Vacancy defect centers in diamond: influence of surface termination

Defect centers such as the negatively charged nitrogen- vacancy defect and the neutral silicon-vacancy and germanium vacancy defect in tiny spherical nanodiamonds are investigated in this work. Quantum mechanical simulations based on density functional theory are performed in order to assess the influence of the surface termination and the defect type in the electronic structure of the defective nanodiamonds. Three elements are taken for the surface termination: hydrogen, nitrogen, and oxygen. Specific insight is given on the relative shift in the electronic energy levels with respect to ideal nanodiamonds. The variation of the charge density around the defect and the spatial distribution of the frontier orbitals of the defective nanodiamonds are analyzed. In the end, this work provides a comparative analysis of the termination effect on the three types of vacancy defect centers for their deeper understanding in view of their technological relevance.