The presence of midgap states introduced by localized defects in wide-band-gap-doped semiconductors can strongly affect the electronic structure and optical properties of materials, generating a wide range of applications. Silicon-divacancy defects in diamond have been recently proposed for probing high-resolution pressure changes and performing quantum cryptography, making them good candidates to substitute for the more common nitrogen-vacancy centers. Using group-theory and ab initio electronic structure methods, the molecular origin of midgap states, zero-phonon line splitting, and size dependence of the electronic transitions involving the silicon-vacancy center is investigated in this paper. The effects of localized defects on the Raman vibrational and carbon $K$-edge x-ray absorption spectra are also explored for nanodiamonds. This paper presents an important analysis of the electronic and vibrational structures of nanosized semiconductors in the presence of midgap states due to localized defects, providing insight into possible mechanisms for modulating their optical properties.

• Received 27 January 2018
• Revised 5 June 2018

DOI:https://doi.org/10.1103/PhysRevB.98.205405