2001 Fiscal Year Final Research Report Summary
| Project/Area Number |
11450128
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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 |
Electronic materials/Electric materials
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| Research Institution | Osaka Prefecture Uiversity |
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Principal Investigator |
NAKAYAMA Yoshikazu Graduate School of Engineering, Osaka Prefecture Uiversity Professor, 工学研究科, 教授 (20128771)
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| Co-Investigator(Kenkyū-buntansha) |
PAN Lujun Graduate School of Engineering, Osaka Prefecture Uiversity, Assistant, 工学研究科, 助手 (50326279)
AKITA Seiji Graduate School of Engineering, Osaka Prefecture Uiversity, Lecture, 工学研究科, 講師 (60202529)
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| Project Period (FY) |
1999 – 2001
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| Keywords | polysilane / orientation / density of states / carrier transport / disorder model / carrier trap / endothermic reaction / photobreaking |
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| Research Abstract |
Oriented polysilane films have been prepared by the constant-air-flow dipping method and the method of stretching along the thickness. The latter provides the stretching rate more than 200% and an orientation degree that the main chains more than 80% align along the thickness. The aligned polysilanes of 90% or more have the ring planes perpendicular to the main chains for the aromatic substituents and the trans planes of CH_2 bonds perpendicular to the main chains for the normal alkyl substituents.
Gap states have been measured by Photothermal deflection spectroscopy. The orientation decreases the Urbach energy and the density of states near the midgap by one order of magnitude for (MeSiPh)_n, indicating that the alignment affects the electronic states. The orientation also lengthens the o conjugat and reduces their distribution.
The hole-drift-mobility measurement has been performed for (MeSiPh)_n and confirmed the ten times increase by the orientation. The disorder model indicates the
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decrease in the polaron binding energy and the averaged hopping distance However, the fluctuation of the hopping distance increases not to increase the mobility as expected.
The polysilanes with aromatic substituents have a specific carrier-trapping center which is a π-π state consisting of two adjacent aromatic rings to trap a photocarrier at room temperature. Only the endothermic motion of the molecules releases the trapped carrier. In general, the carrier release at higher temperatures dominates and its release rate becomes higher for the oriented films. This indicates that the molecules become stiffer due to the molecular interaction, relating to the decrease in the polaron binding energy.
The photobreaking of the main chains also reflects the molecular interaction, and thus the orientation decreases its crosssection by three orders of magnitude. The photobreaking is thermally activated and the distribution of the activation energies becomes small by increasing the order of molecules. Less
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