Kazunaga Horiuchi

Passivation effects of alumina insulating layer on C60 thin-film field-effect transistors

A covering of an alumina insulating layer was deposited on the top of a C60 thin-film field-effect transistor (FET) by rf magnetron sputtering with Ar gas, in order to passivate the FET action from the degradation due to oxygen adsorption. The deposited alumina was amorphous and slightly oxygen deficient from the stoichiometry. The stability of FET action in air was considerably improved and no degradation has been detected even for more than one month.

Low-temperature transport of C60 thin-film FET

Abstract Electrical transport properties of C60 thin-film field-effect transistor (FET) grown at room temperature was investigated with various gate voltages. The conduction above 260 K and below 200 K can be well explained by a thermal activation model. Especially, it is noted that a strong dependence on the gate voltage appeared for the conduction above 260 K .

Conduction carriers in multi-walled carbon nanotubes

Abstract ESR spectra of MWNTs have been studied with isochronal annealing and temperature dependence down to 100 K . Two closely spaced peaks are observed in the ESR signals. The higher-field signal disappears after thermal annealing at 500°C and can be related to the presence of contaminations and /or defects in the MWNTs. However, the lower-field signal is thought to be associated with free carriers in the carbon nanotube and the transport relaxation time can be expected to decrease roughly by one-third after annealing. This suggests an associated enhancement of the spin-relaxation rate of conduction electrons due to an increase of carrier scatterings in the metallic system, consistent with Elliots spin relaxation mechanism.

Fabrication of nanoscale C60 field-effect transistors with carbon nanotubes

A nanoscale C60 field-effect transistor has been fabricated with carbon nanotubes (C60CNT‐FET). A wire of multiwalled carbon nanotube has been anchored by metal pads on a Si wafer, and cut by bombardment with focused Ga2+ ion beam. The cut ends of the wire have been integrated as source-drain electrodes into the C60CNT‐FET, with a vacuum evaporated C60 thin film. The C60CNT‐FET has exhibited an excellent performance of a low-voltage drive operation, without any short-channel effect even at as small as 100 nm of channel length.

Variable range hopping in a C60 field-effect transistor

A variable range hopping (VRH) has been observed in the low-temperature conductance of a C60 field-effect transistor. We have investigated a thermal annealing (TA) effect at 453 and 498K, on the conductance in various gate voltages and several source-drain separations. VRH analysis shows that density of states in the pseudogap clearly decreases as TA temperature increases. However, there might exist the other charge trapping states at interfaces with electrodes and gate dielectric, which could be modulated also by TA.

CESR in multi walled carbon nanotubes

Abstract We have clarified carrier spin relaxation process in multi walled carbon nanotubes (MWCNT) fabricated by DC arc discharge and studied the fundamental transport mechanism in MWCNT by means of electron spin resonance (ESR) in order to discuss on the transport properties in the MWCNT. The g -value and the line width for the ESR signal are gradually increased after thermal annealing. This can be explained by a conduction electron system in the MWCNT.

Bonding Process for Nanoscale Wiring Using Carbon Nanotube by STM Tip

A nano-scale bonding process using a multi-wall carbon nanotube (CNT) has been successfully applied in a scanning electron microscope (SEM)/scanning tunneling microscope (STM) combined system. Under the SEM observation, a Ti-coated STM tip was approached onto a CNT bridging Ti pads, which is patterned with a 4 µm gap on a SiO2 surface, to investigate the conduction property of the CNT. A voltage pulse of 12 V peak and 50 µs duration was applied in order to deposit Ti clusters onto the CNT, which is well known as a field evaporation process in the STM regime. The two-terminal current-voltage characteristics of the CNT have been improved from a nonlinear behavior at 2.5 V of 208 kΩ to a linear one of 1.8 kΩ.

ESR and low-temperature transport in multi-walled carbon nano-tube

Abstract Fundamental transport mechanism in multi-walled carbon nano-tube has been studied by means of electron spin resonance (ESR) in order to discuss on the transport properties in the tube. After thermal annealing, the transport in the tube shows an ordinal metallic conduction. And the g -value and the line width for the ESR signal are gradually increased after the annealing. This also can be originated from a conduction electron system in the nano-tube.

Nano‐scale organic FET fabricated with carbon nanotubes

A nano‐scale C60 field‐effect transistor has been fabricated with carbon nanotubes (C60CN‐FET). A rope of multi‐walled carbon nanotubes has been anchored by metal pads and cut by a focused Ga2+ ion beam ablation. The ablated ends of the rope have been integrated as electrodes into the C60CN‐FET, which exhibits an excellent performance of a low‐voltage operation, even as small as 100 nm of channel length. The electrodes have been applied also for two‐terminal conductance of salmon’s DNA.