Enhanced SiV photoluminescence by oxidation-induced nano-structures on diamond particle surfaces

We successfully constructed nanostructures on the surface of diamond particles by oxidation, which drastically enhanced their silicon-vacancy (SiV) photoluminescence (PL) intensity. The {100} plane of the diamond crystal initially had a smooth surface and strong anti-oxidation ability, which converted to a nano-pyramid structure with the sides resembling a {111} crystal plane orientation after oxidation. The {111} plane originally presented vertically layered or scale-like structures, but exhibited irregular nanoporous structures with some ridges perpendicular to the {111} plane in the edge area after oxidation. Since the crystal orientation of these nano-structures matches the <111> aligned split-vacancy structure of the SiV center, the collection efficiency of SiV luminescence increased, such that the SiV emission intensity increased by 27-fold and 4-fold for the nano-pyramid and the irregular nano-porous structure, respectively. Oxidation also significantly improved the crystal quality of diamond, such that the lattice stress around the SiV color center reduced, narrowing the linewidth of the SiV PL peak to nearly 3 nm. This study provides a feasible way to optimize SiV photoluminescent properties by building nanostructures on the surface of diamond particles.