The electron paramagnetic resonance spectrum of the S2 center in float-zone and Czochralski samples was studied after H2+-ion implantation and subsequent annealing. The spectrum exhibited an isotropic line, g = 2.0066, at room temperature. This then broadened and transformed into a complex spectrum at 120K. The latter spectrum could be decomposed into isotropic and anisotropic components. The relative concentration of the anisotropic component was larger in Czochralski samples, and smaller in float-zone samples, than was the respective isotropic component. The g-tensor which was evaluated from the anisotropic component at 120K showed that the spectrum originated from a center having trigonal symmetry. It was suggested that the S2 center developed in a multi-vacancy defect which contained O and H atoms. From a reversible thermal effect of linewidth-narrowing, the motional properties of the dangling bond in the S2 center were estimated to be described by an activation energy of 0.03eV.

Electron Paramagnetic Resonance Study of S2 Defects in Hydrogen-Implanted Silicon. B.Rakvin, B.Pivac, R.Tonini, F.Corni, G.Ottaviani: Nuclear Instruments & Methods in Physics Research B, 2000, 170[1-2], 125-33