Infrared signals correlated with self-interstitial clusters in neutron-irradiated silicon

Abstract

Using infrared spectroscopy we have investigated the defect spectrum of neutron-irradiated Czochralski–silicon (Cz–Si). The study was focused on three weak signals, mainly on a band at 533 cm−1, as well as on two other bands at 582 and 592 cm−1. The band at 533 cm−1 disappears from the spectra at ~170 °C exhibiting similar thermal stability with the Si-P6 electron paramagnetic resonance spectrum, previously correlated with a di-interstitial defect. The suggested model for the latter defect, comprising two self-interstitials placed symmetrically a lattice site Si atom, is very similar with that of the allene molecule. This allowed the calculation of the vibrational frequency of the suggested di-interstitial structure giving a value close to the 533 cm−1, in further support of the above assignment. The band at 582 cm−1 is stable up to 550 °C. The possible correlation of its origin to large self-interstitial clusters is examined. Also, the origin of the 592 cm−1 band, which is stable up to 200 °C is discussed, with indications tentatively pointing to a CV pair.