1993 Fiscal Year Final Research Report Summary
Dielectric and Ferroelectric Hysteresis loop Measurements for Thin Organic Films by Non-contact Electrode Method
| Project/Area Number |
04650029
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied materials
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| Research Institution | Ariake National College of Technology |
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Principal Investigator |
NAGAMORI Tomomi Ariake National College of Technology, Department of Electrical Engineering, Assistant Professor, 電気工学科, 助教授 (90110204)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIZAKI Katsunori Ariake National College of Technology, Common Technical Courses, Professor, 共通専門科, 教授 (20044331)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Ultrathin Films / Evaporation / Dielectric Constants / Phase Transition / D-E Hysteresis Measurements / Structural Control / Ferroelectricity / FT-IR |
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| Research Abstract |
Dielectric and ferroelectric hysteresis loop(D-E) measurements were conducted for evaporated organic thin films by utilizing a newly developed sample cell with non-contact electrode, showing the structure of the cell. The performance was confirmed for the spin coated film sample of vinylidene fluoride-trifluoroethylene (VDF/TrFE) copolymer. Then, for evaporated thin films of VDF/TrFE copolymer, the characteristic were investigated, exhibiting a ferroelectric nature in dielectric measurement and a hysteresis loop in D-E measurement when an electric field of 30 MV/m was applied during the evaporation process. Moreover, evaporated films of newly synthesized VDF telomer for using in polymerization of PVDF also were measured.
Fourier Transform-IR (FT-IR) spectroscopic measurements were conducted on VDF/TrFE copolymers with 73mol.% VDF content in order to investigate the ferro-to paraelectric phase transitions in evaporated and spin-coated thin films. Upon heating and cooling, several IR band
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s revealed the considerable changes in the wave-numbers with a thermal hysteresis in the evaporated thin film sample as well as spin coated films, reflecting the first order ferroelectric phase transition. Moreover, the degree of the changes differed depending on the kinds of substrates, suggesting that the interaction between the sample and the substrate affects the occurrence of the transitions.
A newly synthesized low molecular weight sample, named vinylidene fluoride telomer (VDF telomer), was employed as a sample because a previous study for a poly (vinylidene fluoride) sample revealed that the pyrolysis of such a polymeric sample took place during the evaporation, causing the lowering of its crystallinity. The molecular orientation and phase transition behavior of the VDF telomer evaporated films were evaluated by means of an energy dispersiv-type total reflection and symmetrical reflection X-ray diffractometer and FT-IR spectroscopy. The results showed that the evaporated films formed a layred structure, were consisted of form II crystals with TGTG'chain segments and the molecular axis in the films was perpendicular to the substrate. Upon heating process, it was also observed the occurrence of the solid-solid phase transition at about 70ﾟC, where the crystals changed from form II to form III, and then the layred structure disappeared above 90ﾟC. Less
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