1994 Fiscal Year Final Research Report Summary
Construction of Ferroelectic Oxide Superlattices by a Laser Ablation Technique and Their Properties
| Project/Area Number |
05452103
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
表面界面物性
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| Research Institution | Osaka University |
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Principal Investigator |
KAWAI Tomoji Osaka Univ.ISIR-Sanken Professor, 産業科学研究所, 教授 (20092546)
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| Co-Investigator(Kenkyū-buntansha) |
KANAI Masaki Osaka Univ.ISIR-Sanken Technical Staff, 産業科学研究所, 教務職員 (50243267)
KITAHARA Katsuki Osaka Univ.ISIR-Sanken Research Associalt, 産業科学研究所, 助手 (20029903)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Laser Ablation / Ferroelectricity / Superlattice / Artificial Lattice / Functional Oxide / Dielectric Constant / Material Design / Layred Growth |
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| Research Abstract |
Artificial dielectric superlattices of SrTiO_3/BaTiO_3 (STO/BTO) and CaTiO_3/BaTiO_3 (CTO/BTO) have been formed by a pulsed laser ablation technique with an in situ monitoring of RHEED (reflection high energy electron diffraction) oscillation. The crystal structures can be controlled with atomic order accuracy and a large stress of 400-500 MPa is introduced at the interface between the BTO and STO layrs. The superlattices show higher dielectric constant than that of (Sr_<0.5>Ba_<0.5>) TiO_3 films against the change of temperature or applied freqency. A large dielectric constant of 900 was observed for the superlattices with a stacking periodicity of 2 unit cells/2 unit cells. The superlattices show drastically different electrical behavior from that of the solid solution (Sr, Ba) TiO_3 films, both with changing temperature and applied frequency. Broad maxima of the dielectric constants occur around 40-50? A1C and the valucs remain large even for the temperature above 200? A1C.On the contrary, in the case fo CTO/BTO superlattices, lattice constans and dielectric constant do not change so much compared with STO/BTO cases. Lattice mismatch in the STO/BTO and the CTO/BTO superlattices are 2.5% and 5.5%, respectively. In the case of CTO/BTO,misfit dislocations such as stacking faults may occur at the interface between CTO and BTO layrs owing to large lattice mismatch. Therefore, lattice strain is introduced effectively below the lattice mismatch of about 3 %.
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