Investigation On Electrical Properties And Correlated Problems Of Carbon Nanotubes In Medium Solution

The idea of using molecules and small chemical groups as the building blocks of a new generation of computers has been around for years. The quest has become more urgent over the last decade; however, as traditional silicon integrated circuit continues to shrink towards the limitation from the technical and economical point of view. Researchers hope to skirt this problem by using nano-materials to create billions of devices that could fit easily into the space of a current chip. Among many approaches to make nano devices and circuits, the development of carbon nanotubes as components in nanoeletronics is more rapid than others. Recently, many excellent achievements have been published in famous learned journals, such as Science and Nature. The nanoscale computing circuits, named the Breakthrough of the Year by Science's editors, leads their list of the top ten scientific developments in December 2001.Carbon nanotubes (CNTs) are a kind of carbon allotrope, which was found by Japanese scientist in 1991. They can be assumed as the result of folding graphite layers into carbon cylinders. Carbon nanotubes can be divided into single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). Carbon nanotubes exhibited good physical and chemical behaviors. Their unique properties offer the possibilities of wide applications, especially in nano-electronics base on their electronic properties. Carbon nanotubes are regarded as ideal materials to make nano devices and circuits in future such as diodes, triodes, field effect transistors and wires, which may lead to huge revolution in integrated circuit industry.Many investigations have shown that carbon nanotubes and their films in electrolyte have many particular behaviors. Therefore, the research on carbon nanotubes in medium solution is a significant work. In this paper, electronic properties of carbon nanotube films in medium solution, especially in electrolyte has been studied, including experimental and theoretical analyses of their rectification characteristics, field effect characteristics, and other electronic properties.1) Carbon nanotube films were characterized and chemically treated in experiments. Spectral analyses present a contrast between chemical treated carbon nanotube films and untreated ones. The resistance model of carbon nanotube films was introduced through heterogeneous fibrillar film resistance model about film resistance built by A. B. Kaiser. Film resistances both in air and water vapor were studied,respectively, and temperature effects on resistance were explored as well.2) The voltage-current curves multi-walled carbon nanotube films in electrolytes (such as KC1, NaCl) were measured in experiments. For the first time, a rectification characteristic at the interface was found. It was affected by the properties, concentrations and temperatures of electrolytes. There was no rectification characteristic found in non-electrolyte, such as alcohol and acetone solution. The results were theoretically analyzed.3) The voltage-current curves of carbon nanotube films in gate structure were measured in experiment. For the first time, it is found that the currents can be controlled by gate voltages applied to electrolytes, i.e. a significant field effect. The transconductance was about 0.3 mA/V at 2 V. There is no field effect appearance in non-electrolyte, such as alcohol and water. The results obtained were discussed.4) The potential in the interface between carbon nanotube films and electrolyte solutions were measured in experiments. It was found that there was a large electrochemical potential at the interface of electrolyte, which was relative to the properties, concentrations and temperature of solutions. There were no potentials found in non-electrolytes, such as alcohol and pure water, and air as well. The results were theoretically analyzed.5) In experiments, carbon nanotube films were immersed in flowing liquids such as NaCl, KC1 and KH2PO4. It was found that a potential could be generated. The experimental results showed that the flow-induced potential on the surface of carbon nanotube films closely depended on the flow rats, concentrations and properties of liquids. The flow-induced potentials were increased with the increasing flow rates and concentrations of liquids. The results were discussed in detail.6) Electronic properties about carbon nanotube films were theoretically analyzed. Electronic tunneling probability and resistivity in carbon nanotube intermolecular junctions were theoretically calculated. Rectification characteristic relationship and field effect transconductance of carbon nanotubes were theoretically investigated.