Electrical and field emission investigation of individual carbon nanotubes from plasma enhanced chemical vapour deposition

Plasma enhanced chemical vapour deposition (PECVD) is a controlled technique for the production of vertically aligned multiwall carbon nanotubes for field emission applications. In this paper, we investigate the electrical properties of individual carbon nanotubes which is important for designing field emission devices. PECVD nanotubes exhibit a room temperature resistance of 1-10 kΩ/μm length (resistivity 10-6 to 10-5 Ω m) and have a maximum current carrying capability of 0.2-2 mA (current density 107-108 A/cm2). The field emission characteristics show that the field enhancement of the structures is strongly related to the geometry (height/radius) of the structures and maximum emission currents of ∼ 10 μA were obtained. The failure of nanotubes under field emission is also discussed. © 2002 Elsevier Science B.V. All rights reserved.

Axial stiffness of journal bearings in zero-field and field-cooled modes

Superconducting journal bearings have been investigated for use in flywheel systems. We report on the zero-field cooled and field-cooled stiffness of these bearings. They are made up of radial magnet rings with alternating polarities, a pole pitch of 11 mm and a surface field of 0.1 T. Field-cooled stiffness of the journal bearings increased four times over the zero-field-cooled stiffness. © 2005 IEEE.

Non-ohmic contact resistance and field-effect mobility in nanocrystalline silicon thin film transistors

Contact resistance has a significant impact on the electrical characteristics of thin film transistors. It limits their maximum on-current and affects their subsequent behavior with bias. This distorts the extracted device parameters, in particular, the field-effect mobility. This letter presents a method capable of accounting for both the non-ohmic (nonlinear) and ohmic (linear) contact resistance effects solely based upon terminal I-V measurements. Applying our analysis to a nanocrystalline silicon thin film transistor, we demonstrate that contact resistance effects can lead to a twofold underestimation of the field-effect mobility. © 2008 American Institute of Physics.

Fabrication of carbon nanotube lateral field emitters

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 (<1 μm). The relative ease of fabrication compared to vertical field emitters and enhanced field emission characteristics observed makes the carbon nanotube lateral field emitter a good candidate for future integrated nano-electronic devices.

IMPORTANCE OF TRACK DESIGN IN GROUND TRANSPORTATION SYSTEMS.

The development of the tracks for the Tracked Hovercraft and Bliss Pendair Systems is described. Comment is made on the relative importance of track and suspension costs and of the need for tracks that are weather, vandal and noise proof. It is argued that the beam section required for a suspended air cushion is more likely to fit these requirements than that for beam riding vehicles, either air-cushion or magnetically suspended.