentum, and ion, electron and neutral gas thermal energies. The effect of varying the plasma power from 0 to 200 W on the gas composition is studied. The dissociation efficiency of the plasma is demonstrated where over 50% of the feedstock is converted to a mixture of hydrogen, nitrogen and hydrogen cyanide at 200 W. Finally, the important role that endothermic ion–molecule reactions play in this conversion is, for the first time, established. Of these reactions, dissociative proton abstraction and collision-induced dissociation are of the greatest significance.

We have fabricated self-aligned, side-gated suspended multi-walled carbon nanotubes (MWCNTs), with nanotube-to-gate spacing of less than 10 nm. Evaporated metal forms an island on a suspended MWCNT, the island and the nanotube act as a mask shielding the substrate, and lift-off then removes the metal island, leaving a set of self-aligned side gates. Al, Cr, Au, and Ti were investigated and the best results were obtained with Cr, at a yield of over 90%.

We report on the fabrication and field emission of carbon nanotube lateral field emitters. Due to its high aspect ratio and mechanical strength, we use vertically aligned multi-wall carbon nanotubes prepared by plasma-enhanced chemical vapour deposition as cathodes, which makes the fabrication of cantilever type lateral field emitters possible. The emission characteristics show that the field emission initiates at 11–17 V. The device has high geometrical enhancement factors (9.3 × 106 cm−1) compared to standard Spindt tips, which may be due to increased field concentration at the nanotube tip and the close proximity of the anode (

We have successfully fabricated a pH-sensor array based on chemical-vapor-deposition (CVD)-synthesized graphene. As large-scale monolayer graphene is synthesized by this method, the size and the position of graphene can be controlled. Therefore, after transferring graphene onto SiO2/Si substrates, a graphene field-effect transistor (FET) array was produced. The sensing characteristics of the CVD-synthesized graphene-based device were investigated using three buffer solutions with different pH values (pHs 4.0, 6.8, and 9.3). The electrical measurements reveal that for most of the graphene FETs in the array, a similar stepwise increment in drain current was observed upon the introduction of each buffer solution with increasing pH value sequence. This will lead to the realization of the fabrication of multiplex hand-held chemical and biological sensors based on CVD-synthesized graphene.

Silicon microheaters for local growth of a vertically aligned carbon nanotube (VACNT) were fabricated. The microheaters had a four-point-probe structure that measured the silicon conductivity variations in the heated region which is a measure of the temperature. Through FEM simulations the temperature was determined on the entire microheater structure, and the simulated temperatures were verified by micro-Raman spectroscopy. The microheaters provided a temperature gradient along which VACNTs were grown at 575–800 °C simultaneously. The VACNT growth activation energy was determined to 0.86 eV from the VACNT growth rate variation along the microheater's temperature gradient.