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We have studied current–voltage (I–V) characteristics of metal-on-tube metal–multiwall carbon nanotube–metal structures as a function of gate voltage. Device resistances ranged from about 10 kΩ to several MΩ, depending on the electrode metal and its deposition condition. When the resistance was much higher than the quantum resistance (RQ=h/4e2≈6.5 kΩ), samples showed clear Coulomb blockade. We find that the tunnel barrier is located in the interface between the MWNT and the metal electrode. As the resistance decreased, the Coulomb oscillations became irregular with respect to the gate voltage, but the high resistance region around V=0 and its dependence on gate voltage survived at resistance smaller than 10 kΩ. [Copyright &y& Elsevier]

In the electrochemical transistor of a single-walled carbon nanotube, we introduced the fourth terminal, which works as a reference electrode. This enables accurate control of change in gate voltage, i.e., potential difference between the electrolyte and the source electrode, and quantitative analyses of the gate capacitance. We found that the geometrical capacitance, which was ignored in the conventional model, makes a crucial contribution to the device characteristics, comparable to that from the chemical capacitance. [ABSTRACT FROM AUTHOR]

The contact resistance (Rcont) between nanotube and metal electrodes was directly measured in a four-terminal configuration of field-effect transistors for individual single-walled carbon nanotube (SWNT) bundles and a multiwalled carbon nanotube (MWNT). Both Rcont and the nanotube resistance (RNT) in a semiconducting SWNT device drastically changed with gate voltage, while Rcont, being more than one-order smaller than Rcont in metallic SWNTs and MWNTs, was almost constant against the gate voltage. Carriers introduced either by gate voltage or chemical doping induced a rapid decrease in Rcont compared with the resistance of semiconducting SWNTs. [ABSTRACT FROM AUTHOR]

We observed an ambipolar behavior in multiwalled carbon nanotubes in a backgate configuration, which allowed us to perform systematic inspection of the low-temperature transport properties against gate voltage. The results revealed that a power-law temperature-dependent conductance, which is a sign of an unconventional metallic state, disappears when a high gate voltage is applied, and conductance becomes temperature independent, indicating a normal Fermi liquid state. This demonstrates a field effect tuning of electronic states in nanoscaled materials. [ABSTRACT FROM AUTHOR]

A pentacene nanocrystal transistor with carbon nanotube electrodes as a nanosize source and drain was realized. In the device fabrication, the evaporated pentacene selectively grew around the nanotube electrodes. This may be caused by the common nanounit combination of the carbon six-membered ring contained in the pentacene and the nanotube. The nanotransistor showed controllable transistor operation at room temperature and Coulomb blockade oscillations at 4.2 K in gate voltage characteristics. [ABSTRACT FROM AUTHOR]

Internanotube charge transport in a multiwalled carbon nanotube (MWNT) was investigated. We directly measured electrical transport from the outer nanotube to the inner nanotubes in a MWNT with two electrodes. The outer nanotubes between the two electrodes were disconnected, leaving the innermost nanotube, so that the current flows into the innermost nanotube via the internanotube junctions. The transport properties of this device clearly showed Coulomb blockade oscillation with a charging energy of 15 meV at 4.2 K. The observed Coulomb blockade oscillation was nonperiodic to the gate voltage, indicating that the multiple internanotube tunnel junctions were formed underneath the electrodes. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Hexabenzocoronene (HBC) nanotubes, prepared by self-assembly of 1-4 with different oligoether chains, all show a p-type conducting profile in a field-effect transistor (FET) setup, where hole mobilities of their film samples are two orders of magnitude greater than that of a cast film composed of ill-defined, nontubular HBC aggregates. Taking into account their time-resolved microwave conductivities, the observed FET properties appear to be largely affected by the kinetics of intertubular hole hopping, which could be less facilitated as the oligoether chains on the nanotube surface are longer. [ABSTRACT FROM AUTHOR]

We report the catalytic synthesis of carbon nanotubes and two approaches to the catalyst patterning. Aligned multi-wall carbon nanotube (MWNT) arrays were synthesized in the presence of Co nanoparticles that were prepared by a reverse micelle method. By taking advantage of the fact that the Co nanoparticles are dispersible in organic solvent, an ink-jet technique has been applied to the Co nanoparticle dispersion for MWNT patterning. Single-wall carbon nanotubes (SWNTs) were synthesized by using Fe and Mo supported catalysts and the catalyst preparation process was combined with lithographic techniques, leading to formation of nanotubes bridging or crossing the catalyst patterns. These catalyst-patterning techniques, together with recent development of nanotube synthetic methods, may find applications in electronic and electrochemical applications, such as field-emission displays, nanodevices, and fuel cells. [Copyright &y& Elsevier]

We have studied magnetic field dependence of electron transport in highly resistive metal-on-tube metal/multi-wall carbon nanotube/metal structures. Current peaks due to Coulomb oscillations shift in a complex manner. The observed behavior is well reproduced by numerical calculation of the level shift due to the Landau level formation. [Copyright &y& Elsevier]