| Project/Area Number |
09555026
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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 | 展開研究 |
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| Research Field |
Applied physics, general
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| Research Institution | RIKEN |
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Principal Investigator |
USHIDA Kiminori Riken, Cyclotron Center, Senior Research Scientist., ビーム分配技術開発室, 先任研究員 (60183018)
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| Project Period (FY) |
1997 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥8,500,000 (Direct Cost: ¥8,500,000)
Fiscal Year 1999: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1998: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1997: ¥6,000,000 (Direct Cost: ¥6,000,000)
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| Keywords | Electron Spin Resonance / Semiconductor Solid / Photocatalyst / Time Resolved Electron Spin Resonance / Surface Radical / Electron Transfer / Solar Cell / Danging Bond / Dielectric Constant / Defects / 光化学反応 / 固体表面ラジカル / ESR / EPR / ラジカル / 光触媒反応 / レーザー光 / 活性中間体 / 半導体表面ラジカル / 光化学初期過程 / マイクロ波 / 光励起 |
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| Research Abstract |
In this research project we have developed a new instrument to realize a time resolved (TR) ESR (EPR) measurement in semiconductor solids such as titanium oxide for which measurement had been impossible until now. Previously, we could only observe extremely long lived radicals formed at the semi-conductor surface with CWESR spectroscopy on steady-state photo illumination. With this new instrument, we will be able to detect a short lived radicals by TRESR In conventional TRESR methods, a sudden change in the dielectric constant, which is induced by short-lived caniers formed on laser pulse in semiconductor solids, disturbs the sample cavities to reduce their sensitivity (Q-value) and to give large transient signals due to the dynamic dielectric change (DDC). We use two sample cavities ; one is for sample and the other is for reference. Two microwave signals coming from either of two cavities are mixed to be cancel out in the microwave circuit by phase matching technique. The sample cavity is located in the external magnetic field which is scanned to obtain TRESR spectra In the experiment with titanium oxide micro particle, we could lower the DDC signal to be less than 1/% and therefore the total sensitivity increased about as 1OO time large as before. We added the extemal automatic tequency controller (AFC) to exclude the effect of instability of cavities to obtain low-noise signal. Until now, the sensitivity of this instrument is too low to succeed in TRESR measurement for titanium oxide which is our initial purpose. In principle. however, it is clear that this method is generally applicable to semiconductor solids to detect short-lived paramagnetic species formed from trapping states existing in the band gap. This apparatus provides a new method which can be generally used for the detection of paramagnetic centers (defects, impurities, etc.) formed in semiconductor solids.
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