| Project/Area Number |
17340105
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | The University of Tokyo |
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Principal Investigator |
LIPPMAA Mikk The University of Tokyo, Institute for Solid State Physics, Associate Professor, 物性研究所, 助教授 (10334343)
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| Co-Investigator(Kenkyū-buntansha) |
OHNISHI Tsuyoshi The University of Tokyo, Institute for Solid State Physics, Research Associate, 物性研究所, 助手 (80345230)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥15,500,000 (Direct Cost: ¥15,500,000)
Fiscal Year 2006: ¥8,500,000 (Direct Cost: ¥8,500,000)
Fiscal Year 2005: ¥7,000,000 (Direct Cost: ¥7,000,000)
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| Keywords | oxide / field effect / transistor / metal-insulator transition / SrTiO3 / mobility / superconductivity / nanowire / 強相関エレクトロニクス / マイクロ・ナノデバイス / MBE、エピタキシャル / 先端機能デバイス / 超薄膜 |
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| Research Abstract |
During H18 we succeeded in fabricating SrTiO3-based field-effect transistors with epitaxial and amorphous CaHfO3 and DyScO3 gate insulator layers. Epitaxial insulator layers of CaHfO3 and DyScO3 could be grown on SrTiO3 to a thickness of about 2 nm without nucleating grain boundaries. By combining a thin epitaxial layer with an amorphous insulator, we achieved transistors where sheet carrier densities of 10^<13> cm^<-2> order could be induced in a thin surface layer of a SrTiO_3 substrate. A rapid increase of the field-effect mobility was observed at low temperature, indicating that the field-induced carriers are equivalent to chemically doped carriers. A metal-to-insulator transition was observed in the SrTiO_3 transistors.
The growth of metallic LaTiO_3 nanowires was studied. A step-flow growth technique was developed that allowed us to fabricate an array of metallic (La, Sr)TiO_3 nanowires along the step edges of an annealed SrTiO_3 substrate. A technique was developed to buffer the surface of an annealed SrTiO_3 single crystal surface with a SrO film pror to the growth of the LaTiO_3 nanowires. This step was necessary in order to reduce the surface conductivity of SrTiO_3 and thus isolate the nanowires from each other. The final nanowire arrays showed nearly ideal one-dimensional conductivity.
The superconducting properties of Nb-doped SrTiO_3 films were studied in collaboration with the group of prof. Triscone at the University of Geneva, Switzerland. We succeeded in fabricating superconducting Nb:SrTiO_3 thin films and demonstrated that the superconductivity can be switched on and off by changing the carrier concentration in the thin films by electrostatic field effect.
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