| Project/Area Number |
14550672
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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 |
Inorganic materials/Physical properties
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| Research Institution | Shonan Institute of Technology |
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Principal Investigator |
HAYASHI Takashi Shonan Institute of Tech., Mat.Sci&Ceram.Tech., Prof., 工学部, 教授 (70023265)
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| Project Period (FY) |
2002 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | Eximer UV / Ferroelectric Thin Films / Chemical Solution Processing / (Bi, Nd)_4Ti_3O_<12> / Spin-coating / Metal Alkoxide / Nonvolatile Memories / Hysterisis loop / エキシマ照射 / 強誘電性 / 薄膜 / 低温作製 / チタン酸ビスマス化合物 / 不揮発メモリ / ネオジウムドープチタン酸ビスマス / ランタンドープチタン酸ビスマス |
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| Research Abstract |
Ferroelectric Bi_4Ti_3O_<12> (BIT) thin films are extensively investigated for applications in nonvolatile ferroelectric random access memories (NvFRAM). Compared with SrBi_2Ta_2O_9(SBT) and its related materials, BIT thin films are known to crystallize at low processing temperature with a high crystallinity and to have a large remanent polarization (P_r), a small coercive field (E_c) and a high Curie temperature (T_c). However, P_r values of polycrystalline BIT thin films were seen to be as low as approximately 7-10 μC/cm^2. Recently, rare-earth (Ln=La, Pr, Nd and Sm)-doped BIT (BLnT) thin films have been intensively investigated. In particular, Bi_<4-x>Nd_xTi_3O_<12> (BNT) thin films have been attacting great attention for their ferroelectric properties which are superior to other rare earth-doped BIT thin films.
In this work, chemical solution processing and properties of ferroelectric (Bi, Nd)_4Ti_3O_<12> (BIT) thin films were investigated by the chemical solution deposition (CSD) m
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ethod using excimer UV lamp. The effects of excimer UV irradiation to as-deposited BNT precurosor films on crystallization, microstructure.
BNT precursor films were deposited on Pt(200nm)/TiO_x(50nm)/SiO_2/Si substrates by the spin-coating technique using metal-organic solutions. The excimer UV irradiation onto as-deposited BNT precursor films in O2 atmosphere was greatly effective in removing organic species of the BNT thin films and improving the ferroelectric properties. The synthesized BNT thin films using excimer UV irradiation showed a random orientation with a strong (117) reflection and a homogeneous microstructure consisting f grain sizes of 100-150 nm with a smooth surface. BNT thin films crystallized at a low temperature of 550℃ through the excimer UV irradiation process and showed a well-saturated P-E hysteresis loop with a P_r of 12.7 μC/cm^2 and E_c of 88 kV/cm.
Their films exhibited a relatively good fatigue endurance up to 10^9 cycles and a good leakage current property with less than 3 x 10^<-7>. Less
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