Attaching chemical functional groups to single wall carbon nanotubes (SWNTs) has been achieved by chemical methods. Oxidized purified nanotubes have been treated by thionyl chloride in order to convert carboxyl groups into acylchloride groups. We observe by XPS and EDX that not only chlorine atoms but sulphur containing functional groups are covalently bound to the nanotubes. This chemical functionalization also causes significant changes in the electrical and mechanical properties of the nanotubes. The electrical conductivity measured on mats (bucky paper) increases from 500 S/cm in pristine tubes to 2500 S/cm in modified tubes. Similarly, the Young's modulus of bucky paper increases by about 100 %.

We have formed suspended bridges of carbon nanotubes between microcantilevers using electron beam dissociation of metal-organic vapours. By electron beam exposure of a surface in the presence of gold-carbon molecules emitted inside an environmental scanning electron microscope, we are able to form tips and other freestanding nanostructures of high metallic content. Suspended bridges made entirely of this material exhibit resistances less than 50 times that of pure gold, and consist of dense metallic cores surrounded by a crust of nanoparticles. We used standard microfabrication techniques to produce silicon chips with multiple microcantilevers extending over the edge. Individual multiwalled carbon nanotubes grown catalyticcally by chemical vapour deposition, were positioned across two cantilevers using in-situ nanomanipulation tools. Drawing a cross-shaped gold-carbon bond on each end of the carbon nanotube consistently resulted in electrical contact with resistances in the range 1-90 Ω and linear current-voltage characteristics. We found that soldering bonds having a line width down to 10-15 nm form connections and last for days in ambient conditions.

Multi walled nitrogen doped nanotubes were synthesized using two different methods. The growth mechanism and nitrogen concentration of the nanotubes synthesized by both methods are discussed and studied. The morphology and nitrogen concentration of the nanotubes are seen to strongly depend on the synthesis methods. The results are based on detailed high resolution transmission electron microscopy (HRTEM) data coupled with electron energy loss spectroscopy (EELS).

Ballistic and spin coherent transport in single walled carbon nanotubes (SWCNT) are predicted to enable high sensitivity single-nanotube devices for strain and magnetic field sensing. Based upon these phenomena, electron beam lithography procedures have been developed to study the transport properties of purified HiPCO single walled carbon nanotubes for development into sensory materials for nondestructive evaluation. Purified nanotubes are dispersed in solvent suspension and then deposited on the device substrate before metallic contacts are defined and deposited through electron beam lithography. This procedure produces randomly dispersed ropes, typically 2 – 20 nm in diameter, of single walled carbon nanotubes. Transport and scanning probe microscopy studies have shown a good correlation between the junction resistance and tube density, alignment, and contact quality. In order to improve nanotubes at specific locations on the substrate surface. Lithographic techniques are used to define local areas where high frequency electric fields are to be concentrated. Application of the aligned with the electric field lines. A second electron beam lithography layer is then used to deposit metallic contacts across the aligned tubes. Experimental measurements are presented showing the increased tube alignment and improvement in the transport properties of the junctions.

Carbon Nanotubes (CNTs) offer extraordinary properties for applications in microelectronics. We assess the methods used to grow CNTs for integration into microelectronics, in particular, metallic carbon nanotubes for vias and interconnects as well as semiconducting CNTs for fieldeffect devices are discussed. State-of-the-art CNTFETs are compared to Si-MOSFETs. A vertical CNTFET (VCNTFET) device concept is presented which offers better growth control, adding a new quality to microelectronics and making real 3-dimensional electronics possible.

N-type multi-walled nanotubes were synthesized by nitrogen doping using pyridine and pyridine-melamine mixtures in chemical vapor deposition, and their donor states were verified by Scanning Tunneling Spectroscopy. Tunneling Electron Microscopy reveals small amounts of residual catalyst and Scanning Electron Microscopy show well aligned mats of the Nitrogen doped nanotubes. Nitrogen is present in the lattice of these MWNTs as pyridine structures and CNx structures. Raman scattering measurements were performed as a function of increasing growth temperature and the results compared to previously studied boron doped multiwalled nanotubes.

Carbon nanotubes (CNT) are interesting candidates for the reinforcement in robust composites and for conducting fillers in polymers due to their fascinating electronic and mechanical properties. For the first time, we report the incorporation of multi walled carbon nanotubes (MWNTs) into silica-glass surfaces by means of partial surface-melting caused by a continuous wave Nd:YAG laser. MWNTs were detected being well incorporated in the silica-surface. The composites are characterized using scanning electron microscopy (SEM) and Raman-spectroscopy. A model for the composite-formation is proposed based on heatabsorption by MWNTs and a partial melting of the silica-surface.

Carbon nanotubes (CNTs) with controlled orientation and diameter (1-4 nm) were grown from thermally stable, highly ordered mesoporous SiO2 thin films by methane chemical vapor deposition (CVD). Controlled incorporation of Fe precursor into pore channels of the mesoporous SiO2 by a sol-gel process results in a nanostructure catalytically active for CNT growth and stable to typical CVD temperatures. Growth of CNTs starts within the mesoporous SiO2, whose pore direction and pore dimension play an important role in the orientation and diameter of the CNTs at the early stage of the growth. Lateral growth results in a parallel assembly of CNTs with controlled tube dimension from a line-micropatterned mesoporous SiO2 film fabricated by soft-lithography.

Poly (methyl methacrylate)/single walled carbon nanotube (PMMA/SWNT) composites were polymerized in the presence of carbon nanotubes via three methods: heat, uv radiation and ionizing radiation (gamma). Samples were solvent processed and cast into films. Thin films with varying degrees of transparency resulted from these composites. Differential Scanning Calorimetry (DSC) characterized glass transition temperatures. Ultraviolet-visible spectroscopy (UV-VIS) quantified the transparency of composites. The dielectric constant (ε') was obtained from Dielectric Analysis (DEA) and correlated to the refractive index values using Maxwell's Relationship. Scanning Electron Microscopy (SEM) provided images of the polymer- nanotube composite.

Composites of high molecular weight polyaniline and single walled carbon nanotubes are investigated for applications to electronic devices. Electrical characteristics of devices fabricated using this composite show an order magnitude higher current level than those measured in the neat polyaniline devices. Composite materials and devices with various weight percentages of single walled carbon nanotubes were also fabricated. Current-voltage (I-V) characteristics of these devices indicate a significant increase in current with an increase in carbon nanotube concentration in the composite. Analysis of the forward I-V characteristics of these composite devices on a log-log scale shows two power law regions. In the lower voltage range, the exponent is 1, which is consistent with ohmic conduction, while in the higher voltage range, the exponent is between 1.1 and 1.5, which is consistent with space-charge-limited conduction.

Single walled carbon nanotubes (SWNT) have unique properties that give them strong potential for applications in high performance sensors and molecular electronics.1 One problem relevant to such technological applications is the functionalization of SWNT sidewalls. Recent experiments at Stanford have shown that 1-pyrene butanoic acid succinimidyl ester (PBSE) shows promise for non-covalent absorption onto SWNT sidewalls. We have conducted studies aimed at understanding the structural arrangement and packing of PBSE on the SWNT sidewall.

Nanotubes forming carbon atoms arrange differently, resulting into three main types of carbon nanotubes: armchair, zigzag, chiral. Thus, depending on their type, nanotubes may be regarded as chiral, molecular electrical conductors. As a consequence of symmetry arguments, the magnetoresistance of such tubes depends on the relative orientation of the traversing current and the external magnetic field. Magnetotransport measurements on single walled carbon nanotubes have been performed showing the expected dependence on both the current and magnetic field. Further, the quantum-mechanical model of a free electron on a helix in an external magnetic field is discussed in order to provide indicators to possible microscopic mechanisms.

We present a novel process methodology for the controlled cutting of nanotubes and other nanostructures to well-controlled lengths and sizes. The continuing increase in complexity of electronic devices, coupled with decreasing size of individual elements, are placing more stringent demands on the resolution and accuracy of fabrication patterns. The ability to fabricate on a nanometer scale guarantees a continuation in miniaturization of functional devices. Particularly interesting is the application of nanotubes' chemical and electronic properties which vary with their dimensions and structure. One realization of this process includes the use of photolithography or electron beam lithography to place protective resist patterns over the nanostructures to be cut. Those sections which are not covered by the resist pattern are removed by reactive ion etching. This is a scaleable process which permits the simultaneous cutting of many nanostructures and ensembles of nanostructures. The lengths, shapes or length distributions can be predicted from theory and thus specified for a given application requirement. Nanostructures which can be cut in this process include nanotubes, nanofibers and nanoplanes. Large scale production of nanostructures with uniform length or specific size-distribution can be used in electronic applications such as field-emission transistors, optoelectronic elements, single electron devices and sensors.

We present the formation of intermolecular nanotube junctions and investigations of their transistor behavior. T-shape junctions were formed by coupling chemically functionalized nanotubes with molecular linkers. An end-to-side or end-to-end heterojunction can be formed by reacting chloride terminated nanotubes with aliphatic diamine. The chemically modified nanotube mats were characterized by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The incorporation of functional groups into nanotubes are first identified by XPS. The carbon binding energy shifts due to the doping effect by attached functional groups. This also leads to a pronounced shift of tangential vibration modes in Raman spectra. To investigate the electrical transport, functionalized nanotubes were deposited on Si substrates, and metal contacts were applied on top of the selected T-shape junctions. The bar of the “T” is used as a transistor channel and the leg of the “T” is used as a gate. In this configuration, the active area is confined to a few nanometers in all three dimensions and gain values of 100 and above are obtained.

Bundles of single walled 0.4 nm carbon nanotubes were prepared by chemical vapor deposition using n-hexane as carbon source catalyzed by ferrocene with additives of thiophene at 1373 K. 8 cm long rope of single walled carbon nanotubes with diameters of 0.8-1.18 nm was also synthesized. The products were characterized by scanning electron microscopy, high resolution transmission electron microscopy and Raman spectroscopy.

A Focused Ion Beam (FIB) microscope was to locally deposit platinum contacts on Multiwalled Carbon Nanotubes (MWNTs) for resistance and current carrying capability measurements. We have determined the resistivity of these ultra-thin Pt lines and the MWNT-Pt contact resistance to account for contributions to the MWNT measurements. We have studied the effects of secondary mental deposition around the contacts (‘halo’ effect) on the MENT electrical measurements as well as effects of ion beam exposure and possible ways to avoid/minimize them. Transmission Electron Microscopy data was used to evalutate MWNT surface modifications due to ion beam exposure and Pt deposition.

The electronic structure and properties of carbon nanotubes (CNTs) strongly depend on their diameter and chirality. The well controlled CNTs diameter is becoming one of the challenges for their applications in microelectronics. In this paper, the patterned CNTs were produced by microwave plasma enhanced chemical vapor deposition technique using a metal catalyst of nickel. The correlation between the CNT diameter and the grain sizes of the nickel catalyst was examined. The experimental results show that nickel films converted to nickel particles when they were heated up. The diameter of CNTs increases with increasing grain sizes of the nickel particles, indicating that the CNT diameter can be controlled by controlling the grain sizes of the nickel catalyst.

Vertically aligned carbon nanorods and multi walled carbon nanotubes (MWNTs) were synthesized by electron cyclotron resonance chemical vapor deposition (ECR-CVD) on Ni- coated glass substrates with the RF-self biasing of –100 and –200 V, respectively. High-resolution transmission electron microscopy indicated that the distance between adjacent graphene layers of carbon nanorods is much larger than that of well-graphitized MWNTs. In electron-energy-loss spectra, the energy of π+σ plasmon peak for the carbon nanorod shifts towards lower value of 23.8 eV, by comparison with the well-graphitized MWNT at 25.5 eV. In addition, the π palsmon peak at 6 eV is clearly defined for the well-graphitized MWNT, but not seen for the carbon nanorod. X-ray photoelectron spectroscopy also showed that the delocalization of π electrons gets more pronounced with the structural evolvement from the carbon nanorod to the well-graphitized MWNT. Therefore, it is suggested that ionic bombardment can provide sufficient internal energy for dehydrogenation from hydrocarbon molecules, and thus, well-graphitized MWNTs could be grown even at low temperatures.

Gum arabic (GA) and polyvinylpyrrolidone (PVP) were used to stabilize relatively high concentration mixtures of single walled carbon nanotubes (SWNTs) in water. Viscosity and electrical conductivity data, along with electron microscopy, suggest that PVP interacts much more strongly with nanotubes than GA does. This strong PVP-SWNT relationship results in better dispersion of the nanotubes, resulting in lower electrical conductivity, but may enhance mechanical behavior in polymer-matrix composites.

Field emissions from the singlewalled carbon nanotubes (SWNTs) attached on various patterned substrates such as silicon wafer and polymer film, are reported. SWNTs were cut into sub-micron length by sonication in an acidic solution. The SWNT emitters were aligned on Au surface at room temperature by self-assembly monolayer technique. The field emission measurements in a silicon wafer and a polymer film showed that the turn-on fields were 2.8 V/ νm and 3.9 V/ νm at the emission current density of 10 μA/cm2, respectively. The current densities were 0.9 mA/cm2 and 1.6 mA/cm2 at 6.0 V/ νm. This room temperature process is suitable for the fabrication of flexible field emission devices with carbon nanotubes.