Bismuth titanate Bi4Ti3O12, is one of the bismuth based layered ferroelectric materials that is a candidate for replacing the lead based ferroelectric materials in for instance non-volatile ferroelectric random access memories (FRAM). This is due to the fact that the bismuth based ferroelectrics consists of pseudo perovskite units sandwiched in between bismuth oxide layers, which gives them a better fatigue nature. In this thesis thin films of Bi4Ti3O12 have been deposited by chemical vapour deposition (CVD) using the metal iodides, BiI3 and TiI4 as precursors. Films grown on MgO(001) substrates were found to grow epitaxially. The electrical properties were determined for films grown on Pt-coated silicon and good properties such as a high dielectric constant (ε) of 200, low tan δ of 0.018, a remnant polarisation (Pr) of 5.3 μC/cm2 and coercive field (Ec) as high as 150 kV/cm were obtained. Thin films in the Bi-Ti-O system were also deposited by atomic layer deposition (ALD) using metalorganic precursors. In addition to the ternary bismuth titanates, films in the binary oxide systems i.e. bismuth oxides and titanium oxides were deposited. Epitaxial TiO2 films were deposited both by CVD and ALD using TiI4 as precursor. The rutile films deposited by ALD were found to grow epitaxially down to a temperature of at least 375 ¢ªC on α-A12O3(0 1 2) substrates. The TiO2 ALD process was also studied in-situ by QCM. Different bismuth oxides were deposited by halide-CVD using BiI3 as precursor on MgO(0 0 1) and SrTiO3(0 0 1) substrates and the results were summarised in an experimental CVD stability diagram. The Bi2O2.33 phase was found to grow epitaxially on both substrates.

In vapour phase deposition, the knowledge and control of homogeneous and heterogeneous reactions in connection to precursor design may lead to the deposition of the desired material; structure or phase. This thesis is a document attempting to increase the knowledge of film growth in the B-N system. In the present work, surface processes like adsorption, abstraction, migration and nucleation have been modelled on an atomic scale using density functional theory (DFT). The systems studied are mainly cubic and hexagonal boron nitride surfaces ((c-BN) vs. (h-BN)), but also the α-boron (001) surface. It has been shown that DFT and a cluster approach is a reliable tool in modelling boron nitride surfaces and surface processes, provided that certain functionals, basis sets and geometrical constraints are used. By using surface stabilisers such as H species in an electron- or radical-rich environment, it has been shown that i) the structure of cubic boron nitride surfaces can be sustained, and ii) c-BN may nucleate on the h-BN (001) basal plane. Furthermore, the nucleation of c-BN from arbitrary and experimental growth species is energetically preferable over a continuous growth of h-BN on the h-BN (001) edges. An atomic layer deposition (ALD) process for boron nitride was developed. It resulted in turbostratic (t-BN), transparent, well-adherent and almost atomically smooth BN films. However, with the cubic phase of boron nitride absent in the ALD films, more effort needs to be put into both the theoretical and the experimental branches of this field of science.

Due to the constantly decreasing dimensions of electronic devices, the conventional dielectric material in transistors and capacitors, SiO2, has to be replaced by a material with higher dielectric constant. Some of the most promising candidates are tantalum oxide,Ta2O5, zirconium oxide, ZrO2 and hafnium oxide, HfO2. This thesis describes new chemical vapour deposition (CVD) and atomic layer deposition (ALD) processes for deposition of Ta2O5, ZrO2 and HfO2 using the metal iodides as starting materials. The layer-by-layer growth in ALD was also studied in real time with a quartz crystal microbalance (QCM) to examine the process characteristics and to find suitable parameters for film deposition. All the processes presented here produced high-purity films at low deposition temperatures. It was also found that films deposited on Pt substrates generally crystallise at lower temperature, or with lower thickness, than on silicon and single-crystalline oxide substrates. Films grown on MgO(001) and α-Al2O3(001) substrates were strongly textured or epitaxial. For example, monoclinic HfO2 deposited on MgO(001) were epitaxial for deposition temperatures of 400-500 C in ALD and 500-600 C in CVD. Electrical characterisation showed that the crystallinity of the films had a strong effect on the dielectric constant, except in cases of very thin films, where the dielectric constant was more dependent on layer thickness.

Si complementary metal-oxide-semiconductor (CMOS) technology has been prospered through continuously scaling of its feature size. As scaling is approaching its physical limitations, new materials and device structures are expected. High electron mobility III-V materials are attractive as alternative channel materials for future post-Si CMOS applications due to their outstanding transport property. High-k dielectrics/metal gate stack was applied to reduced gate leakage current and thus lower the power dissipation. Combining their benefits, great efforts have been devoted to explore III-V/high-k/metal metal-oxide-semiconductor field-effect-transistors (MOSFETs). The main challenges for III-V MOSFETs include interface issues of high-k/III-V, source and drain contact, silicon integration and reliability. A comprehensive study on III-V MOSFETs has been presented here focusing on three areas: 1) III-V/high-k/metal gate stack: material and electrical properties of various high-k dielectrics on III-V substrates have been systematically examined; 2) device architecture: device structures from planar surface channel MOSFETs and buried channel quantum well FETs (QWFETs) to 3D gate-wrapped-around FETs (GWAFETs) and tunneling FETs (TFETs) have been designed and analyzed; 3) fabrication process: process flow has been set up and optimized to build scaled planar and 3D devices with feature size down to 40nm. Potential of high performances have been demonstrated using novel III-V/high-k devices. Effective channel mobility was significantly improved by applying buried channel QWFET structure. Short channel effect control for sub-100nm devices was enhanced by shrinking gate dielectrics, reducing channel thickness and moving from 2D planar to 3D GWAFET structure. InGaAs TFETs have also been developed for ultra-low power application. This research work demonstrates that III-V/high-k/metal MOSFETs with superior device performances are promising candidates for future ultimately scaled logic devices. / text

L'X-ALD et la P-NALD sont deux maladies peroxysomales, métaboliques et neurodégénératives rares. L'X-ALD et la P-NALD résultent de déficiences respectives en ABCD1 et ACOX1. Ces deux maladies dans leurs formes sévères sont associées à des phénomènes de démyélinisation inflammatoire du SNC. Au niveau des lésions, des signes d'oxydation et une mort cellulaire sont observés. L'accumulation des AGTLC plasmatiques et tissulaires est le critère biochimique commun à ces deux maladies. Dans un premier temps, nous avons caractérisé une lignée d'oligodendrocytes murins 158N afin de l'utiliser comme modèle. Cette lignée qui présente des caractéristiques d'oligodendrocytes matures (expression des protéines de myéline MOG, MBP, PLP) possède aussi des peroxysomes fonctionnels possédant les protéines Abcd1 et Acox1. Ensuite, nous avons étudié les effets cytotoxiques et pro-oxydants des AGTLC (C24:0 et C26:0), ainsi que l'incidence de l'extinction d'Abcd1 et d'Acox1 par siRNA sur l'équilibre RedOx et la mort cellulaire. Les effets des AGTLC sur les caractéristiques biophysiques de la membrane cytoplasmique ont aussi été abordés. Par ailleurs, des marqueurs du stress oxydant ont été recherchés sur des plasmas des patients atteints de différentes formes d'X-ALD. In vitro, nous avons montré que l'accumulation d'AGTLC dans les cellules 158N induit une surproduction d'espèces radicalaires de l'oxygène et de l'azote et une perturbation des défenses anti-oxydantes (catalase, SOD, GSH). Ceci s'accompagne d'une peroxydation lipidique, d'une carbonylation des protéines et d'une dégradation de l'ADN. L'extinction d'Abcd1 et d'Acox1 par des siRNA augmente la production d'espèces radicalaires et potentialise le stress oxydant induit par les AGTLC. Sur les plasmas de patients atteints de différentes formes d'X-ALD, comparativement à des sujets sains, nous avons montré l'accumulation des produits de peroxydation lipidiques (7-hydroxycholestérols, HODEs). Le taux de ces deux produits est corrélé avec la sévérité de la maladie: CCALD>AMN>Addison>ACALD. Les AGTLC induisent aussi la mort des cellules 158N par un processus non apoptotique. Cette mort cellulaire est caractérisée par: une perturbation rapide du calcium intracellulaire, une diminution du pH, une chute du potentiel transmembranaire mitochondrial associée à des modifications structurales des mitochondries, une déstabilisation des lysosomes et une formation de figures d'autophagie. Les AGTLC perturbent aussi la fluidité membranaire. Par ailleurs, les AGTLC n'affectent pas l'expression des protéines majeures de la myéline PLP et MBP. Ces travaux ont mis en évidence un lien direct entre l'accumulation des AGTLC, le stress oxydant et l'induction de mort cellulaire faisant intervenir les lysosomes. La déficience en Abcd1 et Acox1 favorise le stress oxydant. En accord avec les résultats obtenus in vitro, la mise en évidence de marqueurs de peroxydation lipidiques dans le plasma de malades atteints d'X-ALD conforte l'hypothèse d'une intervention du stress oxydant dans cette pathologie.

AlGaN/GaN high electron mobility transistors (HEMTs) have appeared as attractive candidates for high power, high frequency, and high temperature operation at microwave frequencies. In particular, these devices are being considered for use in the area of high RF power for microwave and millimeter wave communications transmitter applications at frequencies greater than 100 GHz and at temperatures greater than about 150 °C. However, there are concerns regarding the reliability of AlGaN/GaN HEMTs. First of all, thermal reliability is the chief concern since high channel temperatures significantly affect the lifetime of the devices. Therefore, it is necessary to find the solutions to decrease the temperature of AlGaN/GaN HEMTs. In this study, we explored the methods to reduce the channel temperature via high thermal conductivity diamond as substrates of GaN. Experimental verification of AlGaN/GaN HEMTs on diamond substrates was performed using micro-Raman spectroscopy, and investigation of the design space for devices was conducted using finite element analysis as well. In addition to the thermal impact on reliability, environmental effects can also play a role in device degradation. Using high density and pinhole free films deposited using atomic layer deposition, we also explore the use of ultra-thin barrier films for the protection of AlGaN/GaN HEMTs in high humidity and high temperature environments. The results show that it is possible to protect the devices from the effects of moisture under high negative gate bias stress testing, whereas devices, which were unprotected, failed under the same bias stress conditions. Thus, the use of the atomic layer deposition (ALD) coatings may provide added benefits in the protection and packaging of AlGaN/GaN HEMTs.

Στην παρούσα Εργασία λεπτά υμένια (5 -25 nm) ZrO2 έχουν εναποτεθεί με τη μέθοδο ALD σε μη αδρανοποιημένο (100) Ge τύπου-p, με ειδική αντίσταση 0.2-0.5 Ω-cm. Η εναπόθεση του ZrO2 πραγματοποιήθηκε στους 2500C, με τη χρήση διαδοχικών παλμών H2O και Tetrakis (Dimethylamido) Zirconium που ήταν και οι πρόδρομες ενώσεις. Ο δομικός χαρακτηρισμός των υμενίων (στοιχειομετρία, σύνθεση και τραχύτητα της διεπιφάνειας, κρυσταλλογραφική φάση του διηλεκτρικού κλπ) πραγματοποιήθηκε μέσω των μεθόδων XPS και ΤΕΜ. Ο λεπτομερής ηλεκτρικός χαρακτηρισμός των υμενίων έγινε με παράμετρο τη θερμοκρασία σε δομές (πυκνωτές) MOS που έφεραν λευκόχρυσο, Pt, ως μέταλλο πύλης. Πραγματοποιήθηκαν μετρήσεις C-V, C-f με παράμετρο τη θερμοκρασία και για θερμοκρασίες από 300Κ έως 80 Κ. Σύμφωνα με τα αποτελέσματα που προέκυψαν από την παρούσα μελέτη τα υμένια με πάχος μικρότερο των 15 nm εμφανίζουν πολύ φτωχή ηλεκτρική συμπεριφορά, η οποία βελτιώνεται με την αύξηση του πάχους. Σχετικά παχιά (25 nm) υμένια ZrO2 εμφανίζουν πυκνότητα διεπιφανειακών παγίδων της τάξης των 1011 eV-1cm-2, όπως προκύπτουν από μετρήσεις που πραγματοποιήθηκαν στους 80K. Από μετρήσεις I-V με παράμετρο τη θερμοκρασία προκύπτουν οι μηχανισμοί αγωγιμότητας που διέπουν τις μελετούμενες δομές. Η επίδραση της ανόπτησης σε περιβάλλον Forming Gas μετά την εναπόθεση του μετάλλου μελετάται επίσης. Τέλος, μελετώνται οι ηλεκτρικές ιδιότητες δομών Pt/ZrO2 (25 nm)/p-Ge, σε υποστρώματα που περιέχουν ταυτόχρονα περιοχές που έχουν υποστεί ανόπτηση με Laser και περιοχές που δεν έχουν υποστεί ανόπτηση. Η ανόπτηση με Laser φαίνεται να υποβαθμίζει την ηλεκτρική συμπεριφορά της δομής. Ωστόσο, σύμφωνα με τα αποτελέσματα της παρούσας εργασίας, υπάρχουν ενδείξεις ότι οι δομές σε περιοχές που γειτνιάζουν με αυτές που έχουν υποστεί ανόπτηση με Laser εμφανίζουν βελτιωμένες ηλεκτρικές ιδιότητες ακόμη και σε σχέση με τα δείγματα αναφοράς που περιλαμβάνουν δομές που αναπτύχθηκαν σε μη ακτινοβολημένο υπόστρωμα. / In the present Thesis, thin (5 -25 nm) films of ZrO2 have been deposited by Atomic Layer Deposition (ALD) on non-passivated p-type (100) Germanium substrates with resistivity 0.2-0.5 Ω-cm. ZrO2 deposition has been performed at 2500C using a series of alternating pulses of H2O and Tetrakis(Dimethylamido) Zirconium, which were the deposition precursors. Structural characterization of the films in terms of stoichiometry, interface composition and roughness, crystallographic phase of the dielectric etc., has been performed using XPS and TEM analysis. Detailed electrical characterization [C-V, and C-f measurements] of the films as a function of temperature has been performed in MOS capacitors using Pt as gate metal. It has been observed that the electrical behaviour of the films is extremely poor in thickness range below 15 nm, while they show an improvement in higher thickness regime. Thick (25 nm) ZrO2 showed an interface trap density of the order of 1011 eV-1cm-2 extracted at 80K. The conductivity mechanisms of the structures are revealed by I-V measurement at various temperatures. Finally the effect of post-metallization annealing in Forming Gas ambient has been studied. In parallel the electrical properties of structures Pt/ZrO2 (25 nm)/p-Ge, on substrates containing simultaneously laser annealed and non-annealed areas has been studied. It has been obtained that laser annealing of the substrate deteriorates the electrical behaviour of the structure, while it seems that structures on the areas in proximity to the annealed ones revealed superior electrical properties as compared to the corresponding deposited on non-annealed (reference) samples.

L’X-ALD et la P-NALD sont deux maladies peroxysomales, métaboliques et neurodégénératives rares. L'X-ALD et la P-NALD résultent de déficiences respectives en ABCD1 et ACOX1. Ces deux maladies dans leurs formes sévères sont associées à des phénomènes de démyélinisation inflammatoire du SNC. Au niveau des lésions, des signes d'oxydation et une mort cellulaire sont observés. L’accumulation des AGTLC plasmatiques et tissulaires est le critère biochimique commun à ces deux maladies. Dans un premier temps, nous avons caractérisé une lignée d'oligodendrocytes murins 158N afin de l'utiliser comme modèle. Cette lignée qui présente des caractéristiques d'oligodendrocytes matures (expression des protéines de myéline MOG, MBP, PLP) possède aussi des peroxysomes fonctionnels possédant les protéines Abcd1 et Acox1. Ensuite, nous avons étudié les effets cytotoxiques et pro-oxydants des AGTLC (C24:0 et C26:0), ainsi que l’incidence de l’extinction d’Abcd1 et d’Acox1 par siRNA sur l'équilibre RedOx et la mort cellulaire. Les effets des AGTLC sur les caractéristiques biophysiques de la membrane cytoplasmique ont aussi été abordés. Par ailleurs, des marqueurs du stress oxydant ont été recherchés sur des plasmas des patients atteints de différentes formes d’X-ALD. In vitro, nous avons montré que l’accumulation d'AGTLC dans les cellules 158N induit une surproduction d'espèces radicalaires de l'oxygène et de l'azote et une perturbation des défenses anti-oxydantes (catalase, SOD, GSH). Ceci s'accompagne d'une peroxydation lipidique, d'une carbonylation des protéines et d'une dégradation de l'ADN. L'extinction d'Abcd1 et d'Acox1 par des siRNA augmente la production d'espèces radicalaires et potentialise le stress oxydant induit par les AGTLC. Sur les plasmas de patients atteints de différentes formes d’X-ALD, comparativement à des sujets sains, nous avons montré l’accumulation des produits de peroxydation lipidiques (7-hydroxycholestérols, HODEs). Le taux de ces deux produits est corrélé avec la sévérité de la maladie: CCALD>AMN>Addison>ACALD. Les AGTLC induisent aussi la mort des cellules 158N par un processus non apoptotique. Cette mort cellulaire est caractérisée par: une perturbation rapide du calcium intracellulaire, une diminution du pH, une chute du potentiel transmembranaire mitochondrial associée à des modifications structurales des mitochondries, une déstabilisation des lysosomes et une formation de figures d'autophagie. Les AGTLC perturbent aussi la fluidité membranaire. Par ailleurs, les AGTLC n'affectent pas l'expression des protéines majeures de la myéline PLP et MBP. Ces travaux ont mis en évidence un lien direct entre l'accumulation des AGTLC, le stress oxydant et l'induction de mort cellulaire faisant intervenir les lysosomes. La déficience en Abcd1 et Acox1 favorise le stress oxydant. En accord avec les résultats obtenus in vitro, la mise en évidence de marqueurs de peroxydation lipidiques dans le plasma de malades atteints d'X-ALD conforte l'hypothèse d'une intervention du stress oxydant dans cette pathologie. / X-ALD and P-NALD are two rare, peroxisomal metabolic and neurodegenerative diseases. ABCD1 and ACOX1 are known to be responsible for X-ALD and P-NALD, respectively. The actively demyelinating lesions in CNS, exhibited signs of oxidative stress and cell death. The accumulation of VLCFA in plasma and tissue is the biochemical common hallmark to both diseases. First, we characterized a murine oligodendrocytes cell line 158N to use it as a model. This 158N cell line which has characteristics of mature oligodendrocytes (expression of myelin proteins MOG, MBP, PLP), has also functional peroxisomes with Abcd1 and Acox1 proteins. Then, we studied the cytotoxic and pro-oxidative effects of VLCFA (C24: 0 and C26: 0), and the effects of in vitro silencing of the Abcd1 and Acox1 genes by siRNA on the redox balance and cell death. Effects of VLCFA on the biophysical characteristics of cytoplasmic membrane were also evaluated. Moreover, markers of oxidative stress were researched on plasma of patients with different forms of X-ALD. In vitro, we showed that the accumulation of VLCFA on 158N cells induced overproduction of reactive oxygen and nitrogen species and a disruption of antioxidant defense systems (catalase, SOD, GSH). This was accompanied by lipid peroxidation, protein carbonylation and degradation of DNA. The extinction of Abcd1 and Acox1 by siRNA increased the production of radical species and potentialized the oxidative stress induced by VLCFA. On plasma of patients with different forms X-ALD, compared to healthy subjects, we showed an accumulation of lipid peroxidation products (7-hydroxycholesterol, HODEs). The rate of these two products is correlated with the severity of the disease: CCALD> AMN> Addison> ACALD. The VLCFA also induce cell death on 158N by a non-apoptotic process. This cell death is characterized by: a rapid increased of intracellular Ca2+ level, pH decrease, a loss of mitochondrial transmembrane potential associated with structural changes of mitochondria, a destabilization of lysosomes, and formation of autophagic vacuoles. The VLCFA also disrupt the membrane fluidity. Furthermore, VLCFA do not affect the expression of myelin major proteins PLP and MBP. This work highlighted a direct link between VLCFA accumulation, oxidative stress and induction of cell death involving lysosomes. Abcd1 and Acox1 deficiency promotes oxidative stress. In agreement with results obtained in vitro, the detection of markers of lipid peroxidation in the plasma of X-ALD patients favors the hypothesis of an involvement of oxidative stress in this pathology.

Les hépatopathies métaboliques regroupent les maladies non alcooliques du foie (NAFLD) et les maladies alcooliques du foie (MAF) causées respectivement par l’obésité ou une consommation excessive d’alcool. Ces pathologies vont de la simple stéatose à des formes aggravées pouvant aller jusqu’au carcinome hépatocellulaire. D’autres facteurs que le surpoids ou l’abus d’alcool jouent un rôle dans la susceptibilité des patients à développer une NAFLD ou une MAF. Cette thèse a pour objectif de clarifier et d'étudier les mécanismes et les facteurs participant à l’installation de l’inflammation dans ces deux pathologies. Mes travaux ont porté d’une part sur le rôle de la cellule de Kupffer dans les étapes précoces de la NAFLD et d’autre part sur l’étude du microbiote intestinal comme cofacteur déclenchant de la MAF. La cellule de Kupffer lors de la stéatose, étape précoce de la NAFLD, présente une dérégulation de son homéostasie lipidique qui participe à son phénotype pro-inflammatoire et favorise l’inflammation hépatique. L’impact du fructose, largement utilisé dans notre alimentation actuelle, a été étudié et aggrave l’inflammation hépatique lors d’un régime hyperlipidique et ceci est associé à une dysbiose spécifique. Dans la MAF, une dysbiose intestinale, une diminution des Bacteroides, a été associée aux lésions hépatiques dans un modèle murin d’alcoolisation. L‘utilisation de traitements permettant de maintenir cette population à des taux élevés a corrigé cette dysbiose et protégé les animaux face aux lésions hépatiques. Ces travaux permettent d‘envisager le MI comme une cible prometteuse permettant de contrôler l’évolution des hépatopathies métaboliques vers des formes sévères. / Metabolic hepatopathies is including Non Alcoholic Fatty Liver Disease (NAFLD) and Alcoholic Liver Disease (ALD) due to an excessive consumption of alimentation or alcohol. The pathologies range from simple steatosis to aggravated forms until hepatocellular carcinoma. Other factors than overweight or alcohol abuse play a role in sensitivity of patients to develop NAFLD or ALD. The aim of this thesis is to clarify and study the mechanisms and factors that lead to the installation of inflammation in those pathologies. My work covered in part on the role of Kupffer cell in the early stages of NAFLD and secondly on the study of intestinal microbiota as a cofactor triggering the MAF.The Kupffer cell role in steatosis, the early stages of NAFLD, showed a deregulation of its lipid homeostasis involved in the pro-inflammatory phenotype and promotes liver inflammation. The impact of fructose, widely used in our current diet, was studied and worsening liver inflammation during high fat diet. This is associated with a specific dysbiosis. In ALD, intestinal dysbiosis, a decrease of Bacteroides, leading to liver damage has been established. The use of treatments to maintain this population with high levels corrected the dysbiosis and has protected animals against liver damages. Both works on the NAFLD and ALD establish MI is a promising target to control the evolution of metabolic liver diseases toward aggravated forms.

A new materials system of a single layered Co(W) barrier/liner coupled with a Cu(Mn) alloy seed was investigated. Atom probe tomography visualized the sub-nanoscale structure of Cu(Mn)/Co(W) system, and thereby revealed Cu diffusion behavior of Co(W). Grain boundaries of Co were found to be the diffusion path, and successfully stuffed by W. Mn in Cu(Mn) also segregated to stuff the grain boundaries of Co. Combination of these two additives enabled high barrier property against Cu diffusion of Cu(Mn)/Co(W). Foreseeing tiny and high-aspect-ratio Cu interconnect features, Cu(Mn)/Co(W) was fabricated by ALD/CVD processes. To maximize the performance, minor impurities of the film incorporated from the ligand of the precursors were controlled by precursor selection. Thin, conformal, and smooth films were finally demonstrated onto a trench substrate.