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Chang, Sehoon. "Organic/inorganic hybrid nanostructures for chemical plasmonic sensors". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39545.
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The work presented in this dissertation suggests novel design of chemical plasmonic sensors which have been developed based on Localized Surface Plasmon Resonance (LSPR), and Surface-enhanced Raman scattering (SERS) phenomena. The goal of the study is to understand the SERS phenomena for 3D hybrid (organic/inorganic) templates and to design of the templates for trace-level detection of selected chemical analytes relevant to liquid explosives and hazardous chemicals. The key design criteria for the development of the SERS templates are utilizing selective polymeric nanocoatings within cylindrical nanopores for promoting selective adsorption of chemical analyte molecules, maximizing specific surface area, and optimizing concentration of hot spots with efficient light interaction inside nanochannels. The organic/inorganic hybrid templates are optimized through a comprehensive understanding of the LSPR properties of the gold nanoparticles, gold nanorods, interaction of light with highly porous alumina template, and the choice of physical and chemical attributes of the selective coating.
Furthermore, novel method to assemble silver nanoparticles in 3D as the active SERS-active substrate has been demonstrated by uniform, in situ growth of silver nanoparticles from electroless deposited silver seeds excluding any adhesive polymer layer on template. This approach can be the optimal for SERS sensing applications because it is not necessary to separate the Raman bands of the polyelectrolyte binding layer from those of the desired analyte. The fabrication method is an efficient, simple and fast way to assemble nanoparticles into 3D nanostructures.
Addressable Raman markers from silver nanowire crossbars with silver nanoparticles are also introduced and studied. Assembly of silver nanowire crossbar structure is achieved by simple, double-step capillary transfer lithography. The on/off SERS properties can be observed on silver nanowire crossbars with silver nanoparticles depending on the exact location and orientation of decorated silver nanoparticles nearby silver nanowire crossbars.
As an alternative approach for the template-assisted nanostructure design, porous alumina membrane (PAM) can be utilized as a sacrificial template for the fabrication of the nanotube structure. The study seeks to investigate the design aspects of polymeric/inorganic hybrid nanotube structures with plasmonic properties, which can be dynamically tuned by external stimuli such as pH.
This research suggests several different organic/inorganic nanostructure assemblies by various template-assisted techniques. The polymeric/inorganic hybrid nanostructures including SERS property, pH responsive characteristics, and large surface area will enable us to understand and design the novel chemical plasmonic sensors.
2
Wiley, Benjamin J. "Synthesis of silver nanostructures with controlled shapes and properties /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9923.
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Jin, Kewang. "Fabrication and characterization of 1D oxide nanostructures /". View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202005%20JIN.
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Srivastava, Devesh. "Fabrication of nanostructures and nanostructure based interfaces for biosensor application". Diss., Connect to online resource - MSU authorized users, 2008.
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Bude, Romain. "Synthèses et caractérisations de matériaux thermoélectriques nanostructurés". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC032/document.
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Les marchés de la thermoélectricité sont en pleine expansion avec l’intérêt croissant pour la récupération d’énergie thermique ou encore pour la gestion de la température de composants électroniques. En dépit de ses nombreux avantages, le développement de cette technologie est freiné par les performances des matériaux. Une voie d’amélioration identifiée est leur nanostructuration afin d’en diminuer la conductivité thermique de réseau.Dans ce travail de thèse, cette voie est appliquée au tellurure de bismuth, matériau connu pour posséder les meilleures performances autour de la température ambiante. Les matériaux sont obtenus par synthèse de nanoparticules en solution avant d’être mis en forme par pressage à chaud.Une première étude est réalisée sur la recherche d’un optimum de la taille de grain dans le massif. On montre que le contrôle des conditions de synthèse permet le contrôle des dimensions des nanoparticules. Par ailleurs, les analyses structurales et fonctionnelles des massifs après densification montrent que la variation de la taille initiale des particules permet le contrôle de la microstructure et des propriétés detransport des massifs.Une seconde étude porte sur la recherche d’un optimum en composition des matériaux Bi2Te3-xSex. Les analyses morphologiques mettent en évidence une structure complexe et particulière, laissant apparaitre la présence de trois phases dans les massifs.Les matériaux obtenus par cette méthode de synthèse possèdent a priori des propriétés de transport anisotropes. La caractérisation de leurs performances thermoélectriques est donc difficile. Plusieurs techniques de caractérisation sont mises en oeuvre afin de mieux connaitre leurs conductivités thermiques. Celles-ci sont faibles, ce qui montre l’intérêt de l’approche. Toutefois, leur conductivité électrique est plus basse que leurs homologues obtenus par des techniques plus conventionnelles. On montre néanmoins que l’optimisation des conditions de synthèse des particules entrant dans la composition des massifs alliés permet d’améliorer leurs propriétés électriques et donc leurs performances thermoélectriquesThe global thermoelectric markets are in expansion with a growing interest for the energy harvesting or the thermal management of electronic components. Despite numerous advantages, this technology development is limited by the materials performances. A way to improve them is to use nanostructures in order to decrease the lattice thermal conductivity.In this work, this approach is applied to bismuth telluride, material well known for its high performance around room temperature. Materials are obtained from solution synthesis of nanoparticles before hot press compaction.A first study focuses on the determination of an optimal grain size in the bulk materials. It is shown that control over the synthesis parameters allows control on the size of nanoparticles.Moreover, structural and physical analyses on the bulks after sintering show that the change of thesynthesis parameters allows control over the microstructure and thermoelectric properties of the bulks.A second study is based on the study of an optimal composition of Bi2Te3-xSex materials. Morphological analysis show a specific and complex structure with three phases in the bulks.It is postulated that these materials should have anisotropic transport properties. Consequently, their characterizations are difficult. Different characterization techniques are used in order to have a better understanding of their thermal conductivities. Thermal conductivity of the bulks is found low which confirm the interest of this approach. However the electrical conductivity is lower than the one of the materials obtained by more conventional methods. We show that the synthesis parameters of the particles can be optimized to increase the thermoelectric performances of the bulk materials
6
Akinyeye, Richard Odunayo. "Nanostructured polypyrrole impedimetric sensors for anthropogenic organic pollutants". Thesis, University of the Western Cape, 2007. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5301_1248150815.
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The main aim of this study was to develop a novel strategy for harnessing the properties of electroconductive polymers in sensor technology by using polymeric nanostructured blends in the preparation of high performance sensor devices.
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Mitchell, James Christopher. "DNA nanostructures". Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400206.
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Finbow, Gerard Mark. "Modelling nanostructures". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624252.
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Ventura, João Oliveira. "Magnetic nanostructures". Doctoral thesis, Porto : edição do autor, 2006. http://hdl.handle.net/10216/64289.
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Ventura, João Oliveira. "Magnetic nanostructures". Tese, Porto : edição do autor, 2006. http://catalogo.up.pt/F?func=find-b&local_base=FCB01&find_code=SYS&request=000093736.
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Yiu, Wing-ching James. "Synthesis of one-dimensional tungsten oxide nano-structures by thermal evaporation". Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B32047770.
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Marceau, Ross K. W. "Design in light alloys by understanding solute clustering processes during the early stages of age hardening in Al-Cu-Mg alloys". Connect to full text, 2008. http://ses.library.usyd.edu.au/handle/2123/4008.
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Thesis (Ph. D.)--University of Sydney, 2008.Title from title screen (viewed Jan 07, 2009). Includes two published articles co-authored with others. Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Australina Key Centre for Microscopy and Microanalysis, Electron Microscope Unit, Faculty of Science. Includes bibliographical references. Also available in print form.
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Ung, Thi phuong lien. "Control disorder for electromagnetic localization in plasmonic devices for nanophotonic application". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV013/document.
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Les nanostructures métalliques permettent de confiner la lumière à des échelles sub-longueur d’onde grâce à l'excitation de plasmons de surface. Elles ouvrent la voie à de nombreuses applications que ce soit en imagerie, en élaboration de composants photoniques ou en information quantique. Cette thèse porte sur l’étude de nanostructures métalliques, semi-continues ou constituées par des réseaux de trous au désordre contrôlé, et à leur interaction avec des nanocristaux semi-conducteurs colloïdaux particulièrement photostables. En associant plusieurs approches expérimentales complémentaires (spectroscopie en champ lointain, microscopie de champ proche optique, microscopie avec une sonde active de champ proche, caractérisation par microscopie confocale de l’émission de nanocristaux couplés aux surfaces métalliques), nous avons pu mettre en évidence les caractéristiques spécifiques des modes plasmons de ces différentes structures. Pour les réseaux au désordre contrôlé, nous avons en particulier analysé l’apparition progressive de modes localisés intenses et déterminé l’influence de paramètres tels que l’épaisseur de la couche d’or, le diamètre des trous ou la périodicité initiale du réseau. Les résultats expérimentaux obtenus se sont révélés en très bon accord avec les simulations numériques réalisées par FDTDMetallic nanostructures allow to confine light at subwavelength scales by the excitation of surface plasmon. They open the way for many applications in imaging, photonic components development and quantum information. This thesis deals with the study of metallic nanostructures, semi-continuous or based on holes gratings with a controlled disorder, and their interaction with colloidal semiconductor nanocrystals that are very photostable. Combining several complementary experimental approaches (far-field spectroscopy, near-field optical microscopy, near-field active probe microscopy, characterization by confocal microscopy of the emission of nanocrystals coupled to the metallic surfaces), we were able to highlight specific characteristics of the plasmon modes of these different structures. For the gratings with a controlled disorder, we have in particular analyzed the emergence of intense localized modes and determined the influence of parameters such as the thickness of the gold layer, the diameter of the holes or the initial periodicity of the grating. The experimental results are in very good agreement with the numerical simulations carried out by FDTD
14
Lebold, Timo. "Mesoporous silica nanostructures". Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-118194.
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Grobert, Nicole. "Novel carbon nanostructures". Thesis, University of Sussex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326914.
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Langdo, Thomas Andrew 1974. "Selective SiGe nanostructures". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8450.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001.Includes bibliographical references (p. 206-215).
Selective epitaxial growth (SEG) of SiGe on patterned SiO2/Si substrates by ultra-high vacuum chemical vapor deposition (UHVCVD) shows promise for the fabrication of novel SiGe microelectronic structures. This work explores selective growth conditions in the SiH2Cl2/SiH4/GeH4/H2 system between 650-850⁰C, without the addition of C12 or HC1, on substrates patterned by both conventional and interferometric lithography. We have achieved several important milestones for the fabrication of vertical MOSFETs by selective growth in 100 nm SiO2 features patterned by interferometric lithography. We have observed excellent selectivity to SiO2 masks with SiH2C12 at 750⁰C, perfect epitaxial Si filling of SiO2 features, the facet morphology during growth, and the effects of n-type doping on selective growth. We have also fabricated extremely sharp p-n diode doping profiles. With the above accomplishments we have demonstrated the feasibility of vertical MOSFET fabrication through selective epitaxial growth. To realize the advantages of advanced MOSFET designs on silicon-on-insulator (SOI) substrates, we have developed a facet-free raised source/drain process utilizing moderate n-type doping of Si selective growth and <110>-oriented vertical SiO2 sidewalls. However, to improve SiO2 spacer dimension fidelity and eliminate Si substrate overetching, a novel SiO2/Si3N4 spacer process was developed. The keys to the SiO2/Si3N4 spacer process are removal of the Si3N4 layer prior to growth and increased Si ELO growth by moderate in situ n-type doping. This process has wide ranging application to both SOI and bulk Si technologies for fabrication of low-resistance contacts in advanced devices.
(cont.) By a combination of interferometric lithography Si/SiO2 substrate patterning and Ge selective epitaxial growth, we have demonstrated threading dislocation blocking at the oxide sidewall which shows promise for dislocation filtering and the fabrication of low defect density Ge on Si for III-V device integration. Defects at the Ge film surface only arise at the merging of epitaxial lateral overgrowth (ELO) fronts from neighboring holes. These results confirm that epitaxial necking can be used to reduce threading dislocation density in any lattice-mismatched systems where dislocations are not parallel to growth directions. Investigation of Ge selective growth in micron-sized SiO2 features by plan-view TEM shows that substrate patterning on the order of microns is insufficient to filter dislocations in a large mismatch system ([epsilon] > 2%). Ge p-i-n photodetectors were selectively grown in micron-sized SiO2/Si features to correlate materials properties with electrical characteristics. For chemical protection and compatibility with Si microelectronics, Ge photodetector regions were capped with a thin n+ Si layer. Photodetectors fabricated on unpatterned substrates demonstrated leakage currents comparable to published results on Ge on Si photodetectors while leakage currents were noticeably degraded in devices grown on patterned substrates.
by Thomas Andrew Langdo.
Ph.D.
17
Werra, Julia Franziska Maria. "Probing plasmonic nanostructures". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17658.
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Elektrische und magnetische Emitter können zur Erforschung unterschiedlicher plasmonischer Nanostrukturen genutzt werden. Indem wir die Änderung der Abstrahldynamik und in der Lebensdauer bestimmen, detektieren wir die photonische lokale Zustandsdichte. Diese Zustandsdichte, die eine Eigenschaft der Umgebung ist, ermöglicht uns nicht nur Rückschlüsse auf die elektronischen und andere physikalische Eigenschaften dieser zu treffen sondern auch die allgemeinen Eigenschaften der plasmonischen Nanostruktur im Bezug auf Licht-Materie Kopplung zu bestimmen. Eine starke Licht-Materie-Kopplung ist für die zukünftige Anwendung im Bereich der Quantentechnologien wichtig. Wenn Emitter hierbei mit plasmonischen Nanostrukturen koppeln, fokussieren letztere nicht nur das emittierte Lichts an der Oberfläche im Subwellenlängenbereich sondern ermöglichen durch die Feldüberhöhung an der Oberfläche auch eine starke Licht-Materie-Kopplung. In der Arbeit konzentrieren wir uns auf zwei grundlegend unterschiedliche plasmonische Systeme: zunächst untersuchen wir analytisch den Einfluss von Graphen auf elektrische und magnetische Emitter und diskutieren dann die Lebensdaueränderungen und Strahlungsdynamiken in der Nähe von Silber- und Goldnanostrukturen. Im ersten Teil der Arbeit analysieren wir den Einfluss von Graphen mit einer Bandlücke auf den Emitter und zeigen Möglichkeiten zur experimentellen Bestimmung der Bandlücke auf. Im zweiten Teil modellieren wir die Propagation elektromagnetischer Felder im dreidimensionalen Raum mit Hilfe der Diskontinuierlichen Galerkin Zeitraum Methode mit erweiterten Funktionalitäten. Diese verwenden wir sowohl zur theoretischen Modellierung des ersten dreidimensionalen Fluoreszenlebensdauerabbildungsmikroskopie mit einem einzelnen Quantenemitter als auch zur selbstkonsistent Beschreibung von Emittern in der Nähe eines Goldpentamers. Die Kombination der Studien betont die Stärke von Emittern elektrische, optische und magnetische Eigenschaften zu detektieren.Electric and magnetic emitters can be used to probe different plasmonic nanostructures. By determining the modification of the radiation dynamics and the lifetimes, we can measure the photonic local density of states. This, being a property of the enviroment, does not only allow us to draw conclusions regarding the electronic and other physical properties of the latter but also regarding the general light-matter coupling properties of the plasmonic nanostructure. A strong light-matter coupling is important for future applications in quantum technology. If emitters couple specifically to plasmonic nanostructure, the latter do not only focus the emitted light at the sub-wavelength scale at the surface of the structure but also allow for such a strong light-matter coupling due to the field enhancement at the surface. In this work, we focus on two different basic plasmonic systems: first, we study analytically the influence of graphene on electric and magnetic emitters, and second we discuss lifetime modifications and radiation dynamics close to silver and gold nanostructures. In the first part of this work, we specifically focus on the influence of graphene exhibiting a finite band gap on the emitter. In the second part, we model the propagation of electromagnetic fields in three-dimensional space making use of the discontinuous Galerkin time-domain method with extended functionalities. This framework we apply to model the first three-dimensional scanning-probe fluorescence-lifetime imaging microscopy by use of a single quantum-emitter as well as for a self-consistent description of emitters in the proximity of a gold pentamer. The combination of these studies stress that the strength of emitters lies in the detection of electronic, optical and magnetic properties.
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D'Imperio, Luke A. "Biosensing-inspired Nanostructures:". Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108627.
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Thesis advisor: Michael J. NaughtonNanoscale biosensing devices improve and enable detection mechanisms by taking advantage of properties inherent to nanoscale structures. This thesis primarily describes the development, characterization and application of two such nanoscale structures. Namely, these two biosensing devices discussed herein are (1) an extended-core coaxial nanogap electrode array, the ‘ECC’ and (2) a plasmonic resonance optical filter array, the ‘plasmonic halo’. For the former project, I discuss the materials and processing considerations that were involved in the making of the ECC device, including the nanoscale fabrication, experimental apparatuses, and the chemical and biological materials involved. I summarize the ECC sensitivity that was superior to those of conventional detection methods and proof-of-concept bio-functionalization of the sensing device. For the latter project, I discuss the path of designing a biosensing device based on the plasmonic properties observed in the plasmonic halo, including the plasmonic structures, materials, fabrication, experimental equipment, and the biological materials and protocols
Thesis (PhD) — Boston College, 2019
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
19
Chauvin, Nicolas. "Spectroscopie de la boîte quantique unique dans les systèmes InAs sur InP et InAs sur GaAs émettant à 1,3 µm : application aux sources localisées". Lyon, INSA, 2006. http://theses.insa-lyon.fr/publication/2006ISAL0051/these.pdf.
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Les boîtes quantiques soulèvent actuellement un vif intérêt dans le domaine du traitement quantique de l'information qui nécessite l'utilisation de photons uniques pour la cryptographie ou le calcul quantique. Il est donc nécessaire de comprendre la physique des boîtes quantiques uniques InAs/GaAs et InAs/InP émettant dans la gamme spectrale 1,3 à 1,5 µm, longueurs d'onde adaptées pour la transmission dans les fibres optiques. Dans cette thèse, nous avons étudié le système exciton-biexciton, la structure fine, l'impact de la température ainsi que les excitons chargés pour une boîte quantique unique. Les études en fonction de la température ont montré que les largeurs à mi-hauteur sont de l'ordre du meV à la température de l'azote liquide et se situent entre 10 et 15 meV à température ambiante pour les boîtes InAs/GaAs. De plus, nous avons observé l'évolution de l'énergie de lisaison du biexciton et de la structure fine en fonction de la taille des boîtes InAs/InPQuantum dots are very promising in the field of quantum information which requires the use of single photons for quantum cryptography or quantum calculation. Thus, it is necessary to understand the physic of single InAs/GaAs and InAs/InP quantul dots emitting in 1. 3 to 1. 5 micrometer spectral range, wavelengths adapted for the transmission through optical fibres. In this thesis, we studied the exciton-biexciton complex, the fine structure splitting, the impact of the temperature and charged excitons in single quantum dots. We observed the dependence of the biexciton binding energy and of the fine structure splitting as a function of the InAs/InP quantum dot size. Moreover, the studies as a function of the temperature showed that the linewidth of the exciton recombination is in the meV range nitrogen temperature and in the 10-15 me V range at room temperature for the InAs/GaAs dots
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Bottein, Thomas. "Synergetic combination of top-down and bottom-up lithography processes for large scale nanostructures applied to photonics". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0175/document.
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Le but de cette thèse est d'adopter une approche hybride par la combinaison des méthodes de lithographie ascendantes et descendantes pour la fabrication de nanostructures avec des propriétés structurales et optiques d’intérêt. Cette approche multidisciplinaire est un domaine vaste ou les combinaisons prometteuses sont nombreuses mais restent inexplorées jusqu'à présent. Ces travaux vont s’intéresser aussi bien à la chimie des matériaux qu'aux techniques de nanofabrication de salle blanche afin d'apporter des solutions pratiques aux problèmes actuels rencontrés en nanofabrication. Plus précisément, nous nous intéressons à l’étude de certaines techniques de lithographies (en particulier à la nano-impression) et démontrons la possibilité d’améliorer la cadence de fabrication en obtenant des nanostructures sur une échelle de plusieurs centimètres carrés. Les nanostructures fabriquées sont principalement utilisées comme résonateurs de Mie pour leurs propriétés optiques et leur capacité à modifier la lumière incidente. Des démonstrateurs de plusieurs millimètres carrés sont réalisés et montrent des propriétés optiques intéressantes soulignant la viabilité de notre approcheThe scope of this thesis is to adopt a hybrid approach through the synergetic combination of bottom-up and top-down lithography methods to fabricate nanostructures with interesting structural and optical properties. This multidisciplinary approach is a vast fruitful field where many combinations are promising but remains unexplored so far. By taking interest in, and bringing together, both materials chemistry and clean-room nanofabrication techniques, this work tries to find practical solutions to tackle some of the current challenges in nanofabrication. In details, we focus on the study of selected lithography techniques (in particular nanoimprint) and demonstrate the possibility to increase the fabrication throughput and obtain nanostructures on a centimeter scale. The nanofabricated structures are then mainly used as Mie resonators for their optical properties and their ability to modify incoming light. Demonstrators of several millimeters are produced and are shown to exhibit interesting optical properties; emphasizing the feasibility of our approach
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Bottein, Thomas. "Synergetic combination of top-down and bottom-up lithography processes for large scale nanostructures applied to photonics". Electronic Thesis or Diss., Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0175.
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Le but de cette thèse est d'adopter une approche hybride par la combinaison des méthodes de lithographie ascendantes et descendantes pour la fabrication de nanostructures avec des propriétés structurales et optiques d’intérêt. Cette approche multidisciplinaire est un domaine vaste ou les combinaisons prometteuses sont nombreuses mais restent inexplorées jusqu'à présent. Ces travaux vont s’intéresser aussi bien à la chimie des matériaux qu'aux techniques de nanofabrication de salle blanche afin d'apporter des solutions pratiques aux problèmes actuels rencontrés en nanofabrication. Plus précisément, nous nous intéressons à l’étude de certaines techniques de lithographies (en particulier à la nano-impression) et démontrons la possibilité d’améliorer la cadence de fabrication en obtenant des nanostructures sur une échelle de plusieurs centimètres carrés. Les nanostructures fabriquées sont principalement utilisées comme résonateurs de Mie pour leurs propriétés optiques et leur capacité à modifier la lumière incidente. Des démonstrateurs de plusieurs millimètres carrés sont réalisés et montrent des propriétés optiques intéressantes soulignant la viabilité de notre approcheThe scope of this thesis is to adopt a hybrid approach through the synergetic combination of bottom-up and top-down lithography methods to fabricate nanostructures with interesting structural and optical properties. This multidisciplinary approach is a vast fruitful field where many combinations are promising but remains unexplored so far. By taking interest in, and bringing together, both materials chemistry and clean-room nanofabrication techniques, this work tries to find practical solutions to tackle some of the current challenges in nanofabrication. In details, we focus on the study of selected lithography techniques (in particular nanoimprint) and demonstrate the possibility to increase the fabrication throughput and obtain nanostructures on a centimeter scale. The nanofabricated structures are then mainly used as Mie resonators for their optical properties and their ability to modify incoming light. Demonstrators of several millimeters are produced and are shown to exhibit interesting optical properties; emphasizing the feasibility of our approach
22
France-Lanord, Arthur. "Transport électronique et thermique dans des nanostructures". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS566/document.
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La miniaturisation continue des composants électroniques rend indispensable la connaissance des mécanismes de transport à l’échelle nanométrique. Alors que les processus simples de conduction dans les matériaux homogènes sont bien assimilés, la compréhension du transport à l’échelle nanométrique dans les systèmes hétérogènes reste à améliorer. Par exemple, le couplage entre courant, résistance et flux de chaleur dans des nanostructures doit être clarifié. Dans ce contexte, le sujet de thèse est centré autour du développement et de l’application de méthodes de calcul avancées pour la prédiction des propriétés de transport électronique et thermique à l’échelle nanométrique. Dans une première partie, nous avons paramétré un modèle de potentiel inter-atomique classique adapté à la description de systèmes multicomposants, afin de modéliser les propriétés structurelles, vibratoires et de transport de chaleur de la silice, ainsi que du silicium. Pour ce faire, une approche d’optimisation automatisée et reproductible a été mise en place. En guise d’exemple, nous avons calculé la dépendance en température de la résistance de Kapitza pour le système silice amorphe - silicium cristallin, ce qui a permis de souligner l’importance d’une description structurelle précise de l’interface. Dans une seconde partie, nous avons étudié la décomposition modale de la conductivité thermique du graphène supporté par un substrat de silice amorphe. Plus précisément, l’influence de l’état de surface (hydroxilation, etc) sur le transport thermique a été quantifiée. Le rôle déterminant des excitations collectives de phonons a été mis au jour. Finalement, dans une dernière partie, les propriétés de transport électronique du graphène supporté par une bi-couche de silice, système récemment observé expérimentalement, ont été étudiées. L’influence d’ondulations dans la couche de graphène ou dans le substrat, souvent présentes dans les échantillons réels et dont l’amplitude et la longueur d’onde peuvent être contrôlées, a été dégagée. Nous avons également modélisé le champ électrique généré par une grille, et déterminé son incidence sur le transport électroniqueThe perpetual shrinking of microelectronic devices makes it crucial to have a proper understanding of transport mechanisms at the nanoscale. While simple effects are now well understood in homogeneous materials, the understanding of nanoscale transport in heterosystems needs to be improved. For instance, the relationship between current, resistance, and heat flux in nanostructures remains to be clarified. In this context, the subject of the thesis is centered around the development and application of advanced numerical methods used to predict electronic and thermal conductivities of nanomaterials. This manuscript is divided into three parts. We begin with the parameterization of a classical interatomic potential, suitable for the description of multicomponent systems, in order to model the structural, vibrational, and thermal transport properties of both silica and silicon. A well-defined, reproducible, and automated optimization procedure is derived. As an example, we evaluate the temperature dependence of the Kapitza resistance between amorphous silica and crystalline silicon, and highlight the importance of an accurate description of the structure of the interface. Then, we have studied thermal transport in graphene supported on amorphous silica, by evaluating the mode-wise decomposition of thermal conductivity. The influence of hydroxylation on heat transport, as well as the significant role played by collective excitations of phonons, have come to light. Finally, electronic transport properties of graphene supported on quasi-two-dimensional silica, a system recently observed experimentally, have been investigated. The influence on transport properties of ripples in the graphene sheet or in the substrate, which often occur in samples and whose amplitude and wavelength can be controlled, has been evaluated. We have also modeled electrostatic gating, and its impact on electronic transport
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Wang, Debin. "Thermochemical nanolithography fabrication and atomic force microscopy characterization of functional nanostructures". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34776.
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This thesis presents the development of a novel atomic force microscope (AFM) based nanofabrication technique termed as thermochemical nanolithography (TCNL). TCNL uses a resistively heated AFM cantilever to thermally activate chemical reactions on a surface with nanometer resolution. This technique can be used for fabrication of functional nanostructures that are appealing for various applications in nanofluidics, nanoelectronics, nanophotonics, and biosensing devices.
This thesis research is focused on three main objectives. The first objective is to study the fundamentals of TCNL writing aspects. We have conducted a systematic study of the heat transfer mechanism using finite element analysis modeling, Raman spectroscopy, and local glass transition measurement. In addition, based on thermal kinetics analysis, we have identified several key factors to achieve high resolution fabrication of nanostructures during the TCNL writing process.
The second objective is to demonstrate the use of TCNL on a variety of systems and thermochemical reactions. We show that TCNL can be employed to (1) modify the wettability of a polymer surface at the nanoscale, (2) fabricate nanoscale templates on polymer films for assembling nano-objects, such as proteins and DNA, (3) fabricate conjugated polymer semiconducting nanowires, and (4) reduce graphene oxide with nanometer resolution.
The last objective is to characterize the TCNL nanostructures using AFM based methods, such as friction force microscopy, phase imaging, electric force microscopy, and conductive AFM. We show that they are useful for in situ characterization of nanostructures, which is particularly challenging for conventional macroscopic analytical tools, such as Raman spectroscopy, IR spectroscopy, and fluorescence microscopy.
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Sönnichsen, Carsten. "Plasmons in metal nanostructures". [S.l.] : [s.n.], 2001. http://edoc.ub.uni-muenchen.de/archive/00002367.
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Cazayous, Maximilien. "Interférences Raman et Nanostructures". Phd thesis, Université Paul Sabatier - Toulouse III, 2002. http://tel.archives-ouvertes.fr/tel-00001850.
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Les structurations de la matière à l'échelle nanométrique ont ouvert de larges champs d'étude. L'analyse des propriétés structurales des nanostructures, de leur degré d'organisation ainsi que leur influence sur les propriétés électroniques représentent actuellement un défi de première importance. Pour accéder à ces informations, il est souvent nécessaire de faire appel à un ensemble de techniques expérimentales et numériques souvent complexes dans leur mise en oeuvre. Dans cette contribution, nous étudions l'organisation et le confinement électronique dans des multiplans de boîtes quantiques, en nous appuyant à la fois sur une étude expérimentale et un travail de modélisation. Les interférences Raman, observées dans la gamme des phonons acoustiques, résultent de l'interaction entre ces derniers et les états électroniques localisés dans les nanostructures. Parce qu'ils explorent une gamme allant de quelques nanomètres à plusieurs centaines de nanomètres, les phonons acoustiques représentent une sonde particulièrement efficace pour l'étude des nanosystèmes. Les interférences Raman utilisent leur sensibilité pour la mesure des propriétés structurales et électroniques. Elles permettent de mesurer les effets de corrélation verticale et latérale dans les multiplans de boîtes quantiques. Nous avons développé un modèle général dont le domaine d'application s'étend des systèmes contenant quelques plans au super-réseaux. En utilisant l'analyse de Fourier des interférences, on détermine la fonction d'auto-corrélation de la densité de probabilité électronique selon l'axe de croissance. Sensible à la taille et à la forme de la densité électronique, les interférences Raman ouvrent la voie à une imagerie optique de la densité électronique.
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Sönnichsen, Carsten. "Plasmons in metal nanostructures". Diss., lmu, 2001. http://nbn-resolving.de/urn:nbn:de:bvb:19-23678.
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Rørvik, Per Martin. "Synthesis of ferroelectric nanostructures". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5136.
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The increasing miniaturization of electric and mechanical components makes the synthesis and assembly of nanoscale structures an important step in modern technology. Functional materials, such as the ferroelectric perovskites, are vital to the integration and utility value of nanotechnology in the future. In the present work, chemical methods to synthesize one-dimensional (1D) nanostructures of ferroelectric perovskites have been studied. To successfully and controllably make 1D nanostructures by chemical methods it is very important to understand the growth mechanism of these nanostructures, in order to design the structures for use in various applications. For the integration of 1D nanostructures into devices it is also very important to be able to make arrays and large-area designed structures from the building blocks that single nanostructures constitute. As functional materials, it is of course also vital to study the properties of the nanostructures. The characterization of properties of single nanostructures is challenging, but essential to the use of such structures. The aim of this work has been to synthesize high quality single-crystalline 1D nanostructures of ferroelectric perovskites with emphasis on PbTiO3 , to make arrays or hierarchical nanostructures of 1D nanostructures on substrates, to understand the growth mechanisms of the 1D nanostructures, and to investigate the ferroelectric and piezoelectric properties of the 1D nanostructures. In Paper I, a molten salt synthesis route, previously reported to yield BaTiO3 , PbTiO3 and Na2Ti6O13 nanorods, was re-examined in order to elucidate the role of volatile chlorides. A precursor mixture containing barium (or lead) and titaniumwas annealed in the presence of NaCl at 760 °C or 820 °C. The main products were respectively isometric nanocrystalline BaTiO3 and PbTiO3. Nanorods were also detected, but electron diffraction revealed that the composition of the nanorods was respectively BaTi2O5/BaTi5O11 and Na2Ti6O13 for the two different systems, in contradiction to the previous studies. It was shown that NaCl reacted with BaO(PbO) resulting in loss of volatile BaCl2 (PbCl2 ) and formation and preferential growth of titanium oxide-rich nanorods instead of the target phase BaTiO3 (or PbTiO3 ). The molten salt synthesis route may therefore not necessarily yield nanorods of the target ternary oxide as reported previously. In addition, the importance of NaCl(g) for the growth of nanorods below the melting point of NaCl was demonstrated in a special experimental setup, where NaCl and the precursors were physically separated. In Paper II and III, a hydrothermal synthesis method to grow arrays and hierarchical nanostructures of PbTiO3 nanorods and platelets on substrates is presented. Hydrothermal treatment of an amorphous PbTiO3 precursor in the presence of a surfactant and PbTiO3 or SrTiO3 substrates resulted in the growth of PbTiO3 nanorods and platelets aligned in the crystallographic <100> orientations of the SrTiO3 substrates. PbTiO3 nanorods oriented perpendicular to the substrate surface could also be grown directly on the substrate by a modified synthesis method. The hydrothermal method described in Paper II and III was developed on the basis of the method described in Appendices I and II. In Paper IV, a template-assisted method to make PbTiO3 nanotubes is presented. An equimolar Pb-Ti sol was dropped onto porous alumina membranes and penetrated into the channels of the template. Single-phase PbTiO3 perovskite nanotubes were obtained by annealing at 700 °C for 6 h. The nanotubes haddiameters of 200 - 400 nm with a wall thickness of approximately 20 nm. Excess PbO or annealing in a Pb-containing atmosphere was not necessary in order to achieve single phase PbTiO3 nanotubes. The influence of the heating procedure and the sol concentration is discussed. In Paper V, a piezoresponse force microscopy study of single PbTiO3 nanorods is presented. The piezoelectric properties were studied in both vertical and lateral mode. Piezoelectric activity and polarization switching was observed in the vertical mode, demonstrating the ferroelectric nature of the nanorods. The nanorods decomposed after repeated cycling of the dc bias at one spot on the nanorod, which resulted in parts of the nanorod disappearing and/or accumulation of particles on the surface of the nanorod. In Paper VI, a method to contact single nanorods by electron beam induced deposition of platinum is presented. An organometallic compound, (trimethyl)-methylcyclopentadienylplatinum(IV), was used as precursor. A home-made apparatus was constructed for the purpose and was mounted onto a scanning electron microscope. Calculations based on apparatus geometry and molecular flow were used to estimate the deposition time and the height of the deposits. The location and height of the deposits were controlled so that single nanorods could be successfully contacted at the ends of the nanorods. Fabrication of a sample device for piezoresponse force microscopy studies of single nanorods using an axial dc bias setup is described in Appendix IV. A proposed experimental setup for such studies is also presented.
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Van, Hoof Thibaut. "Modèles de nanostructures bimétalliques". Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210972.
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Hodgson, Matthew J. P. "Electrons in model nanostructures". Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15657/.
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For calculating the properties of solids and molecules, density functional theory (DFT) has become extremely popular because of its inherent computational efficiency. However, despite being in principle exact, an approximation must be introduced into DFT in practice. The accuracy of DFT has been key to its popularity; however, even for some of the simplest systems, using common approximations to the exchange-correlation (xc) functional may give inaccurate results. Therefore, we aim to contribute to the development of improved approximate xc functionals. It is logical to begin by studying the most elementary of systems where the common approximate xc functionals require improvement, as one can model these systems exactly by solving the many-electron Schrödinger equation. By allowing us to study DFT and time-dependent DFT (TDDFT) in the absence of approximations for prototype systems, this approach provides insight into the fundamental principles of the theory, informing the development of new approximations. We show that steps arise in the level of the exact xc potential: steps are known to be important for giving accurate electron and current densities, yet little about their origin is understood. We show that steps form due to a change in the 'local effective ionisation energy' of the electrons: this concept is well defined for strongly localised electrons. We find that the tendency of an electron to exclude others from its vicinity (electron localisation) is surprisingly high in our finite systems; hence, we develop an approximate functional that uses a measure of localisation as an ingredient, with the analytical form of the Kohn-Sham potential in the limit of complete localisation. Our functional, termed the mixed localisation potential, gives accurate electron and current densities for our test systems where local approximations are less valid. The approximation’s success stems in part from its ability to reproduce steps in the xc potential.
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Zhu, Ningjia. "Conductance fluctuations in nanostructures". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30431.pdf.
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Pigeau, Benjamin. "Magnetic vortex dynamics nanostructures". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00779597.
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This thesis is aimed at studying experimentally the magnetisationdynamics of discs in the sub-micron range made of low dampingferromagnetic materials. For this purpose, an extremely sensitivetechnique has been used: the ferromagnetic resonance force microscopy. A firstpart is devoted to the measurement of the eigenmodes of NiMnSb discstaken in their remanent state: a vortex. The influence of aperpendicular magnetic field on the spin wave modes in the vortex state willbe detailled. Then, the coupling mechanism between the vortex core andthese spin wave, eventually leading to its dynamical reversal, ishighlighted. A theoretical framework of the vortex state is presented,allowing to model the experimental observations. In a second part,the problem of the collective magnetisation dynamics in several FeVdiscs is addressed. Measurements of the collective modes coupled bythe dynamical dipolar interaction are presented, associated with atheoretical modelisation which explain quantitatively the experimentalresults.
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Espeland, Erlend. "Gold Nanostructures on Graphite". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22433.
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Gold nanoparticles supported on a graphite substrate are prepared by thermal evaporation, and subsequently studied by X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) of carbon monoxide and scanning electron microscopy (SEM).Increasing the amount of gold deposited leads to a shift of the desorption peak to higher temperatures, and the gold particles become larger.Depositing approximately the same amount of gold at different evaporation ratios does not seem to affect the desorption.Triangularly shaped gold particles appeared at higher evaporation rates.This is thought to be caused by diffusion effects dominating the formation of the particles.
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Zhu, Ningjia. "Conductance fluctuations in nanostructures". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34492.
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In this Ph.D thesis the conductance fluctuations of different physical origins in semi-conductor nanostructures were studied using both diagrammatic analytical methods and large scale numerical techniques. In the "mixed" transport regime where both mesoscopic and ballistic features play a role, for the first time I have analytically calculated the non-universal conductance fluctuations. This mixed regime is reached when impurities are distributed near the walls of a quantum wire, leaving the center region ballistic. I have discovered that the existence of a ballistic region destroys the universal conductance fluctuations. The crossover behavior of the fluctuation amplitude from the usual quasi-1D situation to that of the mixed regime is clearly revealed, and the role of various length scales are identified. My analytical predictions were confirmed by a direct numerical simulation by evaluating the Landauer formula. In another direction, I have made several studies of conductance or resistance oscillations and fluctuations in systems with artificial impurities in the ballistic regime. My calculation gave explanations of all the experimental results concerning the classical focusing peaks of the resistance versus magnetic field, the weak localization peak in a Sinai billiard system, the formation of a chaotic billiard, and predicted certain transport features which were indeed found experimentally. I have further extended the calculation to study the Hall resistance in a four-terminal quantum dot in which there is an antidot array. From my numerical data I analyzed the classical paths of electron motion and its quantum oscillations. The results compare well with recent experimental studies on similar systems. Since these billiard systems could provide quantum chaotic dynamics, I have made a detailed study of the consequence of such dynamics. In particular I have investigated the resonant transmission of electrons in these chaotic systems, and found that the level-s
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De, Jesus Tiago. "Admittance fluctuations in nanostructures". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36906.
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In this thesis, we develop a first principle technique to study linear AC and the nonlinear DC quantum transport in diffusive conductors. Starting from Buttiker's theory for AC and DC transport, the emittance and nonlinear DC conductance are found in terms of the scattering matrix and it's functional derivative. New theoretical tools are developed to compute the functional derivative of the scattering matrix, which would otherwise be unaccessible. These results allows us to compute the linear AC and the nonlinear DC conductance for a diffusive conductor from first principles, for the first time in literature. The sample-to-sample AC conductance fluctuations are computed for a diffusive conductor. In this regime the dynamic response of the conductor can either be capacitive or inductive, depending on impurity configuration. Our results also suggest a crossover for the AC conductance distribution, from a symmetric to a non symmetric distribution function as the number of impurities increases. A degree of generic behavior is discovered, in that the AC fluctuation amplitudes become independent of the strength of the impurities, although it depends on the impurity density. A sample-to-sample analysis of the nonlinear conductance fluctuations, in the diffusive regime, is also reported. In this situation the distribution function is found to be a symmetric Gaussian like function for small disorder and a symmetric exponentially decaying function for large disorder. An interesting result is that the conductance fluctuations increase in an exponential fashion with N, the number of impurities.We also considered in this thesis the magneto-conductance fluctuations of a quasi-1D quantum wire with artificial impurities (antidots). This problem can only be solved numerically because of the finite size of the artificial impurities. We develop a novel transfer matrix technique to solve the quantum scattering problem by computing the scattering wave function, as a function of the external magnetic field. The Landauer-Buttiker equation is used to compute the magneto-conductance. This work is motivated by the experimental study [1], where several conductance fluctuations anomalies were reported. Our numerical results give good quantitative agreement with the experimental data and confirms the physical picture obtained from the experiment.
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Todorov, Tchavdar N. "Quantum transport in nanostructures". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334909.
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Giddings, Alexander Devin. "Dilute magnetic semiconductor nanostructures". Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/10521/.
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The prospect of a new generation of electronic devices based on the fundamental quantum property of angular momentum, known as spin, has led to the rapidly developing field of spintronics. It is envisioned that these advanced devices will have significant advantages over traditional charge based electronics in properties such as speed, power consumption and long coherence times. By combining the properties of magnetics with that of semiconductors, the novel class of materials known as dilute magnetic semiconductors (DMSs) are considered a promising system for exhibiting spintronic functionality. These materials are created by using molecular beam epitaxy (MBE) to incorporate into traditional semiconductors a quantity of transition metal atoms sufficient that ferromagnetism is exhibited. The most widely studied DMS is (Ga,Mn)As which has well characterised behaviour and can be processed using standard III-V fabrication techniques, thus providing an excellent basis for further study. In this research the properties of (Ga,Mn)As based systems are studied as the material dimensions are reduced to nanometre length scales. Three complementary approaches are used for this purpose. The first is to use ultra-high-resolution electron-beam lithography to construct devices. By being able to selectively remove material, laterally patterned structures can have sizes as small as 10 nm. The second approach is to exploit the atomic layer growth of MBE to allow the construction of epilayers and heterostructures with well defined vertical compositions. Thirdly, a theoretical k.p kinetic-exchange model allows the simulation of multilayer structures and an exploration of the parameter spaces available in such materials. Two systems are considered: lateral nanoconstricted magnetic tunnel junctions and vertically defined magnetic superlattices. The nanoconstrictions are analysed using low temperature magnetotransport techniques and novel anisotropic magnetoresistance (MR) effects are measured. Primarily, tunnelling anisotropic magnetoresistance (TAMR) is observed, demonstrating that it is a generic property of ferromagnetic tunnel devices and is therefore of wide interest for other spintronic systems. Secondarily, anisotropic switching behaviour is observed and is interpreted as Coulomb blockade anisotropic magnetoresistance (CBAMR). Additionally, the significance of the processing stages and material properties are highlighted. The magnetic superlattices are firstly considered on a theoretical basis in order to determine structural parameters in which a new MR effect might be observed. This effect derives from the interlayer exchange coupling (IEC) between the magnetic layers which can either be in parallel or opposed orientations. Based on the calculations, samples are measured using low temperature magnetotransport and magnetometry techniques in order to explore the possibility of some of the dramatic properties predicted in magnetic superlattice structures.
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鄭蔚 i Wei Zheng. "Dynamic conductance of nanostructures". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31243939.
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Wang, Chaoming. "Thermally annealled plasmonic nanostructures". Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5556.
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Localized surface plasmon resonance (LSPR) is induced in metal nanoparticles by resonance between incident photons and conduction electrons in nanoparticles. For noble metal nanoparticles, LSPR can lead to strong absorbance of ultraviolet-violet light. Although it is well known that LSPR depends on the size and shape of nanoparticles, the inter-particle spacing, the dielectric properties of metal and the surrounding medium, the temperature dependence of LSPR is not well understood. By thermally annealing gold nanoparticle arrays formed by nanosphere lithography, a shift of LSPR peak upon heating has been shown. The thermal characteristics of the plasmonic nanoparticles have been further used to detect chemicals such as explosive and mercury vapors, which allow direct visual observation of the presence of mercury vapor, as well as thermal desorption measurements.ID: 031001538; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: Ming Su.; Title from PDF title page (viewed August 21, 2013).; Thesis (Ph.D.)--University of Central Florida, 2012.; Includes bibliographical references (p. 95-108).
Ph.D.
Doctorate
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering
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Eisenbach, Markus. "Magnetic anisotropy in nanostructures". Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364862.
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Liljestrand, Julia. "Dynamics of magnetic nanostructures". Thesis, Uppsala universitet, Materialfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-297634.
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Magnetic nanostructures provide the opportunity to investigate a number ofmagnetic phenomena, and are of interest for their possible future applicationsin technology. In this project, the ferromagnetic response (FMR) of magnetic nanostructures to an electromagnetic excitation has been investigated using the micromagnetic simulations program Mumax3. The magnetic nanostructures in question were lattices of stadium shaped magnetic islands known as square articial spin ice. They are often characterized by the vortex in which four islands meet. Depending on the number of magnetic moment directed inwards or outwards from the vortex, four main vortex types can be created according to their magnetic energy. Lattices of square articial spin ice can exhibit articial magnetic monopoles connected by Dirac strings. Four congurations of square articial spin ice were investigated: a single stadium shaped island, two single vertices of different types, a lattice of 24 magnetic islands with two different spacings and types of center vertices, and a lattice of 60 magnetic islands for the case of inserted Dirac strings. The FMR spectra of these structures reveal several resonant modes of different intensities and frequencies. Of particular interest is the relationship between the intensity of a particular resonant mode and the number of inserted stings of reversed magnetization for the 4-by-4 lattice.
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Walton, Stephanie Katharine. "Magnetism in frustrated nanostructures". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25964.
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Artificial Spin Ice (ASI), comprised of ferromagnetic nanobars in a honeycomb geometry, attracts much attention since it is a directly imageable frustrated system which exhibits rich physics including ice-rule behaviour and magnetic monopole excitations. ASI's nanobars undergo domain wall mediated magnetic reversal in external fields. Understanding and indeed controlling the trajectories of field driven domain walls and hence the order in which ASI's nanobars are reversed is a crucial step towards mapping out ASI's full functionality for potential applications. In this thesis, trajectories of domain walls during the early stages of ASI's magnetic reversal are studied. Data showing domain walls executing non-random walks in the transverse domain wall regime and random walks in the vortex domain wall regime is presented. The former behaviour is linked to the domain wall's chirality, and as such, attempts to control a domain wall's initial chirality via triangular injection pads are discussed. In addition, ways in which a vortex domain wall's chirality may be controlled with ellipsoidal hole obstructions are shown. Artificial Dipolar 2D-XY, a complementary system to ASI, also promises interesting behaviour. In this new frustrated architecture, individual nanobars are replaced with single domain nanodiscs whose magnetisations can point in any in-plane direction. In this thesis, intriguing results from preliminary experiments on this new system are presented. One of the best techniques used to study the magnetisations of nanostructures such as those described above is Lorentz Transmission Electron Microscopy (LTEM). Since the contrast yielded for unusual magnetic states was not well documented, software called Micromagnetic Analysis to Lorentz TEM Simulation (MALTS) was developed in order to aid in analysis of LTEM images. MALTS can simulate the LTEM contrast of any magnetic object of any size, shape or state. A description of its full functionality is also included in this thesis.
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Céreyon, Arnaud. "Amplification Raman et nanostructures". Lyon 1, 2008. http://www.theses.fr/2008LYO10133.
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JURE, LIONEL. "Nanostructures sur substrat semiconducteur". Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10113.
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Cette these a pour sujet l'etude de la structure et de la formation d'objets unidimensionnels de taille nanometrique. Ce travail experimental a ete effectue a l'aide d'un microscope a effet tunnel (stm) fonctionnant a temperature variable sous ultravide, il a ete complete par des calculs ab initio (dft-lda). Les nanostructures que nous avons etudiees ont ete obtenues par depot de metaux (pb, in, sn) sur un substrat si(100) reconstruit (21). Apres une presentation succincte des techniques experimentales et du substrat si(100)21, nous presentons les resultats de l'etude statique par stm des depots (in et pb), au cours de laquelle nous avons precise le contraste stm des differents objets (precurseurs, terminaisons et structure interne des lignes de dimeres). Nous proposons un modele de structures pour ces objets en les comparant a ceux obtenus lors de l'etude prealable du depot si/si(100)21. Ensuite, nous nous interessons a la dynamique de ces depots a differentes temperatures. Ces observations nous permettent d'affiner notre modele de structure, de definir des mecanismes d'echange d'atomes. Nous avons elabore un modele de croissance des chaines de dimeres de plomb a partir des mesures a basse temperature. L'etude de depots recuits nous a permis de tester la stabilite des chaines et de mettre en evidence une interaction laterale entre chaines sans doute d'origine elastique mediee par le substrat. Enfin, nous avons etudie des codepots d'indium et d'etain dans le but de former un metal unidimensionnel sous la forme d'une ligne de dimeres mixtes (in-sn). Nous avons mis en evidence une selectivite chimique dans la formation des dimeres qui ne permet d'obtenir qu'un alliage unidimensionnel forme de dimeres homogenes des deux especes dans les chaines.
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Zheng, Wei. "Dynamic conductance of nanostructures /". Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B24367382.
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Carpenter, Robert. "Exchange bias in nanostructures". Thesis, University of York, 2015. http://etheses.whiterose.ac.uk/9080/.
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This study was concerned with two issues facing the technological application of exchange bias. The first is the ferromagnet (F)/antiferromagnet (AF) interface which was investigated via the effect of the IrMn (111) in-plane texture on the magnetisation reversal of IrMn/CoFe samples. The second is the change in the magnitude of the exchange bias (Hex) and the median blocking temperature (Tbmed)with element size in sub-500nm nanostructures. The evolution of the magnetisation reversal over the annealing/field cooling process in CoFe and CoFe/IrMn thin films was measured for samples deposited on Cu and NiCr seed layers. The samples deposited on the Cu seed layer were found to be polycrystalline but randomly oriented whilst those on a NiCr seed layer had a strong (111) in-plane texture. The training effect is the change in the first point to reversal (Hc1) between the first and second hysteresis loops measured after field cooling. This was found to vary drastically with texture where deltaHc1 was found to be (10+/-2.5)Oe and (60+/-2.5)Oe for the samples deposited on the NiCr and Cu seed layers respectively. This was hypothesised to be due to a distribution of orientation of the easy axis of the interfacial spin clusters. In the case of the sample deposited on the Cu seed layer there is a 3-D random distribution of easy axis orientations similar to that of Stoner-Wohlfarth entities whereas for the sample grown on the NiCr seed layer there is a 2-D random distribution of easy axis. It is the tensioning of the cluster-cluster interactions with the easy axis orientation that is thought to give rise to the training effect and other phenomena in exchange bias. The change in Hex and Tbmed with element size was measured in 4x4mm arrays of nanodots patterned through e-beam lithography and fabricated using the lift-off method. Following an initial decrease of 66% due to the patterning process, Hex decreased from (105+/-5)Oe to (40+/-5)Oe with element size from 425 to 80nm. However whilst an initial decrease in Tbmed from (448+/-5)K to ~405K occured due to the patterning process no significant change is seen with element size. This implies that the change in Hex is due to a modification of the interface i.e. non-planar deposition as a result of depositing the film through a mask.
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Xia, Sijing. "Fabrication of protein nanostructures". Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/10126/.
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Barr, Joshua. "Transport in Interacting Nanostructures". Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301551.
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Transport through nanostructures is studied at the many-body level using exact diagonalization and nonequilibrium Green's functions. Organic molecular junctions are a particular focus because of their technological promise. Work is presented regarding: (1) A π-electron model of organic molecular junctions developed using effective field theory; (2) series transmission and transmission node structure in interacting systems; (3) the effect of interactions on quantum interference and thermoelectricity in polycyclic junctions; and (4) nanoscale transport calculations using self-consistent statistical ensembles.
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Hagelberg, Frank. "Magnetism in Carbon Nanostructures". Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu_books/151.
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Magnetism in carbon nanostructures is a rapidly expanding field of current materials science. Its progress is driven by the wide range of applications for magnetic carbon nanosystems, including transmission elements in spintronics, building blocks of cutting-edge nanobiotechnology, and qubits in quantum computing. These systems also provide novel paradigms for basic phenomena of quantum physics, and are thus of great interest for fundamental research. This comprehensive survey emphasizes both the fundamental nature of the field, and its groundbreaking nanotechnological applications, providing a one-stop reference for both the principles and the practice of this emerging area. With equal relevance to physics, chemistry, engineering and materials science, senior undergraduate and graduate students in any of these subjects, as well as all those interested in novel nanomaterials, will gain an in-depth understanding of the field from this concise and self-contained volume.https://dc.etsu.edu/etsu_books/1164/thumbnail.jpg
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SPEISER, EUGEN. "Raman spectroscopy on nanostructures". Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/566.
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One of the most current and also most promising fields of research in solid state physics is that of nano-structured materials. In particular, there is a great interest in nanostructured semiconductors, thanks to the latest developments in preparation techniques. These techniques allow to prepare nano-sized semiconductors with excellent crystalline structure and most often also with epitaxially determined orientations with respect to a template.
The interest in nano-structures is triggered by the discovery that their physical properties (electronic, optical, thermodynamical) are different from those of the corresponding bulk material due to confinement. Consequently, the size becomes a new design parameter for new electronic and optoelectronic devices, for example.
The goal of this work is to study nano-structures by optical methods, especially by Raman spectroscopy. 1-dimensional nano-structures are the main focus because of their recently intensively investigated and improved growth mechanisms. This research enables the synthesis of nano-materials of high crystalline quality, controlled orientation and size.
To obtain measurements from 1- dimensional (quantum wires, nanorods, nanotubes) and 0-dimensional nanostructures (quantum dots)—in contrast to well-investigated 2- dimensional quantum wells—an additional requirement for the measurement technique is that the probe must provide lateral resolution in the nanometer range. This requirement excludes or limits many of the standard surface science techniques and is especially true for the standard optical tools with diffraction limited spatial resolution in the sub-micrometer range. If possible, samples with modified growth process parameters are chosen in order to reduce the spatial density of the nanostructures in a way that only one structure is contained in the probing area. The goal is to exclude averaging of their properties by summing contributions from different structures. This is achieved also by using confocal microscopy spectroscopy providing diffraction limited spatial resolution in the micrometer range (~ 1μm). Confocal micro Raman measurements are performed on low dimensional semiconductor structures such as Si, GaAs, AlGaAs, SnO2 and ZnO nanowires.
Another important goal of this work is to design and build a new experimental set-up in order to extend the spatial resolution to the nanometer range, exploiting near field optics in combination with scanning probe microscopy (Scanning Tunnelling Microscopy and Atomic Force Microscopy). This enables simultaneous measurements of topography and spectroscopy, thus permitting direct correlation of morphological and optical properties. Moreover the internal structure of nano-samples can be made accessible by optical spectroscopy. For this purpose an apertureless scanning near field optical microscope (a-SNOM) set-up was developed. Scanning Probe Microscopy (SPM) equipment was integrated into a confocal Raman spectroscopy apparatus and preliminary test measurements are performed.
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Anand, Aman Roberts James Andrew. "Studying interactions of gas molecules with nanomaterials loaded in a microwave resonant cavity". [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-4009.
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