Cathodoluminescence of nitrogen vacancies in nanodiamonds and plasmonic nanostructures

Abstract

Emission and scattering of light by nanostructures depends strongly on the ambient dielectric properties resulting in phenomena, such as Purcell enhancement of radiation or emission suppression. Free-electron beams have emerged as the ideal probe for the investigation of such effects and have been used extensively for the characterization of plasmonic and dielectric nanostructures, shedding light to the underlying physical mechanisms and leading to new applications, such as nanoscale electron beam driven light sources. In this thesis, I have investigated the emission properties of nitrogen-vacancy (NV) centres in nanodiamond and plasmonic nanostructures by cathodoluminescence. In particular, I have demonstrated by time-resolved cathodoluminescence (TR-CL) and control of the emission of NV centres through tailoring the dielectric properties of the host medium (including dielectric, plasmonic). I have also analyzed the underlying mechanisms linking dielectric properties, geometry and emission statistics. Conversely, I have demonstrated that machine learning can be employed to retrieve information about arrangements of plasmonic nanostructures for the their emission properties and vice versa. In particular, in this thesis I have, for the first time:
• Employing TR-CL to experimentally demonstrate a two-fold enhancement of the decay rate of NV centers on a diamond-covered Si substrate as opposed to a bare Si substrate. I link the emission statistics to the interplay between the excitation of substrate modes and the presence of non radiative decay channels and show that the radiative decay rate can vary by up to 90% depending on the thickness of the diamond film.
• Employing TR-CL to experimentally demonstrate that the distribution of the decay rates of NV centers in nanodiamonds can be made narrower by as much as five times once the nanodiamonds have been embedded into chalcogenide films. This result paves the way towards the dynamic control of the emitter decay rate through the phase change properties of chalcogenides.
• Numerically demonstrated that the cathodoluminescence spectra emitted by sets of subwavelength plasmonic apertures can be predicted from their configurations and, inversely, information about the configurations of subwavelength plasmonic apertures can be inferred from the cathodoluminescence spectra they emit.

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Identifiers

ORCID for Hao Li: orcid.org/0000-0001-6698-9868

ORCID for Nikitas Papasimakis: orcid.org/0000-0002-6347-6466

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