EPR studies of defects in electron-irradiated silicon: A triplet state of vacancy-oxygen complexes

Abstract

Three new EPR spectra ($\mathrm{Si}-A14,-A15, \mathrm{and} -A16$) and two previously known spectra ($\mathrm{S}\mathrm{i}-P2\mathrm{} \mathrm{and} -P4\mathrm{}$) are observed for the first time in electron-irradiated silicon. The microscopic defect models are established as multivacancy-oxygen complexes with the oxygen(s) in Si-O-Si structure inside the vacancy chain: a (divacancy plus oxygen) for $\mathrm{S}\mathrm{i}-A14$, a (divacancy plus two oxygen) for $\mathrm{S}\mathrm{i}-P2\mathrm{}$, a (trivacancy plus oxygen) for $\mathrm{S}\mathrm{i}-P4\mathrm{}$, a (trivacancy plus two oxygen) for $\mathrm{S}\mathrm{i}-P5\mathrm{}$, and a (trivacancy plus three oxygen) for $\mathrm{S}\mathrm{i}-A15$. The number of vacancies in the chain is determined from the zero-field fine structure and the number of oxygens from the evolutionary kinetics, with the $g$ tensor, ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ hyperfine structure, and stress response providing strong supportive evidence. It is emphasized that some of these oxygen-dependent defects play an important role as trapping centers for other point defects.