Control of NV, SiV and GeV centers formation in single crystal diamond needles

Single-crystal diamond needles in the form of micrometer-scale sharp pyramids were produced using a combination of chemical vapor deposition and thermal oxidation processes. These diamond needles with atomic-sized fluorescent defects (color centers) attract great interest for practical applications as a platform for creation of optical quantum sensing probes and optical quantum communication elements. Particular color centers localization providing suitable luminescence characteristics is required for these applications. Here we report about formation of nitrogen-vacancy (NV), silicon-vacancy (SiV) and germanium-vacancy (GeV) centers in the single-crystal diamond needles during direct current discharge plasma enhanced chemical vapor deposition (PE CVD). Luminescent characteristics of the needles were observed by confocal photoluminescence mapping. Analysis of experimental results allows us proposing possible mechanisms of impurities introduction into the crystal lattice during needles growth. These mechanisms include gas decomposition and etching of substrate material during CVD. The proposed mechanisms were approved by realization of CVD process protocols resulting in controllable formation of NV, SiV and GeV centers in single-crystal diamond needles including formation of thin NV- and SiV- enriched layers by tuning deposition process parameters. The proposed experimental approaches in combination with revealed mechanisms for introduction of favorable impurities make single-crystal diamond needles promising candidates for scanning quantum sensing, quantum communication and hyperpolarization experiments.