SiV center photoluminescence induced by C=O termination in nanocrystalline diamond and graphite loops hybridized films

Abstract

We performed a series of thermal oxidation at different temperatures on nanocrystalline diamond (NCD) films to construct various surface termination states of NCD grains and investigated their effects on silicon-vacancy (SiV) photoluminescence (PL) at 738 nm. Experiments and first principles calculations show that the negative electron affinity surface induced by C-H bond termination quenches the SiV PL, while the positive electron affinity surface originating from C=O bond termination removes this quenching. Moreover, oxidation at 600 °C results in the transition from amorphous carbon to graphite loops with an interlayer space of 0.4 nm, so that NCD and graphite loops' hybridized structure is formed. This allows oxygen atoms to contact with inside NCD grains to form more C=O bonds on the surface, producing much larger positive electron affinity in the surface. It traps the excited state electrons, lets them scatter back to the ground state, and emits SiV PL. These results reveal that C=O bonds play a crucial role in SiV PL of NCD grains and well explain the experimentally observed quenching effect. A novel way by changing the surface termination states is proposed to control the PL of NCD grains with SiV centers for potential quantum information processing and biological sensing.