Interstitial carbon defects in silicon. A quantum mechanical characterization through the infrared and Raman spectra.

The Infrared (IR) and Raman spectra of various interstitial carbon defects in silicon are computed at the quantum mechanical level by using an all electron Gaussian type basis set, the hybrid B3LYP functional and the supercell approach, as implemented in the CRYSTAL code (Dovesi et al. J. Chem. Phys. 2020, 152, 204111). The list includes two 〈100〉 split interstitial I defects, namely I and I , a couple of related defects that we indicate as I I , the so called in its A and B form, as well as SiC Si and C C C , in which the interstitial carbon atom is twofold coordinated. The second undergoes a large relaxation, and the final configuration is close to I C . Geometries, relative stabilities, electronic, and vibrational properties are analysed. All these defects show characteristic features in their IR spectrum (above 730 cm ), whereas the Raman spectrum is dominated, in most of the cases, by the pristine silicon peak at 530 cm , that hides the defect peaks.