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| 2. |
- Isoya, J., et al.
(författare)
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EPR Identification of Defects and Impurities in SiC : To Be Decisive
- 2009
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Ingår i: Materials Science Forum, Vols. 600-603. - : Trans Tech Publications. ; , s. 279-284
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Konferensbidrag (refereegranskat)abstract
- In EPR (electron paramagnetic resonance) identification of point defects, hyperfine (HF) interaction is decisive information not only for chemical identity but also for the local geometry and the electronic state. In some intrinsic defects in SiC, the wave function of the unpaired electron extends quite unevenly among major atoms comprising the defects. In such a case, the determination of the number of equivalent atoms and the chemical identity (Si or C) of those atoms even with weak HF splitting are useful to compare with HF parameters obtained theoretically. For vacancy-related defects of relatively deep levels, the sum of the spin densities on the nearest-neighbor shell is found to be 60-68%.
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| 3. |
- Isoya, J., et al.
(författare)
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EPR identification of intrinsic defects in SiC
- 2008
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 245:7, s. 1298-1314
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Tidskriftsartikel (refereegranskat)abstract
- The structure determination of intrinsic defects in 4H-SiC, 6H-SiC, and 3C-SiC by means of EPR is based on measuring the angular dependence of the 29Si/13C hyperfine (HF) satellite lines, from which spin densities, sp-hybrid ratio, and p-orbital direction can be determined over major atoms comprising a defect. In most cases, not only the assignment of the variety due to the inequivalent sites (h- and k-sites in 4H-SiC) but also the identification of the defect species is accomplished through the comparison of the obtained HF parameters with those obtained from first principles calculations. Our works of identifying vacancy-related defects such as the monovacancies, divacancies, and antisite-vacancy pairs in 4H-SiC are reviewed. In addition, it is demonstrated that the observation of the central line of the TV2a center of S = 3/2 has been achieved by pulsed-ELDOR. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
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| 5. |
- Nguyen, Son Tien, 1953-, et al.
(författare)
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Divacancy in 4H-SiC
- 2006
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 96:5, s. 055501-1-055501-4
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Tidskriftsartikel (refereegranskat)abstract
- Electron paramagnetic resonance and ab initio supercell calculations suggest that the P6/P7 centers, which were previously assigned to the photoexcited triplet states of the carbon vacancy-antisite pairs in the double positive charge state, are related to the triplet ground states of the neutral divacancy. The spin density is found to be located mainly on three nearest C neighbors of the silicon vacancy, whereas it is negligible on the nearest Si neighbors of the carbon vacancy.
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| 7. |
- Nguyen, Tien Son, et al.
(författare)
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Identification of divacancies in 4H-SiC
- 2006
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Ingår i: Physica B: Condensed Matter, Vols. 376-377. - : Elsevier BV. ; , s. 334-337
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Konferensbidrag (refereegranskat)abstract
- The P6/P7 centers in 4H-SiC were studied by electron paramagnetic resonance (EPR) and ab initio supercell calculations. The hyperfine coupling constants of C and Si neighbors obtained by EPR are in good agreement with the calculated values for the neutral divacancy, VCVsi0. Our results suggest that the P6/P7 centers, which were previously assigned to the photo-excited triplet states of the carbon vacancy-carbon antisite pairs in the double positive charge state (VCCsi2+), are related to the triplet ground states of the C-3v/C-1h si configurations of VCVsi0 (c) 2006 Elsevier B.V. All rights reserved.
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| 8. |
- Umeda, T, et al.
(författare)
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Dicarbon antisite defect in n-type 4H-SiC
- 2009
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 79:11, s. 115211-
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Tidskriftsartikel (refereegranskat)abstract
- We identify the negatively charged dicarbon antisite defect (C-2 core at silicon site) in electron-irradiated n-type 4H-SiC by means of combined electron paramagnetic resonance (EPR) measurements and first-principles calculations. The HEI5 and HEI6 EPR centers (S=1/2; C-1h symmetry) are associated with cubic and hexagonal dicarbon antisite defects, respectively. This assignment is based on a comparison of the measured and calculated hyperfine tensors of C-13 and Si-29 atoms as far as the second neighborhood around the defects. Theoretically, the dicarbon antisites are stable in a single negative charge state under a wide range of n-type samples. We found that the defects can be created under a wide range of irradiation conditions, and our measurements strongly suggest the existence of carbon antisite defects in the as-grown samples. Annealing studies revealed several atomistic processes such as recombination of carbon interstitials with vacancies and formation of carbon aggregates. These processes were activated at about 1000 degrees C, and as theoretically predicted, the dicarbon antisite is much more stable than the dicarbon interstitial defect (C-2 core at carbon site). The measured activation temperature is consistent with the temperature range for forming various carbon aggregate-related photoluminescence centers.
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