Bottom up Engineering of Group IV Color Centers in Nanodiamonds and Nanoscale Diamond Membranes by MPCVD

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Single crystal diamonds have emerged as important elements in a wide range of technological applications spanning from photonics, to sensing, quantum metrology, and computing boosted by the commercial availability of high-quality synthetic diamonds and improvements in nanofabrication methods. This thesis responds to the current need to develop robust, cost-effective, and reliable protocols to engineer a homogeneous distribution of selected optically active emitters (called color centers) into nanoscale diamond membranes and nanodiamonds, extensively investigating the introduction of group IV impurities (silicon, germanium, tin, and lead). The importance of group IV emitters has been demonstrated as they operate as photo-stable, single photon sources at room temperature and present suitable candidates for solid-state quantum applications. The fabrication methods herein presented are based on a bottom up approach employing a microwave plasma chemical vapor deposition reactor with different types of doping precursors. In this thesis I describe a detailed fabrication protocols that led to the generation of silicon, germanium, and tin vacancies into nanoscale single crystal diamond membranes and nanodiamonds using a combination of different precursors. The fabrication of different types of optical cavities from these membranes by electron beam lithography demonstrates the feasibility to grow high quality membranes that can be immediately processed for realization of photonic resonators with quality factors of Q ~ 1500, enabling superior light confinement and field enhancement. The doping processes are further improved by matching the melting temperature of the precursors to the plasma temperature reached during the growth. The main advantage consists in the minute amount of dopants required (only 8 µL droplet), being often toxic and harmful, for the successful generation of emitters, making this method greener and safer for the operator and the environment. Finally, I illustrate for the first time the feasibility to couple group IV emitters hosted in ~ 300 nm thick diamond membranes to plasmonic silver nanodisk arrays. The resulting photoluminescence intensity is increased by a factor of ~ 1.5 – 4, associated with a lifetime reduction achieving the resonant coupling of emitters with plasmonic lattices which enables a wide range of future applications for flat hybrid photonic-plasmonic systems based on color centers in diamonds. My research opens the way for broader adaptation of doping protocols to engineer diamonds with color centers beyond the group IV elements showing the potential to accelerate the integration of solid-state emitters embedded in thin diamond membranes with scalable devices for photonic and quantum applications.
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