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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

COMPUTATIONAL DESIGN AND EXPERIMENTAL VALIDATION OF DIAMOND-BASED QUANTUM EMITTERS

Oluseye Akomolede (11706230) 15 November 2021 (has links)
<p>The enhancement of the emission from nitrogen vacancy color centers will help facilitate advancements in quantum information technology. To this end, the reduction of the excited state lifetimes of NVs as well as the design of devices which support electroluminescence of nitrogen vacancies, as well as the broadband enhancement of the emission from these centers is of great importance.</p> <p> </p> <p>In this study, we create diamond thin films containing nitrogen vacancy color centers using salt-assisted ultrasonic disaggregation techniques and electrophoretic deposition. These films are implanted with xenon atoms and the resulting structures are characterized optically. We report a reduction in the bulk emission lifetime of nitrogen vacancy color centers of two orders of magnitude. A coupled-mode theory approach is used to analyze the emission from the xenon-doped nanodiamond species. It is determined that the lifetime reduction occurs due to coupling between nitrogen vacancy color centers and xenon color centers within the diamond lattice.</p> <p> </p> <p>A diamond field effect transistor is investigated via simulations utilizing Sentaurus TCAD software. The device is scaled by three orders of magnitude from previous experiments involving the same structure. Transport characteristics are obtained from simulation results. We confirm the existence of a decreasing saturation voltage with a decrease in gate length in the diamond field effect transistor. Further investigation into the device’s viability as a quantum emitter is conducted. </p> <p> </p> <p>The design of a single photon source utilizing plasmonic structures to enhance emission from nitrogen vacancy color centers is proposed. The plasmonic structure is investigated to extract operating parameters and to quantify the optical coupling and propagation characteristics for various physical dimensions</p> <p> </p> The design of a plasmonic device which features both electroluminescence via nitrogen vacancy color centers and their enhancement via plasmonic effects is numerically simulated. The device features large Purcell enhancement factor and good photon emission rate. In summary, this work paves the way towards the advancement of the nitrogen vacancy color center as a stable source of room temperature photons for quantum information applications.
272

Plazmonické rezonanční antény / Plasmonic Resonant Antennas

Břínek, Lukáš January 2008 (has links)
Tato diplomová práce se zabývala plazmonickými anténami pro infračervenou oblast spektra elektromagnetického záření. K hledání zesílení pole bylo použito FDTD (Finite-Difference Time-Domain Method) simulací. Podle očekávání, byla shledána lineární závislost rezonanční vlnové délky na délce raménka platinové antény na křemíkovém povrchu. Diplomová práce se také zabývala výrobou antén pomocí fokusovaného iontového svazku (FIB) a následným měřením rezonančních vlastností pomocí mikroskopické metody FT-IR (Fourier Transform Infrared Spectroscopy). Posun rezonanční vlnové délky byla registrována pouze pro negativní antény. Nakonec se tato práce zabývala vysvětlením saturace křivky závislosti rezonanční vlnové délky na rozměru raménka platinové antény na substrátu ze SRONu (silicon-rich oxynitride).
273

Povrchové plazmonové rezonance na koloidních nanočásticích / Surface Plasmon Resonances on Colloidal Nanoparticles

Beránek, Jiří January 2013 (has links)
The presented diploma thesis is focused on the Localized Surface Plasmons (LSP). The far-field optical response of the colloidal solutions of gold nanoparticles caused by LSP was investigated and compared with the numerical calculations. For the simulations, the Discrete Dipole Approximation (DDA) and Finite-Difference Time Domain (FDTD) techniques were employed. In particular, the shape and size effects of spherical particles and nanorods were studied. The simulations performed by both methods are in a good agreement for the spheres. For the nanorods, the resonance was found to be affected markedly by their geometry. Also, broader resonance peaks were found. This effect was assigned to the sample size distribution and its influence is discussed by comparing the simulations with experiments. In addition, synthesis of nanorods was carried out as well. Finally, the results on the study of optical properties of silver clusters formed under equilibrium conditions are presented.
274

Supramolecular self-assemblies for plasmonics : a bottom-up approach to efficient photonic nanodevices / Auto-assemblages supramoléculaires pour la plasmonique : une approche ascendante pour la réalisation de nano-systèmes photoniques efficaces

Le Liepvre, Sylvain 26 September 2017 (has links)
Dans cette thèse, nous avons étudié les propriétés photoniques et vibrationnelles de monocouches moléculaires auto-assemblées sur graphène et la possibilité d'utiliser des multicouches auto-assemblées de pérylène comme milieu à gain pour l'amplification de plasmons. Le graphène, en tant que matériau transparent et conducteur, a permis pour la première fois de corréler la géométrie du réseau de l’auto-assemblage supramoléculaire avec ses propriétés optiques, grâce à la microscopie à effet tunnel et à des mesures de spectroscopiques optiques et Raman. En comparant plusieurs colorants autoassemblés sur le graphène, nous avons mis en lumière les effets des interactions intermoléculaires et des interactions colorant-graphène sur le spectre d'absorption du colorant adsorbé. Le transfert d'énergie rapide des colorants vers la couche degraphène par les mécanismes de Förster et de Dexter empêche toute relaxation radiative du colorant..Néanmoins, nous avons démontré la première fonctionnalisation fluorescente non-covalente du graphène par une monocouche de colorants autoassemblée en mettant en place une stratégie à base d’espaceurs. Nous avons exploité l’extinction rapide de la fluorescence des colorants par le graphène pour étudier les spectres Raman des auto-assemblages moléculaires sur graphène, et nous avons révélé l'apparition d'un mode vibrationnel couplé entre les molécules adsorbées et le substrat de graphène. Nous avons démontré le régime de couplage fort entre un auto-assemblage tri-dimensionnel de pérylène et un plasmon polariton de surface en optimisant l'orientation et l'organisation des molécules de colorant par rapport au champ électrique du mode de plasmon. Nous avons prouvé que les milieux de gain auto-assemblés en agrégats-J peuvent théoriquement conduire à des milieux de gain efficaces pour l'amplification de plasmons. Cependant, nous avons révélé expérimentalement que les recombinaisons exciton-exciton limitent le taux de pompage à des fluences élevées dans ces milieux denses. / In this work, we have studied thephotonic and vibrational properties of selfassembled molecular monolayers on graphene and the possibility to use perylene self-assembled multilayers as a gain medium for plasmon amplification. Graphene, as a transparent and conductive material, has offered for the first time to correlate the self-assembly structure as deduced from scanning tunneling microscopy to photonic properties as analyzed by optical and Raman spectroscopy measurements. By comparing several self-assembled dyes on graphene we have shed lighton how intermolecular and dye-graphene interactions modify the absorption spectrum of the adsorbed dye.Fast Förster and Dexter energy transfer from the adsorbed dyes to the graphene layer prevent any radiative decay of the dye.Nevertheless, we have demonstrated the first fluorescent non-covalent functionalization of graphene by a supramolecular self-assembled monolayer using a spacer approach.We have exploited the fast dye fluorescence quenching by graphene to study Raman spectra of self-assembled dye on graphene, and we have shown the appearance of a coupled vibrational mode between the adsorbed molecules and the graphene substrate. We have demonstrated the strong couplingregime between a three-dimensional perylene self-assembly and a propagating plasmon polariton by optimizing the orientation and the organisation of the dye molecules compared to the electric field of the plasmon mode. We have shown that J-aggregated self-assembled gain media may theoretically lead to efficient gain media for plasmon amplification. However, we experimentally demonstrated that exciton-exciton recombination limits the achievable pumping rate at high fluences in such dense media.
275

A chemical route to design plasmonic-semiconductor nanomaterials heterojunction for photocatalysis applications / Voie chimique pour concevoir les hétérojonctions des nanomatériaux plasmiques-semi-conducteurs pour des applications en photocatalyse

Shahine, Issraa 26 April 2019 (has links)
L’ingénierie de nanomatériaux hybrides semi-conducteurs/plasmoniques représente une technologie durable en raison de l’efficacité parfaite du couplage pour améliorer, rénover et enrichir les propriétés des composants intégrés. Ce couplage a pour résultat la variation des propriétés fonctionnelles du système, grâce auquel les plasmons de surface générés par les métaux peuvent améliorer la séparation des charges, l’absorption de la lumière et la luminescence du semi-conducteur. Ce phénomène permet de fortes interactions avec d'autres éléments photoniques tels que les émetteurs quantiques. Ces fonctionnalités aux multiples facettes découlent de l'interaction synergique exciton-plasmon entre les unités liées. Ainsi, les nanomatériaux hybrides conviennent à diverses applications, notamment : conversion de l'énergie solaire, dispositifs optoélectroniques, diodes électroluminescentes (LED), photocatalyse, détection biomédicale, etc. Les nanostructures Au-ZnO suscitent un intérêt croissant dans ces applications où le couplage de ZnO à de nanoparticules d’or (GNPs) favorise la réponse du système dans le domaine du visible grâce à leur résonance plasmon de surface (SPR). En fonction de la taille de deux nanomatériaux, de la distance qui les sépare et leurs rapports massiques dans un échantillon, les propriétés des particules hybrides peuvent varier. Dans ce contexte, nous nous sommes concentrés sur la construction de nano-cristaux (NCs) de ZnO purs de dimensions contrôlables, puis incorporés dans des solutions de GNPs par une simple voie chimique. Ce travail est divisé en deux parties : la première consiste à effectuer une synthèse de nanocristaux de ZnO (NCs) purs présentant d'excellentes propriétés de photoluminescence dans l’UV. Ceci a été réalisé par une synthèse à basse température, aboutissant à des structures rugueuses et amorphes. La synthèse a été suivie d'un traitement post-thermique afin de cristalliser les nanoparticules obtenues. Une étude structurale et optique poussée a été établie à la suite de la synthèse (SEM, TEM, DRX, photoluminescence). Les activités photocatalytiques des ZnO NCs ont été étudiées en mesurant leur capacité à dégrader le bleu de méthylène (MB). De plus, la relation entre les structures en ZnO, la luminescence et les propriétés photocatalytiques a été explorée en détail. Dans la deuxième étape, les ZnO NCs obtenus ont été couplés ajoutés à des nanoparticules d'or de tailles et fractions volumiques variables. Le rôle effectif des GNPs concernant leur morphologie, leur contenu et leur effet SPR sur la photoémission des nanostructures de ZnO est souligné par le transfert de charge et / ou d'énergie entre les constituants du système hybride. De plus, l’activité photocatalytique du système hybride a été examinée. Comme débouché et perspective de ce travail de thèse, l'intégration des ZnO NC dans une couche nanoporeuse de polymère (PMMA) a été réalisée et caractérisée afin d'obtenir un substrat de large surface à base de ZnO. Les ZnO NCs assemblés dans du PMMA pourraient être des substrats prometteurs en tant que catalyseurs pour la croissance de nanofils de ZnO, de nanomatériaux métalliques et de matériaux hybrides. / Hybrid heterojunctions composed of semiconductors and metallic nanostructures have perceived as a sustainable technology, due to their perfect effectiveness in improving, renovating, and enriching the properties of the integrated components. The cooperative coupling results in the variation of the system’s functional properties, by which the metal-generated surface plasmon resonance can enhance the charge separation, light absorption, as well as luminescence of the semiconductor. This phenomenon enables strong interactions with other photonic elements such as quantum emitters. These multifaceted functionalities arise from the synergic exciton-plasmon interaction between the linked units. Thereby, hybrid systems become suitable for various applications including: solar energy conversion, optoelectronic devices, light-emitting diodes (LED), photocatalysis, biomedical sensing, etc. Au-ZnO nanostructures have received growing interest in these applications, where the deposition of gold nanoparticles (GNPs) promotes the system’s response towards the visible region of the light spectrum through their surface plasmon resonance (SPR). Based on a specific size and purity of ZnO nanostructures, as well as the GNPs, and a definite inter-distance between the nanoparticles, the properties of the ZnO nanostructures are varied, especially the photoemission and photocatalytic ones. In this context, we have focused on the construction of size-tunable ZnO nanocrystals (NCs), then incorporated into GNPs solutions using a simple chemical way. This work is divided into two parts: the first is to perform synthesis of pure ZnO NCs having excellent UV photoluminescence. This was achieved through a low-temperature aqueous synthesis, resulting in rough and amorphous structures. The synthesis was followed by a post-thermal treatment in order to crystallize the obtained particles. The synthesis was followed by structural and optical studies (SEM, TEM, XRD, photoluminescence). The photocatalytic activities of ZnO NCs were studied through tailoring their ability to degrade the methylene blue (MB) dye. In addition, the relationship between ZnO structures, luminescence, and photocatalytic properties was explored in details. In the second step, the obtained ZnO NCs were added to gold nanoparticles of various sizes and volume fractions. The effective role of GNPs concerning their size, amount, and their capping molecule on the photoemission of the ZnO nanostructures was emphasized through the charge and/or energy transfer between the constituents in the hybrid system. In the same way, the systems photocatalytic activities were examined after coupling ZnO to GNPs. Further advancement in the integration of the ZnO NCs into PMMA polymer layers was featured in order to obtain large area template of homogenous ZnO properties. The PMMA-assembled ZnO nanoparticles could be promising substrates as catalysts for growing ZnO nanowires, metallic nanoparticles and hybrid nanomaterials.
276

From Single Colloidal Particles to Coupled Plasmonic Systems

Mayer, Martin 07 December 2019 (has links)
By down-sizing noble metals to the nanoscale, striking new optical properties arise—investigated in the scientific field of plasmonics. The steady rise of developments, innovations, and interest in plasmonics is directly linked with the much broader field of (colloidal) nanotechnology and its breakthroughs. In order to harvest the full potential of colloidal plasmonics, optimizing the synthesis of colloidal nanoparticles, controlling the subsequent assembly of them into complex architectures, and fully understanding the emerging plasmonic properties is inevitable. Wet-chemical seed-mediated growth of colloidal building blocks and colloidal self-assembly offer the tool-sets to tackle the challenges of plasmonic applications. Due to the intrinsic properties of colloids and the resulting (coupled) assemblies, distinct differences are evident in comparison to top-down fabrication based plasmonics. Among these properties, this thesis focuses on the true three-dimensionality of colloids—in vast contrast, top-down processes always rely on stacking of layered architectures. Strong plasmonic coupling interactions are predominantly defined by the inter-particle distances and the geometry of the cross section area by which adjacent particles interact. Consequently, unique plasmonic features emerge from the three-dimensional structure of colloids and the possibility to tune the dielectric environment by surface functionalization. The objective of this work is to investigate and understand the plasmonics of coupled colloidal systems. Following this scope, the first part of this thesis introduces a new synthetic concept, which thereby aims to provide colloidal building blocks for plasmonic assemblies. The optical quality and spectral range can be boosted by applying silver nanoparticles instead of gold as plasmonic material. Herein, a general synthetic concept is introduced resulting in monodispersed and shape-pure silver nanoparticles in a highly controlled manner. By transferring the concept of living polymerization reactions to nanoparticle growth, secondary nucleation is successfully suppressed and the particle dimensions are freely tunable. Finally, chemical stability toward oxidation and functionalization reactions is obtained by covering silver particles with a sub-skin depth gold shell. The second part summarizes the plasmonic properties arising from coupled particle assemblies fabricated by colloidal self-assembly. Therefore, the complexity of the coupled systems was systematically increased to observe the transition from local to collective coupling interactions. Starting from metallic film-coupled gold nanorods, the presence of a highly sensitive magnetic mode and its impact on the magnetic permeability were investigated. Next, the transition from local to collective coupling was observed by stepwise increase of the number of particles in a linear gold nanoparticle chain revealing the formation of a plasmon band in quasi-infinite particle chains. Consequently, this work aims to advance the field of colloidal metasurfaces by optimizing the building blocks and by further comprehending the plasmonic coupling effects in colloidal assemblies. / Durch das Herunterskalieren von (Edel-)Metallen in den Nanometerbereich entstehen neue optische Eigenschaften, die im Wissenschaftsfeld der Plasmonik untersucht werden. Die stetige Weiterentwicklung, Innovation, und das steigende Interesse an der Plasmonik ist direkt mit dem weiter gefassten Gebiet der (kolloidalen) Nanotechnologie verbunden. Um das Potenzial der kolloidalen Plasmonik voll ausschöpfen zu können, ist es unumgänglich, die Synthese kolloidaler Nanopartikel zu optimieren, deren anschließende Anordnung zu komplexen Architekturen gezielt zu steuern, und die entstehenden plasmonischen Effekte vollständig zu verstehen. Das nasschemische Keim-vermittelte Wachstum kolloidaler Bausteine und die kolloidale Selbstanordnung bieten die geeigneten Werkzeuge für plasmonische Anwendungen. Aufgrund der intrinsischen Eigenschaften kolloidaler Partikel und den daraus resultierenden optischen Eigenschaften ihrer Anordnungen, ergeben sich deutliche Unterschiede zur Plasmonik von Top-down Systemen. Im Gegensatz zu diesen Systemen, die immer aus geschichteten Architekturen bestehen, handelt es sich bei kolloidalen Systemen um echte dreidimensionale Objekte. Starke plasmonische Kopplungswechselwirkungen werden hauptsächlich durch die Abstände zwischen Partikeln und die Geometrie des Querschnitts definiert, über die benachbarte Partikel interagieren. Folglich ergeben sich aus der dreidimensionalen Struktur von kolloidalen Nanopartikeln und der Möglichkeit, diese mit verschiedenen dielektrischen Umgebung zu funktionalisieren, einzigartige plasmonische Effekte. Das übergeordnete Ziel dieser Arbeit besteht darin, die plasmonischen Effekte gekoppelter kolloidaler Systeme zu untersuchen und besser zu verstehen. Diesem Ziel folgend, wird im ersten Teil der Arbeit ein neues Synthesekonzept vorgestellt, das darauf abzielt geeignete kolloidale Bausteine für plasmonische Anordnungen zur Verfügung zu stellen. Verglichen mit Gold als Bausteinmaterial kann die optische Qualität und der Spektralbereich durch Nutzung der überlegenen plasmonischen Eigenschaften von Silbernanopartikeln gesteigert werden. Hier wurde ein allgemeines Synthesekonzept entwickelt, das auf kontrollierte Weise zu monodispersen und formreinen Silbernanopartikeln führt. Durch die Übertragung des Konzepts lebender Polymerisationsreaktionen auf das Nanopartikelwachstum, werden Nebenreaktionen (z.B. sekundäre Keimbildung) erfolgreich unterdrückt und die Partikelgröße wird dadurch genau einstellbar. Schließlich wurde durch die Überwachsung der Silberpartikel mit einer Goldschale unterhalb der Leitschichtdicke chemische Stabilität gegenüber Oxidations- und Funktionalisierungsreaktionen erhalten. Im zweiten Teil werden die plasmonischen Eigenschaften gekoppelter Partikelanordnungen untersucht. Dafür wurde die Komplexität der gekoppelten Systeme systematisch erhöht, um den Übergang von lokalen zu kollektiven Kopplungsinteraktionen zu beobachten. Ausgehend von Goldstäbchen, die mit einem Metallfilm gekoppelt sind, wurde eine hochempfindliche magnetische Mode nachgewiesen und deren Einfluss auf die magnetische Permeabilität untersucht. Desweiteren wurde der direkte Übergang von lokaler zu kollektiver Kopplung durch schrittweise Erhöhung der Anzahl der Partikel in einer linearen Goldnanopartikelkette beobachtet, was zur Bildung eines Plasmonenbandes für quasi-unendlich lange Partikelketten führt. Letztendlich ist das Ziel dieser Arbeit, kolloidale Metaoberflächen durch Optimierung der Bausteine und durch besseres Verständnis der plasmonischen Kopplungseffekte voranzubringen.
277

Metal Nanoparticles/Nanowires Self-assembly on Ripple Patterned Substrate: Mechanism, properties, and applications

Ranjan, Mukesh 06 June 2011 (has links)
Plasmonic properties of self-assembled silver nanoparticles/nanowires array on periodically patterned Si (100) substrate are reported with special attention on the mechanism of nanoparticles self-assembly. The advantage of this bottom up approach over other self-assembling and lithographic methods is the flexibility to tune array periodicity down to 20 nm with interparticle gaps as low as 5 nm along the ripple. Ripple pattern have shallow modulation (~2 nm) still particles self-assembly was observed in non-shadow deposition. Therefore adatoms diffusion and kinetics is important on ripple surface for the self-assembly. PVD e-beam evaporation method used for deposition has proven to be superior to sputter deposition due to lower incident flux and lower atom energy. It was found that particles self-assembly largely dependent on angle of incidence, substrate temperature, and deposition direction due to ripple asymmetric tilt. Ostwald ripening observed during annealing on ripples substrate has striking dependency on ripple periodicity and was found to be different compared to Ostwald ripening on flat Si surface. In-situ RBS measurements of deposited silver on flat and rippled substrate confirmed different sticking of atoms on the two surfaces. The difference between maximum and minimum of the calculated local flux show a peak at an incidence angle of 70o with respect to surface normal. This explains the best alignment of particles at this angle of incidence compare to others. Self-assembled nanoparticles are optically anisotropic, i.e. they exhibit a direction dependent shift in LSPR. The reason of the observed anisotropy is a direction dependent plasmonic coupling. Different in plane and out of the plane dielectric coefficients calculated by modelling Jones matrix elements, confirms that nanoparticle/nanowire array are biaxial anisotropic (ex ¹ ey ¹ ez). The nanoparticles are predominantlyinsulating while nanowires are both metallic and insulating depending on the dimension. Silver nanoparticles/nanowires self-aligned on pre-patterned rippled substrate are presented for the first time as an active SERS substrate. Anisotropic SERS response in such arrays is attributed to different field enhancement along and across the ripples. Strong plasmonic coupling in elongated nanoparticles chain results in significantly higher SERS intensity then spherical nanoparticles/nanowires and non-ordered nanoparticles. Higher SERS intensity across the nanowires array in comparison to along the array (bulk silver) confirms electromagnetic field enhancement (hot-junction) is responsible for SERS phenomenon. Self-assembly of cobalt nanoparticle on ripple pattern substrate is also reported. Due to less adatom mobility and higher sticking cobalt self-assembly is possible only at much higher temperature. A strong uniaxial magnetic anisotropy was observed not observed for non ordered cobalt particles.
278

Metal-Oxide Nanocomposite for Tunable Physical Properties

Shikhar Misra (9132629) 05 August 2020 (has links)
<p>Understanding how light interacts with the matter is essential for developing future opto-electronic devices. Furthermore, tuning such light-matter interaction requires designing new material platforms that is essential for developing devices which are functional in different light wavelength regimes. Among these designs, particle-in-matrix, multilayer or nanowire morphology, consisting of metal and dielectric materials, have been demonstrated for achieving improved physical and optical properties, such as ferroelectricity, ferromagnetism and negative refraction. For example, Au-TiO<sub>2</sub> two phase nanocomposite has been explored in this dissertation as a way of achieving enhanced photocatalysis. However, due to the availability of a limited range of structures in terms of crystallinity and morphology in the two-phase nanocomposites, a greater design flexibility and structural complexity along with versatile growth techniques are needed for developing next generation integrated photonic and electronic devices. This can be achieved by incorporating a third phase through the three phase nanocomposite designs by judicious selection of materials and functionalities. </p> <p>In this dissertation, a new nanocomposite design having three different phases has been introduced: Au, BaTiO<sub>3</sub> and ZnO, which grow in a highly ordered ‘nanoman’-like structure. More interestingly, the three phases in the novel ‘nanoman’-like structure combine to give an emergent new property which are not found individually in the three phases. The ordered ‘nanoman’-like structures enable a high degree of tunability in their optical and electrical properties, including the hyperbolic dispersion in the visible and near infrared regime, in addition to the prominent ferroelectric/piezoelectric properties. Moreover, the growth kinetics and the thermal stability (using in-situ Transmission Electron Microscopy) of the ‘nanoman’ structures has also been studied. This study introduces a new growth paradigm of fabricating three-phase nanocomposite that will surely generate wide interests with potential applications to different systems. The ordered three-phase ‘nanoman’ structures present enormous opportunities for novel complex nanocomposite designs towards future optical, electrical and magnetic property tuning.</p>
279

Functional optical surfaces by colloidal self-assembly: Colloid-to-film coupled cavities and colloidal lattices

König, Tobias A.F. 03 February 2021 (has links)
Future developments in nanophotonics require facile, inexpensive and parallelizable fabrication methods and need a fundamental understanding of the spectroscopic properties of such nanostructures. These challenges can be met through colloidal self-assembly where pre-synthesized colloids are arranged over large areas at reasonable cost. As so-called colloidal building blocks, plasmonic nanoparticles and quantum dots are used because of their localized light confinement and localized light emission, respectively. These nanoscopic colloids acquires new hybrid spectroscopic properties through their structural arrangement. To explore the energy transfer between these nanoscopic building blocks, concepts from physical optics are used and implemented with the colloidal self-assembly approach from physical chemistry. Through an established synthesis, the nanocrystals are now available in large quantities, any they receive the tailored spectroscopic properties through directed self-assembly. Moreover, the tailored properties of the colloids and the use of stimuli-responsive polymers allow a functionality that goes beyond current developments. The basics developed in this habilitation thesis can lead to novel functional devices in the field of smart sensors, dynamic light modulators, and large-area quantum devices.:1 Abstract 2 2 State of the art 4 2.1 Metallic and semiconductive nanocrystals as colloidal building blocks 4 2.2 Concept of large-scale colloidal self-assembly 7 2.3 Functional optical nanomaterials by colloidal self-assembly 9 2.4 Scope 13 2.5 References 14 3 Single colloidal cavities 20 3.1 Nanorattles with tailored electric field enhancement 20 4 Colloidal -to-film coupled cavities 31 4.1 Template-assisted colloidal self-assembly of macroscopic magnetic metasurfaces 31 4.2 Single particle spectroscopy of radiative processes in colloid-to-film-coupled nanoantennas 50 4.3 Active plasmonic colloid-to-film coupled cavities for tailored light-matter interactions 65 5 Colloidal polymers 74 5.1 Direct observation of plasmon band formation and delocalization in quasi-infinite nanoparticle chains 74 6 Colloidal lattice 84 6.1 Hybridized guided-node resonances via colloidal plasmonic self-assembled grating 84 6.2 Mechanotunable surface lattice resonances in the visible optical range by soft lithography templates and directed self-assembly 94 6.3 Tunable Circular Dichroism by Photoluminescent Moiré Gratings 103 7 Conclusion and perspective 112 8 Appendix 113 8.1 Further publications during the habilitation period 113 8.2 Curriculum vitae of the author 116 9 Acknowledgments 117 10 Declaration 118 / Zukünftige Entwicklungen in der Nanophotonik erfordern einfache, kostengünstige und parallelisierbare Herstellungsmethoden und benötigen ein grundlegendes Verständnis der spektroskopischen Eigenschaften solcher Nanostrukturen. Diese Herausforderungen können durch kolloidale Selbstorganisation erfüllt werden, bei der kostengünstige und zuvor synthetisierte Kolloide großflächig angeordnet werden. Als sogenannte kolloide Bausteine werden wegen ihrer lokalisierten Lichtfokussierung unterhalb der Beugungsbegrenzung plasmonische Nanopartikel sowie wegen ihrer lokalisierten Lichtemission Quantenpunkte verwendet. Diese nanoskopischen Kolloide werden in dieser Habilitationsschrift verwendet und durch Selbstanordnung in ihre gewünschte Nanostruktur gebracht, die neue hybride Eigenschaften aufweist. Um den Energietransfer zwischen diesen nanoskopischen Bausteinen zu untersuchen, werden Konzepte aus der physikalischen Optik verwendet und mit dem kolloidalen Selbstorganisationskonzept aus der physikalischen Chemie großflächig umgesetzt. Durch eine etablierte Synthese sind die Nanokristalle nun in großen Mengen verfügbar, wobei sie durch gerichtete Selbstorganisation die gewünschten spektroskopischen Eigenschaften erhalten. Darüber hinaus ermöglicht die Verwendung von stimulierbaren Polymeren eine Funktionalität, die über die bisherigen Entwicklungen hinausgeht. Die in dieser Habilitationsschrift entwickelten Grundlagen können bei der Entwicklung neuartiger Funktionsgeräte im Bereich für intelligente Sensorik, dynamischer Lichtmodulatoren und großflächiger Quantengeräte genutzt werden.:1 Abstract 2 2 State of the art 4 2.1 Metallic and semiconductive nanocrystals as colloidal building blocks 4 2.2 Concept of large-scale colloidal self-assembly 7 2.3 Functional optical nanomaterials by colloidal self-assembly 9 2.4 Scope 13 2.5 References 14 3 Single colloidal cavities 20 3.1 Nanorattles with tailored electric field enhancement 20 4 Colloidal -to-film coupled cavities 31 4.1 Template-assisted colloidal self-assembly of macroscopic magnetic metasurfaces 31 4.2 Single particle spectroscopy of radiative processes in colloid-to-film-coupled nanoantennas 50 4.3 Active plasmonic colloid-to-film coupled cavities for tailored light-matter interactions 65 5 Colloidal polymers 74 5.1 Direct observation of plasmon band formation and delocalization in quasi-infinite nanoparticle chains 74 6 Colloidal lattice 84 6.1 Hybridized guided-node resonances via colloidal plasmonic self-assembled grating 84 6.2 Mechanotunable surface lattice resonances in the visible optical range by soft lithography templates and directed self-assembly 94 6.3 Tunable Circular Dichroism by Photoluminescent Moiré Gratings 103 7 Conclusion and perspective 112 8 Appendix 113 8.1 Further publications during the habilitation period 113 8.2 Curriculum vitae of the author 116 9 Acknowledgments 117 10 Declaration 118
280

Electrically Tunable Absorption and Perfect Absorption Using Aluminum-Doped Zinc Oxide and Graphene Sandwiched in Oxides

Adewole, Murthada Oladele 12 1900 (has links)
Understanding the fundamental physics in light absorption and perfect light absorption is vital for device applications in detector, sensor, solar energy harvesting and imaging. In this research study, a large area fabrication of Al-doped ZnO/Al2O3/graphene/Al2O3/gold/silicon device was enabled by a spin-processable hydrophilic mono-layer graphene oxide. In contrast to the optical properties of noble metals, which cannot be tuned or changed, the permittivity of transparent metal oxides, such as Al-doped ZnO and indium tin oxide, are tunable. Their optical properties can be adjusted via doping or tuned electrically through carrier accumulation and depletion, providing great advantages for designing tunable photonic devices or realizing perfect absorption. A significant shift of Raman frequency up to 360 cm-1 was observed from graphene in the fabricated device reported in this work. The absorption from the device was tunable with a negative voltage applied on the Al-doped ZnO side. The generated absorption change was sustainable when the voltage was off and erasable when a positive voltage was applied. The reflection change was explained by the Fermi level change in graphene. The sustainability of tuned optical property in graphene can lead to a design of device with less power consumption.

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