Rozprawy doktorskie na temat „Micro and nano electronics”

Thesis (Ph.D.) - University of Glasgow, 2004.
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This thesis describes experimental and numerical investigations of various electrokinetic techniques on fluorescent particles, bacteria and protein motors. The aim of this work is to extend the knowledge on the object manipulation, which is an essential part of a practical microfluidic device. The dissertation consists of three major sections that contain novel approaches to object manipulation using electric fields. The effect of dielectrophoretic force on fluorescent particles is analysed first. Using an experimental setup with a controlled switch for the input signal, the theoretical framework for amplitude modulated responce of dielectrophoretic force is developed. Also presented is the image processing software for quantitative particle motion analysis. Another analysis of various electrokinetic techniques (dielectrophoresis, AC electroosmosis, AC electrothermal flow and electrophoresis) was carried out on Pseudomonas Fluorescence bacteria in a solution that supports its growth. These bacteria usually live in geometrically restricted spaces and so spatially confined transparent channels were created to mimic their natural environment. It was noted that in these conditions the motile bacteria do not experience the effect of dielectrophoretic force. The minimum frequency that can be applied to the solution without forming bubbles is too high to distinguish AC electroosmotic effect. Using the numerical simulation, however, the experimental setup that utilises the observed effect of electrophoresis and AC electrothermal flow is designed. The final study was carried out on protein molecular motors. The novel experimental setup to investigate the effect of the electric field on the actin filament motility on five different surfaces, covered with myosin II motors, was developed. The application of higher external electric fields resulted in different velocity increases on different surfaces. Using the numerical simulation, this difference is quantitatively explained by the variation of the number of motors on surfaces. Also presented is a novel method that enables determining the forces exerted by the population of active and resistive motors without the need of expensive equipment.

Research in the field of conjugated polymers (CPs) has led to the emergence of a number of interesting research areas and commercial applications, including solar cells, flexible displays, printed electronics, biosensors, e-textiles and more. Some of the advantages of organic electronics materials, as compared to their inorganic counterparts, include high elasticity, and mechanical flexibility, which allows for a natural integration of CPs into fabrics, making them ideal for e-texile. In this thesis, a novel approach for creating transistors is presented, through the construction of electrolyte gated transistors, directly embedded on functional textile fibers. Furthermore theoretical and experimental results of the integration of functional woven devices based on these transistors are shown. The realization of woven digital logic and design schemes for devices that can be placed inside living tissue, for applications such as neural communication, are demonstrated. Reducing feature sizes in organic electronics is necessity just as in conventional microelectronics, where Moore's law has been the most impressive demonstration of this over the past decades. Here the scheme of self-assembly (SA) of biomolecular/CP hybrid nano-structures is used for creating nano electronics. It is demonstrated that proteins in the form of amyloid fibrils can be coated with the highly conducting polythiophene derivative (PEDOT-S) through molecular self-assembly in water, to form conducting nanowire networks and nanodevices at molecular dimensions. In a second SA scheme, large area patterning of connected micro-nano lines and nano transistors from the conducting polymer PEDOT-S is demonstrated through assembly of these from fluids using soft lithography. Thereby the problems of large area nano patterning, and nano registration are solved for organic electronics. The construction of functional nanoscopic materials and components through molecular self-assembly has the potential to deliver totally new concepts, and may eventually allow cheap mass production of complex three dimensional nano electronic materials and devices.

This Ph.D. thesis is intended to provide a contribution to understanding some aspects of doping by MD through systematic experimental work. In chapter 1, in order to better understand this work, the main aspects of semiconductor properties, the techniques commonly used for doping these materials and the MD are briefly recalled. In chapter 2 some aspects of MD are discussed. In particular a physico-chemical characterization of molecular precursors in standard conditions, the role of the surface treatments and the role of the dilution of the precursor solution was examined. In chapter 3, the results about the role of the deposition parameters in MD are discussed, focusing on the role of coating time and sampling time and on the role of the solvent and the molecular precursor. Chapter 4 examines the results obtained by studying the effects of the post-deposition treatments. The following aspects are discussed in detail: the role of the annealing parameters: Temperature and time, the competition between evaporation and diffusion and the role of the cap layer. In chapter 5 an example of application of MD to Si nanowires are investigated. Finally, the results of this work and the perspectives of this activity are discussed and possible experimental approaches for the study of some unclear aspects in this thesis work are proposed. These aspects were studied by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), transmission electronic microscopy (TEM) and Raman Spectroscopy, electrical measurements were performed by spreading resistance profiles (SRP).

The composition of the top-most molecular layers of solid materials is of great importance in the understanding of many technologically important processes. This is especially so, for example for devices exposed to the in vivo environment of our bodies especially if long term functionality is required. Cardiovascular stents or scaffolds are a biomedical implant that must maintain structural and functional integrity for periods of months to achieve their therapeutic goal. In this work, the fully polymeric drug-eluting bioresorbable scaffold, ArterioSorbTM is characterised, paying particular attention to surface and near surface properties. The introduction of cardiovascular stents has considerably enhanced the potential of surgical intervention via angioplasty. Biomaterials used for implants may be metallic, ceramic, polymeric or composite. A new generation of drug eluting stent are now emerging, such as the Poly(L-lactide) (PLLA) based fully biodegradable stents studied here, that have the potential to increase the therapeutic potential of this approach even further. PLLA is a bioabsorbable semi-crystalline polymer that possesses a low elongation and high tensile strength, which makes it appropriate for this medical application. Using a spray-coating method a sirolimus/PDLLA layer was coated onto the surface of a bioresorbable PLLA scaffold by Arterius Ltd. The aim of this thesis is the study of the drug distribution and physiochemical properties of the biomedical device and to relate this information to likely drug release mechanisms under physiological conditions. Complementary surface and near-surface analysis techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS) and confocal Raman imaging (CRM) have been used to assess structure, composition and their relation to drug release. Primarily, this work was carried out on a series of extruded and orientated (die-drawn) PLLA tubing before considering the actual bioresorbable medical device (uncoated, coated expanded and crimped scaffolds). ToF-SIMS has been used to confirm the chemical homogeneity of the PLLA coating and provide evidence of some minor surface elemental contamination likely due to transfer of fluorine from packaging/sample handling. The drug (sirolimus) was clearly observed and mapped at the microscale at the surface and in the bulk of the scaffold coating. In addition, the physical properties of these materials were investigated using nano and micro thermal analysis. The percentage of crystallinity of the PLLA materials was studied using Differential Scanning Calorimetry (DSC). Attenuated total reflection infrared (ATR-IR) helped in assessing the structure of PLLA. Factors including the manufacturing process used have been shown to have an effect on the materials. The degradation in vitro has been shown to be influenced by the molecular weight of the polymer and the concentration of the drug. This thesis is organised into six chapters. Chapter 1 provides an introduction to the technical requirements needed for bioresorbable stent and outlines the literature review and research context for the development of the scaffold, including materials used for the manufacturing of the scaffold, spray coating method and laser cutting techniques. Chapter 2 describes the instrumentation and methodology used for characterising such medical device as well as a description of laser cutting used in manufacture. Chapter 3 presents a feasibility study on the extruded and oriented tubing. Chapter 4 describes the characterisation of the drug distribution in the drug/polymer matrix. Chapter 5 provides a detailed characterisation of the in vitro degradation of sirolimus/PDLLA coating layer revealing the release kinetics of the device. Finally, Chapter 6 gathers information learnt throughout this thesis and explored future directions to improve release and performance of such a device.

In this thesis we have reported novel developments in the field of femtosecond laser micro-machining within the bulk of transparent materials. Thanks to its unique properties, the femtosecond laser writing technique offers the potential for realizing three-dimensional multi-component photonic devices, fabricated in a single step and in a variety of transparent materials. When we began to research in this field, there had been no studies conducted on the ability of femtosecond lasers to fabricate diffractive optical components in the bulk of a dielectric material. These are necessary components for the realization of monolithic optical devices. Our work led to the first demonstration of femtosecond directly written diffractive optic devices (Fresnel zone plates) embedded in a silica substrate. Both the focusing properties and efficiencies of the devices compared well with the theoretical values.

This thesis outlines the development of two new techniques that exploit very small structures, on the micro- and nano-scale, to enable innovative electrical transport measurements on a variety of materials of current interest in condensed matter physics. The first technique aims to apply the versatility of electron-beam lithography for micro-fabrication of patterned electronic circuitry to the problem of performing transport experiments on individual crystallites taken from a typical powder sample. We show that these small samples, tens of microns in size, are actually often very high quality single crystals and can be exploited for measurements of electrical transport in materials of which no larger crystals are available. By way of demonstration, we present the results of preliminary transport measurements on a crystallite of the layered oxide chalcogenide Sr₂MnO₂Cu_1.5Se₂. We report a phase transition in the resistivity at 213K which may correspond to the onset of previously reported short-range order in copper and vacancy sites in the Cu_1.5Se₂ planes. The second technique is designed to investigate the topological protection of surface transport in 3-D topological insulators. We decorate the surfaces of single-crystal samples with two different species from a well-characterised family of single-molecule magnets. The two coatings have an electrostatically identical influence on the sample surface, but differ in that one species carries a spin and the other is spinless. The spinless molecule acts as a control, to allow us to cleanly determine the influence of the magnetic component of a scattering potential on transport in the surface. With this technique we investigate proposed topological Kondo insulator SmB₆. We find that the surface state dominates low-temperature transport and demonstrate that the momentum relaxation is very sensitive to a spin degree of freedom in the scatterer, in keeping with expectations of a topological insulator.

This thesis aims at providing a better understanding of the micro- and nanofabrication of conducting polymers for biomedical devices and presents novel processes that widen the application range of conducting polymers in this field. The thesis is divided in four chapters, namely “Materials and Methods”, “Biocatalytically-produced polypyrrole thin films and microelectrodes on insulating surfaces”, “Azide-PEDOT electrodes. Application to DNA sensors” and “Fabrication of polypyrrole single nanowire devices”. Chapter 1, entitled “Materials and Methods”, describes the materials used in this work and the fabrication and characterization methods required for the development of the thesis. Here, theoretical and experimental details about the techniques employed, are provided. Chapter 2, entitled “Biocatalytically-produced polypyrrole thin films and microelectrodes on insulating surfaces”, presents a new on-surface biocatalytical procedure for the fabrication of polypyrrole microelectrodes on insulating surfaces, with resolutions comparable to the ones of conventional photolitography. This is an environmentally respectful microfabrication method that allows the entrapment of biomolecules during the polymer synthesis in a single step. As a proof of concept, biotin was trapped in the polypyrrole matrix and then released in a controlled way through electrical stimulation. It was proven that the polymer keeps its electroactivity after the fabrication and functionalization processes. This biocatalytical-based technique represents a straightforward method for the microfabrication of biological-active conducting polymers, which could be implemented in implantable devices for remotely controlled tissue interactions. Chapter 3, entitled “Azide-PEDOT electrodes. Application to DNA sensors”, describes the fabrication and testing of an electrochemical label-free DNA hybridization sensor, based on novel azidomethyl-modified poly(3,4-ethylenedioxythiophene) electrodes (azide-PEDOT electrodes). These azide-PEDOT electrodes were used as platforms for the immobilization of acetylene-DNA probes, complementary to the “Hepatitis C” virus. The acetylene-DNA probes were covalently grafted to the polymer backbone via the robust “Click” reaction, which a part from being a very selective functionalization method, preserves DNA from denaturation during the synthesis of the polymer. DNA hybridization was detected by Differential Pulse Voltammetry (DPV), where the electrochemical change of the polymer behaviour, produced by the recognition event, was directly evaluated. This fabrication procedure is a powerful tool for the preparation of label-free DNA sensors able to selectively recognize a specific DNA sequence, down to the nanomolar range. Finally, Chapter 4, entitled “Fabrication of polypyrrole single nanowire devices”, discusses the fabrication of polypyrrole at the nanoscale. Two fabrication techniques were investigated here, namely dip pen nanolithography and electrochemical polymerization on template-assisted surfaces. On one hand, the dip pen nanolithography proved to be a simple deposition technique with good control over size and location of the polypyrrole nanowires. On the other hand, the electrochemical polymerization on template-assisted surfaces provided as well nanoscaled polypyrrole, but added the possibility to chemically manipulate the polymer. This chemical manipulation was translated into polymer devices with different electrical properties. By the use of these techniques, the capability of fabricating single nanowire devices (ready to use in different applications) and arrays of ordered nanowires based on conducting polymers is demonstrated. Additionally, two appendixes can be found at the end of the thesis: Appendix A: “Fabrication of azide-PEDOT microwire-based devices” and Appendix B: “Fabrication of nanopatterns by electron-sensitive silanes”. They provide short experimental results obtained during the course of this work, which are first steps for future investigations. A general conclusions section can be found at the end of the thesis, where a summary of the main achievements and contributions of this thesis are listed.
Aunque los polímeros conductores se presentan como una alternativa viable a los materiales convencionalmente usados en aplicaciones biomédicas, las técnicas de fabricación adaptadas a ellos y el aprovechamiento de sus propiedades están lejos de ser completos. Existen importantes limitaciones en la fabricación de micro y nano estructuras basadas en polímeros conductores. Debido a la agresividad de las técnicas tradicionalmente usadas en microelectrónica, se hace necesaria la búsqueda de nuevas estrategias de fabricación adaptadas a polímeros conductores, así como de nuevos procesos que puedan mejorar el rendimiento de los dispositivos diseñados. En esta tesis titulada “Conducting polymers micro and nano electrodes. Application to biomolecule sensing and release”, se han investigado nuevas técnicas de fabricación y de funcionalización de polímeros conductores, poniendo un especial interés en su aplicación biomédica. Una nueva técnica de fabricación de microestructuras de polipirrol por método biocatalítico sobre superficies aislantes ha sido desarrollada con resoluciones comparables a las de la litografía óptica. Dicha técnica es compatible con la incorporación de biomoléculas durante el proceso de síntesis, lo que garantiza su utilización en entornos biológicos. Esto fue demostrado mediante la incorporación de biotina durante el proceso de polimerización y su posterior liberación, mediante estimulo eléctrico. También se ha desarrollado un nuevo sensor de ADN sin marcaje basado en electrodos de azida-PEDOT, para la detección de secuencias basadas en la “Hepatitis C”. Estos electrodos, permiten la directa y covalente funcionalización con secuencias de ADN, modificadas con grupos acetileno, por medio de la química “Click”. La hibridación fue detectada mediante la evaluación de la electroactividad del polímero tras el suceso de reconocimiento. Esta novedosa modalidad de sensores demostró ser selectiva y sensible, siendo capaz de detectar secuencias complementarias en el rango nM, sin necesidad de marcajes, ni complejas técnicas de microfabricación. Finalmente, se estudiaron dos técnicas de fabricación de nanohilos de polímero conductor: nanolitografía de dip-pen y electropolimerización sobre superficies con plantillas. Estos estudios proveen al incompleto campo de la fabricación de nanoestructuras de polímeros conductores de resultados adicionales, que amplían el campo de aplicación de dichos materiales.

Ce travail porte sur l’automatisation du traitement des données de tomographie électronique analytique appliquée aux nano-dispositifs électroniques. La technique utilisée est la spectroscopie de dispersion en énergie des rayons-X en mode balayage en microscopie électronique en transmission (STEM-EDX : Scanning Transmission Electron Microscopy, Energy Dispersive X-ray spectroscopy). Si la tomographie électronique STEM-EDX a bénéficié d’avancées technologiques récentes, comme de nouvelles sources électroniques ‘X’-FEG (Field Emission Gun) et des détecteurs X sensibles, les SDD (Silicon Drift Detectors), elle reste chronophage avec une statistique de comptage souvent faible pour éviter des durées prohibitives et une dégradation de l’échantillon par irradiation électronique. L’empilement des projections STEM-EDX, acquises sous différents angles d’inclinaison, est par ailleurs très volumineux et les logiciels commerciaux actuels ne peuvent pas le traiter automatiquement et de manière optimale. Pour améliorer cette situation, nous avons développé un programme utilisant la librairie Hyperspy en langage python, dédiée au traitement de données multi-dimensionnelles. L’analyse statistique multivariée permet d’optimiser et d’automatiser le débruitage des données, la calibration des spectres et la séparation des raies d’émission X superposées pour l’obtention de reconstructions tridimensionnelles quantitatives. Une technique de reconstruction avancée, l’acquisition comprimée, a aussi été mise en œuvre, diminuant le nombre de projections sans réduire l’information 3D finale. La méthode développée a été utilisée pour l’analyse chimique 3D de quatre nanostructures issues de la microélectronique : des transistors FET multi-grilles, HEMT et GAA, et un film mince GeTe. Les échantillons ont été taillés en pointe par FIB (Focused Ion Beam: Faisceau d’ions focalisés), et les données obtenues sur un microscope Titan Themis muni d’un système à 4 détecteurs SDD. L’évaluation du programme atteste qu’il permet d’obtenir des résultats précis et fiables sur les architectures 3D étudiées. Des pistes d’améliorations sont discutées en perspective d’un futur logiciel dédié au traitement de données en tomographie électronique analytique
The aim of this thesis is to automate the process of hyperspectral analysis for analytical electron tomography applied to nanodevices. The work presented here is focused on datasets obtained by energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope (STEM-EDX). STEM-EDX tomography has benefited greatly from recent developments in electron sources such as the ‘X’-FEG (Field Emission Gun), and multiple X-ray detector systems such as the Super-X, incorporating four SSD (Silicon Drift Detectors) detectors. The technique remains however very time-consuming, and low X-ray count rates are necessary to minimize the total acquisition time and avoid beam damage during the experiment. In addition, tomographic stacks of STEM-EDX datacubes, acquired at different tilt angles, are too large to be analyzed by commercial software packages in an optimal way. In order to automate this process, we developed a code based on Hyperspy, a Python library for multidimensional data analysis. Multivariate statistical analysis techniques were employed to optimize and automate the denoising, the energy calibration and the separation of overlapping X-ray lines, with the aim to achieve quantitative, chemically sensitive volumes. Moreover, a compressed sensing based algorithm was employed to achieve high fidelity reconstructions with undersampled tomographic datasets. The code developed during this thesis was used for the 3D chemical analysis of four microelectronic nanostructures: FinFET, HEMT and GAA transistors, and a GeTe thin film for memory device applications. The samples were prepared in a needle shape using a focused ion beam, and the data acquisitions were performed using a Titan Themis microscope equipped with a super-X EDX detector system. It is shown that the code yields 3D morphological and chemical information with high accuracy and fidelity. Ways to improve the current methodology are discussed, with future efforts aiming at developing a package dedicated to analytical electron tomography

Les convertisseurs de puissance occupent une place importante dans l'ingénierie des systèmes électriques. Les puissances nominales augmentent et les convertisseurs statiques doivent répondre à ces besoins notamment en termes de compacité. Cette amélioration s'explique notamment par l'utilisation de dispositifs semi-conducteurs à large bande interdite (WBG) à base de carbure de silicium (SiC) et de nitrure de gallium (GaN) qui autorisent des fréquences de découpage et une température de fonctionnement nettement plus élevées. Cependant, les temps de commutation plus courts qui en découlent ne sont exploitables que si les éléments parasites du boîtier sont réduits au minimum afin de profiter pleinement de ces nouveaux composants.Les éléments parasites, inductances en particulier, sont source de pertes qui réduisent l'efficacité et la fiabilité du convertisseur, et ce en générant du bruit par IEM (Interférences électromagnétiques). Les améliorations à apporter sont fondamentalement difficiles à obtenir avec les boîtiers d'aujourd'hui utilisant la technologie de câblage filaire comme interconnexion des composants actifs. Dans certaines applications, les dispositifs WBG peuvent fonctionner à des températures plus élevées que les composants en silicium (Si). La température maximale de jonction (Tj) des composants en SiC peut être supérieure à 200°C, alors que celle des interrupteurs en Si est d'environ 125°C. Les assemblages doivent pouvoir supporter des températures plus élevées et résister aux régimes transitoires de température qui en découlent. La technologie des PCB a l'avantage d'être un processus peu coûteux et bien maitrisé offrant la possibilité de produire des dispositifs à grande échelle, d'utiliser un pas fin, du cuivre épais pour le transport de la chaleur et du courant, des structures multicouches répétables, etc. L'intégration de puces de puissance dans les PCB a récemment suscité un grand intérêt. Plusieurs types d'interconnexion ont été proposés, sachant que l'un des plus grands avantages de la technologie d'enfouissement PCB des interrupteurs de puissance est la réduction des inductances parasites à un niveau proche du minimum théorique. La tendance est d'interconnecter les composants par micro-vias laser. Cependant, la conductivité thermique du diélectrique utilisé est inférieure à 1 W.m-1.K-1 pour le matériau polyimide, tel que le kapton, contre 170 W.m-1.K-1 pour le nitrure d'aluminium (AlN) des substrats céramique (DBC). À cela s'ajoutent des limites en termes de densité imposée par le procédé de fabrication, ce qui entraîne des limitations de courant et de flux thermique. Les commutations des composants actifs du convertisseur sont une source de variations de température du système. Un gradient de température est présent le long des interconnexions qui, combiné aux différents coefficients de dilatation thermique de chaque matériau, peut conduire à la fissure de l'interface micro- vias/puce et donc à la défaillance dans le temps. Ces mises en défaut des interconnexions attribuées aux contraintes cycliques appliquées affectent fortement la fiabilité du convertisseur. La solution proposée et développée au cours de ces travaux combine des technologies avancées des circuits imprimés et une solution d'interconnexion innovante " non rigide ", basée sur le dépôt électrolytique d'interfaces macro et nano structurées, suivi d'une thermocompression. L'ensemble peut ainsi constituer un bloc élémentaire pour la conception de convertisseurs de puissance avec un haut niveau d'intégration et de fiabilité grâce à une interconnexion entièrement en cuivre, espérée flexible, permettant un refroidissement double face. Les nano-fils utilisés comme interface thermique et électrique de la puce sont également espérés résistants aux contraintes cycliques
The power converters hold a central position in electrical engineering. The power ratings are increasing and the converters have to meet these needs in compact systems. For example, the current power density of commercialized power converters of 2 kW for photovoltaic application is around 1 kW.l-1, whereas in the "Little Box Challenge" organized by Google and IEEE reached 12 kW.l-1. This improvement is mainly explained by using wide band-gap (WBG) semiconductor devices based on silicon carbide (SiC) and gallium nitride (GaN) materials that permit significantly higher switching frequencies. However, the associated shorter switching times are only possible when all stray elements in the package are minimized in order to take all the benefit of these new components. The parasitic elements, and the package stray inductances in particular, are source of losses which reduce the efficiency and also cause less reliable operation and EMI noise. This is fundamentally difficult to achieve with the popular packages using wire-bonded interconnections. In some application, the WBG devices are expected to be able to work at higher temperature than silicon (Si) components. The junction temperature (Tj) of SiC components can be higher than 200°C in comparison of Si switches around 125°C. The package must endure high temperature and resist the ensuing large temperature transitions as well. The PCB technology has the advantage of being a cost efficient and well-established process. There is a possibility of massive parallel manufacturing, fine pitch, thick copper for heat and current transport, repeatable multilayer structures, etc. The embedding of power dies in PCB recently has solicited great interest. There are several kinds of proposed interconnections. The greatest advantage of the technology for power device packaging is the strip-line approach of distributing current, bringing down the stray inductance close to the theoretical minimum. The trend in PCB-embedding technology is to interconnect the components by using laser micro-vias. The thermal conductivity of the PCB core is less than 1 W.m-1.K-1 for the polyimide material such a kapton against 170 W.m-1.K-1 for aluminum nitride (AlN) for direct bonded copper (DBC) substrate. The micro-via approach suffers from the manufacturing limits imposed on their density, resulting in current and heat flux limitations. This variation of the conveyed power through the converter is a source of temperature variations in the power assembly. Temperature gradient is present along the interconnections which, combined with different thermal expansion coefficient of each material, leads to crack at micro-via/die interface and delaminates over time. These interconnection defects are affecting strongly the reliability of the converter, attributed to the applied cyclical stresses. The proposed solution combines advanced PCB technologies and " not rigid " innovative interconnection, based on electrolytic deposition of macro and nano structured interfaces, followed by thermo-compression. The assembly may thus be an elementary block for the design of power converters with high level of integration and reliability by means of a full copper and flexible interconnection allowing double-sided cooling. It is expected that the nano wires used as thermal and electrical die interface will be also more resistant to cyclical stresses

Cette thèse présente la conception et le développement d'un imageur CMOS pour bio-capteurs optiques basé sur la résonance plasmonique de surface ou SPR (de l'anglais Surface Plasmon Resonance). Premièrement, les conditions optimales pour la résonance de plasmon dans une interface compatible avec un processus CMOS/Post-CMOS sont obtenus par modélisation avec le logiciel COMSOL. Deuxièmement, un imageur CMOS à Colonne Active de 32x32 pixels est réalisé en technologie CMOS 0,35 m. Dans une interface or-eau avec excitation du prisme et une longueur d'onde de 633 nm, on constate que pour des prismes avec des indices de réfraction de 1,55 et 1,46, le couplage SPR optimal se produit à des angles d'incidence de 68,45◦ et 79,05◦ avec les épaisseurs des couches d'or de 50 nm et 45 nm respectivement. Dans ces conditions, environ 99,19% et 99,99% de l' ́energie de la lumière incidente sera transférée au plasmon de surface. Nous montrons aussi qu'un changement de 10−4 RIU dans l'indice de réfraction du milieu diélectrique, produit un changement de 0,01◦ dans l'angle de résonance de plasmonique, pour un schéma de modulation d'intensité lumineuse ce changement correspond à une variation de 0,08% dans l'énergie de la lumière réfléchie vue par le photodétecteur. Pour l'imageur CMOS conu, une photodiode caisson-N/subtrat-P est choisie en raison de sa faible capacit ́e de jonction, qui se traduit par un rendement quantique élevé et un gain de conversion élevé. Les simulations sur ordinateur avec Cadence et Silvaco donnent une capacité de jonction de 31 fF et un rendement quantique maximum de 82%. Le pixel de l'imageur est basé sur une configuration à trois transistors (3T) et a un facteur de remplissage de 61%. Le circuit de lecture utilise une technique de Colonne Active (ACS) pour réduire le bruit spatial (FPN) associés aux capteurs à pixels actifs traditionnels (APS). En outre pour compléter la réduction du bruit, un Double Echantillonnage Non-Corrélé (NCDS) et un Double Echantillonnage Delta (DDS) sont utilisés. Un montage optique expérimental est utilisé pour caractériser les performances de l'imageur, les résultats obtenus sont un gain de conversion de 7.3 V/e-, une photodiode avec une capacité de jonction de 21.9 fF, un bruit de lecture de 324,5 μV, ́equivalant approximativement à 45 lectrons, et une gamme dynamique de 62,2 dB. Les avantages de l'ACS et NCDS-DDS sont observés dans les bas niveaux de FPN de pixel et colonne de 0,09% et 0,06% respectivement. Le travail présenté dans cette thèse est une première étape vers le but de d ́evelopper une plateforme de biocapteur entièrement intégrée basée sur SPR, incorporant la source de lumière, l'interface SPR, le canal microfluidique, les éléments optiques et l'imageur CMOS.

Cette thèse de doctorat porte sur le développement d'un banc de mesure pour la caractérisation thermique de la matière. Les techniques et instruments employés pour la mesure des propriétés thermo-physiques sont nombreux, évoluent constamment. Ils sont aujourd'hui encore le centre d'attention de multiples recherches. Ils sont néanmoins bien souvent adaptés préférentiellement à un état de la matière et à la mesure spéci fique d'un paramètre thermique. Le banc développé repose sur la méthode dite 3!, qui consiste à observer la réponse thermique fréquentielle d'un matériau soumis à un flux thermique harmonique. Cette technique met à pro t l'e et thermo-résistif qui accomplit la transduction du domaine thermique vers le domaine électrique. Elle permet alors de mesurer simplement les variations de température en fonction de la fréquence d'excitation donnant ainsi accès aux propriétés thermo-physiques du milieu étudié. Nous montrons que la méthode 3w permet eff ectivement d'une part de mesurer e fficacement la conductivité thermique, mais également d'estimer la capacité thermique isobare. De plus, alors qu'elle a été initialement introduite pour la caractérisation des solides, nous élargissons le champ d'application de cette technique, via un dispositif expérimental adapté, pour l'étendre aux autres états de la matière, à savoir les liquides et aux gaz. Le capteur proposé est fabriqué à l'aide des techniques de la micro-électronique et basé sur la technologie du silicium, ce qui permet de réduire fortement ses dimensions et o re des perspectives intéressantes en termes de miniaturisation et d'intégration

Three-dimensional (3D) integration of micro- and nano-electromechanical systems (MEMS/NEMS) with integrated circuits (ICs) is an emerging technology that offers great advantages over conventional state-of-the-art microelectronics. MEMS and NEMS are most commonly employed as sensor and actuator components that enable a vast array of functionalities typically not attainable by conventional ICs. 3D integration of NEMS and ICs also contributes to more compact device footprints, improves device performance, and lowers the power consumption. Therefore, 3D integration of NEMS and ICs has been proposed as a promising solution to the end of Moore’s law, i.e. the slowing advancement of complementary metal-oxide-semiconductor (CMOS) technology.In this Ph.D. thesis, I propose a comprehensive fabrication methodology for heterogeneous 3D integration of NEM devices directly on top of CMOS circuits. In heterogeneous integration, the NEMS and CMOS components are fully or partially fabricated on separate substrates and subsequently merged into one. This enables process flexibility for the NEMS components while maintaining full compatibility with standard CMOS fabrication. The first part of this thesis presents an adhesive wafer bonding method using ultra-thin intermediate bonding layers which is utilized for merging the NEMS components with the CMOS substrate. In the second part, a novel NEM switch concept is introduced and the performance of CMOS-integrated NEM switch circuits for logic and computation applications is discussed. The third part examines two different packaging approaches for integrated MEMS and NEMS devices with either hermetic vacuum cavities or low-cost glass lids for optical applications. Finally, a novel fabrication approach for through silicon vias (TSVs) by magnetic assembly is presented, which is used to establish an electrical connection from the packaged devices to the outside world.
Tredimensionell (3D) integration av mikro- och nano-elektromekaniska system (MEMS/NEMS) med integrerade kretsar (ICs) är en ny teknik som erbjuder stora fördelar jämfört med konventionell mikroelektronik. MEMS och NEMS används oftast som sensorer och aktuatorer då de möjliggör många funktioner som inte kan uppnås med vanliga ICs.3D-integration av NEMS och ICs bidrar även till mindre dimensioner, ökade prestanda och mindre energiförbrukning av elektriska komponenter. Den nuvarande tekniken för complementary metal-oxide-semicondictor (CMOS) närmar sig de fundamentala gränserna vilket drastiskt begränsar utvecklingsmöjligheten för mikroelektronik och medför slutet på Moores lag. Därför har 3D-integration identifierats som en lovande teknik för att kunna driva vidare utvecklingen för framtidens elektriska komponenter.I denna avhandling framläggs en omfattande fabrikationsmetodik för heterogen 3D-integration av NEMS ovanpå CMOS-kretsar. Heterogen integration betyder att både NEMS- och CMOS-komponenter byggs på separata substrat för att sedan förenas på ett enda substrat. Denna teknik tillåter full processfrihet för tillverkning av NEMS-komponenter och garanterar kompatibilitet med standardiserade CMOS-fabrikationsprocesser.I den första delen av avhandlingen beskrivs en metod för att sammanfoga två halvledarskivor med en extremt tunn adhesiv polymer. Denna metod demonstreras för 3D-integration av NEMS- och CMOS-komponenter. Den andra delen introducerar ett nytt koncept för NEM-switchar och dess användning i NEM-switch-baserade mikrodatorchip. Den tredje delen presenterar två olika inkapslingsmetoder för MEMS och NEMS. Den ena metoden fokuserar på hermetisk vakuuminkapsling medan den andra metoden beskriver en lågkostnadsstrategi för inkapsling av optiska komponenter. Slutligen i den fjärde delen presenteras en ny fabrikationsteknik för så kallade ”through silicon vias” (TSVs) baserad på magnetisk självmontering av nickeltråd på mikrometerskala.

20170519

Due to an increasing attention to environment preservation and the need to accomplish new regulations, a general interest to improve the recyclability of composite materials has recently emerged. In order to fulfill this new requirements, a possible strategy could be represented by the development of so-called "single polymer composites" (SPCs), i.e. composite materials in which both matrix and reinforcement have the same chemical composition. The main advantage of SPCs is that, unlike traditional heterogeneous composites (such as glass- or carbon reinforced polymer composites), they can be entirely melted down at the end of the product life for recycling. After an optimization of the annealing treatment to improve the mechanical properties and thermal stability of the reinforcing phase, SPCs containing Vectran® micro- and nano- fibers as a reinforcement were prepared, and their thermo-mechanical properties and recyclability were investigated using a multidisciplinary approach. Single polymer micro composites (SPMCs) containing up to 30 wt% of reinforcing microfibers showed a outstanding improvement of tensile modulus (up to 160 %) compared with the unfilled matrix. FESEM observations evidenced some pull-out phenomena, indicating a poor interfacial adhesion. After a surface treatment on the reinforcement, a composite containing up to 20 wt% showed a remarkable improvement of almost 180% in the tensile modulus compared with the unfilled matrix. FTIR and thermal analysis evidenced its recyclability. Single polymer nano composites (SPNCs) containing up to 10 vol% of reinforcing nanofibers showed an increase by almost 20% of their tensile modulus and strength in comparison with the unfilled matrix. Optical observations revealed a consolidation problem in the unfilled matrix due to the adapted film-stacking process used. However, the addition of the nanofibers in the composite eliminated the problem. Thermal analysis was used to ensure the SPNCs recyclability. Vectran® single polymer micro- and nano- composites have been proven to be possible candidates to substitute traditional heterogeneous composites materials, with enhanced recyclability features.

L'information est devenue le bien le plus précieux au monde. Ce mouvement vers la nouvelle ère de l'information a été propulsé par la capacité à transmettre l'information plus rapidement, à la vitesse de la lumière. Il est donc apparu nécessaire de mener des recherches plus poussées pour contrôler plus efficacement les supports d'information. Avec les progrès réalisés dans ce secteur, la plupart des technologies actuelles de contrôle de la lumière se heurtent à certains obstacles tels que la taille et la consommation d'énergie et sont conçues pour être passives ou sont limitées technologiquement pour être moins actives (technologie Si-back). Même si rien ne voyage plus vite que la lumière, la vitesse réelle à laquelle les informations peuvent être transportées par la lumière est la vitesse à laquelle nous pouvons la moduler ou la contrôler. Ma tâche dans cette thèse visait à étudier le potentiel du VO2, un matériau à changement de phase, pour la nano-photonique, avec un accent particulier sur la façon de contourner les inconvénients du matériau et de concevoir et démontrer des dispositifs intégrés efficaces pour une manipulation efficace de la lumière à la fois dans les télécommunications et le spectre visible. En outre, nous démontrons expérimentalement que les résonances multipolaires supportées par les nanocristaux de VO2 (NC) peuvent être réglées et commutées dynamiquement en exploitant la propriété de changement de phase du VO2. Et ainsi atteindre l'objectif d'adaptation de la propriété intrinsèque basée sur le formalisme de Mie en réduisant les dimensions des structures de VO2 comparables à la longueur d'onde de fonctionnement, créant un champ d'application pour un métamatériau accordable défini par l'utilisateur
Information has become the most valuable commodity in the world. This drive to the new information age has been propelled by the ability to transmit information faster, at the speed of light. This erupted the need for finer researches on controlling the information carriers more efficiently. With the advancement in this sector, majority of the current technology for controlling the light, face certain roadblocks like size, power consumption and are built to be passive or are restrained technologically to be less active (Si- backed technology). Even though nothing travels faster than light, the real speed at which information can be carried by light is the speed at which we can modulate or control it. My task in this thesis aimed at investigating the potential of VO2, a phase change material, for nano-photonics, with a specific emphasis on how to circumvent the drawbacks of the material and to design and demonstrate efficient integrated devices for efficient manipulation of light both in telecommunication and visible spectrum. In addition to that we experimentally demonstrate the multipolar resonances supported by VO2 nanocrystals (NCs) can be dynamically tuned and switched leveraging phase change property of VO2. And thus achieving the target tailoring of intrinsic property based on Mie formalism by reducing the dimensions of VO2 structures comparable to the wavelength of operation, creating a scope for user defined tunable metamaterial

Single-molecule electronics have attracted widespread attention for both basic scientific interests and potential in technological applications. However, development has been limited by the difficulty in fabricating robust nano-electrodes suitable for contacting individual molecules. Carbon based materials have recently emerged as alternative electrode materials and possess several distinct advantages over conventional gold based electrodes. This DPhil project is undertaken with the goal of developing graphene nano-electrodes and the subsequent fabrication and characterisation of graphene based single-molecule devices. By combining the best of two prevalent approaches for fabricating graphene nano-gaps: feedback controlled electroburning and plasma etching, it is possible to produce graphene nano-gap with sizes 1-2 nm. The fabrication procedure is performed at room temperature and in ambient conditions with a high yield. Furthermore, arrays can be produced which makes the technique suitable for integration with conventional semiconductor technologies for scalable applications. The graphene nano-electrodes are used to fabricate single-molecule transistors using porphyrin molecules. Due to the stability of the graphene nano-electrodes, the porphyrin single-molecule transistors show reproducible single-electron charging behaviour even at room temperature. High bias and gate transport spectroscopy can be performed where the excited energy spectrum of the molecule is measured. Graphene-fullerene single-molecule transistors are studied. We observe electron avalanche transport and redox-dependent Franck-Condon blockade as a result of the strong electron-vibron coupling and weak vibronic relaxation of the system. The vibrational modes of the molecule are found to be due to both intrinsic vibrational and center-of-mass motion as verified by transport spectroscopy, Raman spectroscopy and DFT calculations. The current stability diagram of our device compares well with a rate equation model from which we extract the electron-vibron coupling constant.

Le champ d'application des microsystèmes n'a cessé de s'élargir pendant les quinze dernières années en particulier vers la communication ou vers les biotechnologies. Pour augmenter les fonctionnalités des microsystèmes, l'utilisation de nano-objets semble devenir une voie incontournable, mais qui butte souvent sur des problèmes mes de manipulation spatiale visant à les intégrer dans une architecture fonctionnelle. Pour résoudre ces problèmes d'intégration, l'utilisation de phénomènes d'assemblage dirigé, c'est à dire des phénomènes physiques permettant de manipuler collectivement des nano-objets semble très prometteuse. Dans ce contexte, l'objectif de notre thèse a été de concevoir des outils fluidiques innovants capables de réaliser des opérations de manipulation spatiale ou conformationnelle de nano-objets ou de molécules. Il s'agit d'une recherche pluridisciplinaire à la frontière entre la micro- et nano-fabrication, la micro- et nano-fluidique, la biologie moléculaire, l'imagerie de molécules individuelles, et la biophysique. La thèse est composée de deux projets assez indépendants : une étude de nanofluidique pour le contrôle conformationnel de chromosomes issus de cellules vivantes, et un travail de microfluidique sur un phénomène d'assemblage spontané sur gel hydrophile. Dans un premier temps, nous décrivons un procédé de fabrication d'hydrogels structurés, et nous montrons que ces hydrogels constituent un support efficace pour organiser spatialement des nano-objets. Ce phénomène d'organisation est spontané, et il se produit lors du séchage du liquide. Nous avons donc voulu comprendre les mécanismes fluidiques ayant lieu au cours du séchage en utilisant des traceurs fluorescents. Nous identifions plusieurs phénomènes expliquant les phénomènes d'organisation spatiale de particules, et nous proposons des applications pour ce procédé innovant. Grâce aux dispositifs nanofluidiques que nous avons fabriqués, nous menons des expériences de manipula tion de molécules d'ADN individuelles en milieu confiné. Nous analysons le comportement de l'ADN - son élongation, sa mobilité, l'effet de la salinité, le rôle du matériau dans lesquels le nanocanaux sont inscrits - en utilisant deux modes d'actionnement, à savoir l'électrophorèse et l'hydrodynamique, et nous montrons, pour la première fois, l'intérêt de l'hydrodynamique pour la manipulation d'ADN dans des nanostructures. Nous proposons enfin quelques applications pour ce procédé de manipulation d'ADN innovant.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references.
Current electronics and micro-electromechanical systems (MEMS) manufacture is optimized for the production of very high-volume parts on a limited range of substrates. These processes are long, consume large amounts of resources, and require expensive machines and facilities, but yield excellent products. Cheaper, faster printing processes are beginning to emerge with the ability to economically produce low or high-volume electronics and MEMS on flexible substrates. This thesis describes the theoretical and practical design of a suite of printing processes including liquid embossing and offset liquid embossing (OLE). These printing techniques have created resistors, capacitors, and thin-film transistors without etching, vacuum deposition, or high temperatures. Here, the fabrication of all-printed electrostatic actuators is described In liquid embossing a polydimethylsiloxane (PDMS) stamp with bas-relief features is brought into intimate contact with a thin liquid film such as a metal or semi-conductor nanoparticle colloid, spin-on-glass, or polymer to create patterns as small as 100 nm. A simulation of liquid embossing was developed by coupling fluid flow in a thin liquid film to the diffusion of solvent into a PDMS stamp. The model accurately predicts real aspects of the printing process including the time required to stamp and usable stamp geometries. OLE was designed to address some of the limitations of liquid embossing. In OLE the patterned liquid film is transferred to a different substrate, allowing finer control over geometry and material placement and leaving behind excess material trapped during stamping. All-printed electrostatic actuators were fabricated using OLE by patterning gold on flexible polyimide and then under-etching with oxygen plasma.
The polyimide acts as a sacrificial material, dielectric layer, and mechanical substrate. Square electrostatic actuators 50 microns on a side can modulate light up to approximately 1 kHz with fields of 1-2 volts per micron. These actuators also show a sharp non-linear response to driving voltage that could be used as part of a passive row-column addressing scheme.
by Eric Jamesson Wilhelm.
Ph.D.

Photonic devices are key to implement future communication and information technologies. Their success is largely determined by our capability to appropriately control light in such devices, especially in future reconfigurable networks. Light does not interact with itself, thus one usually needs the use of an active material. Phase change materials are a potential candidate to implement this functionality. These materials are a group of chemical compounds that exist in more than one stable phase, each with largely different electrical and optical properties. Moreover, they can be rapidly and reversibly switched between these phases using electrical or optical pulses. This thesis is devoted to the design and implementation of micronano structured photonic devices incorporating the phase-change material Ge2Sb2Te5 (GST). The thesis first investigates how to fabricate thin films of different phase-change materials in a repeatable manner and characterizes their main properties, especially those of GST. This includes an investigation of their composition, the conditions required to reversibly switch between the amorphous and crystalline phases, as well as their optical properties in each of the stable phases. Three different applications are then demonstrated, each of them based on a different functionality. The first application is an optical switch operating at telecommunication wavelengths. The device is implemented using a racetrack resonator partially covered with GST. The transmission resonances present in this system are controlled using an infrared laser that triggers phase transitions in the GST layer, thus modifying the shape and position of the resonance wavelength between two states. The switch has an on/off ratio of _ 12dB and response times of ~5μs. In the second application, control of surface plasmon polaritons in Au waveguides is demonstrated. This is achieved using a cladding layer of GST. 100 % modulation is achieved for large GST areas and thermal crystallization, while up to 30 % modulation is achieved using small GST areas and laser crystallization. The third application is related to nanohole arrays covered with GST thin films. The effect of phase transitions in the transmission resonances of these structures is investigated for three geometries. Wavelengths shifts as large as 385 nm are demonstrated in devices with broad resonances. Additionally, excitation of GST with short pulses allows for ultrafast tuning of these resonances in the ps regime without the need for a phase transition. Finally, tuning of narrow resonances with shifts of 13 nm is also shown.In summary, the studies and applications contained in this thesis demonstrate the potential of GST and, in general, phase-change materials, to address optical tunability, which is an essential function in a wide range of optical devices.
Els dispositius fotònics són un dels principals candidats per implementar les futures tecnologies de la informació i de la comunicació. El seu èxit dependrà en gran mesura de la capacitat de controlar la llum en aquests dispositius, en particular en dispositius reprogramables. Degut a que la llum no interactua amb ella mateixa normalment es necessita usar un material actiu per assolir aquest control. Els materials de canvi de fase són un dels possibles candidats per implementar aquesta funcionalitat. Aquest conjunt de compostos químics es caracteritzen per tenir més d’una fase estable. Cada una d’aquestes fases presenta unes propietats òptiques I elèctriques molt diferents. A més a més els canvis de fase en aquests materials es poden realitzar molt ràpidament i de manera reversible mitjançant polsos elèctrics o òptics. Aquesta tesis descriu el disseny i la implementació de nous dispositius òptics micro i nanoestructurats usant el material de canvi de fase Ge2Sb2Te5 (GST). A la primera part de la tesis s’investiga com fabricar capes primes de diferents materials de canvi de fase de manera repetible i es caracteritzen les seves propietats principals, en especial les del GST. Això inclou una investigació de la seva composició, les condicions necessàries per induir reversiblement transicions de fase entre els estats amorf i cristal·lí, així com mesures de les propietats òptiques de cada una de les fases. Aquests resultats es faran servir per implementar després tres aplicacions, cada una de les quals té una funció diferent. La primera aplicació és un interruptor òptic que treballa a una longitud dona de 1550 nm. El dispositiu està implementat en un anell ressonador parcialment recobert amb una capa prima de GST. Les ressonàncies en iv transmissió d’aquest sistema són controlades amb un làser infraroig que indueix transicions de fase en la capa de GST, modificant la forma i posició de la ressonància entre dos estats. L’interruptor té una relació entre els estats “on” i “off” de 12 dB i un temps de resposta d’uns 5 s. En la segona aplicació es demostra el control de plasmons de superfície propagant-se a través d’una guia d’ona d’or. Això s’aconsegueix fent servir una capa de GST dipositada sobre el dispositiu. Usant grans àrees de GST i cristal·lització per temperatura es poden aconseguir modulacions del 100 %, mentre que usant petites àrees de GST i cristal·lització làser es demostren modulacions de fins el 30 %. La tercera aplicació explora la combinació d’estructures periòdiques de nanoforats amb capes de GST. En aquest experiment s’investiga l’efecte de les transicions de fase en les ressonàncies de transmissió usant tres geometries diferents. En dispositius amb ressonàncies amples es poden desplaçaments en la longitud d’ona d’aquestes ressonàncies de 385 nm. A més a més, excitant la capa de GST amb polsos curts es mesuren canvis d’aquestes ressonàncies en una escala de temps de ps sense la necessitat d’induir una transició de fase. Per últim també es demostren desplaçaments en la longitud d’ona de fins a 13 nm en dispositius amb ressonàncies estretes. Els estudis i aplicacions descrits en aquesta tesi demostren el potencial del GST i dels materials de canvi de fase en general per implementar dispositius òptics sintonitzables, que realitzaran una funció essencial en futures tecnologies basades en la llum.

Aquest document resumeix el treball d'investigació realitzat per l'obtenció del títol de Doctor en Enginyeria Electrònica a la Universitat Autònoma de Barcelona (UAB).
El treball ha estat elaborat al Centre Nacional de Microelectrònica (CNM), a l'Institut de Microelectrònica de Barcelona (IMB).
Les activitats del CNM-IMB estan dividides en 6 àrees d'investigació diferents, cobrint un ampli rang de dispositius microelectrònics: microsistemes i tecnologia de silici, transductors químics, dispositius i sistemes de potència, aplicacions biomèdiques, diseny de circuits electrònics i nanotecnologia. Aquest treball s'ha dut a terme dins d'aquesta última àrea.
La major part de la feina s'ha emmarcat en el projecte d'investigació europeu FP6 NOVOPOLY (Novel functional polymer materials for MEMS and NEMS applications) que té com a objectius desenvolupar nous materials per aplicacions en l'àrea de la tecnologia dels micro- i dels nano- sistemes (MEMS i NEMS). Una altra part de la Tesi es va realitzar en el marc del projecte d'investigació europeu FP6 NaPa (Emerging Nanopatterning Methods) que pretén desenvolupar noves tècniques d'estampació nanomètrica com poden ser el NIL, soft lithography, la litografia basada en MEMS, etc. Ambdós projectes han estat fonts de motivacions, capital per recursos y col·laboradors que han contribuït notòriament en la formació d'aquesta Tesi.
El primer objectiu d'aquest treball va ser el de establir les bases de la tecnologia de fabricació amb polímers en la Sala Blanca del CNM. El CNM sempre ha treballat amb tecnologia de silici però, donat que el polímers estan demostrant ser una alternativa de baix cost, era interessant (a nivell local) optimitzar aquests processos.
Per altra banda, existeix un gran interès en modificar els polímers fotoestructurables existents, com la SU-8, afegint-los diferents funcionalitats i superant així les actuals limitacions d'aquests materials pel que fa a les seves propietats mecàniques, a la seva conductivitat elèctrica, a millorar la seva estabilitat a altes temperatures, etc. Aquests nous polímers poden representar en un futur pròxim les bases de l'avanç de la tecnologia de polímers, tant per aplicacions acadèmiques com industrials. Gràcies a les col·laboracions establertes en els projectes europeus abans mencionats, s'ha pogut presentar en aquesta Tesi el processat d'alguns nous polímers per algunes aplicacions concretes.
Per tots aquests motius esmentats, aquesta Tesi és un compendi de diferents dispositius polimèrics, cadascun d'ells fabricat amb processos diferents, perquè o bé els materials o bé les tècniques no eren les mateixes. Per aquesta raó, la Tesi es divideix en 7 Capítols:
La introducció pretén repassar l'estat de l'art de les tècniques de fabricació amb polímers. Com aquesta Tesi està enfocada en l'ús de polímers fotoestructurables per a la fabricació de dispositius, el principal procés és la UV lithography tot i que altres mètodes han estat desenvolupats per assolir millor resolució i millors resultats. Les tècniques litogràfiques que es poder utilitzar amb polímers estan breument descrites i també s'introdueixen tres tipus diferents de polímers per donar un coneixement bàsic dels conceptes més fets servir al llarg d'aquesta memòria.
El Capítol 2 presenta la fabricació de sondes d'AFM polimèriques que podes ser utilitzades en qualsevol equip d'AFM comercial, demostrant així el seu camp d'aplicació, el seu baix cost de producció i la seva capacitat per a ser comercialitzades. Aquesta és la principal responsabilitat de què el CNM tenia dins del projecte Novopoly.
El Capítol 3 és una extensió del capítol anterior però usant un nou material compost per nanopartícules i polímer. El nou material millora algunes de les propietats del polímer original i també s'afegeixen propietats que abans no tenia com pot ser l'actuació magnètica.
En el Capítol 4 s'introdueix un nou polímer. En aquest cas, es demostra que el material és capaç de proporcionar actuació optotèrmica degut a que té un coeficient d'expansió tèrmic més elevat que la versió no dopada. A més, donat que el material és negre, l'actuació òptica en el espectre del visible és possible, el que obre noves possibilitats comparat amb el polímer estàndard. Un model teòric i un estudi complert del comportament d'aquesta actuació estan detallats.
El Capítol 5 descriu com definir estructures de polímer utilitzant l'ink-jet printing i la soft-lithography. Aquestes dues tècniques han estat emprades per evitar la contaminació creuada entre els dipòsits d'un, prèviament fabricat, xip de microfluídica. Aquest capítol és un clar exemple de la flexibilitat que ofereix la tecnologia de polímer.
Les tècniques d'Scanning Probe Lithography (SPL), Litografia per Feix d'Electrons (EBL) i la litografia UV es poden combinar per imprimir en fines capes de polímers tal i com es descriu en el Capítol 6. En aquest capítol s'inclouen els detalls del mecanisme de modificació local del polímers fent servir el Microscopi de Forces Atòmiques (AFM).
Finalment, aquesta Tesi acaba amb les conclusions que estan resumides en el Capítol 7. En ell es comenten els principals resultats de cada un dels processos de fabricació desenvolupats en aquesta memòria.
Este documento resume el trabajo de investigación realizado para la obtención del título de Doctora en Ingeniería Electrónica en la Universitat Autònoma de Barcelona (UAB).
El trabajo ha sido elaborado en el Centro Nacional de Microelectrónica (CNM), en el Instituto de Microelectrónica de Barcelona (IMB).
Las actividades del CNM-IMB están divididas en 6 áreas de investigación diferentes, cubriendo un amplio rango de dispositivos microelectrónicos: microsistemas y tecnología de silicio, transductores químicos, dispositivos y sistemas de potencia, aplicaciones biomédicas, diseño de circuitos electrónicos y nanotecnología. Este trabajo se ha ejecutado dentro de esta última área.
La mayor parte del trabajo se ha elaborado en el marco del proyecto de investigación europeo FP6 NOVOPOLY (Novel functional polymer materials for MEMS and NEMS applications) que tiene como objetivos desarrollar nuevos materiales para aplicaciones en el área de la tecnología de los micro- y de los nano- sistemas (MEMS y NEMS). Otra parte de la Tesis se realizó en el marco del proyecto de investigación europeo FP6 NaPa (Emerging Nanopatterning Methods) cuya meta es el desarrollo de nuevas técnicas de estampación nanométrica como puede ser el NIL, soft lithography, la litografía basada en MEMS, etc. Ambos proyectos han sido fuentes de motivaciones, capital para recursos y colaboradores que han contribuido notoriamente en la formación de esta Tesis.
El primer objetivo de este trabajo fue el de establecer las bases de la tecnología de fabricación con polímeros en la Sala Blanca del CNM. El CNM siempre ha trabajado con tecnología de silicio pero, dado que los polímeros están demostrando ser una alternativa de bajo coste, era interesante (a nivel local) optimizar estos procesos.
Por otra parte, existe un gran interés en modificar los polímeros fotoestructurables existentes, como la SU-8, añadiéndoles diferentes funcionalidades y superar así las actuales limitaciones de estos materiales con respecto a sus propiedades mecánicas, a su conductividad eléctrica, a mejorar su estabilidad en altas temperaturas, etc. Estos nuevos polímeros pueden representar en un futuro próximo las bases del avance de la tecnología de polímeros, tanto para aplicaciones académicas como industriales. Gracias a las colaboraciones establecidas en los proyectos europeos antes mencionados, se ha podido presentar en esta Tesis el procesado de algunos nuevos polímeros para algunas aplicaciones concretas.
Por todos los motivos mencionados, esta Tesis es un compendio de diferentes dispositivos poliméricos, cada uno de ellos fabricado con procesos distintos, porque o bien los materiales o bien las técnicas no eran las mismas. Por esta razón, la Tesis se divide en 7 Capítulos:
La introducción pretende repasar el estado del arte de las técnicas de fabricación con polímeros. Como esta Tesis está enfocada en el uso de polímeros fotoestructurables para la fabricación de dispositivos, el principal proceso es la UV lithography aunque otros métodos han sido desarrollados para alcanzar mayor resolución y mejores resultados. Las técnicas litográficas que pueden ser usadas con polímeros están brevemente descritas y también se introducen tres tipos diferentes de polímeros para dar un conocimiento básico de los conceptos más usados a lo largo de esta memoria.
El Capítulo 2 presenta la fabricación de sondas de AFM poliméricas que pueden ser usadas en cualquier equipo de AFM comercial, demostrando así su campo de aplicación, su bajo coste de producción y su capacidad para ser comercializadas. Esta es la principal responsabilidad que el CNM tenía dentro del proyecto Novopoly.
El Capítulo 3 es una extensión del capítulo anterior pero usando un nuevo material compuesto por nanopartículas y polímero. El nuevo material mejora algunas de las propiedades del polímero original y también se añaden propiedades que antes no tenía como puede ser la actuación magnética.
En el Capítulo 4 se introduce otro nuevo polímero. En este caso, se demuestra que el material es capaz de proporcionar actuación optotérmica debido a que tiene un mayor coeficiente de expansión térmica que la versión no dopada. Además, dado que el material es negro, la actuación óptica en el visible es posible, lo que abre nuevas posibilidades comparado con el polímero estándar. Un modelo teórico y un estudio completo del comportamiento de esta actuación están detallados.
El Capítulo 5 describe cómo definir estructuras de polímero usando el ink-jet printing y la soft-lithography. Estas dos técnicas han sido usadas para evitar la contaminación cruzada entre los depósitos de un previamente fabricado chip de microfluídica. Este capítulo es un claro ejemplo de la flexibilidad que ofrece la tecnología de polímero.
Las técnicas de Scanning Probe Lithography (SPL), Litografía por Haz de Electrones (EBL) y la litografía UV se pueden combinar para imprimir en finas capas de polímeros tal y como se describe en el Capítulo 6. En este capítulo se incluyen los detalles del mecanismo de modificación local de polímeros usando en Microscopio de Fuerzas Atómicas (AFM).
Finalmente, esta Tesis termina con las conclusiones que están resumidas en el Capítulo 7. En él se comentan los principales resultados de cada uno de los procesos de fabricación desarrollados en esta memoria.
This document summarizes the research work performed in order to obtain the Ph.D. degree in Electronic Engineering at the Universitat Autònoma de Barcelona (UAB).
The work has been done at the National Centre for Microelectronics (Centro Nacional de Microelectrónica CNM), at the Institute of Microelectronics in Barcelona (IMB).
CNM-IMB activities are divided into 6 different research areas covering a wide range of microelectronic devices: microsystems and silicon technology, chemical transducers, power devices and systems, biomedical applications, electronic circuits design and nanotechnology. The present work has been performed in the latter area.
Most of the work has been performed in the frame of the FP6 European research project NOVOPOLY (Novel functional polymer materials for MEMS and NEMS applications) which aims to develop new functional materials for applications in the area of micro- and nano- systems technology (MEMS and NEMS). Also, a part of the thesis was performed within the frame of the FP6 European research project NaPa (Emerging Nanopatterning Methods) which aims the development of novel nanopatterning techniques as can be NIL, soft lithography, MEMS-based lithography, etc. Both projects have been source of funding, motivations and collaborators that have contributed notoriously to the development of this Thesis.
The first objective of the project was to establish the basis for polymer fabrication technology in the CNM Clean Room. CNM has always been working on silicon technology but, provided that polymer technology is showing itself as a low-cost alternative, it was interesting (at a local level)
to optimize these processes.
On the other hand, there is a large interest in adding functionality to existing photostructurable polymers, like SU-8, and overcome the current limitations of these systems with respect to mechanical, electrical conductivity and high temperature stability properties. These novel polymers can represent in the near future a cornerstone in the development of polymer technology, with both academic and industrial applications. Taking profit of some collaborations established in the projects mentioned above, the processing of some novel polymers is also presented in this Thesis for a few targeted applications.
Therefore, the Thesis is a compendium of different polymeric devices, each of them fabricated with a different process, because either the materials or the techniques were different; and the memory is divided in seven different chapters:
The introduction, aims to review the state of the art of polymer fabrication techniques. As this Thesis is focused in the use of photostructurable polymers for the fabrication of devices, the main process is the UV lithography although others methods have been developed in order to achieve higher resolution and better performance. Lithographic techniques usable for polymers are briefly described and the three kinds of polymers used are introduced in order to give the basic knowledge and main concepts used through all the work.
Chapter 2 presents the fabrication of usable polymeric AFM probes, demonstrating their field of application and low cost production and its feasibility to commercialization. This is the main activity that CNM had in Novopoly project.
Chapter 3 is an extension of the previous chapter but using a new composite material. The new material overcomes some of the drawbacks properties of the original epoxy based resist and also adds functional properties as it can be magnetic actuation.
In Chapter 4 another new composite is shown. In this case, optothermal actuation is demonstrated because this material has a higher thermal expansion coefficient than the undoped version. In addition, given the fact that the material is black, which means that optical actuation in the visible is possible, opening new possibilities compared with the standard polymer. A theoretical model and a fully study of the actuation behaviour is reported.
Chapter 5 describes polymer structures definition by ink-jet printing and soft-lithography. These two techniques were used to avoid the cross contamination between dispensing holes of a previously fabricated microfluidic chip. This chapter is itself an example of how flexible polymer technology is.
Scanning Probe Lithography (SPL), Electron-Beam Lithography (EBL) and UV lithography techniques have been combined to pattern thin layers of polymers as it is depicted in Chapter 6. This chapter includes details mechanism and operation of the local modification of polymers using an Atomic Force Microscope (AFM).
Finally, this Thesis ends with the conclusions that are summarized in Chapter 7. The main results of each fabrication process developed are commented.

Femtosecond laser interaction with dielectrics has unique characteristics for micromachining, notably non-thermal interaction with materials, precision and flexibility. The nature of this interaction is highly nonlinear due to multiphoton ionization, so the laser energy can be nonlinearly absorbed by the material, leading to permanent change in the material properties in a localized region of Mu-m3. This dissertation demonstrated the potential of these nonlinear interactions induced changes (index modification and ablation for machining) in the dielectrics and explored several practical applications. We studied femtosecond laser ablation of Poly-methayl methacrylate (PMMA) under single and multiple pulse irradiation regimes. We demonstrated that the onset of surface ablation in dielectric surface is associated with surface swelling, followed by material removal. Also, the shape of the ablation craters becomes polarization dependent with increasing fluence, except for circular polarization. The morphology of the damaged/ablated material was examined by optical and scanning electron microscopy. The dynamics of laser ablation of PMMA was simulated using a 2 dimensional Molecular Dynamics model and a 3 dimensional Finite Difference Time Domain model. The results from numerical simulations agreed well with experimental results presented in this thesis. We also demonstrated the formation of nano-pillar within the ablation crater when the surface of bulk-PMMA was irradiated by two femtosecond pulses at a certain delay with energies below single shot ablation threshold. With increasing fluence, the nano-pillar vanished and the structure within the ablation crater resembled volcanic eruption. At higher fluences we demonstrated nanoscale porosity in PMMA. For application, a novel in-line fiber micro-cantilever was fabricated in bend insensitive fiber, that provides details of in-line measurement of frequency and amplitude of vibration, and can be further extended to be used as chemical/bio and temperature sensors. By modifying the refractive index at random spacing within the single mode fiber core, a unique quasi-random micro-cavities fiber laser was fabricated, which exhibits comparable characteristics with a commercial fiber laser in terms of narrow linewidth and frequency stability.

This study aimed to characterize the in-situ mechanical property and morphology of individual collagen fibril in osteoarthritic (OA) cartilage using indentation-type atomic force microscopy (IT-AFM). The specimens with intact articular cartilage (AC), mild to severe degenerated OA cartilage were collected with informed consent from the postmenopausal women who underwent hip or knee arthroplasty. The fresh specimens were cryo-sectioned by layers with 50m thick for each from the articular surface to calcified cartilage, and then processed for AFM imaging and nanoindentation test. For each layer, a total of twenty collagen fibrils were randomly selected for testing. AFM tips with the nominal radius less than 10 nm were employed for probing the individual collagen fibril, and the obtained cantilever deflection signal and displacement were recorded for calculating its elastic modulus. Besides AFM nanoindentation, AFM and scanning electron microscopy (SEM) images, haematoxylin & eosin (H&E) staining and micro-indentation were performed on AC to study the changes of ultrastructure and composition between intact AC and OA cartilage. Results showed that an intact AC exhibited a gradation in elastic modulus of collagen fibrils from surface region (2.65±0.31GPa) to bottom region (3.70±0.44GPa). It was noted in the initial stage of OA cartilage that the coefficient of variation for mechanical properties of collagen fibers, ranging from 25~48%, significantly increased as compared with intact one (12%). The thickened and stiffened collagen fibrils initially occurred at either surface region (3.11±0.91GPa) or bottom region (5.64±1.10GPa) with OA progression. Besides thickens, alteration of D-periodic banding patterns of collagen fibrils was observed. It was echoed by fibrotic changes of surface region and tidemark irregularities. On the contrast, the micromechanical properties of cartilage decreased while AC suffered from OA. This result revealed the different approachs of nano and micro-mechanical properties changes in AC. In summary, the alteration of mechanical properties of collagen fibrils started from calcified cartilage as well as articular surface during OA onset, and the low compliance of thickened collagen fibrils deteriorated along disease progression. This study also reveals that the outstanding ability by AFM, in investigating the structure and mechanical properties of collagen fibrils and AC in nanometer scale, is impressive and this nanotechnological instrument is worth to be expected in further development for clinical use.
published_or_final_version
Mechanical Engineering
Master
Master of Philosophy

Dissertation presented to obtain the PhD degree in Chemistry-Nanotechnology
Nano- and microtechnology is one of the hottest topics in food science and technology. Current applications of nano- and microtechnology in the food sector includes the processing and formulation of food ingredients into nano- and micro- structures/-sized/-encapsulated or engineered particle additives. These systems have been incorporated in food to improve functionality, enhancing physical properties (i.e. colour, texture), protecting chemical ingredients from degradation (i.e antioxidants, flavour) and biological degradation (i.e. antimicrobials), and increasing bioavailability. Moreover, it has been used for the development of active/intelligent packaging, sensors and for encapsulation of bioactives, flavour and nutrients.(...)
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Avec le développement des nanotechnologies, il est devenu possible et souhaitable de créer et d'assembler des nano-objets. Afin d'obtenir des processus automatisés robustes et fiables, la manipulation à l'échelle nanométrique est devenue, au cours des dernières années, une tâche primordiale. La vision est un moyen indispensable pour observer le monde à l'échelle micrométrique et nanométrique. Le contrôle basé sur la vision est une solution efficace pour les problèmes de contrôle de la robotique. Dans cette thèse, nous abordons la problématique du micro- et nano-positionnement par asservissement visuel via l'utilisation d'un microscope électronique à balayage (MEB). Dans un premier temps, la formation d'image MEB et les modèles géométriques de la vision appliqués aux MEB sont étudiés afin de présenter, par la suite, une méthode d'étalonnage de MEB par l'optimisation non-linéaire considérant les modèles de projection perspective et parallèle. Dans cette étude, il est constaté qu'il est difficile d'observer l'information de profondeur à partir de la variation de la position de pixel de l'échantillon dans l'image MEB à un grossissement élevé. Afin de résoudre le problème de la non-observabilité du mouvement dans l'axe de la profondeur du MEB, les informations de défocalisation d'image sont considérées comme caractéristiques visuelles pour commander le mouvement sur cet axe. Une méthode d'asservissement visuelle hybride est alors proposée pour effectuer le micro-positionnement en 6 degrés de liberté en utilisant les informations de défocalisation d'image et de photométrique d'image. Cette méthode est ensuite validée via l'utilisation d'un robot parallèle dans un MEB. Finalement, un système de contrôle en boucle fermée pour l'autofocus du MEB est introduit et validé par des expériences. Une méthode de suivi visuel et d'estimation de pose 3D, par la mise en correspondance avec un modèle de texture, est proposée afin de réaliser le guidage visuel dans un MEB. Cette méthode est robuste au flou d'image à cause de la défocalisation provoquée par le mouvement sur l'axe de la profondeur car le niveau de défocalisation est modélisée dans ce cadre de suivi visuel
With the development of nanotechnology, it became possible to design and assemble nano-objects. For robust and reliable automation processes, handling and manipulation tasks at the nanoscale is increasingly required over the last decade. Vision is one of the most indispensable ways to observe the world in micrioscale and nanoscale. Vision-based control is an efficient solution for control problems in robotics. In this thesis, we address the issue of micro- and nano-positioning by visual servoing in a Scanning Electron Microscope (SEM). As the fundamental knowledge, the SEM image formation and SEM vision geometry models are studied at first. A nonlinear optimization process for SEM calibration has been presented considering both perspective and parallel projection model. In this study, it is found that it is difficult to observe the depth information from the variation of the pixel position of the sample in SEM image at high magnification. In order to solve the problem that the motion along the depth direction is not observable in a SEM, the image defocus information is considered as a visual feature to control the motion along the depth direction. A hybrid visual servoing scheme has been proposed for 6-DoF micro-positioning task using both image defocus information and image photometric information. It has been validated using a parallel robot in a SEM. Based on the similar idea, a closed-loop control scheme for SEM autofocusing task has been introduced and validated by experiments. In order to achieve the visual guidance in a SEM, a template-based visual tracking and 3D pose estimation framework has been proposed. This method is robust to the defocus blur caused by the motion along the depth direction since the defocus level is modeled in the visual tracking framework

Thesis (Ph.D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 24, 2009) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2008.
Title from electronic title page (viewed Jun. 26, 2009). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.

Nanotechnology-based devices are believed to be the future possible alternative to CMOS-based devices. It is predicted that the high integration density offered by emerging nanotechnologies will be accompanied by high manufacturing defect rates and high operation-time fault rates. This thesis is concerned with developing defect and fault tolerance techniques to address low manufacturing yield due to permanent defects and reduced computational reliability due to transient faults projected in nanoscale devices and nanometre CMOS circuits. The described research makes four key contributions. The first contribution is a novel defect tolerance technique to improve the manufacturing yield of nanometre CMOS logic circuits. The technique is based on replacing each transistor by an N2-transistor structure (N ≥ 2) that guarantees defect tolerance of all (N−1) defects. The targeted defects include stuck-open, stuck-short and bridging defects. Extensive simulation results using ISCAS benchmark circuits, show that the proposed technique achieves manufacturing yield higher than recently proposed techniques and at a reduced area overhead. The second contribution is two new repair techniques, named Tagged Replacement and Modified Tagged Replacement, to improve the manufacturing yield of nanoscale cross-bars implementing logic circuits as look-up tables (LUTs). The techniques are based on highly efficient repair algorithms that improve yield by increasing the resolution of repair. Simulation results show that the proposed techniques are able to provide higher levels of defect tolerance and have lower redundancy requirements than recently reported techniques. Another popular crossbar-based circuit implementation is nanoscale programmable logic arrays (PLAs). The third contribution is a probabilistic defect tolerance design flow that improves the manufacturing yield of nanoscale PLAs and significantly reduces post-fabrication test and diagnosis time. This is achieved by limiting defect diagnosis to the nanowire level rather than the crosspoint level as in previously proposed graph-based techniques. The final contribution involves improving both manufacturing yield and computational reliability of nanoscale crossbars implementing logic circuits as LUTs. This is achieved by combining Hamming and Bose-Chaudhuri-Hocquenghem (BCH) codes together or with N-Modular Redundancy and Bad Line Exclusion techniques. Simulation results show a significant improvement in fault tolerance by the proposed techniques (targeting fault rates upto 20%) when compared to previously reported single coding schemes

Low-dimensional semiconductor structures, such as one-dimensional nanowires (NWs) and zerodimensional quantum dots (QDs), are materials with novel fundamental physical properties and a great potential for a wide range of nanoscale device applications. Here, especially promising are direct bandgap II-VI and III-V compounds and related alloys with a broad selection of compositions and band structures. For examples, NWs based on dilute nitride alloys, i.e. GaNAs and GaNP, provide both an optical active medium and well-shaped cavity and, therefore, can be used in a variety of advanced optoelectronic devices including intermediate band solar cells and efficient light-emitters. Self-assembled InAs QDs formed in the GaAs matrix are proposed as building blocks for entangled photon sources for quantum cryptography and quantum information processing as well as for spin light emitting devices. ZnO NWs can be utilized in a variety of applications including efficient UV lasers and gas sensors. In order to fully explore advantages of nanostructured materials, their electronic properties and lattice structure need to be comprehensively characterized and fully understood, which is not yet achieved in the case of aforementioned material systems. The research work presented this thesis addresses a selection of open issues via comprehensive optical characterization of individual nanostructures using micro-Raman ( -Raman) and micro-photoluminescence ( -PL) spectroscopies. In paper 1 we study polarization properties of individual GaNP and GaP/GaNP core/shell NWs using polarization resolved μ-PL spectroscopy. Near band-edge emission in these structures is found to be strongly polarized (up to 60% at 150K) in the orthogonal direction to the NW axis, in spite of their zinc blende (ZB) structure. This polarization response, which is unusual for ZB NWs, is attributed to the local strain in the vicinity of the N-related centers participating in the radiative recombination and to their preferential alignment along the growth direction, presumably caused by the presence of planar defects. Our findings therefore show that defect engineering via alloying with nitrogen provides an additional degree of freedom to control the polarization anisotropy of III-V nanowires, advantageous for their applications as a nanoscale source of polarized light. Structural and optical properties of novel coaxial GaAs/Ga(N)As NWs grown on Si substrates, were evaluated in papers 2-4. In paper 2 we show by using -Raman spectroscopy that, though nitrogen incorporation shortens a phonon correlation length, the GaNAs shell with [N]<0.6% has a low degree of alloy disorder and weak residual strain. Additionally, Raman scattering by the GaAs-like and GaNlike phonons is found to be enhanced when the excitation energy approaches the E+ transition energy. This effect was attributed the involvement of intermediate states that were created by N-related clusters in proximity to the E+ subband. Recombination processes in these structures were studied in paper 3 by means of μ-PL, μ-PL excitation (μ-PLE), and time-resolved PL spectroscopies. At low temperatures, the alloy disorder is found to localize photo-excited carriers leading to predominance of localized exciton (LE) transitions in the PL spectra. Some of the local fluctuations in N composition are suggested to create three-dimensional confining potentials equivalent to that for QDs, based on the observation of sharp PL lines within the LE contour. In paper 4 we show that the formation of these QD-like confinement potentials is somewhat facilitated in spatial regions of the NWs with a high density of structural defects, based on correlative spatially-resolved structural and optical studies. It is also concluded the principal axis of these QD-like local potentials is mainly oriented along the growth direction and emit light that is linearly polarized in the direction orthogonal to the NW axis. At room temperature, the PL emission is found to be dominated by recombination of free carriers/excitons and their lifetime is governed by non-radiative recombination via surface states. The surface recombination is found to become less severe upon N incorporation due to N-induced modification of the surface states, possibly due to partial surface nitridation. All these findings suggest that the GaNAs/GaAs hetero-structures with the onedimensional geometry are promising for fabrication of novel optoelectronic devices on foreign substrates (e.g. Si). Fine-structure splitting (FSS) of excitons in semiconductor nanostructures has significant implications in photon entanglement, relevant to quantum information technology and spintronics. In paper 5 we study FSS in various laterally-arranged single quantum molecular structures (QMSs), including double QDs (DQDs), quantum rings (QRs), and QD-clusters (QCs), by means of polarization resolved μ-PL spectroscopy. It is found that FSS strongly depends on the geometric arrangements of the QMSs, which can effectively tune the degree of asymmetry in the lateral confinement potential of the excitons and can reduce FSS even in a strained QD system to a limit similar to strain-free QDs. Fabrication of nanostructured ZnO-based devices involves, as a compulsory step, deposition of thin metallic layers. In paper 6 we investigate impact of metallization by Ni on structural quality of ZnO NWs by means of Raman spectroscopy. We show that Ni coating of ZnO NWs causes passivation of surface states responsible for the enhanced intensity of the A1(LO) in the bare ZnO NWs. From the resonant Raman studies, strong enhancement of the multiline Raman signal involving A1(LO) in the ZnO/Ni NWs is revealed and is attributed to the combined effects of the Fröhlich interaction and plasmonic coupling. The latter effect is also suggested to allow detection of carbon-related species absorbed at the surface of a single ZnO/Ni NW, promising for utilizing such structures as efficient nano-sized gas sensors.

Recent advances in micro- and nanotechnology have produced a number of new materials which exhibit exceptional potential for the design of novel sensing strategies and to enhance the analytical performance of biosensing systems. In this thesis three different types of miniaturisation pathways were investigated for electrochemical biosensing applications. Vertically aligned carbon nanotube thin films were designed and tested as platforms for DNA immobilisation and for the development of a model electrochemical genosensor. The sensor format involved the immobilisation of oligoucleotide probes onto the sensor surface, hybridisation with the target sequence and electrochemical detection of the duplex formation. By combining such an electrode platform with an enzyme labeling, a detection limit of oligonucleotide targets in the nanomolar range was achieved. A novel magnetic particle-based microfluidic sensor was also realised by integrating a microfluidic platform with a new analytical procedure based on the use of paramagnetic beads for the detection of real PCR samples. The hybridisation reaction was carried out on probe-modified beads in a flow-through format, thus enhancing the surface area-to-volume ratio and consequently the sensitivity. Moreover, the magnetic properties of the beads greatly facilitated the delivery and removal of reagents through the microfluidic channels. This format allowed the detection of nanomolar levels of double-stranded DNA sequences, with high reproducibility and fast time of analysis. Finally, polyaniline nanotubes arranged in an ordered structure directly on gold electrode surfaces were realised and employed to create a model molecularly imprinted (MIP) polymer -sensor for catechol detection. The advantages of using nanostructures in this particular biosensing application have been evaluated by comparing the analytical performance of the sensor with an analogous non-nanostructured MIP-sensor that we had previously developed. A significantly lower limit of detection (one order of magnitude) was achieved, thus demonstrating that the nanostructures enhanced the analytical performance of the sensor.

The ongoing interest in bacterial interactions with various surfaces, followed by attachment and subsequent biofilm formation, has been driven by the importance of bacterial activities in number of medical, industrial and technological applications. However, bacterial adhesion to surfaces has not been completely understood due to the complexity of parameters involved. The study presented herein investigates the attachment pattern of nine medically and environmentally significant bacteria belonging to different taxonomic lineages: Firmicutes - Bacillus, Gammaproteobacteria, Alphaproteobacteria and Bacteriodetes. Physicochemical assessment techniques such as contact angle and surface charge measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), confocal microscopy (CLSM), as well as X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) analysis were all employed in order to attain better insight into the factors that influence bacterial interactions with surfaces. Bacterial surface characteristics such as surface wettability and charge in addition to substratum surface wettability, tension, charge and chemistry were also considered. However due to the recent interest in designing micro-textured surfaces with antibacterial and/or antifouling effects the prime was given to the influence of micro- and nano-meter scale surface textures on bacterial adhesion. The interactions between selected bacteria and glass, polymer and optical fibre surfaces were studied. Carefully designed methods for surface modification allowed alteration of the topography of glass, polymer and optical fibre surfaces while maintaining other surface parameters near constant. This allowed isolated assessment of only the effects of surface roughness on bacterial adhesion. Obtained results indicated consistent cellular inclination towards the smoother surfaces for all of the tested species. Enhanced bacterial presence on the smoother surfaces was also accompanied by changes in the bacterial metabolic activity as indicated by the elevated levels of secreted extracellular polymeric materials (EPS) and modifications in the cells morphology. The results indicate that nano-scale surface roughness exert greater influence on bacterial adhesion than previously believed and should therefore be considered as a parameter of primary interest alongside other wellrecognized factors that control initial bacterial attachment.

Online test is a technology that has great importance and value in many applications. It provides unique benefit of real-time condition monitoring, based on which early warning of system failure or degradation and potentially system self-repair can be achieved to avoid more significant impact. In the context of on-line test, embedded off-line test is still a challenging issue for MEMS device, mainly due to their micro scale and what is typically multi energy domain functionality. There are very limited methods to observe and characterize the MEMS components under test, especially for the dynamic behavior. It is also in general more difficult to verify their performance under real working conditions. This work attempts to deliver real online test solutions and methodologies which can be adapted to wide range of MEMS devices. Novel techniques of Bias-Superposition and Multi-Mode Sensing are conceived and engineered with due consideration of the availability of on board resources (e.g. signal processing power) and design/cost overhead. The proposed techniques are demonstrated on two existing MEMS systems: a capacitive MEMS accelerometer and a resistive MEMS based conductance sensor. The concepts are further studied through the design of a piezoresistive multi-functional humidity/pressure sensor. By developing the theoretical model and applying the proposed methodologies on these different structures and applications, this work pushed the State-of-the-Art of micro & nano system's online test in three areas: firstly the work potentially enabled many existing electrical induced off-line test so lutions for MEMS systems to be transfonned to on-line; secondly an on-line test solution for electro-chemical microsystems has been conceived which by traditional methods is difficu lt to implement; last but not least the work advanced from on-l ine test to fault-to lerance within NJEMS sensor systems through resilience of the sensor network.

There is a current industrial requirement for the development of suitable testmethodology that is capable of in-situ mechanical and physical characterisation of the interface and interfacial region in composite materials. The most promising tool for micro- and nano-scale measurements is the atomic force microscope (AFM) although, for suitable test-methodology to be realised, further development is required. The work contained within this thesis documents the development of AFM procedures for the measurement of elastic moduli variation across the interface and considers the physical size of the interfacial region. The first AFM procedure is for the analysis of multiple (AFM) indentations and the quantification of each indentation (in terms of reduced elastic moduli). Results of interfacial testing using this procedure highlighted short transition regions of apparently increased elastic moduli between the glass reinforcement and the polymeric matrix. It was not possible to identify whether the increase in elastic moduli was representative of an interphase due to the possibility that the indentations in this region were restricted by the presence of the glass fibrereinforcement. A second, novel procedure was then developed to independently verify whether or not any indentations were restricted, and identify whether a measured transition is representative of an interphase. This procedure was based on the principle that the any indentation performed in close proximity to the glass fibre-reinforcement would have an uneven distribution of loading between the surface and the indenter tip. The uneven distribution of loading resulted in torsion of the indenter tip, which was measured during multiple indentations across the interface of a glass fibre-reinforced phenolic composite. It was found that the apparent increase in elastic moduli measured across the interface was directly related to restriction due to, and contact with, the proximity of the glass fibrereinforcement. Finally, the latest AFM technique with the potential for quantitative measurement, is reviewed. The work has shown that AFM nanomechanical mapping has the potential to be a useful supplement to liT for measuring the small-scale elastic modulus of a polymer surface. It was found that the technique can provide repeatable measurements of polymer moduli for a number of different probes provided that careful calibration procedures are used.

This thesis presents the investigation of the liquid crystal (LC) - particle suspensions. Particles from nano- to micro-size, spherical to two-dimensional shapes, with different functionality are dispersed into nematic and smectic phases. The aim is to create ordered nanoparticle (NP) assemblies and thereby modify the common properties of the liquid crystal, such as dielectric anisotropy and electro-optical, revealing any interaction between particles and LC properties. It is found that for concentrations (>0.5vol%), the ferroelectric NPs have increased the sensitivity of the nematic liquid crystal to the electric field through electro-optical responses, which is seen by an enhancement in the dielectric anisotropy. This could be induced by the coupling of the electrical dipole moments in the spherical NPs with the LC director field. The electro-optical properties of the chiral smectic (SmC*) phase (tilt angle Θ, switching time τ_s and spontaneous polarisation P_s) are found to be independent of the concentration and sizes of the doped NPs. The relaxation frequency f_R of the Goldstone mode is faster in the ferroelectric NPs suspensions of 2.0vol% compared to the paraelectric NPs. In the graphene oxide (GO) - nematic LC (5CB) suspensions, the small GO sizes of mean size 560 nm are more easily dispersible than larger flakes of 2.8 micro metre mean size. As the GO concentration is increased, each of the threshold voltage and splay elastic constant dramatically increases, reaching saturation at ≈1.0wt%. The field driven switching-on time is practically not affected, while the purely elastically driven switching-off time is strongly sped-up. Interestingly, thermotropic and lyotropic LC phases are exhibited in the GO-5CB suspensions when heating the thermotropic liquid crystal into its isotropic phase. The isotropic phase of 5CB acts as a solvent for the GO particles, forming a lyotropic nematic phase with largely reduced birefringence. It is found that the nematic to isotropic phase transition is shifted toward higher temperature for the GO-5CB system compared to the BaTiO3-5CB system. Dispersions of different sizes of GO flakes are prepared in isotropic and nematic fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature range (25-60 ℃) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes were found to exhibit varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. The relaxation frequencies in the isotropic media were lower compared to the nematic medium. Relaxation frequencies (~10 kHz) are observed in the GO-isotropic media, which are reduced as the size of the GO flakes are decreased, are anticipated to be inherited from GO flakes. However, the fast relaxations (~100 kHz) that are observed in the nematic suspensions could imply strongly slowed down molecular relaxation modes of the nematogenic molecules. Finally, the phase diagram of lyotropic LC as a function of the lateral dimensions of the GO flakes, their concentration, geometrical confinement configuration and solvent polarity was investigated. Polarising optical microscopy was used to determine isotropic-biphasic-nematic phase evolution. The confinement volume and geometry of the sample relative to the GO size are shown to be vital to the observation of the lyotropic phase. GO LCs have the potential for a range of applications from display technologies to conductive fibres. The confinement related LC phase transition is critical toward their applications. It is also found that the stability of the LC phase is higher for the solvent of higher dielectric constant.

This document is a compilation of my selected research publications in micro and nano fabrications. The papers are largely arranged in chronological order to show the development of research interests. The research works are grouped into three sections. Section one consists of 34 research papers on micro fabrication in various materials. The research was motivated by the development of a finger nail sized micro engine as explained in Papers 1 and 2. Section two of the document includes some research activities and achievements on nanocomposite materials embedded in metallic and ceramic matrices. Section 3 includes the papers to reflect the research in developing nanostructure fabrication processes. The research contained in this DSc submission shows a continuous exploration and development of novel micro/nano fabrication processes. Although the submission covers research activities spanning 15 years, from 2000 to 2015, many of the research results represent the top technology of the time. They have contributed to the ever progressing manufacturing capability of the world. The research has encompassed both theoretical and experimental studies, contributing to the understanding of the processes and materials involved.

This research concerns the development of a risk analysis and mitigation methodology for assessing the impact of uncertainties and complexity of the design requirements arising in new process and product developments in micro and nano manufacturing. The risk analysis methodology integrates different computational approaches for process and product analysis, including the reduced order modelling using design of experiments, risk analysis using sampling-based and analytical methods and optimisation techniques. The integrated risk analysis and optimisation methodology is applied to two applications: (1) the FIB sputtering process control, and (2) a flip chip design. Three different FIB processes using different ion sources were investigated in order to evaluate their process performance with respects to different process parameter uncertainties. A critical comparison of the process capability against the specification limits of different processes was studied. As parts of the research, a new modified computational model is developed for a material sputtering process using focused ion beam (FIB). This model allows the analysis of micro- and nano-structures shape with the FIB machine controlled through multiple beam scans and different beam overlapping. The FIB model related studies also address the modelling requirements for including material re-deposition effects that occur during FIB milling. The model has been validated using an experimental test case. Good agreement is observed between the analytical shape using the model and the actual experiment. The validated model enhances the accuracy of the dwell time prediction. This approach overcomes the dependence of a trial-and-error approach of the process control in nano-manufacturing industry. The proposed methodology is also used to address a design problem of a flip chip design. A novel method for the evaluation of the environmental impact of the flip chip design in a multi-disciplinary optimisation problem is proposed. The goal is to address materials constraints due to environmental regulations and to handle different types of requirements such as the reliability and cost. An optimal flip chip design reliability function is identified. The approach allows electronics manufacturers to consider the environmental impact amongst different design alternatives at an early stage of the design of the product before any real prototyping in order to reduce the total manufacturing life cycle.