著者

Umeda T. Isoya J. Morishita N. Ohshima T. Kamiya T. Gali A. Deák P. Son N. T. Janzén E.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.70, pp.235212, 2004-12

被引用文献数

50

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The carbon vacancy is a dominant defect in 4H-SiC, and the "EI5" electron-paramagnetic-resonance (EPR) spectrum originates from positively charged carbon vacancies (VC+) at quasicubic sites. The observed state for EI5, however, has been attributed to a motional-averaged state with the C3v symmetry, and its true atomic structure has not been revealed so far. We here report low temperature (<40 K) EPR measurements on EI5 and show that this center has a C1h-symmetric structure due to Jahn-Teller distortion. We also performed ab inito calculations of the hyperfine tensors for EI5, and obtained a good agreement between experiment and theory in not only their principal values but also their principal axis directions. A good agreement was also demonstrated for the EI6 center (hexagonal-site VC+) in this paper. The transition from EI5(C1h) to EI5(C3v) was found to be thermally activated and its activation energy was measured as 0.014 eV.