Infrared spectroscopy studies of localized vibrations in neutron irradiated silicon

We investigate neutron irradiation-induced defects in p-type Czochralski silicon (Cz–Si) subjected initially to heat treatments under high hydrostatic pressure (HTHP), by means of infrared spectroscopy (IR). A pair of bands at 592 and 883 cm⁻¹ arises in the spectra immediately after irradiation and disappears upon isochronal annealing just below 350 °C in as-grown Si, although they disappear at a smaller temperature ~ 280 °C in the HTHP treated Si. Another pair of bands at 535 and 556 cm⁻¹ arises in the spectra at ~ 320 °C and disappears at ~ 430 °C in as-grown Si, although they show a shift in their thermal stability of ~ 50 °C towards lower temperatures in HTHP Si. The activation energies characterizing their annihilation were found smaller in the HTHP Si, for each one of the four bands correspondingly. It is argued that the applied hydrostatic pressure affects the annealing behavior of the bands promoting their annihilation. From the LVM frequency values, the temperature range they appear and their annealing behavior we tentatively correlate them with structures involving self-interstitial clusters, presumably perturbed by an impurity atom. Four other bands at 562, 642, 654 and 678 cm⁻¹ show similar thermal stability arising in the spectra in the course of the isochronal annealing at ~ 250 °C and disappearing at ~ 400 °C, both in as-grown and in HTHP Si. However, the changes exhibited in the values of the activation energies of the bands between the HTHP and the as-grown Si, suggest that may not all of them have exactly the same origin, at least the 678 cm⁻¹ band. The origin of the above family of bands is discussed in regards with previous works reported in the literature. Connection with complexes comprising boron atoms and self interstitials, in short (B_n–Si_Im), was considered.