2007 Fiscal Year Final Research Report Summary
Development of transparent light emiting devices based on titanium dioxide
| Project/Area Number |
17550171
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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 |
Functional materials/Devices
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| Research Institution | Kanagawa Academy of Science and Technology |
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Principal Investigator |
FURUBAYASHI Yutaka Kanagawa Academy of Science and Technology, Nano-structured magneto-optical devices project, researcher (70392925)
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| Co-Investigator(Kenkyū-buntansha) |
HITOSUGI Taro University of Tokyo, department of chemistry, assistant (90372416)
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| Project Period (FY) |
2005 – 2006
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| Keywords | titanium dioxide / thin films / optical properties / transport properties / p-type semiconductors / light emitting devises |
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| Research Abstract |
(1) Investigation of transport properties for transparent conducting oxide (TCO), anatase Ti_<1-x>Nb_xO_2
We investigated effective masses and scattering factors of carriers for epitaxial anatase Ti_<1-x>Nb_xO_2 films. Optical conductivity in visible and infrared region had a good agreement with Drude model. Effective masses with low carrier concentration are approximately 0.4 m_0 and increase rapidly with regard to carrier concentration. We found that an optical phonon scattering is dominant and scatterings by ionized impurities are suppressed, which is due to the high dielectric constant of anatase TiO_2.
(2) Exploration of p-type TiO_2 by chemical substitution
The first principle calculation suggested that yttrium (Y) substituted anatase TiO_2 is a possibly p-type semiconductor. Combinatorial-technology revealed the existence of anatase Ti_<1-x>Y_xO_2 films. However, all of these films were insulating and no sign of p-type properties were observed.
(3) Optical and transport properties of anatase Ti_<0.97-y>Nb_0.03Si_yO_2
In order to apply TCO anatase TiO_2 to optical devices, it is required to control refractive indices of a TCO itself, because of a suppression of energy loss caused by reflections in interfaces and on a surface. We confirmed that Si-substituted anatase Ti_<0.97-y>Nb_0.03Si_yO_2 has an effectively low refractive indices, while maintaining a low resistivity less than 10^<-3>Ωcm.
(4) Positive Hall coefficient of strongly reduced TiO_<2-x>
We confirmed that strongly reduced TiO_<2-x> films grown under hydrogen atmosphere have the same crystal structure as that of γ- Ti_3O_5, and positive Hall coefficient, with a high reproducibility. The absence of anomalous Hall effects suggests that the positive Hall coefficient is not due to magnetic impurities. Also, we found that positive Hall coefficient of γ-Ti_3O_5 films is possibly due to the slightly smaller effective mass of holes than that of electrons.
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Research Products
(15 results)
