Nanoscale ion implantation and nanopillars integration of GeV color centers into a diamond membrane

Diamond color centers are solid-state single-photon sources with optical properties suitable for quantum technologies applications. Color centers related to Group-IV impurities are experiencing an increasing relevance thanks to their narrow emission linewidth at room temperature, robust optical coherence and one of the shortest lifetime among the known solid-state color centers1, 2. A key enabler for the technological uptake of these emitters consists in their deterministic fabrication and subsequent characterization. Ion implantation technique offers the highest spatial accuracy in the positioning control of the fabricated defects. Moreover, it is crucial to evaluate the conversion yield of the implanted ions to luminescent complexes within the diamond lattice to ensure the formation of single emitters at specific implantation sites. We report on a systematic characterization of GeV single emitters fabricated upon nanoscale ion implantation and integrated into diamond nanopillars. A diamond membrane sample was irradiated in two different regions with Ge++ ions respectively at 70 and 35 keV energies, employing a Focused Ion Beam (FIB) with ~25 nm spatial accuracy. The implantation was performed according to regular patterns with 3 µm spacing. Different ion fluences were considered, ranging from 50 to 150 ions per implanted spot. Then, the implanted regions were integrated in nanopillars to enhance the photoluminescence collection. A thermal annealing (1000 °C, 2 hours) was performed to achieve the conversion of the implanted species into optically active centers. The implanted spots were systematically characterized in photoluminescence confocal microscopy to estimate the formation efficiency of single emitters. The achieved results were compared with those discussed in literature3. This study is helpful in defining a fabrication protocol relying on ion implantation and nanofabrication that guarantees the formation of stable single photon emitters, which represents the main challenge in the perspective of exploiting these systems for scalable quantum photonic devices.