| Project/Area Number |
09650366
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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 |
Electronic materials/Electric materials
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| Research Institution | Himeji Institute of Technology |
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Principal Investigator |
SHIMIZU Masaru Himeji Institute of Technology, Fac.of Eng., Asso.Prof., 工学部, 助教授 (30154305)
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| Co-Investigator(Kenkyū-buntansha) |
FUJISAWA Hironori Himeji Institute of Technology, Fac.of Eng, Research Asso., 工学部, 助手 (30285340)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1998: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1997: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | ferroelectric thin film / memory / size effect / MOCVD / Pb(Zr, Ti)O_3 thin film / film thickness / grain size / grain boundary / 強誘電体 / Pb(Zr,Ti)O_3 / 薄膜 / メモリデバイス |
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| Research Abstract |
The size effects, including thickness and grain size, have become more and more iimportant for the realization of low voltage operation and ultra high integration in memory devices. In order to investigate the size effect of ferroelectric Pb(Zr, Ti)0_3 (PZT) thin films prepared by MOCVD (metalorganic chemical vapor deposition), two types of experiments were performed.
In the first set of experiments, dependence of electrical properties of PZT thin films on the film thicknesswas investigated. Thickness was controlled from 70 to 600nm by changing the deposition time.The dielectric constants, remanent polarizations and grain size decreased and the coercive fields increased as film thickness decreased. This experimental result means that the gain size effect was included in the thickness effect when films were prepared by MOCVD.
In order to separate the garin size effect from the thickness effect, grain size dependence of films was investigated. Grain size of PZT films was successfully controlled by changing the thickness of bottom I* electrode and by changing the growth rate of PZT films.
The dielectric constants and remant polarizations decreased, and current densities and coercive fields of films with a film thickness of 200nm incresed as grain size decreased from 240 to l2Onm. This dependence of electrical properties on the grain size coincided with that of ceramics. Polarization switching endurance properties were also influenced by the garin size. PZT films with grain size of 190 and 240nm showed no switching fatigue up to a switching cycle of 10'. On the other hand, PZT film with a grain size of l2Onm showed the fatigue.
Our experimental results also means that grain boundaries of thin films play very important roles in determining electrical properties.
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