| Project/Area Number |
11450242
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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 |
Inorganic materials/Physical properties
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
SHINOZAKI Kazuo Tokyo Institute of Technology Graduate School, Ass. Prof., 大学院・理工学研究科, 助教授 (00196388)
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| Co-Investigator(Kenkyū-buntansha) |
SAIKI Atsushi Tokyo Institute of Technology Faculty of Eng., Res. Ass., 工学部, 助手 (50221255)
WAKIYA Naoki Tokyo Institute of Technology Graduate School, Res. Ass., 大学院・理工学研究科, 助手 (40251623)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥12,600,000 (Direct Cost: ¥12,600,000)
Fiscal Year 2000: ¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 1999: ¥8,700,000 (Direct Cost: ¥8,700,000)
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| Keywords | Pulsed MO-CVD / Buffer Layer / Ferroelectric Material / Remanent Polarization / Pb(Zr, Ti)O_3(PZT) / PbTiO_3 / PbZrO_3 / Nb-SrTiO_3 / Nb-SiTiO_3 / 組成傾斜膜 |
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| Research Abstract |
The purpose of this study is to realize the single crystal like thin films with controlled residual stress by introducing the buffer layer between thin film and substrate. Several kinds of buffer layers with different composition or compositionally gradient were chosen at the standing points of the lattice mismatch and the thermal expansion coefficient difference between the thin film and the substrate.
To clarify the effects of residual stress on the electrical properties of the thin film, the electrical properties of the (001) PbTiO_3 thin film deposited on the (100) SrTiO_3 substrates with different residual stresses were measured. The residual stress was changed by the mechanical thinning of the substrate after thin film deposition or mechanical bending of the substrate. Increasing the inplane tensile stress of the thin film, the remnant polarization and the coercive field of the PbTiO_3 were decreasing.
The residual stress was successively controlled by introducing the various buffe
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r layers between epitaxially grown (001)Pb(Zr, Ti)O_3 thin film and (100) SrTiO_3 substrate. PbTiO_3 and compositionally gradient films with PbTiO_3→Pb(Zr, Ti)O_3 or PbZrO_3→Pb(Zr, Ti)O_3 were used as buffer layers. Since lattice mismatch among Pb(Zr, Ti)O_3, buffer layer and SrTiO_3 is rather small in this system, the effect of the lattice mismatch might be negligible compared with the effect of thermal expansion coefficient differences. Introducing the buffer layers with higher thermal expansion coefficient than SrTiO_3 and Pb(Zr, Ti)O_3 such as PbTiO_3 or PbTiO_3→Pb(Zr, Ti)O_3, the in-plane tensile stress of the Pb(Zr, Ti) O_3 film was relaxing. In contrast, the buffer layer with lower thermal expansion coefficient such as PbZrO_3→Pb(Zr, Ti)O_3 extended the in-plane tensile stress.
From these results we tried to change the electrical properties by introducing the buffer layer. Pt/PbTiO_3 buffer layers with different PbTiO_3 thickness were introduced between epitaxial (001)PbTiO_3 film and (100)SrTiO_3 substrate to realize Pt/PbTiO_3 /Pt/PbTiO_3 buffer/SrTiO_3. Increasing the thickness of the PbTiO_3 buffer, the remnant polarization was increasing by decreasing the in-plane tensile stress. Less
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