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

Abstract

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 IXY defects, namely ICC and ICSi, a couple of related defects that we indicate as IXIY, the so called CiCs0 in its A and B form, as well as SiCiSi and CsCiCs, in which the interstitial carbon atom is twofold coordinated. The second undergoes a large relaxation, and the final configuration is close to ICCCs. Geometries, relative stabilities, electronic, and vibrational properties are analysed. All these defects show characteristic features in their IR spectrum (above 730\u2009cm−1), whereas the Raman spectrum is dominated, in most of the cases, by the pristine silicon peak at 530\u2009cm−1, that hides the defect peaks.