New low symmetry configuration of the two carbon–interstitial silicon complex in irradiated silicon

Using the spin-dependent microwave photoconductivity detection of electron paramagnetic resonance (EPR), a new low-symmetry configuration of a complex containing an interstitial silicon and two carbon atoms was found in irradiated silicon. This configuration can be considered as an intermediate state formed during annealing the substitution carbon–interstitial silicon–substitution carbon (Cs–Sii–Cs) complexes, giving rise to the Si-PT4 spin-1 EPR spectrum of monoclinic symmetry which transforms at temperatures below 20 K to the new triclinic spin-1 spectrum labeled Si-WL5. The identification of the Si-PT4 and Si-WL5 spectra was made using silicon enriched with the 13C isotope.