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  What is Carbon Nanotubes?


Carbon nanotubes (CNTs) are, as that name implies, the tubes of a diameter of several "nano" meters made of carbon atoms. Nanometer is a very small value. One nanometer equals one billionth of a meter. The diameter of human hair is about a micron meter (equals one millionth of a meter). It shows how small the carbon nanotubes are. The carbon nanotubes attract many attentions as the fourth form of the carbon atoms (other three forms are the graphite, the diamond and the charcoal). Those materials are made of same carbon atoms, but the different crystal structure produces such an interesting forms. The crystal structure of the carbon nanotubes is a tube of rounded graphite sheet. In fact, a material called the fullerene was discovered before the carbon nanotubes. The fullerene is looks like a soccer ball made of the carbon. The fullerene and the carbon nanotubes are discovered by electron microscope observation. Therefore, we can say that they are the materials representing nanotechnology.

The characteristics of CNTs

What is the property of those CNTs? There are two kinds of CNT structure types which are shown in Figure 1 (a) and (b). The CNT of Figure 1 (a) is called SWNT (Single-walled carbon nanotube) and the one of Figure 1 (b) is MWNT (Multi-walled carbon nanotube). SWNTs are made of single layer of graphite sheet and MWNTs are made of multiple graphite sheets. The diameter of those SWNTs is smaller than 3 nanometers and that of MWNTs is bigger than 4 nanometers to several tens of nanometers. Furthermore, each nanotube has different spiral structure (chirality) because it changes by how to scroll the graphite sheet, and the electrical property (metallic or semiconductive) of CNTs also changes depending on the chirality of each CNT. The CNTs are expected to applied in various technologies, for example the Feild Effect Transistor (FET), the field emission display, the needle of the probe microscope and interconnect wiring because they have other interesting property such as high heat stability, strong carbon bonding and lightness.


Figure 1 (a) SWNT (b) MWNT


In Kawarada laboratory, we work on wide research that spreads from the synthesis to the device application of those CNTs. Some of those researches are shown in below link.

Application of Carbon Nanotube for LSI Interconnects

Application to electrode of electrical double layer capacitor (EDLC)

Implantation of Metal Catalyst by Focused Ion Beam

Synthesis of long CNTs