| Project/Area Number |
09680480
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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 |
エネルギー学一般・原子力学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
OKADA Moritami Kyoto University, Research Reactor Institute, Instructor, 原子炉実験所, 助手 (00027450)
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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 |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1997: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Neutron irradiation effect / Defect recovery process / Absorption spectrum / Wide-gap semiconductor / Silicon carbide / Irradiation-induced defect / Electrical property / Irradiation temperature dependence |
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| Research Abstract |
Optical and electrical properties of silicon carbide (4H and 6H-SiC) single crystals irradiated with reactor neutrons have been evaluated by the optical spectroscopy and electric measurement methods. The irradiations were carried out at some temperatures in the low temperature irradiation loop facility of the Kyoto University Reactor (KUR-LTL) and at room temperature in the fast neutron reactor of the Tokyo university (YAYOI), In the irradiated samples, a broad absorption band at 780mm was observed. The origin of the 780mm band was attributed to the defect of silicon vacancy type (V_<si>-type center) because it has similar annealing behavior with the paramagnetic defect center consisting of a Si vacancy and a trapped electron.
The production efficiency of the V_<si>-type center in SiC crystals irradiated at several temperatures by the KUR-LTL has a maximum about 200K.The characterization of the irradiation temperature dependence of the V_<si>-type center is evidently different from that of oxides or metals which has negative steep gradient from 20K to 400K.
On the other hand, the change of electric resistivity in the neutron-irradiated SiC samples was observed. The resistivity for as-irradiated samples increases with fast neutron fluence. The increase of resistivity can be explained by the decreases of the carrier density. From elevated temperature annealing behaviors, it has been clarified that the electric resistivity and the carrier mobility have two annealing stages (350K 500K). By the 800K annealing, both of them recovered about 40%, whereas the change of the carrier density did not found.
Also, the effect of the neutron transmutation doping of SiC has been studied. The result shows that a part of ^<30>P which is produced by ^<29>Si(n, gamma)^<30>Si reaction, can effectually act as the electron donor.
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