Formation and Luminescence of Single Oxygen Impurities on the Surface of SiC Nanocrystals.

Impurities that hinder luminescence are a common problem in the synthesis of nanocrystals, and controlling the synthesis reaction could provide a way to avoid or use impurities beneficially. Excited state molecular dynamics is used to determine how oxygen impurities appear in the plasma synthesis of silicon carbide nanocrystals (SiC NCs). Formation of impurities is studied by considering the intermediate structures in the simulated photoreaction. The results show the most probable bonding patterns of silicon, carbon, and oxygen. These intermediates are used as a basis for studying the luminescence of expected oxygen impurities in SiC NCs, where luminescence is studied by first-principles modeling and density matrix dissipative dynamics based on on-the-fly non-adiabatic couplings and the Redfield tensor. Modeling the dissipation of energy from electronic to nuclear degrees of freedom reveals multiple impurities with significant photoluminescence quantum yields.