Single‐Photon Emitters Based on Ge‐V Centers in Nanoparticles Obtained From CVD‐Grown Nanocrystalline Diamond Films

A method for obtaining luminescent diamond nanoparticles doped with germanium from nanocrystalline diamond (NCD) films grown by microwave plasma‐assisted chemical vapor deposition (MPCVD) is presented. Thermal etching in the presence of an alkali metal nitrate enables the selective disruption of intercrystallite boundaries, resulting in the formation of individual particles without mechanical grinding. Structural and morphological characterization by scanning and transmission electron microscopy, atomic force microscopy, Raman spectroscopy, and dynamic light scattering reveals the formation of particles with characteristic sizes down to ~100 nm, along with a minor fraction of larger microcrystals. The particles retain the crystalline quality of the parent film and exhibit photoluminescence associated with Ge‐V and Si‐V centers. Second‐order correlation measurements reveal single‐photon emission from a minority of Ge‐V‐related diffraction‐limited spots, demonstrating the presence of isolated optically active Ge‐V emitters in the nanoparticle sample. The proposed approach provides a scalable route for producing luminescent diamond nanoparticles for photonic and quantum applications.