Creation and modification of solid-state quantum emitters via charged particle beams

Gale, Angus J.

Creation and modification of solid-state quantum emitters via charged particle beams

Gale, Angus J.

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Publication Type:: Thesis
Issue Date:: 2024

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Field	Value	Language
dc.contributor.author	Gale, Angus J.
dc.date.accessioned	2025-01-20T23:12:34Z
dc.date.available	2025-01-20T23:12:34Z
dc.date.issued	2024
dc.identifier.uri	http://hdl.handle.net/10453/183884
dc.description	University of Technology Sydney. Faculty of Science.	en_US.UTF-8
dc.description.abstract	Solid state quantum emitters are building blocks for emerging photonic based quantum technologies. These emitters take the form of atomic scale defects that can be used as sources to generate single photons. Many materials have been identified to host quantum emitters; in particular, diamond and hexagonal boron nitride (hBN) are two promising platforms hosting a number of different defect types. There are many creation methods available but in order to realise real world applications they must be efficient, deterministic and scalable. Charged particle microscopy systems are widespread in research and industry settings and can be utilised to engineer, modify and characterise quantum emitters. This thesis outlines three procedures to create, modify and characterise solid state quantum emitters using charged particle microscopy systems. Firstly, creation of nitrogen vacancy (NV) centres in diamond via recoil implantation of gaseous precursors is presented. The method uses a commercially available focused ion beam (FIB) system to expand and simplify documented methods utilising solid-thin films. Creation of NV centres is demonstrated with three nitrogen containing precursor gases exhibiting the robustness of the method. The next works focus on two defects in hBN; the blue emitter and boron vacancy (VB). Using electron irradiation in a scanning electron microscope (SEM), a technique for site-specific fabrication of single defects is shown. The fabricated emitters demonstrate a single emission energy of 2.8~eV (436~nm), site selectivity and controllable defect density. The ability to fabricate emitters is linked to another existing defect type with emission at 305~nm (4.1~eV). Blue emitter generation is attributed to the fragmentation of carbon clusters by electron impact. The robustness and universality of the emitter fabrication technique is enhanced by a pre-irradiation annealing treatment. These results provide important insights into photophysical properties and structure of defects in hBN, outlining a framework for site-specific fabrication of quantum emitters in hBN. Finally, charge state control of the VB defect is shown using a customised SEM setup with in-situ scanning confocal photoluminescence (PL) microscopy. Charge state switching between the 0 and -1 states is demonstrated under concurrent electron and laser excitation. The switching is shown to be deterministic and reversible. Further control over the charge states is shown using a heterostructure device to adjust the rates of electrons and holes injected into the hBN, stabilising the system to the spin-active -1 charge state.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/183884/1/thesis.pdf
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	© 2024 Angus J. Gale
dc.rights	au.edu.uts.lib/cph
dc.title	Creation and modification of solid-state quantum emitters via charged particle beams	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Solid state quantum emitters are building blocks for emerging photonic based quantum technologies. These emitters take the form of atomic scale defects that can be used as sources to generate single photons. Many materials have been identified to host quantum emitters; in particular, diamond and hexagonal boron nitride (hBN) are two promising platforms hosting a number of different defect types. There are many creation methods available but in order to realise real world applications they must be efficient, deterministic and scalable. Charged particle microscopy systems are widespread in research and industry settings and can be utilised to engineer, modify and characterise quantum emitters. This thesis outlines three procedures to create, modify and characterise solid state quantum emitters using charged particle microscopy systems. Firstly, creation of nitrogen vacancy (NV) centres in diamond via recoil implantation of gaseous precursors is presented. The method uses a commercially available focused ion beam (FIB) system to expand and simplify documented methods utilising solid-thin films. Creation of NV centres is demonstrated with three nitrogen containing precursor gases exhibiting the robustness of the method. The next works focus on two defects in hBN; the blue emitter and boron vacancy (VB). Using electron irradiation in a scanning electron microscope (SEM), a technique for site-specific fabrication of single defects is shown. The fabricated emitters demonstrate a single emission energy of 2.8~eV (436~nm), site selectivity and controllable defect density. The ability to fabricate emitters is linked to another existing defect type with emission at 305~nm (4.1~eV). Blue emitter generation is attributed to the fragmentation of carbon clusters by electron impact. The robustness and universality of the emitter fabrication technique is enhanced by a pre-irradiation annealing treatment. These results provide important insights into photophysical properties and structure of defects in hBN, outlining a framework for site-specific fabrication of quantum emitters in hBN. Finally, charge state control of the VB defect is shown using a customised SEM setup with in-situ scanning confocal photoluminescence (PL) microscopy. Charge state switching between the 0 and -1 states is demonstrated under concurrent electron and laser excitation. The switching is shown to be deterministic and reversible. Further control over the charge states is shown using a heterostructure device to adjust the rates of electrons and holes injected into the hBN, stabilising the system to the spin-active -1 charge state.

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