Infrared studies of the evolution of the CiOi(SiI) defect in irradiated Si upon isothermal anneals

Carbon-oxygen-self-interstitial complexes were investigated in silicon by means of Fourier transform infrared spectroscopy. Upon irradiation, the CiOidefect (C3) forms which for high doses attract self-interstitials (SiIs) leading to the formation of the CiOi(SiI) defect (C4) with two well-known related bands at 939.6 and 1024 cm−1. The bands are detectable in the spectra both in room temperature (RT) and liquid helium (LH) temperature. Upon annealing at 150 °C, these bands were transformed to three bands at 725, 952, and 973 cm−1, detectable only at LH temperatures. Upon annealing at 220 °C, these bands were transformed to three bands at 951, 969.5, and 977 cm−1, detectable both at RT and LH temperatures. Annealing at 280 °C resulted in the transformation of these bands to two new bands at 973 and 1024 cm−1. The latter bands disappear from the spectra upon annealing at 315 °C without the emergence of other bands in the spectra. Considering reaction kinetics and defect metastability, we developed a model to describe the experimental results. Annealing at 150 °C triggers the capturing of SiIs by the C4defect leading to the formation of the CiOi(SiI)2 complex. The latter structure appears to be bistable: measuring at LH, the defect is in configuration CiOi(SiI)2 giving rise to the bands at 725, 952, and 973 cm−1, whereas on measurements at RT, the defect converts to another configuration CiOi(SiI)2* without detectable bands in the spectra. Possible structures of the two CiOi(SiI)2 configurations are considered and discussed. Upon annealing at 220 °C, additional SiIs are captured by the CiOi(SiI)2defect leading to the formation of the CiOi(SiI)3 complex, which in turn on annealing at 280 °C converts to the CiOi(SiI)4 complex. The latter defect anneals out at 315 °C, without being accompanied in the spectra by the growth of new bands.