Irradiation temperature dependence of production efficiency of defects induced in neutron-irradiated silicon carbides

Production efficiency of vacancy-type defects induced in neutron-irradiated silicon carbide single crystals (4H and 6H SiC) is observed as a function of irradiation temperature. The crystals were irradiated at several tempera tures (20, 50, 100, 150, 200 and 370 K) using the low temperature irradiati on-loop facility of Kyoto University Reactor. In the irradiated crystals, a broad absorption band at 780 nm was observed. The origin of the 780 nm ban d was attributed to the Si vacancy defect (V-si-type center) because it has similar annealing behavior as a paramagnetic center consisting of a Si vac ancy that was identified by electron spin resonance (ESR) measurement. The defect concentration of the Vsi-type centers was estimated using the Smakul a formula from the absorption intensity of the 780 nm band. The production efficiency of the Vsi-type center in SiC crystals irradiated at several tem peratures has a maximum at about 200 K. The characterization of the irradia tion temperature dependence of the Vsi-type center is extremely different f rom that of MgO or Al2O3 which has a steep negative gradient from 20 to 400 K. (C) 2000 Elsevier Science B.V. All rights reserved.