Electron Paramagnetic Resonance of the Neutral (S=1) One- Vacancy-Oxygen Center in Irradiated Silicon

A new EPR spectrum, labeled $\mathrm{S}\mathrm{i}-S1\mathrm{}$, has been observed in electron- or neutron-irradiated, $n$- or $p$-type, crucible-grown silicon under illumination with approximately band-gap light. The $\mathrm{S}\mathrm{i}-S1\mathrm{}$ spectrum consists primarily of a fine-structure spectrum and a ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ hyperfine spectrum. By incorporating ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ atoms into vacuum-float-zone silicon by ion implantation, the $\mathrm{S}\mathrm{i}-S1\mathrm{}$ ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ hyperfine spectrum was also observed. An analysis of the coupling tensors in the spin Hamiltonian which characterize the fine structure and ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ hyperfine spectrum is presented and suggests that the $\mathrm{S}\mathrm{i}-S1\mathrm{}$ center is the neutral charge state of the one-vacancy-oxygen center in an excited spin-triplet state. This model for the $\mathrm{S}\mathrm{i}-S1\mathrm{}$ center is in agreement with stress measurements, which are also presented. These measurements indicate that the time-temperature dependence in the reorientation of the $\mathrm{S}\mathrm{i}-S1\mathrm{}$ center is the same as that of the neutral one-vacancy-oxygen center as monitored by the $\mathrm{S}\mathrm{i}-B1\mathrm{}$ spectrum.