Formation of SiV centers by doping in bottom-up grown HPHT nanodiamonds and its implication for optical nanosensig

We investigate doping and formation of luminescent point defects in nanodiamond at high pressures and high temperatures (HPHT) in fluorine-containing hydrocarbon growth systems with an excessive content of dopant organosilicon component. It is shown experimentally that the average concentration of silicon-vacancy centers (SiV-) tends to increase proportionally to the diameter of the nanocrystals. Respectively, the local concentration of the dopant in a crystal linearly increases with the distance from the crystal center. This phenomenon is explained by competition between growth of a perfect crystal and doping. The kinetics of the crystal growth are determined by the diffusion of carbon containing precursors to the surface of the crystal and the doping takes place at a very high concentration of the dopant in the growth mixture and that is defined by the rate of the chemical reaction on the crystal surface. Electrodynamic effects in the nanocrystals affecting the observed intensity of the photoluminescence are also considered. Although these results are obtained using important for applications SiV- photo luminescent centers, they have much wider implications.