2001 Fiscal Year Final Research Report Summary
electronic process of carbon nanotubes and fullerene network
| Project/Area Number |
11165210
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas (A)
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| Allocation Type | Single-year Grants |
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TAMURA Ryo Graduate School of Science, University of Tokyo, research associate, 大学院・理学系研究科, 助手 (20282717)
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| Co-Investigator(Kenkyū-buntansha) |
TSUKADA Masaru Graduate School of Science, University of Tokyo, Professor, 大学院・理学系研究科, 教授 (90011650)
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| Project Period (FY) |
1999 – 2000
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| Keywords | carbon nanotube / nantube junction / tight binding model / pentagon-heptagon defect pair / Schottky Barrier / Hartree-Fock approximation / Green's function method / rectification |
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| Research Abstract |
Carbon nanotubes become semi-conducting (S) and metallic (M) according to their radius and helicity of the honeycomb lattice. We studied the transmission rate of the carbon nanotube junctions with the pentagon-heptagon defect pair. For the junction connecting two metallic tubes (M-M junction), it is calculated by the tight binding model and the effective mass theory. It is clarified that the transmission rate is determined only by the radius ratio and the normalized energy E/Ec and independent of the angle between the two tube axes. Here energy region |E|<EC in which the channel number is kept to two is considered. Furthermore the Schottky barrier in the M-S junction doped by electrostatic field effect of the gate electrode is calculated based on the tight binding model with Hartree-Fock approximation and Green's function method. It is found that Electron density and electron potential are higher at the pentagon and lower at the heptagon. These are localized within the distance comparable the lattice constant. On the other hand, the spatial width of the Schottky barrier is much larger than the lattice constant when the density of the doped carrier is low. The width, however, can be decreased by approaching the gate electrode to the junction due to the screening effect. When the distance between the nanotube and the gate is comparable with the diameter, the tunneling current becomes dominant and the forward bias of the rectification can be reversed compared to the conventional MS junction.
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