| Project/Area Number |
15204029
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 |
TANDA Satoshi Hokkaido University, Eng. Appl. Phys., Prof. (80217215)
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| Co-Investigator(Kenkyū-buntansha) |
INAGAKI Katsuhiko HOKKAIDO UNIVERSITY, Eng. Appl. Phys, Inst (60301933)
UJI Sinya , Nano System Functionality Center, Senior Researcher (80344430)
HATAKENAKA Noriyuki Hiroshima Univ., Integrated Art and Sci., Prof. (70363009)
HAYASHI Masahiko Tohoku Univ., Information Sci., Prof. (60301040)
MATSUYAMA Toyoki Nara Univ. of Education, Dept. of Phys, Prof. (70202330)
浅野 泰寛 北海道大学, 大学院・工学研究科, 助教授 (20271637)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥48,230,000 (Direct Cost: ¥37,100,000、Indirect Cost: ¥11,130,000)
Fiscal Year 2005: ¥8,190,000 (Direct Cost: ¥6,300,000、Indirect Cost: ¥1,890,000)
Fiscal Year 2004: ¥11,830,000 (Direct Cost: ¥9,100,000、Indirect Cost: ¥2,730,000)
Fiscal Year 2003: ¥28,210,000 (Direct Cost: ¥21,700,000、Indirect Cost: ¥6,510,000)
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| Keywords | Tonological Material / Ring crystals / Superconductor / Charge Density Wave / Topology / NbSe3 MX3 / Low dimension / Nanotubes / メビウス結晶 / NbSe2 / NbSe3 |
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| Research Abstract |
We develop a new method to enhance two dimensionality of the system by making a thinner film using the "dechalcogenide method". The starting material is TaSe3 fibre, which is used as a template. The TaSe3 crystals are synthesized by the conventional chemical vapour transport method. The size of the TaSe3 crystals is typically 10 nm-1mm (thickness and width) and 100 nm-1 cm (length). We convert the TaSe3 crystals with nanoscale to TaSe2 ultrathin films. The TaSe3 crystals are set on a quartz plate in a sample chamber (Thermo Riko IVF298) evacuated to about 1×10^5 Torr. The sample chamber at approximately 1×10^3 Torr is filled with hydrogen gas in order to remove the oxygen gas. The TaSe3 crystals are heated rapidly from room temperature to 600K and then reacted with hydrogen gas for about 30 min. The chemical reaction is expressed as TaSe3 +H2(gas)=TaSe2+H2Se(gas). One selenium atom is removed from the TaSe3 template per unit cell (TaSe3=TaSe2+Se), resulting in the growth of a TaSe2 thi
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n film on the surface of TaSe3 fibre. The surface TaSe3 crystal is converted into a TaSe2 monolayer near the surface during the de-chalcogenide processes These obtained crystals are suspended in isopropyl alcohol by sonic dispersion of 30 min to strip ultrathin TaSe2 film from TaSe3 surface. The size of the TaSe2 crystals is typically 10nm-10mm (width and length) and 10 nm (thickness). Submicron TaSe2 crystals are deposited on a substrate. We analyze these crystals by their transmission electron diffraction (TED) pattern. We discover a supercluster of electrons in the ultrathin TaSe2 crystals synthesized by our developed de-chalcogenide method. The supercluster has an unexpected structure containing 61 electrons denoted by 61×61, in addition to supercluster based on 7×7 clusters expected in triangle lattices. This new hierarchal structure and successive clustering cannot be explained by a conventional electron clustering mechanism assisted by background lattice distortions, i.e., charge-density-wave formation mechanism based on Fermi surface nesting. We propose an alternative possible formation mechanism based on saddle-point nesting, taking into account a trigonal symmetry as well as lattice distortion energy. Less
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