Effect of H-Terminated Surfaces on "Silicon-Vacancy" Fluorescence in High-Pressure Nanodiamonds

A new generation of fluorescent diamond nanoparticles synthesized from hydrocarbons at high pressure appears to be promising for the design of efficient single-photon diamond sources and nanometer-sized optical sensors. A characteristic feature of such nanodiamonds (NDs) is the termination of their surface with hydrogen. This hydrogen induces the formation of free holes at the diamond surface, thereby affecting the charge state of nearby fluorescent centers. In this study, the effect of the H-terminated ND surface on negatively charged silicon-vacancy (SiV^-) fluorescence as a function of the ND size was investigated. Raman, photoluminescence and scanning electron microscopy techniques were used to characterize the NDs. Diamond nanoparticles of various sizes in the 50-300 nm range were analyzed before and after H desorption from their surface. It was shown that a significant increase in SiV^- fluorescence (>50%) upon hydrogen removal starts for particles smaller than 100 nm. The effective thickness of the diamond surface layer, within which charge neutralization of SiV^- centers occurs under the hydrogen influence, was determined to be 6 nm.