Technische Physik - Halbleiterphysik, Nanostrukturierung & Analytikhttps://kobra.uni-kassel.de:443/handle/123456789/20060425101442024-03-28T22:51:10Z2024-03-28T22:51:10ZFabrication and Investigation of Diamond Membranes for Photonic NanostructuresHeupel, Julia Rebeccahttps://kobra.uni-kassel.de:443/handle/123456789/147492023-05-25T08:10:07Z2023-01-01T00:00:00ZDue to its exceptional physical and chemical characteristics, diamond in a form of thin membranes is a particularly promising material for the fabrication of high-quality photonic devices. Especially for envisioned applications in quantum information technologies and communication, diamond gained, as a host material, an ever-increasing scientific interest based on remarkable properties of different color centers in its crystal lattice, e.g. nitrogen-vacancy centers, serving as single-photon emitters. As a high index material only a small fraction of the emitted photons by the color centers can be collected outside diamond. Therefore, to enhance the photon collection efficiency the color centers needs to be coupled to light confining architectures like open micro cavities or photonic diamond nanostructures.
The focus of this work was the fabrication and optimization of thin diamond membranes. Thereby, one main goal was to reduce by different planarization procedures the overall surface roughness and defects acting as scattering centers. The diamond membranes were used either for an integration into open fiber-based Fabry-Pérot microcavities to enhance the color centers’ emission or for further fabrication of photonic nanostructures. In this context processes for structuring of membranes and photonic nanostructures were developed and improved by different parameters during the cleaning processes, electron beam lithography and reactive ion etching. Their impact on the generated structures have been investigated.; Aufgrund seiner einzigartigen physikalischen und chemischen Eigenschaften ist Diamant in Form von dünnen Membranen ein vielversprechendes Material für die Herstellung hochwertiger photonischer Bauelementen. Insbesondere für Anwendungen in der Quanteninformationstechnologie und Kommunikation, hat Diamant als Material aufgrund der bemerkenswerten Eigenschaften verschiedener Farbzentren, z.B. Stickstoff-Leerstellen Zentren, die als Einzelphotonen-Emitter dienen, ein immer größeres wissenschaftliches Interesse erlangt. Da Diamant einen hohen Brechungsindex hat, kann nur ein kleiner Teil der von den Farbzentren emittierten Photonen gesammelt werden. Um die Effizienz zu erhöhen, müssen die Farbzentren daher an lichtbegrenzende Strukturen wie offene Mikrokavitäten oder photonische Diamant-Nanostrukturen gekoppelt werden. Der Schwerpunkt dieser Arbeit lag auf der Herstellung und Optimierung dünner Diamantmembranen. Ein Hauptziel war es dabei, durch verschiedene Planarisierungsverfahren die Oberflächenrauheit und als Streuzentren wirkenden Defekte zu reduzieren. Die Membranen wurden entweder zur Integration in faserbasierte Fabry-Pérot-Mikrokavitäten verwendet, um die Emission der Farbzentren zu verstärken, oder zur weiteren Herstellung von photonischen Nanostrukturen. In diesem Zusammenhang wurden Prozesse für die Membranen und photonischen Nanostrukturen entwickelt und durch verschiedene Parameter während der Reinigungsprozesse, Elektronenstrahllithographie und des reaktiven Ionenätzens verbessert. Deren Einfluss auf die erzeugten Strukturen wurde untersucht.
2023-01-01T00:00:00ZHeupel, Julia RebeccaDue to its exceptional physical and chemical characteristics, diamond in a form of thin membranes is a particularly promising material for the fabrication of high-quality photonic devices. Especially for envisioned applications in quantum information technologies and communication, diamond gained, as a host material, an ever-increasing scientific interest based on remarkable properties of different color centers in its crystal lattice, e.g. nitrogen-vacancy centers, serving as single-photon emitters. As a high index material only a small fraction of the emitted photons by the color centers can be collected outside diamond. Therefore, to enhance the photon collection efficiency the color centers needs to be coupled to light confining architectures like open micro cavities or photonic diamond nanostructures.
The focus of this work was the fabrication and optimization of thin diamond membranes. Thereby, one main goal was to reduce by different planarization procedures the overall surface roughness and defects acting as scattering centers. The diamond membranes were used either for an integration into open fiber-based Fabry-Pérot microcavities to enhance the color centers’ emission or for further fabrication of photonic nanostructures. In this context processes for structuring of membranes and photonic nanostructures were developed and improved by different parameters during the cleaning processes, electron beam lithography and reactive ion etching. Their impact on the generated structures have been investigated.
Aufgrund seiner einzigartigen physikalischen und chemischen Eigenschaften ist Diamant in Form von dünnen Membranen ein vielversprechendes Material für die Herstellung hochwertiger photonischer Bauelementen. Insbesondere für Anwendungen in der Quanteninformationstechnologie und Kommunikation, hat Diamant als Material aufgrund der bemerkenswerten Eigenschaften verschiedener Farbzentren, z.B. Stickstoff-Leerstellen Zentren, die als Einzelphotonen-Emitter dienen, ein immer größeres wissenschaftliches Interesse erlangt. Da Diamant einen hohen Brechungsindex hat, kann nur ein kleiner Teil der von den Farbzentren emittierten Photonen gesammelt werden. Um die Effizienz zu erhöhen, müssen die Farbzentren daher an lichtbegrenzende Strukturen wie offene Mikrokavitäten oder photonische Diamant-Nanostrukturen gekoppelt werden. Der Schwerpunkt dieser Arbeit lag auf der Herstellung und Optimierung dünner Diamantmembranen. Ein Hauptziel war es dabei, durch verschiedene Planarisierungsverfahren die Oberflächenrauheit und als Streuzentren wirkenden Defekte zu reduzieren. Die Membranen wurden entweder zur Integration in faserbasierte Fabry-Pérot-Mikrokavitäten verwendet, um die Emission der Farbzentren zu verstärken, oder zur weiteren Herstellung von photonischen Nanostrukturen. In diesem Zusammenhang wurden Prozesse für die Membranen und photonischen Nanostrukturen entwickelt und durch verschiedene Parameter während der Reinigungsprozesse, Elektronenstrahllithographie und des reaktiven Ionenätzens verbessert. Deren Einfluss auf die erzeugten Strukturen wurde untersucht.Investigations on Diamond Thin Films as Implant Coating and Biosensing PlatformMerker, Danielhttps://kobra.uni-kassel.de:443/handle/123456789/134432021-12-16T18:00:06Z2021-01-01T00:00:00ZDiamond is researched in biological context for decades. Fundamental research has established diamond as a material that combines a pronounced compatibility with biological entities and resilience against even the harshest chemical and physical conditions. The present dissertation strives to improve the abilities of diamond in this matter even further by utilizing methods of nanostructuring and biochemical functionalization. Numerous characterization methods are used to monitor each step in detail and to evaluate the benefit at any given time in the development process. In detail, the promising applications of thin diamond films as implant coating and biosensing platform are investigated.; Diamant wird seit Jahrzehnten im biologischen Kontext erforscht. Ziel der vorliegenden Dissertation ist es, die Biokompatibilität durch den Einsatz von Nanostrukturierung und biochemischer Funktionalisierung noch zu erweitern. Zahlreiche Charakterisierungsmethoden werden verwendet, um jeden Schritt im Detail zu überwachen und den Nutzen zu jedem Zeitpunkt im Entwicklungsprozess abzuwägen. Im Detail werden die vielversprechenden Anwendungen von Diamantschichten als Implantatbeschichtung und Biosensorplattform untersucht.
2021-01-01T00:00:00ZMerker, DanielDiamond is researched in biological context for decades. Fundamental research has established diamond as a material that combines a pronounced compatibility with biological entities and resilience against even the harshest chemical and physical conditions. The present dissertation strives to improve the abilities of diamond in this matter even further by utilizing methods of nanostructuring and biochemical functionalization. Numerous characterization methods are used to monitor each step in detail and to evaluate the benefit at any given time in the development process. In detail, the promising applications of thin diamond films as implant coating and biosensing platform are investigated.
Diamant wird seit Jahrzehnten im biologischen Kontext erforscht. Ziel der vorliegenden Dissertation ist es, die Biokompatibilität durch den Einsatz von Nanostrukturierung und biochemischer Funktionalisierung noch zu erweitern. Zahlreiche Charakterisierungsmethoden werden verwendet, um jeden Schritt im Detail zu überwachen und den Nutzen zu jedem Zeitpunkt im Entwicklungsprozess abzuwägen. Im Detail werden die vielversprechenden Anwendungen von Diamantschichten als Implantatbeschichtung und Biosensorplattform untersucht.High temperature-stable InGaAs QDs for the monolithic integration in external-cavity surface-emitting lasersFinke, Tanjahttps://kobra.uni-kassel.de:443/handle/123456789/127212023-04-25T07:42:35Z2021-01-01T00:00:00ZOptically pumped vertical external-cavity surface-emitting lasers (VECSELs), also called semiconductor disk lasers (SDLs), benefit from the flexibility and versatility of the semiconductor material. With a simple cavity layout, fundamental transverse mode operation with a circular output beam and high beam quality is possible. They have excellent heat-sink properties and only require inexpensive multimode diode lasers for pumping. The complete VECSEL structure is only a few micrometers thick which leads to a strong pump absorption during optical pumping. An ultrafast laser can be established by passive modelocking of the VECSELs with semiconductor saturable absorber mirrors (SESAMs). Hereby, femtosecond or picosecond pulses can be obtained from a simple resonator. By integrating quantum dots (QDs) instead of most commonly used quantum wells (QWs) in the gain and absorber region of these devices, their optical properties could be tailored over a wide range. During this thesis, self-assembled InxGa1-xAs QDs gain material was grown by molecular beam epitaxy and optimized towards high dot density (up to 1.8 × 1011 cm-2) and narrow photoluminescence emission linewidth (26 meV) for the integration in VECSEL and modelocked integrated external-cavity surface-emitting laser (MIXSEL). Complete QD-VECSEL structures were grown by MBE and processed with a solder-based flip-chip bonding technique. A CW setup was designed and built to characterize the fabricated devices. The influence of the number of QD active layers, the heat spreader material and the measurement conditions on the threshold and maximum output power was investigated. Up to 5.7 W output power with a slope efficiency of 34% was achieved at 4 °C heat sink temperature. Furthermore, a new approach for QD-based temperature-stable SESAMs has been developed, in which high-quality InxGa1−xAs QDs grown at 480 °C and modulation p-type doping were implemented. The typically used QD or QW absorber layers grown at very low temperature (< 400 °C) will be annealed during long-term overgrowth and lose their high-speed performance. This new type of QD-SESAM is temperature-stable and suitable for the monolithic integration into MIXSELs. The introduction of recombination centers with p-type modulation doping and additional post-growth annealing improves the absorption of the high-quality QDs. Hence, low saturation fluences below 10 µJ/cm2 and a reduction of the τ1/e recovery time to values below 2 ps were achieved.
2021-01-01T00:00:00ZFinke, TanjaOptically pumped vertical external-cavity surface-emitting lasers (VECSELs), also called semiconductor disk lasers (SDLs), benefit from the flexibility and versatility of the semiconductor material. With a simple cavity layout, fundamental transverse mode operation with a circular output beam and high beam quality is possible. They have excellent heat-sink properties and only require inexpensive multimode diode lasers for pumping. The complete VECSEL structure is only a few micrometers thick which leads to a strong pump absorption during optical pumping. An ultrafast laser can be established by passive modelocking of the VECSELs with semiconductor saturable absorber mirrors (SESAMs). Hereby, femtosecond or picosecond pulses can be obtained from a simple resonator. By integrating quantum dots (QDs) instead of most commonly used quantum wells (QWs) in the gain and absorber region of these devices, their optical properties could be tailored over a wide range. During this thesis, self-assembled InxGa1-xAs QDs gain material was grown by molecular beam epitaxy and optimized towards high dot density (up to 1.8 × 1011 cm-2) and narrow photoluminescence emission linewidth (26 meV) for the integration in VECSEL and modelocked integrated external-cavity surface-emitting laser (MIXSEL). Complete QD-VECSEL structures were grown by MBE and processed with a solder-based flip-chip bonding technique. A CW setup was designed and built to characterize the fabricated devices. The influence of the number of QD active layers, the heat spreader material and the measurement conditions on the threshold and maximum output power was investigated. Up to 5.7 W output power with a slope efficiency of 34% was achieved at 4 °C heat sink temperature. Furthermore, a new approach for QD-based temperature-stable SESAMs has been developed, in which high-quality InxGa1−xAs QDs grown at 480 °C and modulation p-type doping were implemented. The typically used QD or QW absorber layers grown at very low temperature (< 400 °C) will be annealed during long-term overgrowth and lose their high-speed performance. This new type of QD-SESAM is temperature-stable and suitable for the monolithic integration into MIXSELs. The introduction of recombination centers with p-type modulation doping and additional post-growth annealing improves the absorption of the high-quality QDs. Hence, low saturation fluences below 10 µJ/cm2 and a reduction of the τ1/e recovery time to values below 2 ps were achieved.Fabrication and characterization of diamond nanopillars, waveguides and AFM tips with incorporated color centersSchmidt, Alexanderhttps://kobra.uni-kassel.de:443/handle/123456789/118722021-06-23T14:24:18Z2020-06-01T00:00:00ZDiamond is a unique material with outstanding properties and the perfect host for different crystal defects in its lattice, so-called color centers, which provide exceptional spin properties, rendering them a promising platform for the development of novel devices and components in quantum information technologies (QIT) and quantum sensing applications. To overcome diamond's high internal reflection due to its high refractive index, color centers need to be incorporated in photonic diamond structures, leading to enhanced photon collection efficiencies and therefore better performances of the final devices. In addition, the incorporation of NV centers in diamond AFM tips allows for the realization of scanning probes as magnetic sensors in nanoscale magnetometry.
The focus of this thesis was on the fabrication and optimization of different photonic diamond nanostructures, such as suspended waveguides and nanopillars for the integration of NV and SiV centers, as well as AFM tips for the incorporation of NV centers within their apices. In this regard, different fabrication parameters during electron beam lithography and reactive ion etching and their impact on the final quality of the nanostructures have been investigated. SiV centers have been generated in situ during diamond growth in nanopillars, while NV centers were created at nanotips by vacancy-induced He ion implantation into nitrogen-rich type Ib diamond and subsequent annealing.
The thesis starts with a short introduction, highlighting the importance of the current research. The second chapter covers the theoretical background, which provides an adequate understanding of the fundamental diamond properties, diamond growth, color centers and the application of diamond nanostructures. The experimental procedures, systems and materials are introduced in chapter 3. The following chapter 4 presents the main results in regard to the development of fabrication processes for diamond waveguides, nanopillar arrays and AFM tips. The presence of incorporated color centers within the fabricated diamond nanostructures are discussed on the basis of optical measurements (fluorescence mapping and photoluminescence) in chapter 5. Finally, the thesis concludes with a summary and an outlook, including possibilities for future work.
2020-06-01T00:00:00ZSchmidt, AlexanderDiamond is a unique material with outstanding properties and the perfect host for different crystal defects in its lattice, so-called color centers, which provide exceptional spin properties, rendering them a promising platform for the development of novel devices and components in quantum information technologies (QIT) and quantum sensing applications. To overcome diamond's high internal reflection due to its high refractive index, color centers need to be incorporated in photonic diamond structures, leading to enhanced photon collection efficiencies and therefore better performances of the final devices. In addition, the incorporation of NV centers in diamond AFM tips allows for the realization of scanning probes as magnetic sensors in nanoscale magnetometry.
The focus of this thesis was on the fabrication and optimization of different photonic diamond nanostructures, such as suspended waveguides and nanopillars for the integration of NV and SiV centers, as well as AFM tips for the incorporation of NV centers within their apices. In this regard, different fabrication parameters during electron beam lithography and reactive ion etching and their impact on the final quality of the nanostructures have been investigated. SiV centers have been generated in situ during diamond growth in nanopillars, while NV centers were created at nanotips by vacancy-induced He ion implantation into nitrogen-rich type Ib diamond and subsequent annealing.
The thesis starts with a short introduction, highlighting the importance of the current research. The second chapter covers the theoretical background, which provides an adequate understanding of the fundamental diamond properties, diamond growth, color centers and the application of diamond nanostructures. The experimental procedures, systems and materials are introduced in chapter 3. The following chapter 4 presents the main results in regard to the development of fabrication processes for diamond waveguides, nanopillar arrays and AFM tips. The presence of incorporated color centers within the fabricated diamond nanostructures are discussed on the basis of optical measurements (fluorescence mapping and photoluminescence) in chapter 5. Finally, the thesis concludes with a summary and an outlook, including possibilities for future work.