This thesis reports on new solutions for sensing and controlling the electromagnetic radiation, and explores some novel effects of electrodynamics, using metamaterials. I have demonstrated the first superconducting metamaterial-based electro-optical modulator controlled by passing current through the network of meta-molecules. The meta- material, fabricated out of thin niobium film, modulated the sub-terahertz radiation through magnetic-field-induced suppression of superconductivity as well as through thermal effect. Transmission modulation up to 45% has been observed and main mechanisms of modulation have been studied. I have demonstrated a resonant radiation-harvesting bolometer for the sub-terahertz frequency range using a superconducting metamaterial fabricated out of thin niobium film. The strong electromagnetic interactions between the meta-molecules allowed harnessing of the radiation incident on the metamaterial and channeling it into a small radiation sensor, thus boosting the device sensitivity and selectivity. Bolometer sensitivity band-width of 1% has been achieved. I have suggested and experimentally demonstrated a new type of quantum metamaterial that engages the quantization of magnetic flux trapped in the meta-molecules. The metamaterial, fabricated out of high-temperature superconductor YBCO, has been designed to display nonlinear response associated with switching between the magnetic flux states. Although switching experiments have not been performed, a detailed characterization of the metamaterial, including the study of superconducting metamaterial structures that model different switching states, has been conducted. I have, for the first time, investigated highly nonlinear superconducting sub-terahertz metamaterial that exploits critical current and thermal nonlinearity. The metamaterial was fabricated out of thin niobium film with every meta-molecule containing wire segments of nanoscale thickness. The transmission change of up to 13% has been observed in response to ramping up the intensity of incident radiation to 8 W/m2. I have developed a novel analytical formalism that, for the first time, linked the reflection and the transmission of the metamaterial with the microscopic multipole excitations taking into account the electric, magnetic and toroidal multipoles of the constituent meta-molecules. A planar superconducting metamaterial with strong toroidal dipole response has been fabricated to test the formalism experimentally, and a very good agreement between the experiment and the analytical predictions has been observed. I have, for the first time, numerically and analytically studied the non-radiating configuration observed in the microwave experiment with the toroidal void metamaterial. It has been found that the non-radiating configuration is non-trivial and results from the destructive interference between the co-located electric and toroidal dipoles. Such non-radiating configurations shall allow designing high-Q metamaterial resonances and the generation of oscillating vector-potential for the study of the time-dependent Aharonov-Bohm effect.

Plasmon enhanced micromanipulation addresses some of the drawbacks associated with more traditional optical based methods, particularly in regard to the nature of laser excitation required for actuation. The resonant electromagnetic field enhancement observed as a result of the plasmon resonance phenomenon, enables trapping of nanoscale objects, and reduces the risk of photoinduced sample damage by reducing excitation power required for trapping. Plasmon resonance introduces an unavoidable heating effect which hinders stable trapping in microfluidic environments as a result of phenomena such as convection. In this work, the heating associated with plasmon resonance is used constructively, to devise a new micromanipulation technique. Plasmonic nanostructures are patterned on pyroelectric substrates which create an electric field in response to changes in temperature. This electric field results in the generation of local and global electrokinetic phenomena which are used in high throughput trapping of suspended particles. To demonstrate the versatility of this technique, particles are patterned into arbitrary shapes. A suggested application for this technique is as an optically controlled photoresist free lithographic method for use in microfluidic environments.

We use an accurate sp3V* tight-binding Hamiltonian to present a strong case to support the theory of a two-band anti-crossing model describing the electronic structure of GaNxAs1-x and InyGa1-yNxAs1-x alloys, in terms of the interaction between the conduction band edge and a higher-lying band of resonant nitrogen states. For the first time, we derive the functional dependence of the matrix elements of the two-band model and evaluate its parameters α, β and En. The model is shown to be accurate for band gap calculations up to a range of nitrogen composition, x of around 0.1 and is used to calculate other important properties of the alloy throughout this range. We explicitly identify and track the resonant state in GaNxAs1-x even to alloy compositions as large as x=0.25, where we find that the conduction band edge energy can be described analytically assuming independent resonant states up to x~0.03, but interactions between neighbouring resonances must be included for larger x. We find that the resonant state in InyGa1-yNxAs1-x alloys is strongly influenced by its local environment and show that a unique N state exists for each of the five different nearest neighbour configurations. We develop a simple yet accurate model that can describe the InyGa1-yNxAs1-x system with a very large number of randomly distributed N atoms by representing the resonant state for a given x and y as a linear combination of the five unique 'isolated' N states. We use the model to show how a statistical distribution of N states effects the resonant band spectrum and its variation with N and In composition; and show how variations in this distribution can lead to fluctuations in the energy gap and other calculated transition energies. In this we demonstrate the importance of N-N pair states. We carry out a detailed analysis to show how the various components of the defect Hamiltonian that describes the perturbation In a Ga32N1As31 system, affect the values of β and En, and show that in its complete form isoelectronic impurities other than nitrogen only give rise to a minor perturbation in the band structure of III-V compounds. We also find that for a Ga32N1As31 system, the resonant state can be given by an A1-symmetric combination of L and two-thirds Σ states weighted approximately two-to-one. This result also applies to most other A32N1B31 systems. Using this and a generalised form for the A1-symmetric defect Hamiltonian, we derive simple yet accurate expressions for β and En in terms of just two atomic properties and the energy of the L and two-thirds Σ points in the host compound. Finally, we extend the two-band anti-crossing model and derive a multi-band k.P Hamiltonian that describes the band structure of ordered GaNAs systems and of GaNAs with a statistical distribution of N states.

Cette thèse a trait au Contrôle Non Destructif par courants de Foucault. L'objet est de développer de nouvelles méthodes de calcul de la variation d'impédance d'une bobine émettrice placée au-dessus d'’une plaque conductrice contenant ou non des fissures. Les approches standards les plus robustes nécessitent le maillage par éléments finis volumiques, ce qui peut entraîner des coûts de calculs et de stockage élevés. Dans ces travaux, une géométrie idéalisée, donc simplifiée, est considérée permettant d’envisager une résolution du problème en choisissant de l'appréhender comme un problème de transmission sur l'’interface entre le conducteur et l'’air ambiant contenant la bobine. Dans le cas d'’un conducteur non fissuré, une méthode d'approximation de la variation d'impédance d'une bobine placée à la surface de la plaque est développée. Sa mise en œuvre nécessite uniquement l'’inversion de systèmes linéaires creux, diminuant ainsi le coût de calcul et de stockage. Dans le cas d'un conducteur contenant une fissure, la fissure est prise en compte à l'aide d'’une densité fictive de courant. Une fois le problème ainsi formulé, la difficulté revient au calcul de la charge fictive. Une méthode de calcul de la charge fictive de courant dans le cas de conducteurs ayant une conductivité élevée est proposée. Cette méthode s'appuie sur des développements asymptotiques pour des nombres d'onde grands / This thesis is about Non Destructive Testing by eddy currents. The goal is to develop new methods to compute the impedance variation of emitting coil placed over a conductive plate, possibly containing cracks. Standard methods require volume finite element meshes. This usually implies a computation cost and data storage high. In this thesis, we consider a solution to the problem by choosing to see is as a transmission problem on the interface between the conducting plate and the air containing the coil. When the conductor has no crack, we develop an approximate method to compute the impedance variation of a coil placed on the conductive plate. Applying this method only requires inverting sparse linear systems, this reduces the computation cost and the data storage requirements. If the plate containing a crack, the crack modeled as fictive current charge. After formulating the problem this way, the difficult part is to compute the fictive charge. We offer a method to compute it when the conducting plate has a high conductivity. It is based on asymptotic developments for high wave numbers

This work is on the characterisation of radiated fields from electronic devices. An equivalent dipole approach is used. Previous work showed that this was an effective approach for single layer printed circuit boards where an infinite ground plane can be assumed. In this work, this approach is extended for the characterisation of more complex circuit boards or electronic systems. For complex electronic radiators with finite ground planes, the main challenge is characterising field diffracting around the edges and boundaries. It is shown that this can be satisfactorily characterised using passive dipoles located along the edge. It is also shown that the number of dipoles used to characterise a device can be further optimised by using a complex location for the dipoles. Novel optimisation approaches such as particle swarm optimisation were also investigated. It is concluded that characterisation of complex electronic devices can be achieved in 3D space using edge dipoles to represent diffraction effects and available optimisation strategies.

This thesis describes investigations into the superconducting and magnetic properties of the rare earth nickel borocarbides, RNi2B2C. In chapter 1 the field of study is introduced and the basic properties of the materials described. Key theoretical concepts in superconductivity and properties of a vortex lattice are discussed in chapter 2. Chapter 3 describes how crystals are grown and characterised in the laboratory. The theoretical background and experimental techniques used in neutron scattering, the principal tool used in the experiments, are given in chapter 4. An investigation into the magnetic field distribution around vortices through the form factor ratio, F II/F \0, in the non-magnetic compounds Y - and LuNbB2C, is detailed in chapter 5. It is found that the current theoretical approaches do not provide a good description of this field distribution. Chapter 6 consists of an enquiry into the magnetic structures formed in ErNbB2C both with and without the application of a magnetic field. In zero field the development of a ferromagnetic component at low temperatures is analysed. The response to a magnetic field applied along three distinct crystallographic directions reveals more complicated behaviour than anticipated, including superlattice behaviour in the vicinity of the superconducting upper critical field for two of the orientations. Finally, a survey of the properties of the vortex lattice with applied field and temperature in ErNbB2C is presented in chapter 7. The 90° reorientation of the rhombic lattice at a critical field HI and the square-to-rhombic symmetry transition at H2 are investigated. The development of magnetic order is found to have a dramatic impact on the vortex lattice in this material. The principal results arising from this thesis are summarised in chapter 8.

The aim of this project is the conception, implementation, and application of a simulation tool for the accurate modeling of electromagnetic fields within inhomogeneous materials with complex shapes and the propagation of the resulting fields in the surrounding environment. There are many methods that can be used to model the scattering of an electromagnetic field, however one of the most promising for hybridisation is the Boundary Element Method (BEM), which is a surface technique, and the Unstructured Transmission Line Modeling (UTLM) method, which is a volume technique. The former allows accurate description of the scatterer's boundary and the field's radiation characteristics, but cannot model scattering by materials characterized by a non-uniform refraction index. The latter, on the contrary, can model a very broad range of materials, but is less accurate, since it has to rely on approximate absorbing boundary conditions. A method resulting in the hybridisation of BEM and UTLM can be used to construct a tool that takes into account both the interaction with non-uniform tissue and propagation in its environment. The project aims to describe in detail the implementation of the novel method, and deploy it in a heterogeneous distributed computing environment.

En el primer capítulo de ésta tesis, se les dará un resumen del transistor MOSFET y de las consecuencias del escalado de dispositivos electrónicos. También se explican las alternativas posibles para permitir mantener dicha tendencia, como la introducción de dieléctricos high-k y el potencial del grafeno para aplicaciones en nanoelectrónica. El segundo capítulo se dedica a describir con más detalle el AFM (Atomic Force Microscope), que se ha utilizado para investigar las propiedades eléctricas de los diferentes materiales en la nanoescala. En el tercer capítulo, diferentes condiciones de fabricación de dispositivos basados en capas de HfO2, tales como la temperatura de recocido (y polycrystallization), el espesor y el precursor con el que se crece dichas capas, serán investigadas en la nanoescala. La influencia de una tensión eléctrica a nivel del dispositivo también se estudió. En el capítulo 4, el impacto de las diferentes estreses eléctricos en las propiedades eléctricas de los MOSFETs basados en capas de SiON ultrafinas se investigó a escala manométrica. El uso de un CAFM, el óxido de puerta ha sido analizada después de una NBTI (Bias Temperature Instability) y CHC estrés (Canal portadores calientes). Puesto que con la punta CAFM áreas muy pequeñas pueden ser estudiados, se analizó la degradación inducida a diferentes regiones del óxido de puerta a lo largo del canal. Capítulo 5 describe la invención de un enfoque completamente nuevo para mejorar significativamente las propiedades mecánicas y eléctricas intrínsecas de puntas CAFM disponibles en el mercado por recubrimiento de las mismas con grafeno. Por último, en el capítulo 6, el uso de grafeno para aplicaciones en nanoelectrónica será investigado en la nanoescala. Un aspecto que se analizará es la presencia de ondulaciones, las arrugas y los límites de grano, que se muestran para aumentar la variabilidad de dispositivo a dispositivo. También se estudió el impacto del sustrato sobre el que se transfiere a grafeno. Dado que el grafeno se ha empezado a ser utilizado como electrodo superior en los dispositivos de memoria, en la segunda parte de este capítulo, la variabilidad y la fiabilidad de grafeno-aislante-semiconductor estructuras (GIS) basado en HfO2 serán previamente investigados. / In the first chapter of this thesis, the MOSFET transistor and an overview of the implications of ongoing device shrinking will be given. Possible alternatives to allow the scaling down such as the introduction of high-k dielectrics and the potential of graphene for nanoelectronic applications are also explained. The second chapter will be devoted to describe in more detail the AFM (Atomic Force Microscope), which has been used to investigate the electrical properties of different materials at the nanoscale. In the third chapter, different fabrication conditions of HfO2 layers based devices, such as the annealing temperature (and polycrystallization), the thickness and the precursor with which it was grown will be investigated at the nanoscale. The influence of an electrical stress at the device level is also studied. In chapter 4, the impact of different electrical stresses on the nanoscale electrical properties of ultra-thin SiON based MOSFETs is investigated. Using a CAFM, the gate oxide has been analyzed after a BTI (Bias Temperature Instability) and CHC (Channel Hot Carriers) stress. Since with the CAFM tip very small areas can be studied, the degradation induced at different regions of the gate oxide along the channel was analyzed. Chapter 5 describes the invention of a completely new approach to significantly improve the intrinsic mechanical and electrical properties of commercially available CAFM tips by coating them with graphene. Finally, in chapter 6, the usability of graphene for nanoelectronic applications will be investigated at the nanoscale. One aspect that will be analyzed is the presence of corrugations, wrinkles and grain boundaries, which are shown to increase the device-to-device variability. The impact of the substrate on which graphene is transferred to will be also studied. Since graphene has been recently started to be used as top electrode in memory devices, in the second part of this chapter, the variability and reliability of Graphene-Insulating-Semiconductor (GIS) structures based on HfO2 will be preliminarily investigated.

No description available.

Lori Faith Lamel. / Also issued as Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1988. / Includes bibliographical references. / Supported by the Defense Advanced Research Projects Agency, Vinton-Hayes, Bell Laboratories (GRPW), and Inference Corporation.