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The experimentally verified electrical properties of carbon nanotube structures and manifestations in related phenomena such as thermoelectricity, superconductivity, electroluminescence, and photoconductivity are reviewed. The possibility of using naturally formed complex nanotube morphologies, such as Y-junctions, for new device architectures are then considered. Technological applications of the electrical properties of nanotube derived structures in transistor applications, high frequency nanoelectronics, field emission, and biological sensing are then outlined. The review concludes with an outlook on the technological potential of nanotubes and the need for new device architectures for nanotube systems integration.

Carbon-nanotube-based electronics offers significant potential as a nanoscale alternative to silicon-based devices for molecular electronics technologies. Here, we show evidence for a dramatic electrical switching behaviour in a Y-junction carbon-nanotube morphology. We observe an abrupt modulation of the current from an on- to an off-state, presumably mediated by defects and the topology of the junction. The mutual interaction of the electron currents in the three branches of the Y-junction is shown to be the basis for a potentially new logic device. This is the first time that such switching and logic functionalities have been experimentally demonstrated in Y-junction nanotubes without the need for an external gate. A class of nanoelectronic architecture and functionality, which extends well beyond conventional field-effect transistor technologies, is now possible.

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We consider some of the significant aspects of Silicon nanowires (NWs), referring to their various modes of fabrication and their measured properties. Lithographic patterning as well as individual NW synthesis, e.g., through chemical vapor deposition based processes, has been utilized for their fabrication. It is seen that the properties of these nanostructures, to a large extent, are determined by the enhanced surface area to volume ratio and defects play a relatively major role. A diminished size also brings forth the possibility of quantum confinement effects dictating their electronic and optical properties, e.g., where NWs can possess a direct energy gap in contrast to the indirect bandgap of bulk Si. While new challenges, such as enhanced Ohmic contact resistance, carrier depletion-which can severely influence electrical conduction, and surface passivation abound, there also seem to be exciting opportunities. These include, e.g., high sensitivity sensors, nanoelectromechanical systems, and reduced thermal conductivity materials for thermoelectrics. Much preliminary work has been done in these areas as well as investigating the possible use of Si NWs for transistor applications, photovoltaics, and electrochemical batteries etc., all of which are briefly reviewed.

We indicate the fundamental rationale underlying the control of temperature and the manipulation of thermal flux, with reference to a multilayered composite material. We show that when the orientation of the layers in the composite is physically rotated with respect to a constant temperature gradient, there would then be a corresponding introduction of off-diagonal components in the thermal conductivity tensor and thermal anisotropy is induced. The consequent bending of the heat flux lines is found to depend on both the (i) composite rotation angle, as well as the (ii) ratio of the thermal conductivities of the constituent materials.

The generation of electrical voltage through the flow of an electrolyte over a charged surface may be used for energy transduction. Here, we show that enhanced electrical potential differences (i.e., streaming potential) may be obtained through the flow of salt water on liquid-filled surfaces that are infiltrated with a lower dielectric constant liquid, such as oil, to harness electrolyte slip and associated surface charge. A record-high figure of merit, in terms of the voltage generated per unit applied pressure, of 0.043 mV Pa−1 is obtained through the use of the liquid-filled surfaces. In comparison with air-filled surfaces, the figure of merit associated with the liquid-filled surface increases by a factor of 1.4. These results lay the basis for innovative surface charge engineering methodology for the study of electrokinetic phenomena at the microscale, with possible application in new electrical power sources.