Origin of the 0.97 eV luminescence in irradiated silicon

Optical detection of magnetic resonance studies are described for the well-studied optical center with zero phonon line at 0.97 eV in irradiated silicon. Analysis of the S=1 ODMR spin Hamiltonian reveals a low symmetry (Csub(1h)) center and a resolved 29Si hyperfine interaction with a single silicon atom. In a specially enriched 13C doped sample we find additional hf interactions with two equivalent carbon atoms. At elevated temperatures, the defect reorients easily from one (Csub(1h)) distortion to another around a common <111> axis; during this reorientation the spin density remains located on the same silicon atom and the same carbon pair. From these results we construct a model comprising two adjacent (substitutional) carbon atoms and an interstitial silicon atom which has distorted out from a bond-centered position. We conclude that the same defect gives rise to the Si-G11 EPR spectrum when positively charged. (orig.)