2006 Fiscal Year Final Research Report Summary
STM/STS study on the ground state of layered dichalcogenide nanotubes
| Project/Area Number |
17540308
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | Hokkaido University |
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Principal Investigator |
ICHIMURA Koichi Hokkaido University, Faculty of Science, Instructor, 大学院教育学研究科, 助手 (50261277)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUNAGA Noriaki Hokkaido University, Faculty of Science, Lecturer, 大学院教育学研究科, 講師 (10222308)
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| Project Period (FY) |
2005 – 2006
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| Keywords | layered material / nanotube / STM / STS |
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| Research Abstract |
Layered compound NbSe_2 nanotubes were studied by low temperature scanning tunneling microscope (STM). NbSe_2 nanotube is an interesting material since it is the first nanotube material, of which bulk phase undergoes the condensed state such as the density wave and superconductivity. NbSe_2 nanotubes were synthesized by the chemical vapor transport method. The nanotube sample for STM measurement was prepared by dropping NbSe_2 nanotubes agitated ultrasonically in 2-propanol on cleaved highly oriented pyrolytic graphite (HOPG).
Topographic STM images of NbSe_2 nanotubes on the substrate of HOPG were taken at room temperature. The length of nanotubes is estimated as 300-2000 nm. Almost NbSe_2 nanotube has length over 600 nm. The nanotube structure is confirmed by STM scan profiles. Diameter of nanotubes is estimated as 2-50 nm, which is much smaller than that of multi-walled nanotubes studied by transmission electron microscope. We think that nanotubes with diameter of less than 10 nm are single-walled one. We are interested in the relation between the chirality (helicity) and electronic structure in single-walled NbSe_2 nanotubes. The bundle structure, which is popular in single-walled carbon nanotube, is found in NbSe_2 nanotubes. The bundle consists of about hundred nanotubes. The Y-junction, which is the connected structure with three nanotubes, is also found similarly to carbon nanotubes.
Although we can not take STM image with atomic resolution at room temperature, clear images with atomic arrangement are obtained below 4.2 K. The chirality of NbSe_2 nanotube is successfully determined from these images. The chiral index is found to vary from sample to sample. We also find that all nanotubes, of which atomic arrangement is determined, are so-called chiral type with low symmetry in helicity. It might give some suggestion to growing mechanism of NbSe_2 nanotubes.
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Research Products
(14 results)
