Diamond based nanoelectronics and imaging

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To investigate new pathways for numerous quantum technologies it is necessary to efficiently fabricate various interesting materials. Single photon sources that are optically and electrically triggerable are the fundamental building blocks required to push the boundaries of several applications, such as realising secure communication technologies. Accordingly, various platforms are being investigated for generation of single photon emitters (SPEs). Diamond is one platform of great interest, due to its ability to host several photostable, optically active SPE defects that can operate at room temperature. Numerous diamond defects have been studied extensively, including the Nitrogen vacancy (NV), Silicon vacancy (SiV) and, recently, the Germanium vacancy (GeV) colour centres. All were shown to be robust room temperature SPEs. Despite promising reports on quantification and applications of diamond-based defects, the search continues to find an emitter that can excel at most applications. Another important factor for the utility of colour centres is the method of excitation. While optical pumping is common practice, the ability to electrically excite emitters is highly desired for optoelectronic applications. Several reports exist on the fabrication and characterisation of electrical device structures of various materials, including Gallium Nitride, Silicon Carbide, Zinc Oxide and diamond defects. The central part of the thesis delves into the fabrication of high aspect ratio, thin, nanoscale, conductive diamond membranes hosting SiV colour centres, which demonstrate key advantages, such as being easily transferrable to a variety of structures. Secondly, I investigate unknown narrowband SPEs in diamond nanocrystals, which are preferable for nanophotonic, quantum communications and bio-imaging applications. The origin of the narrowband emission is determined to be point defects localised at extended morphological defects in individual nanodiamond particles. Furthermore, a highly polarised, narrowband, possessing sub GHz optical linewidths was observed at cryogenic temperatures. Finally, I exploit the optimal fluorescent, chemical and biocompatibility properties for multi-colour tagging of CHO-K1 and U937 cell lines using both NV- and, for the first time, SiV diamond colour centres, to investigate their intracellular properties. The non-toxic SiV diamond nanocrystals initially dispersed throughout the cell interior while tagged NV nanocrystals localised close to the nucleus. Therefore, this work reports new findings in spectroscopic studies of diamond-based colour centres that can be excited optically and electrically. Furthermore, it provides detailed evidence which forms the building blocks for future investigation into diamond-based devices and SPEs for a wide variety of applications. The results presented in this thesis therefore provide a new and interesting platform for applications using defect based nanophotonics.
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