Le graphène est une nanoparticule bidimensionnelle d'épaisseur atomique présentant des propriétés uniques, qu'elles soient mécaniques, électriques ou thermiques. Ceci ajouté à une faible densité et une très grande surface spécifique, fait que l'ajout de graphène et de nanoparticules dérivées (oxyde de graphène, graphite exofilé) pour renforcer des matrices polymères est devenu un sujet d'études d'intérêt majeur dans le domaine des nanocomposites. Cependant, l'influence de la variation de la viscoélasticité de la matrice due à l'ajout de graphène ainsi que la mécanique interfaciale reste aujourd'hui peu étudiée. De plus, il n'existe aujourd'hui pas de procédé permettant d'obtenir des nanocomposites présentant du graphène dans le plan orienté dans une matrice polymère afin de réaliser un renforcement à deux dimensions. Ce travail de thèse est composé principalement de trois projets portant sur ces problèmes.La première partie de ce travail se concentre sur la façon d'utiliser l'approche micromécanique viscoélastiques pour soustraire l'effet de changement de Tg pour corriger la rigidité apparente de nanocomposites d'oxyde de graphène. On a ainsi trouvé que l'oxyde de graphène rigidifie « indirectement » les matrices polymères en augmentant de manière significative la Tg de la matrice, ce qui modifie largement la viscoélasticité du matériau. Le mécanisme de renforcement est ainsi largement causé par cet effet plutôt que du fait de la rigidité de l'oxyde de graphène lui-même.La deuxième partie se concentre sur l'utilisation d'un procédé de mise en œuvre innovant, la coextrusion multinanocouches, ou assemblage forcé, pour créer des films nanocomposites constitués de couches alternées de polymères et de polymères chargés de nanoplaquettes de graphène orientées. Cette orientation est induite par le nanoconfinement imposé par le procédé. La morphologie des couches (35 ~ 40 nm d'épaisseur) contenant du graphène orienté a été étudiée par microscopie électronique. Les propriétés mécaniques des matériaux ont été déterminées et le renforcement bidimensionnel a pu être corrélé à une orientation (imparfaite) des nanoplaquettes de graphène dans les films stratifiés.La troisième partie se concentre sur l'utilisation de la méthode de l'inflation de nano-bulle pour obtenir les réponses mécaniques d'un « nano-sandwich » (nanofilm de polymère / feuille de graphène / nanofilm de polymère). Aux petites déformations, des renforts mécaniques significatifs ont été observées pour le système PEMA / graphène, tant à l'état caoutchouteux qu'à l'état vitreux. Les mécanismes d'interface entre le graphène et les polymères ont été étudiés et un glissement interfacial a été observé. / Graphene is an atomically thick, two-dimensional nano-sheet with advanced mechanical, electrical, and thermal properties. As a result, the addition of graphene and graphene derivative nanoparticles to polymer matrices has been a major strategy towards development of new materials in the field of composites. However, from a fundamental point of view, the origins of the advanced properties of graphene-based nanocomposites have been little investigated. In particular, changes in the viscoelastic properties of the polymer matrix due to specific interactions between the polymer and the graphene reinforcing elements can cause higher than expected apparent reinforcement. In addition, there is little work on characterizing the strength of the interface between the graphene used for reinforcement and the polymer matrixes. From a more engineering point of view, the design of polymer nanocomposites made of in-plane oriented graphene to create a two-dimensionally reinforced structure has also not been previously undertaken. The present dissertation is composed of three major works focusing on these problems.The first part focuses on how to use a viscoelastic micromechanics approach to account for the effects of glass transition temperature Tg changes to correct the apparent stiffening of graphene oxide nanocomposites. It is found that graphene oxide stiffens the polymer matrices by increasing the Tg, which significantly modifies their thermo-viscoelasticity. This leads to apparent reinforcements that are not due to the stiffness of the graphene oxide itself, and largely explains anomalously high moduli reported in the literature for such graphene oxide/polymer matrix nanocomposites.The second part focuses on a forced assembly multi-layer co-extrusion method to create films made of alternating layers of neat polymer / oriented graphene nanoplatelet filled polymer. The morphology of the layers (35 ~ 40 nm thick) containing oriented graphene was established by electron microscopy. Mechanical properties of the materials were determined and the two-dimensional stiffening could be related to the oriented graphene nanoplatelets in the layered films. Taking into account the change of Tg, more than 100% intrinsic reinforcement was estimated for 2 wt % of graphene in the nanolayers. The results were analyzed and interpreted via an analytical model based on Mori-Tanaka analysis.The third part focuses on extending a nano-bubble inflation method to the investigation of a novel graphene nano-sandwich with the purpose of investigation of the graphene / polymer interface. At small strains, significant mechanical reinforcement was observed for both graphene-reinforced rubbery and glassy PEMA layers. The interfacial mechanics between graphene and polymer layers was investigated and a “yield-like” interfacial slip was observed in the mechanical response of the nano-sandwich structures.

Thin Film Transistors (TFTs) are widely used in large area electronics because they offer the advantage of low cost fabrication and wide substrate choice. TFTs have been conventionally used for switching applications in large area display arrays. But when it comes to designing a sensor actuator system on a flexible substrate comprising entirely of organic and inorganic TFTs, there are two main challenges – i) Fabrication of complementary TFT devices is difficult ii) TFTs have a drift in their threshold voltage (VT) on application of gate bias. Also currently there are no circuit simulators in the market which account for the effect of VT drift with time in TFT circuits. The first part of this thesis focuses on integrating the VT shift model in the commercially available AIM-Spice circuit simulator. This provides a new and powerful tool that would predict the effect of VT shift on nodal voltages and currents in circuits and also on parameters like small signal gain, bandwidth, hysteresis etc. Since the existing amorphous silicon TFT models (level 11 and level 15) of AIM-Spice are copyright protected, the open source BSIM4V4 model for the purpose of demonstration is used. The simulator is discussed in detail and an algorithm for integration is provided which is then supported by the data from the simulation plots and experimental results for popular TFT configurations. The second part of the thesis illustrates the idea of using negative feedback achieved via contact resistance modulation to minimize the effect of VT shift in the drain current of the TFT. Analytical expressions are derived for the exact value of resistance needed to compensate for the VT shift entirely. Circuit to realize this resistance using TFTs is also provided. All these are experimentally verified using fabricated organic P-type Copper Phthalocyanine (CuPc) and inorganic N-type Tin doped Zinc Oxide (ZTO) TFTs. The third part of the thesis focuses on building a robust amplifier using these TFTs which has time invariant DC voltage level and small signal gain at the output. A differential amplifier using ZTO TFTs has been built and is shown to fit all these criteria. Ideas on vertical routing in an actual sensor actuator interface using this amplifier have also been discussed such that the whole system may be “tearable” in any contour. Such a sensor actuator interface can have varied applications including wrap around thermometers and X-ray machines.

In this dissertation, a systematic modeling study has been conducted to investigate the microwaveassisted magnetic recording (MAMR) and its related physics. Two different modeling approaches including effective field modeling and recording signal-to-noise ratio (SNR) modeling has been conducted to understand the MAMR mechanism on segmented thin film granular medium. First the background information about perpendicular magnetic recording (PMR) and its limitation has been introduced. The motivation of studying MAMR is to further improve the recording area density capacity (ADC) of the hard disk drive (HDD) and to overcome the theoretical limitation of PMR. The development of recording thin film medium has also been discussed especially the evolvement of the multilayer composite medium. Since the spin torque oscillator (STO) is the essential component in MAMR, different STO structures have been discussed. The relation between STO setting (thickness, location and frequency) to the ac field distribution has also been explored. In effective field modeling, both head configuration and medium structure optimization have been investigated. The head configuration study includes the effective field distribution in relation to the fieldgeneration- layer thickness, location, and frequency. Especially an interesting potential erasure is detected due to the imperfect circularity of the ac field. Several approaches have been proposed to prevent the erasure. Meanwhile, notched and graded segmentation structure have been compared through effective field analysis in terms of the field gradient and track width. It has been found that MAMR with notched Hk distribution is able to achieve both high field gradient and narrow track width simultaneously. In recording SNR modeling, first the behavior of MAMR with single layer medium has been studied and three phases have been discovered. As proceed to the multi-layer medium, a practical issue which is MAMR with insufficient ac field power and high medium damping has been introduced. Since the fabrication of STO with high ac power is highly difficult, the issue has been investigated from the medium side which is through an optimized medium structure, the provided ac field can be utilized more efficiently. It has been found that more segmentation on upper part of the grain to fit the ac field yields more efficient ac field power usage. Following this scenario, the graded and notched segmentation structure have been studied in terms of SNR and track width. The traditional dilemma between recording SNR and track width in the conventional PMR is partially solve using MAMR with notched segmentation structure.

Ces travaux de recherches concernent l'association de la technologie des polymères à empreintes moléculaires aux dispositifs acoustiques à onde de Love afin de réaliser un biocapteur dans le cadre d'un projet ANR Tecsan. La première partie de ces travaux de thèse a dressé plus spécifiquement la mise au point d'un protocole de dépôt localisé de polymères imprimés (MIP) et non imprimés (NIP) en films minces compatibles avec la propagation de l'onde élastique. La seconde aprtie des travaux a visé une caractérisation des films et des capteurs ainsi réalisés, par microscopie à balayage et apr mesures de détection sous gaz. Des éléments relatifs aux propriétés mécaniques (porosité, surfaces spécifiques) des MIPs et NIPs, avant extraction de la molécule cible, puis après extraction et après recapture, ont permis de valider le principe du capteur, ouvrant la voie à l'application en milieu liquide. / This work deals with the association of molecularly imprinted polymers technology and Love wave devices in order to develop a biosensor in the frame of ANR project, Tecsan. The first part of this work concerned the development and the validation of a protocol for localized deposition of imprinted (MIP) and non-imprinted (NIP) polymeric thin film compatible with the propagation of acoustic wave. The second part exhibited the cahracterization of the coated sensors, by scanning microscopy and deep gas characterization. The proposed characterization technique gives information on surface morphology and porosity of thin MIP films before extraction of the target molecule, then after extraction and after rebinding. It allowed hence, the validation of the sensor principle. These results constitute a god background for future application in medium liquid.

L’objectif premier de ce travail a été de trouver une méthode de synthèse permettant depréparer des terpolymères ABC linéaires et en étoile en gardant la masse molaire des blocs A et B(PS et P2VP) constantes, tout en faisant varier la masse molaire du bloc C (PI) de sorte à avoiraccès à différentes morphologies. Le deuxième objectif consistait en l’auto-assemblage desterpolymères synthétisés sous forme de films minces.Afin de répondre au premier objectif de cette thèse, une voie de synthèse, combinant lapolymérisation anionique avec une méthode de couplage, a été mise au point. La polymérisationanionique séquentielle des blocs PS et P2VP a donné lieu à des chaînes PS-b-P2VPfonctionnalisées qui ont été ensuite couplées à différents blocs PI via une estérification de Steglich.Cette méthode de synthèse s’est révélée pertinente car des terpolymères ABC linéaires et en étoiletrès bien définis (c-à-d ayant une dispersité inférieure à 1.1) ont pu être synthétisés. De plus, laméthode de couplage, ayant un rendement proche de 100%, ne met pas en jeu l’utilisation de métalen tant que catalyseur.Dans un deuxième temps, l’auto-organisation des terpolymères a permis d’obtenir denouvelles morphologies sous forme de films minces. Un recuit par vapeur de solvant a été utilisépour apporter de la mobilité aux chaînes terpolymères. Ainsi, nous avons montré que l’autoorganisationde chaînes terpolymères linéaires (PS-b-P2VP-b-PI) permettait la formation d’unephase double gyroid coeur-écorce en film mince. De plus, l’auto-organisation des terpolymères enétoile (3 μ-ISP) a permis d’obtenir un pavage d’Archimède de type (4.6.12) pour la première foisen film mince. Dans ce cas, nous avons aussi montré que varier la masse molaire du bloc PI ainsique la nature du solvant de recuit permettait une rotation des domaines au sein la structure.Typiquement le coeur de la structure peut être occupé soit par le PI ou bien le PS. / The first objective of this work was to develop a synthesis method enabling the preparationof linear and star ABC terpolymers. The molecular weights of the A and B (PS and P2VP) blockswere kept constant while the size of the C (PI) block was varied to achieve different morphologies.The second objective of this work was devoted to the study of the self-assembly of linear and starABC terpolymer thin films. A synthesis route combining the anionic polymerization with acoupling method was developed. The PS and P2VP blocks were synthesized by a sequential anionicpolymerization. The PI block separately synthesized by anionic polymerization was then coupledto the PS-b-P2VP diblock via a Steglich esterification. This method revealed to be efficient sinceit is a catalyst metal-free reaction enabling to achieve well-defined terpolymers with a dispersitybelow 1.1The study of star and linear ABC terpolymer self-assembly led to new morphologies in thinfilm. A solvent vapor annealing treatment was used to promote the mobility of the polymericchains. A core-shell double gyroid structure was produced from the self-assembly of linear PS-b-P2VP-b-PI thin films. Four different crystallographic planes were observed depending on the filmthickness. Moreover, the self-assembly of star ABC terpolymer chains into a thin film (4.6.12)Archimedean tilling pattern was demonstrated for the first time. Here, the PS and PI blocksoccupied different places within the (4.6.12) tiling pattern depending on the PI volume ratio andthe solvent selected to swell the film.

Li-ion thin film battery technology has attracted much attention in recent years due to its highest need in portable electronic devices. Development of new materials for lithium ion battery (LIB) is very crucial for enhancement of the performance. LIB can supply higher energy density because Lithium is the most electropositive (-3.04V vs. standard hydrogen electrode) and lightest metal (M=6.94 g/mole). LIBs show many advantages over other kind of batteries such as, high energy density, high power density, long cycle life, no memory effect etc. The major work presented in this thesis is on the development of nanostructured materials for anode of Li-ion battery. It involves the synthesis and analysis of grapheme nanosheet (GNS) and its performance as anode material in Li ion battery. We studied the synthesis of GNS over different substrates and performed the anode studies. The morphology of GNS has great impact on Li storage capacity. Tin and Tin oxide nanostructures have been embedded in the GNS matrix and their electrochemical performance has been studied. Chapter 1 gives the brief introduction about the Li ion batteries (LIBs), working and background. Also the relative advantages and characterization of different electrode materials used in LIBs are discussed. Chapter 2 discusses various experimental techniques that are used to synthesize the electrode materials and characterize them. Chapter3 presents the detailed synthesis of graphene nanosheet (GNS) through electron cyclotron resonance (ECR) microwave plasma enhanced chemical vapor deposition (ECR PECVD) method. Various substrates such as metallic (copper, Ni and Pt coated copper) and insulating (Si, amorphous SiC and Quartz) were used for deposition of GNS. Morphology, structure and chemical bonding were analyzed using SEM, TEM, Raman, XRD and XPS techniques. GNS is a unique allotrope of carbon, which forms highly porous and vertically aligned graphene sheets, which consist of many layers of graphene. The morphology of GNS varies with substrate. Chapter 4 deals with the electrochemical studies of GNS films. The anode studies of GNS over various substrates for Li thin film batteries provides better discharge capacity. Conventional Li-ion batteries that rely on a graphite anode have a limitation in the capacity (372 mAh/g). We could show that the morphology of GNS has great effect in the electrochemical performance and exceeds the capacity limitation of graphite. Among the electrodes PtGNS shown as high discharge capacity of ~730 mAh/g compare to CuGNS (590 mAh/g) and NiGNS (508 mAh/g) for the first cycle at a current density of 23 µA/cm2. Electrochemical impedance spectroscopy provides the various cell parameters of the electrodes. Chapter 5 gives the anodic studies of Tin (Sn) nanoparticles decorated over GNS matrix. Sn nanoparticles of 20 to 100nm in size uniformly distributed over the GNS matrix provides a discharge capacity of ~1500 mAh/g mAh/g for as deposited and ~950 mAh/g for annealed Sn@GNS composites, respectively. The cyclic voltammogram (CV) also shows the lithiation and delithiation process on GNS and Sn particles. Chapter 6 discusses the synthesis of Tinoxide@GNS composite and the details of characterization of the electrode. SnO and SnO2 phases of Tin oxide nanostructures differing in morphologies were embedded in the GNS matrix. The anode studies of the electrode shows a discharge capacity of ~1400 mAh/g for SnO phase (platelet morphology) and ~950 mAh/g for SnO2 phase (nanoparticle morphology). The SnO phase also exhibits a good coulumbic efficiency of ~95%. Chapter 7 describes the use of SnO2 nanowire attached to the side walls of the GNS matrix. A discharge capacity of ~1340 mAh/g was obtained. The one dimensional wire attached to the side walls of GNS film and increases the surface area of active material for Li diffusion. Discharge capacity obtained was about 1335 mAhg-1 and the columbic efficiency of ~86% after the 50th cycle. The research work carried out as part of this thesis, and the results have summarized in chapter 8.

L’évolution rapide des communications sans fil a favorisé l’augmentation du nombre de standards alloués aux systèmes de communication fonctionnant sur différentes bandes de fréquences. Pour accompagner les derniers développements de systèmes sans fil, il est indispensable de concevoir des antennes miniatures intégrables. Cependant, la miniaturisation des antennes s’accompagne d’une réduction significative de la bande passante et de leur efficacité de rayonnement ainsi qu’à l’apparition d’un décalage fréquentiel de leurs fréquences de fonctionnement lorsqu’elles sont étudiées dans leur contexte d’utilisation. L’intégration de dispositifs accordables au sein d 'une antenne permet de répondre favorablement à ces problématiques. Parmi les solutions proposées dans la littérature, l’utilisation de matériaux ferroélectriques en couche mince permet de concevoir un condensateur accordable en fonction du champ électrique appliqué. Ces dispositifs réalisés à base de couches minces ferroélectriques ont été développés pour répondre aux exigences particulières et extrêmes des systèmes de télécommunication actuels (miniaturisation, faible coût, facilité de fabrication et d’intégration et bonne tenue en puissance). Cette thèse s’inscrit dans la continuité des recherches sur les antennes reconfigurables en fréquences à base de matériaux ferroélectriques. Deux axes principaux ont été développés au cours de ces travaux de recherche : le développement et la réalisation de condensateurs intégrant un film BST au sein du laboratoire XLIM et leurs caractérisations en hyperfréquence. La seconde partie de nos travaux concerne l’intégration de l’un de ces dispositifs accordables au sein d’une antenne miniature afin d’étudier son accordabilité en fréquence. / The rapid growth of wireless communication has promoted the increase of the number of standards for wireless applications. This progress requests new manufacturing processes of smart devices that are able to work on several frequency bands. However, the miniaturization of antennas is accompanied by a significant reduction of the bandwidth as well as its radiation efficiency and it becomes dependent on its using context. Tunable devices can be integrated within antennas in order to overcome these main issues. Among the solutions proposed in the literature, thin-film ferroelectric materials are used to realize tunable capacitors. The use of such materials allows the design of a tunable capacitor that can be tuned by an applied electric field. The advances of these ferroelectric thin-film devices were developed in order to meet particular and extreme requirements for today's telecommunication systems (miniaturization, low cost, ease of the manufacture process, integration and good power handling). This thesis is part of ongoing research over frequency reconfigurable antennas which are based on ferroelectric materials. Two main axes were developed during this work: The development and realization of capacitors that incorporate a BST film along with their microwave characterizations within XLIM lab. The second part of our work is dedicated to the realization of the complete tunable antenna.

No description available.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14871号 / 工博第3139号 / 新制||工||1470(附属図書館) / 27293 / UT51-2009-K667 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 伊藤 紳三郎, 教授 長谷川 博一, 教授 金谷 利治 / 学位規則第4条第1項該当

En quelques années, l'efficacité des cellules solaires à base de Cu(In,Ga)Se2 (CIGS) est passée de 20% à 22.6%. La rapidité de ce développement montre que le CIGS est un matériaux idéal pour les technologies solaires en couches minces. Pourtant, le coût de production cette technologie doit encore être abaissé pour une meilleure compétitivité. La fabrication d'un module avec une couche CIGS plus fine permettrait d'augmenter la production d'une usine et de réduire sa consommation en métaux. Ce travail de thèse vise à réduire l'épaisseur du CIGS d'un standard de 2.0-2.5 µm à une épaisseur inférieure à 500 nm sans altérer les performances des cellules. Cependant, comme rapporté dans la littérature, nous avons observé une diminution des rendements, ce que nous avons analysé en détail en comparant simulations et caractérisations d'échantillons. Celle-ci est causée à la fois par une faible absorption de la lumière dans la couche de CIGS et par un impact important du contact arrière (fortes recombinaisons et faible réflectivité). Pour dépasser ces limites, nous démontrons à la fois théoriquement et expérimentalement que le contact arrière en molybdène peut être remplacé par un oxyde transparent conducteur couplé à un miroir métallique. Nous obtenons de cette manière de meilleurs rendements de cellules. Pour atteindre ce résultat, une optimisation du dépôt de CIGS a été nécessaire. De plus, nous prouvons qu'une couche d'oxyde perforée, insérée entre le CIGS et le contact arrière, limite les recombinaisons des porteurs de charges et réduit l'influence des courants parallèles. Au final, nous avons fabriqué une cellule avec un rendement de 10.7% sur SnO2:F passivé par Al2O3. / In the past three years, record efficiency of Cu(In,Ga)Se2 (CIGS) based solar cells has improved from 20% up to 22.6%. These results show that CIGS absorber is ideal for thin-film solar cells, even if this technology could be more competitive with a lower manufacture cost. The fabrication of devices with thinner CIGS absorbers is a way to increase the throughput of a factory and to reduce material consumption. This PhD thesis aims to develop cells with a CIGS thickness below 500 nm instead of the conventional 2.0-2.5 µm. However, as reported in the literature, we observed a decrease in cell performance. We carefully analyzed this effect by the comparison between simulations and sample characterizations: it is attributed, on one hand, to a lack of light absorption in the CIGS layer and, on the other hand, to an increased impact of the back-contact (high recombination and low reflectivity). To resolve these problems, we demonstrated theoretically and experimentally that the use of an alternative back-contact, other than molybdenum, such as a transparent conducting oxide coupled with a light reflector, improves the cell efficiency. To achieve this result, an optimization of the CIGS deposition was necessary. Moreover, we proved that a porous oxide layer inserted between the CIGS and the back-contact limits the charge-carrier recombination and removes some parasitic resistance. Finally, an efficiency of 10.7% was achieved for a 480-nm-thick CIGS solar cell with a SnO2:F back-contact passivated with a porous Al2O3 layer.