Das Konzept neuartiger, resistiv schaltender Langzeitspeicherzellen sieht eine enorme Erhöhung der Speicherdichte bei gleichzeitig geringem Energieverbrauch und hoher Skalierbarkeit vor. In diesem Zusammenhang sind unterschiedlichste Übergangsmetalloxide Gegenstand der aktuellen Forschung, die zwischen Metallelektroden in einer Metall-Isolator-Metall-Struktur eingebettet sind. Ein anerkanntes Modell zur Klärung der lokalen Struktur innerhalb des Schaltmechanismus beschreibt die Änderung des resistiven Zustandes in der wechselnden Ausbildung und Auflösung eines leitfähigen Pfades in der Oxidschicht, der beide Elektroden miteinander verbindet. Die vorliegende Arbeit befasst sich auf dieser Grundlage mit der Untersuchung solcher Speicherzellen, wobei anhand der gewählten Elektrodenmaterialien Speichereffekte rein auf Änderungen im Oxid zurückzuführen sind. Die sich daraus ergebende Möglichkeit der gezielten Änderung des efekthaushaltes und des resistiven Schaltverhaltens der Oxidschichten durch deren Ausheizung oder Modifikation mittels Ionenimplantation stand im Fokus der Arbeit. Dementsprechend muss für eine genaue Lokalisierung des Schaltmechanismus die gewählte Oxidstruktur nicht nur genauestens bekannt, sondern auch möglichst rein sein. Zur Vereinigung all diese Faktoren wird das Modellsystem SrO-TiO2 mit den beiden Vertretern TiO2 und SrTiO3 untersucht, da seine Eigenschaften in der Literatur bereits rege diskutiert wurden. Zur Gewährleistung der Reinheit der Schichten wird die Herstellung der Isolatorschichten durch Atomlagenabscheidung eingesetzt und deren Optimierung, sowie Schichtcharakterisierung im ersten Teil der Arbeit vorgestellt. Mittels einer Vielzahl optischer und struktureller Analysemethoden lassen sich definierte Rückschlüsse über die Eigenschaften der Oxide ziehen. Sämtliche Veröffentlichungen zur Herstellung von SrTiO3 mittels Atomlagenabscheidung beziehen sich entweder auf eigens hergestellte Anlagensysteme oder Präkursormaterialien, wodurch die Schichten industriell nicht reproduzierbar sind. Eines der Ergebnisse der vorliegenden Arbeit ermöglicht eben dies durch die erstmalige Kombination einer kommerziell erhältlichen Anlage mit kommerziellen Präkursormaterialien. Nach deren Optimierung werden die Oxidschichten zwischen den beiden Metallelektroden Au und TiN integriert und die daraus resultierenden Speicherzellen elektrisch charakterisiert. Es kann bipolares, nichtflüchtiges, resistives Schaltverhalten in amorphen und ex situ kristallisierten Oxiden nachgewiesen werden. Anhand von Struktur-Eigenschaft-Korrelationen gelingt es, die Leitungsmechanismen in den untersuchten Speicherzellen als Schottky-Emission und bei ausreichend hohen Spannungen als volumendominierte Poole-Frenkel-Emission zu charakterisieren. Bei den dafür notwendigen Defekten handelt es sich um flache Donatorzustände. Die Annahme des resistiven Schaltens über einen reversiblen leitfähigen Pfad basierend auf Defektzuständen wird durch die Änderung der Coulomb-Barrierenhöhe bei konstanter Schottky-Barrierenhöhe innerhalb derselben Mikrostruktur bestätigt. Besonders das untersuchte TiO2 amorpher Struktur mit Schalt- und Lesegeschwindigkeiten von wenigen Millisekunden, aber auch polykristallines SrTiO3 zeigen ein hohes Potential für deren zukünftige Anwendung auf dem Gebiet resistiv schaltender Speicherzellen. Durch Kr+-Ionenimplantation ändern sich nachweislich sowohl die elektrischen als auch die strukturellen Eigenschaften in TiO2 und SrTiO3. XRD-Messungen an polykristallinen TiO2-Schichten bestätigen die mittels SRIM durchgeführten Simulationsdaten und zeigen für Implantationen ausreichend hoher Fluenzen eine Amorphisierung der kristallinen Strukturen durch atomare Umverteilung im Oxid. Dadurch bilden sich zusätzlich intrinsische, tiefe Defektniveaus in den Oxidschichten, welche das resistive Schalten modifizieren. Die Implantation polykristalliner TiO2-Schichten führt nachweislich zur Umwandlung flüchtiger in nichtflüchtige Schaltkurven, die im Vergleich zu amorphen Ausgangsproben stabilere Widerstandswerte bei geringerem Energieaufwand zeigen. / The concept of novel, longterm resistive switching memories is based on an enormous increase of the storage density with a simultaneous low energy consumption and a high scalability. In this context, different transition metal oxides, which are embedded between metal electrodes in a metal-insulatormetal structure, are part of the ongoing research. A widely recognized model for an explanation of the local structure within the switching mechanism discribes the alteration of the resistive state as a result of an alternating forming and interruption of a conducting path inside an oxide layer. The presence of such a filament acts like a linkage between the electrodes. Based on that, the present study deals with the investigation of such memory storages. In the wake of this the chosen electrode materials enables the determination of memory effects due to pure modifications inside the oxide layers. Thus, a targeted manipulation of defects and the resistive switching mechanism becomes possible by annealing of the layer or its modification by ion implantation which was the central challenge. Therefore the used oxide structures have to be well reputed and, additionally, almost free of defects to be able to localize changes in the switching mechanism exactly. To combine all this facts, the model system SrO-TiO2 is investigated with the two compounds TiO2 und SrTiO3. The properties of this system are already well discussed in literature. To ensure the purity of the layers, they are created by atomic layer deposition. The optimisation of the deposition process and layer characterization is presented in the first part of this study. Using a variety of optical and structural analysis methods allows defined conclusions about the oxide properties. All publications concerning the atomic layer deposition of SrTiO3 deal with self-made devices or precursor materials foreclosing an industrial reproduction. One of the results of this thesis enables exactly that by a combination of a commerically available device and commercial precursor materials. After its optimisation, the oxide layers are integrated between the two electrode materials Au and TiN in order to characterize the electrical properties of the resulting memory cells. Bipolar, nonvolatile resistive switching can be proved for amorphous and ex situ crystallised oxides. Based on structure-property correlations the conduction mechanism within the investigated cells can be identified as Schottky emission and for sufficiently high voltage as volume-dominated Poole Frenkel emission. The necessary defects therefore are determined to be shallow donor states. The assumption of resistive switching based on a reversible conducting filament consisting of defect states is confirmed by a changing Coulomb barrier high during the high of the Schottky barrier remains contant. Especially amorphous TiO2 with switching and reading speeds up to a few milliseconds, but also polycrystalline SrTiO3 showing high potential for future implementation in resistive switching memory cells. By use of Kr+ ion implantation the electrical and structural properties of TiO2 and SrTiO3 are changed. XRD measurements at crystalline TiO2 layers verify simulation data carried out by SRIM. For high enough fluences it shows an amorphisation of the crystalline structures by atomic redistribution inside the oxids. Thus, additionally intrinsic deep defects are created inside the oxide layers which modify the resistive switching character. A special focus is on the transformation of crystalline volatile switching TiO2 layers into amorphous non-volatile memory devices which shows more stable resistance values combined with lower energy input compared to initial amorphous layers.

Le cerveau humain est composé d’un grand nombre de réseaux neuraux interconnectés, dont les neurones et les synapses en sont les briques constitutives. Caractérisé par une faible consommation de puissance, de quelques Watts seulement, le cerveau humain est capable d’accomplir des tâches qui sont inaccessibles aux systèmes de calcul actuels, basés sur une architecture de type Von Neumann. La conception de systèmes neuromorphiques vise à réaliser une nouvelle génération de systèmes de calcul qui ne soit pas de type Von Neumann. L’utilisation de mémoire non-volatile innovantes en tant que synapses artificielles, pour application aux systèmes neuromorphiques, est donc étudiée dans cette thèse. Deux types de technologies de mémoires sont examinés : les mémoires à changement de phase (Phase-Change Memory, PCM) et les mémoires résistives à base d’oxyde (Oxide-based resistive Random Access Memory, OxRAM). L’utilisation des dispositifs PCM en tant que synapses de type binaire et probabiliste est étudiée pour l’extraction de motifs visuels complexes, en évaluant l’impact des conditions de programmation sur la consommation de puissance au niveau du système. Une nouvelle stratégie de programmation, qui permet de réduire l’impact du problème de la dérive de la résistance des dispositifs PCM est ensuite proposée. Il est démontré qu’en utilisant des dispositifs de tailles réduites, il est possible de diminuer la consommation énergétique du système. La variabilité des dispositifs OxRAM est ensuite évaluée expérimentalement par caractérisation électrique, en utilisant des méthodes statistiques, à la fois sur des dispositifs isolés et dans une matrice complète de mémoire. Un modèle qui permets de reproduire la variabilité depuis le niveau faiblement résistif jusqu’au niveau hautement résistif est ainsi développé. Une architecture de réseau de neurones de type convolutionnel est ensuite proposée sur la base de ces travaux éxperimentaux. La tolérance du circuit neuromorphique à la variabilité des OxRAM est enfin démontrée grâce à des tâches de reconnaissance de motifs visuels complexes, comme par exemple des caractères manuscrits ou des panneaux de signalisations routières. / The human brain is made of a large number of interconnected neural networks which are composed of neurons and synapses. With a low power consumption of only few Watts, the human brain is able to perform computational tasks that are out of reach for today’s computers, which are based on the Von Neumann architecture. Neuromorphic hardware design, taking inspiration from the human brain, aims to implement the next generation, non-Von Neumann computing systems. In this thesis, emerging non-volatile memory devices, specifically Phase-Change Memory (PCM) and Oxide-based resistive memory (OxRAM) devices, are studied as artificial synapses in neuromorphic systems. The use of PCM devices as binary probabilistic synapses is studied for complex visual pattern extraction applications, evaluating the impact of the PCM programming conditions on the system-level power consumption.A programming strategy is proposed to mitigate the impact of PCM resistance drift. It is shown that, using scaled devices, it is possible to reduce the synaptic power consumption. The OxRAM resistance variability is evaluated experimentally through electrical characterization, gathering statistics on both single memory cells and at array level. A model that allows to reproduce OxRAM variability from low to high resistance state is developed. An OxRAM-based convolutional neural network architecture is then proposed on the basis of this experimental work. By implementing the computation of convolution directly in memory, the Von Neumann bottleneck is avoided. Robustness to OxRAM variability is demonstrated with complex visual pattern recognition tasks such as handwritten characters and traffic signs recognition.

Les mémoires non-volatiles sont devenues récemment un moteur clé de la croissance du secteur des semiconducteurs, et constituent un pivot pour les nouvelles applications et les nouveaux concepts dans le domaine des technologies de l'information et de la communication (TIC). Afin de surmonter les limites en termes de miniaturisation, de consommation électrique et de complexité de fabrication des mémoires non-volatiles à grille flottante (FLASH), l'industrie des semiconducteurs évalue actuellement des solutions alternatives. Parmi celles-ci, les mémoires résistives à pont conducteur ou CBRAM (Conductive Bridge Random Access Memory), qui reposent sur la commutation de résistance d'un électrolyte par migration et oxydo/réduction d'ions métalliques, semblent être des plus prometteuses. L'attractivité de cette technologie innovante vient d'une part de la simplicité de sa structure à deux terminaux et d'autre part de ses performances électriques très prometteuses en termes de consommation électrique et vitesse d'écriture/effacement. De surcroît la CBRAM is une technology mémoire qui s'intègre facilement dans le back end of line (BEOL) du procédé CMOS standard. Dans cette thèse, nous étudions les performances électriques et la fiabilité de deux technologies CBRAM, utilisant des chalcogénures (GeS2) ou un oxyde métallique pour l'électrolyte. Tout d'abord nous nous concentrons sur les CBRAM à base de GeS2, ou l'effet du dopage de l'électrolyte avec de l'argent (Ag) ou de l'antimoine (Sb) est étudié à la lumière d'une analyse des caractérisations électriques. Les mécanismes physiques gouvernant la cinétique de commutation et la stabilité thermique sont aussi discutés sur la base de mesures électrique, d'un modèle empirique et des résultats de calculs ab initio. L'influence des différentes conditions de set/reset est étudiée sur une CBRAM à base d'oxyde métallique. Grâce à cette analyse, les conditions permettant de maximiser la fenêtre mémoire, améliorer l'endurance et minimiser la variabilité sont déterminées. / Non-volatile memory technology has recently become the key driver for growth in the semiconductor business, and an enabler for new applications and concepts in the field of information and communication technologies (ICT). In order to overcome the limitations in terms of scalability, power consumption and fabrication complexity of Flash memory, semiconductor industry is currently assessing alternative solutions. Among them, Conductive Bridge Memories (CBRAM) rely on the resistance switching of a solid electrolyte induced by the migration and redox reactions of metallic ions. This technology is appealing due to its simple two-terminal structure, and its promising performances in terms of low power consumption, program/erase speed. Furthermore, the CBRAM is a memory technology that can be easily integrated with standard CMOS technology in the back end of line (BEOL). In this work we study the electrical performances and reliability of two different CBRAM technologies, specifically using chalcogenides (GeS2) and metal oxide as electrolyte. We first focus on GeS2-based CBRAM, where the effect of doping with Ag and Sb of GeS2 electrolyte is extensively investigated through electrical characterization analysis. The physical mechanisms governing the switching kinetics and the thermal stability are also addressed by means of electrical measurements, empirical model and 1st principle calculations. The influence of the different set/reset programming conditions is studied on a metal oxide based CBRAM technology. Based on this analysis, the programming conditions able to maximize the memory window, improve the endurance and minimize the variability are determined.

Introdução: Estudos têm mostrado a magnitude das cargas resistivas inspiratórias adicionadas externamente segue uma relação previsível com a percepção de dispneia, na qual a magnitude psicológica cresce conforme o aumento das cargas adicionadas. O efeito de medidas repetidas de percepção de dispneia utilizando o sistema de cargas resistivas não está claro na literatura. Objetivo: Estudar a repetibilidade da percepção da dispneia avaliada através de um sistema de carga resistiva inspiratória em indivíduos normais. Métodos: Estudo transversal, com coleta de dados prospectiva, realizado em indivíduos sadios com idade ≥ 18 anos. A percepção da dispneia foi avaliada através de um sistema de cargas resistivas inspiratórias, utilizando dispositivo que compreende uma válvula unidirecional (Hans-Rudolph) e um circuito de reinalação. A sensação de dispneia foi mensurada durante ventilação com o aumento na carga resistiva inspiratória (≅0, 6,7, 15, 25, 46,7, 67, 78 e ≅0 L/s/cmH2O) para um fluxo de 300 mL/s. Após respirar em cada nível de resistência por dois minutos, o indivíduo expressava sua sensação de falta de ar (dispneia) usando a escala de Borg modificada. Os indivíduos foram submetidos a dois testes (intervalos de 3 a 7 dias). Resultados: Foram incluídos no estudo 16 indivíduos sadios, sendo 8 homens e 8 mulheres, todos da raça branca. A média de idade foi 36,3 ± 11,9 anos. A média do índice de massa corporal foi de 23,9 ± 2,8 kg/m2. As medianas dos escores da Escala de Borg no primeiro teste foram 0, 2, 3, 4, 5, 7, 7 e 1 ponto, respectivamente para os momentos de aplicação de carga resistiva de ≅ 0, 6,7,15, 25, 46,7, 67, 78 e ≅ 0 L/s/cmH2O. As medianas dos escores no segundo teste foram, respectivamente, 0, 0, 2, 2, 3, 4, 4 e 0,5 pontos. A concordância pelo coeficiente de correlação intraclasse foi, respectivamente para cada momento, 0,57, 0,80, 0,74, 0,80, 0,83, 0,86, 0,91 e 0,92. Observou-se diferença estatisticamente significativa entre momentos de cargas resistiva (p < 0,001) e entre os testes (p = 0,003), através do modelo de análise linear generalizada. Os valores dos escores de dispneia entre os diferentes momentos foram significativamente menores no segundo teste. As pressões inspiratórias resistivas (p=0,59) e as frequências respiratórias (p=0,81) não foram diferentes entre os testes. Conclusão: A concordância entre os dois testes de percepção de dispneia foi apenas moderada e os escores de dispneia foram menores no segundo teste. Estes resultados sugerem um efeito de aprendizagem. A sensação de dispneia pode ser modificada por uma experiência prévia. O indivíduo poderia controlar melhor o sentido de aferência cortical e/ou aprender a ventilar no sistema com medidas repetidas. / Introduction: Studies have shown that the magnitude of externally added inspiratory resistive loads follows a predictable relationship with dyspnea perception, in which the psychological magnitude grows as a power of the added loads. The effect of repeated measures of dyspnea perception using resistive loading system is not clear in literature. Objective: To study the repeatability of the dyspnea perception using an inspiratory resistive loading system in normal subjects. Methods: Cross sectional study conducted in healthy individuals aged ≥ 18 years, with data collected prospectively. Dyspnea perception was assessed using an inspiratory resistive load system previously described that comprises a unidirectional valve (Hans-Rudolph) and a rebreathing circuit. The sensation of dyspnea was assessed during ventilation with increasing in inspiratory resistive loads (≅ 0, 6.7, 15, 25, 46.7, 67, 78 and ≅ 0 L/s/cmH2O), for a flow 300 ml/s, returning to the resistance of 0. After breathing in each level of resistance for two minutes, the subject expressed the feeling of shortness of breath (dyspnea) using the modified Borg scale. Subjects were tested twice (intervals from 3 to 7 days). Results: The study included 16 healthy individuals, 8 men and 8 women and all were white. The mean age was 36.3 ±11.9 years. The body mass index averaged 23.9±2.8 kg/m2. The median scores dyspnea perception in the first test were 0, 2, 3, 4, 5, 7, 7 and 1 point, respectively, during ventilation with resistive loads of ≅ 0, 6.7,15, 25, 46.7, 67, 78 and ≅ 0 L/s/cmH2O. The median scores in the second test were, respectively, 0, 0, 2, 2, 3, 4, 4 and 0.5 points. The agreement assessed by intraclass correlation coefficient was, respectively, for each resistive load, 0.57, 0.80, 0.74, 0.80, 0.83, 0.86, 0.91, and 0.92. In a generalized linear model analysis, there was a statistically significant difference between the moments of resistive loads (p<0.001) and between tests (p=0.003). Dyspnea scores were significantly lower in the second test. There were no difference for inspiratory pressures (p=0.59) and respiratory frequency (p=0.81) between two tests. Conclusion: The agreement between the two tests of dyspnea perception was only moderate and dyspnea scores were lower in the second test. These findings suggested an evidence for a learning effect. Dyspnea perception may be modified by previous experience. The subject could control better the sense of cortical afference and/or learn to ventilate in the system with repeated measures.

Introdução: Estudos têm mostrado a magnitude das cargas resistivas inspiratórias adicionadas externamente segue uma relação previsível com a percepção de dispneia, na qual a magnitude psicológica cresce conforme o aumento das cargas adicionadas. O efeito de medidas repetidas de percepção de dispneia utilizando o sistema de cargas resistivas não está claro na literatura. Objetivo: Estudar a repetibilidade da percepção da dispneia avaliada através de um sistema de carga resistiva inspiratória em indivíduos normais. Métodos: Estudo transversal, com coleta de dados prospectiva, realizado em indivíduos sadios com idade ≥ 18 anos. A percepção da dispneia foi avaliada através de um sistema de cargas resistivas inspiratórias, utilizando dispositivo que compreende uma válvula unidirecional (Hans-Rudolph) e um circuito de reinalação. A sensação de dispneia foi mensurada durante ventilação com o aumento na carga resistiva inspiratória (≅0, 6,7, 15, 25, 46,7, 67, 78 e ≅0 L/s/cmH2O) para um fluxo de 300 mL/s. Após respirar em cada nível de resistência por dois minutos, o indivíduo expressava sua sensação de falta de ar (dispneia) usando a escala de Borg modificada. Os indivíduos foram submetidos a dois testes (intervalos de 3 a 7 dias). Resultados: Foram incluídos no estudo 16 indivíduos sadios, sendo 8 homens e 8 mulheres, todos da raça branca. A média de idade foi 36,3 ± 11,9 anos. A média do índice de massa corporal foi de 23,9 ± 2,8 kg/m2. As medianas dos escores da Escala de Borg no primeiro teste foram 0, 2, 3, 4, 5, 7, 7 e 1 ponto, respectivamente para os momentos de aplicação de carga resistiva de ≅ 0, 6,7,15, 25, 46,7, 67, 78 e ≅ 0 L/s/cmH2O. As medianas dos escores no segundo teste foram, respectivamente, 0, 0, 2, 2, 3, 4, 4 e 0,5 pontos. A concordância pelo coeficiente de correlação intraclasse foi, respectivamente para cada momento, 0,57, 0,80, 0,74, 0,80, 0,83, 0,86, 0,91 e 0,92. Observou-se diferença estatisticamente significativa entre momentos de cargas resistiva (p < 0,001) e entre os testes (p = 0,003), através do modelo de análise linear generalizada. Os valores dos escores de dispneia entre os diferentes momentos foram significativamente menores no segundo teste. As pressões inspiratórias resistivas (p=0,59) e as frequências respiratórias (p=0,81) não foram diferentes entre os testes. Conclusão: A concordância entre os dois testes de percepção de dispneia foi apenas moderada e os escores de dispneia foram menores no segundo teste. Estes resultados sugerem um efeito de aprendizagem. A sensação de dispneia pode ser modificada por uma experiência prévia. O indivíduo poderia controlar melhor o sentido de aferência cortical e/ou aprender a ventilar no sistema com medidas repetidas. / Introduction: Studies have shown that the magnitude of externally added inspiratory resistive loads follows a predictable relationship with dyspnea perception, in which the psychological magnitude grows as a power of the added loads. The effect of repeated measures of dyspnea perception using resistive loading system is not clear in literature. Objective: To study the repeatability of the dyspnea perception using an inspiratory resistive loading system in normal subjects. Methods: Cross sectional study conducted in healthy individuals aged ≥ 18 years, with data collected prospectively. Dyspnea perception was assessed using an inspiratory resistive load system previously described that comprises a unidirectional valve (Hans-Rudolph) and a rebreathing circuit. The sensation of dyspnea was assessed during ventilation with increasing in inspiratory resistive loads (≅ 0, 6.7, 15, 25, 46.7, 67, 78 and ≅ 0 L/s/cmH2O), for a flow 300 ml/s, returning to the resistance of 0. After breathing in each level of resistance for two minutes, the subject expressed the feeling of shortness of breath (dyspnea) using the modified Borg scale. Subjects were tested twice (intervals from 3 to 7 days). Results: The study included 16 healthy individuals, 8 men and 8 women and all were white. The mean age was 36.3 ±11.9 years. The body mass index averaged 23.9±2.8 kg/m2. The median scores dyspnea perception in the first test were 0, 2, 3, 4, 5, 7, 7 and 1 point, respectively, during ventilation with resistive loads of ≅ 0, 6.7,15, 25, 46.7, 67, 78 and ≅ 0 L/s/cmH2O. The median scores in the second test were, respectively, 0, 0, 2, 2, 3, 4, 4 and 0.5 points. The agreement assessed by intraclass correlation coefficient was, respectively, for each resistive load, 0.57, 0.80, 0.74, 0.80, 0.83, 0.86, 0.91, and 0.92. In a generalized linear model analysis, there was a statistically significant difference between the moments of resistive loads (p<0.001) and between tests (p=0.003). Dyspnea scores were significantly lower in the second test. There were no difference for inspiratory pressures (p=0.59) and respiratory frequency (p=0.81) between two tests. Conclusion: The agreement between the two tests of dyspnea perception was only moderate and dyspnea scores were lower in the second test. These findings suggested an evidence for a learning effect. Dyspnea perception may be modified by previous experience. The subject could control better the sense of cortical afference and/or learn to ventilate in the system with repeated measures.

En raison de leur faible consommation d'énergie, les mémoires non volatiles (MNV) sont En raison de leur faible consommation d'énergie, les mémoires non-volatiles sont particulièrement intéressantes pour l'électronique portative (clé USB, téléphone, ordinateur portable …). Les mémoires Flash, qui dominent le marché, atteignent leurs limites physiques et doivent être remplacées. L'introduction de nouveaux matériaux et architectures mémoire est proposée. Les mémoires OxRRAM (Oxide Resistive Random Access Memory) sont des candidats potentiels. Il s'agit de structures M-O-M (Métal-Oxyde-Métal). Le stockage de l'information est basé sur la modulation de la résistance de l'oxyde à l'application d'un champ électrique ou d'un courant. Une meilleure compréhension du mécanisme de changement de résistance de ces dispositifs est nécessaire pour contrôler leurs performances. Nous nous intéressons au claquage diélectrique de l'oxyde, qui initie le mécanisme de changement de résistance. Les mesures physico-chimiques à l'échelle nanométrique sont indispensables à sa compréhension et font défaut dans la littérature. Dans cette thèse, nous proposons des mesures physico-chimiques, des mesures électriques et des méthodes de préparation d'échantillon adaptées. Les oxydes de nickel et d'hafnium sont investigués. En plus de la dégradation électrique (chute de résistance), les modifications de ces deux oxydes sont investiguées à trois niveaux : la composition chimique, la morphologie et la structure électronique. Mots-clés : mémoire résistive, mécanisme de changement de résistance, claquage diélectrique, NiO, HfO2, spectroscopie de photoélectrons, microscopie électronique en transmission, microscopie à forme atomique, lacunes d'oxygène. / With low energy consumption, non-volatile memories are interesting for portative applications (USB, mobile phone, laptop …). The Flash memory technology is reaching its physical boundaries and needs to be replaced. New materials and architectures are currently investigated. Oxide Resistive Random Access Memory (OxRRAM) is considered as a good candidate. It is based on a M-O-M (Metal-Oxide-Metal) stack. The information is stored using an electric field or a current that modulates the resistance of the oxide. A better understanding of the resistance switching mechanism is required in order to control the performances of the devices. We investigate the dielectric breakdown that activates the resistance switching properties. Physico-chemical characterization at the nanoscale is required. In this work, we propose proper physico-chemical and electrical measurements. Sample preparation is also considered. Nickel and hafnium oxide are investigated. Besides the evolution of the electrical properties, we analyze the oxide modification at three levels : the chemical composition, the morphology and the electronic structure. Keywords : resistive memory, resistance switching mechanism, dielectric breakdown, NiO, HfO2, photoelectron spectroscopy, electronic transmission microscopy, atomic force microscopy, oxygen vacancies.

La détection et la surveillance des gaz est un enjeu important tant pour la sécurité industrielle que pour la protection de l’environnement et des personnes. Le dihydrogène, prend une place de plus en plus importante en tant que combustible et vecteur énergétique mais il est extrêmement inflammable et explosif dans un large domaine de 4 à 75 % dans l’air. De même, l’ammoniac est très utilisé dans l’industrie comme gaz réfrigérant ou comme élément de base pour la production chimiques d’autres composés. Ce gaz présente des risques sur l’environnement et sur les êtres vivants et peut former des mélanges explosifs avec l’air dans les limites de 15 à 28 % en volume. Les capteurs de gaz permettant d’indiquer la présence et/ou la quantification de ces gaz prennent alors toute leur importance. Dans la continuité de nos nombreux travaux sur les capteurs résistifs à base d’assemblages discontinus de nano-objets, l’objet de ce travail de thèse a été de préparer des capteurs résistifs pour la détection de H2 et NH3. Ces capteurs sont à base d’assemblages 2D de nanoparticules de compositions complexes. Trois types de nanoparticules cœur-coquille ont été synthétisés : Au@ZnO, Au@SnO2 et Au@Ag. Différentes techniques physico-chimiques (UV-Visible/TEM / DRX etc) ont permis de caractériser les particules obtenues. L’étape suivante a consisté à les assembler en monocouches compactes. Les films ont été obtenus par la méthode d’assemblage de Langmuir-Blodgett. Après transfert à la surface d’un substrat en verre supportant des électrodes inter digitées, les performances de détection des capteurs résistifs fabriqués ont été alors évaluées. Les capteurs à base de Au@ZnO et Au@SnO2 ont été testés sous H2, tandis que les capteurs à base de Au@Ag l’ont été sous NH3. Les capteurs fabriqués ont montré des performances attractives de détection de H2 et NH3 dans des gammes de concentration étendues. Une autre contribution importante de ce travail concerne la compréhension des mécanismes de détection. Diverses techniques analytiques, tels que la TPD (Température désorption Programmed) et la TPR (Température de réduction programmée) ont été utilisés pour permettre la discussion des les mécanismes impliqués. / Gas sensing and monitoring are important issues for both industrial safety and protection of the environment and human beings. Dihydrogen, is increasingly used as fuel and energy carrier but it is extremely flammable and explosive in a wide range between 4 and 75% in air.Similarly, ammonia is widely used in industry as a cooling gas or as a reagent for the chemical production of other compounds.This gas presents risks to the environment and to living beings and can form explosive mixtures with air within 15 to 28% by volume.Gas sensors, indicating the presence and /or quantification of these gases, are very important.In continuation of our work on resistive sensors based on discontinuous assembly of nano-objects, the aim of this thesis was to prepare resistive sensors for the detection of H2 and NH3.These sensors are based on 2D assemblies of complex compositions of nanoparticles. Three types of core-shell nanoparticles were synthesized: Au@ZnO, Au@SnO2 and Au@Ag. Different physicochemical techniques (UV-Visible / TEM / DRX etc.) were used to characterize the particles. The next step was to assemble them in compact monolayers. The films were obtained by Langmuir-Blodgett assembling technique. Then, they were transferred to the surface of a glass slide supporting interdigitated electrodes. Sensing performances of the as-fabricated resistive sensor were evaluated.Sensors based on Au@ZnO and Au@SnO2 nanoparticles were tested towards H2, while Au@Ag based sensors were tested under NH3.The sensors showed attractive performances in H2 and NH3 detection within wide concentration ranges. Another important contribution of this work is the understanding of detection mechanisms. Various analytical techniques such as TPD (Temperature Programmed Desorption) and TPR (temperature programmed reduction) were used for the discussion of the mechanisms involved.

O objetivo desse trabalho foi o de obter-se fios de cobre em três composições químicas distintas da liga Cu-Mg a partir de cobre eletrolítico e de magnésio. Foram avaliadas as etapas envolvidas, começando com a fusão de botões em forno a arco na composição do eutético Cu-Mg, diluição destes botões em forno resistivo, vazamento em lingoteira de cobre, seguido de tratamento térmico de homogeneização em forno resistivo a 910 ºC por 2 h. Os tarugos foram posteriormente trabalhados mecanicamente por forjamento rotativo seguido de um passe final de acabamento por trefilação, para obtenção do fio. As análises químicas realizadas nos lingotes indicaram que a rota de preparação dos fios mostrou-se adequada aos estudos em escala de laboratório, suficiente para a confecção de fios com área de seção transversal de 4 mm2 por 10 m de comprimento, para cada composição de liga. Os fios foram caracterizados mecanicamente por ensaio de tração e de dureza após tratamento térmico de recristalização a 510 ºC por 1 h. Os fios também tiveram as condutividades elétricas medidas na condição recristalizada e os resultados foram comparados com dados experimentais da literatura. Os materiais obtidos mostraram-se adequados à utilização como fio condutor de energia elétrica. Os limites de escoamento e de resistência a tração tiveram seus valores melhorados com o aumento do teor de magnésio na liga, 11 % e 24 %, respectivamente, enquanto houve queda nos valores de condutividade elétrica para cerca de 60 % IACS (International Annealed Copper Standard). / The aim of this work was to obtain copper wires in three different chemical compositions starting from electrolytic copper and magnesium. The mains steps were evaluated, starting from the melting of small eutectic cooper-magnesium specimens in an electric arc furnace, followed by further dilution of this buttons in a resistive furnace and casting it in a copper mould. The as cast billets were homogenized in a resistive furnace at 910 ºC for 2 h. The billets were mechanically cold worked by swaging and a final drawing step to attain a round shape and a reasonable surface quality. The cast ingots chemical analysis indicated that the processing route showed to be adequate, in laboratory scale, to obtain wires with cross sectional area of 4 mm2 and 10 m in length. The wires in both conditions as cold worked and after a recovering heat treatment at 510 ºC for 1 h, were mechanically characterized by tensile testing and hardness. The wires had also the electric conductivity assessed in the recovered heat-treated state and the results were compared to the literature data. The obtained material showed to be adequate to be used as electric conductor. The yield strain and ultimate tensile strength were improved with the increasing amount of Mg in the alloy, 11 % and 24 %, respectively, while the electric conductivity decreased to 60 % IACS (International Annealed Copper Standard).

Introdução: Estudos têm mostrado a magnitude das cargas resistivas inspiratórias adicionadas externamente segue uma relação previsível com a percepção de dispneia, na qual a magnitude psicológica cresce conforme o aumento das cargas adicionadas. O efeito de medidas repetidas de percepção de dispneia utilizando o sistema de cargas resistivas não está claro na literatura. Objetivo: Estudar a repetibilidade da percepção da dispneia avaliada através de um sistema de carga resistiva inspiratória em indivíduos normais. Métodos: Estudo transversal, com coleta de dados prospectiva, realizado em indivíduos sadios com idade ≥ 18 anos. A percepção da dispneia foi avaliada através de um sistema de cargas resistivas inspiratórias, utilizando dispositivo que compreende uma válvula unidirecional (Hans-Rudolph) e um circuito de reinalação. A sensação de dispneia foi mensurada durante ventilação com o aumento na carga resistiva inspiratória (≅0, 6,7, 15, 25, 46,7, 67, 78 e ≅0 L/s/cmH2O) para um fluxo de 300 mL/s. Após respirar em cada nível de resistência por dois minutos, o indivíduo expressava sua sensação de falta de ar (dispneia) usando a escala de Borg modificada. Os indivíduos foram submetidos a dois testes (intervalos de 3 a 7 dias). Resultados: Foram incluídos no estudo 16 indivíduos sadios, sendo 8 homens e 8 mulheres, todos da raça branca. A média de idade foi 36,3 ± 11,9 anos. A média do índice de massa corporal foi de 23,9 ± 2,8 kg/m2. As medianas dos escores da Escala de Borg no primeiro teste foram 0, 2, 3, 4, 5, 7, 7 e 1 ponto, respectivamente para os momentos de aplicação de carga resistiva de ≅ 0, 6,7,15, 25, 46,7, 67, 78 e ≅ 0 L/s/cmH2O. As medianas dos escores no segundo teste foram, respectivamente, 0, 0, 2, 2, 3, 4, 4 e 0,5 pontos. A concordância pelo coeficiente de correlação intraclasse foi, respectivamente para cada momento, 0,57, 0,80, 0,74, 0,80, 0,83, 0,86, 0,91 e 0,92. Observou-se diferença estatisticamente significativa entre momentos de cargas resistiva (p < 0,001) e entre os testes (p = 0,003), através do modelo de análise linear generalizada. Os valores dos escores de dispneia entre os diferentes momentos foram significativamente menores no segundo teste. As pressões inspiratórias resistivas (p=0,59) e as frequências respiratórias (p=0,81) não foram diferentes entre os testes. Conclusão: A concordância entre os dois testes de percepção de dispneia foi apenas moderada e os escores de dispneia foram menores no segundo teste. Estes resultados sugerem um efeito de aprendizagem. A sensação de dispneia pode ser modificada por uma experiência prévia. O indivíduo poderia controlar melhor o sentido de aferência cortical e/ou aprender a ventilar no sistema com medidas repetidas. / Introduction: Studies have shown that the magnitude of externally added inspiratory resistive loads follows a predictable relationship with dyspnea perception, in which the psychological magnitude grows as a power of the added loads. The effect of repeated measures of dyspnea perception using resistive loading system is not clear in literature. Objective: To study the repeatability of the dyspnea perception using an inspiratory resistive loading system in normal subjects. Methods: Cross sectional study conducted in healthy individuals aged ≥ 18 years, with data collected prospectively. Dyspnea perception was assessed using an inspiratory resistive load system previously described that comprises a unidirectional valve (Hans-Rudolph) and a rebreathing circuit. The sensation of dyspnea was assessed during ventilation with increasing in inspiratory resistive loads (≅ 0, 6.7, 15, 25, 46.7, 67, 78 and ≅ 0 L/s/cmH2O), for a flow 300 ml/s, returning to the resistance of 0. After breathing in each level of resistance for two minutes, the subject expressed the feeling of shortness of breath (dyspnea) using the modified Borg scale. Subjects were tested twice (intervals from 3 to 7 days). Results: The study included 16 healthy individuals, 8 men and 8 women and all were white. The mean age was 36.3 ±11.9 years. The body mass index averaged 23.9±2.8 kg/m2. The median scores dyspnea perception in the first test were 0, 2, 3, 4, 5, 7, 7 and 1 point, respectively, during ventilation with resistive loads of ≅ 0, 6.7,15, 25, 46.7, 67, 78 and ≅ 0 L/s/cmH2O. The median scores in the second test were, respectively, 0, 0, 2, 2, 3, 4, 4 and 0.5 points. The agreement assessed by intraclass correlation coefficient was, respectively, for each resistive load, 0.57, 0.80, 0.74, 0.80, 0.83, 0.86, 0.91, and 0.92. In a generalized linear model analysis, there was a statistically significant difference between the moments of resistive loads (p<0.001) and between tests (p=0.003). Dyspnea scores were significantly lower in the second test. There were no difference for inspiratory pressures (p=0.59) and respiratory frequency (p=0.81) between two tests. Conclusion: The agreement between the two tests of dyspnea perception was only moderate and dyspnea scores were lower in the second test. These findings suggested an evidence for a learning effect. Dyspnea perception may be modified by previous experience. The subject could control better the sense of cortical afference and/or learn to ventilate in the system with repeated measures.

Orientadores: Guido Costa Souza de Araújo, Rodolfo Jardim de Azevedo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-23T10:06:28Z (GMT). No. of bitstreams: 1 Hoffman_Caio_M.pdf: 5338735 bytes, checksum: d93e38ef7846b0ba3f7f3b0ea459fc67 (MD5) Previous issue date: 2013 / Resumo: Phase-change memory (PCM) traz novos ensejos para indústria eletrônica. Devido às projeções de alta escalabilidade do processo de fabricação da PCM, cogita-se usá-la como memória principal em sistemas de computação, substituindo à tradicional DRAM cujos problemas de miniaturização do processo de fabricação demandam tecnologias ainda desconhecidas. Contudo, PCM tem problemas de durabilidade e técnicas de recuperação de falhas robustas são extremamente necessárias para recuperação e prolongamento do seu tempo de vida, medido em número de escritas. As técnicas mais comuns de recuperação de falhas são os códigos de correção de erros. Porém, outras técnicas de recuperação vêm sendo propostas na literatura, aproveitando as características de não-volatilidade da PCM. Neste trabalho, usando uma modelagem matemática, analisou-se como a probabilidade de bit-ip dos principais códigos de correção de erros { paridade, SECDED e BCH { e das principais técnicas de recuperação de falhas { ECP e SAFER { está relacionada _a durabilidade da PCM. A partir da taxa de bit-ip medida através da execução do SPEC2006 e por meio dos modelos matemáticos, comparou-se os resultados dos modelos de simulação utilizando-se a probabilidade teórica de 50% e a taxa obtida experimentalmente de 15%. Os resultados revelaram uma visível degradação da durabilidade dos mecanismos de recuperação de falhas que usam códigos de correção de erros, contradizendo os resultados da literatura. A técnica ECP foi à única que não mostrou degradação. Além disso, uma análise de eficiência energética foi feita, relacionando durabilidade da PCM e o consumo de energia. Novamente, a técnica ECP se destacou nos resultados, como também a técnica SAFER. Finalmente, foram propostos modelos analíticos probabilísticos das técnicas ECP, SECDED e uma análise da técnica PAYG baseada no modelo analítico da ECP / Abstract: Phase-change memory brings new opportunities for the electronics industry. Due to projections of high scalability of the fabrication process, PCM is seen as a new main memory in computing systems, replacing the traditional DRAM, whose scale problems require new future technologies that are still unknown. However, PCM has low endurance when compared with DRAM and robust failure recovery techniques are required to increase its lifetime. To address that, some error correcting techniques have been proposed, based on the non-volatile features of the PCM memories. In this work, we model and analyze the bit-ip probabilities of five such techniques (ECP, parity, SECDED, SAFER and BCH), in order to evaluate its impact to the wear out of the PCM. Using the bit-ip rate of 15%, obtained experimentally from the execution of the SPEC2006 benchmark, we mathematically modeled and simulated these techniques using both an empirical and theoretical probability rates. Our results show a clear degradation in techniques that use error-correcting codes, contradicting the previous results in the literature. Only ECP has not shown any degradation. We have also done power analyses of the above listed techniques so as to relate the endurance and the energy required by each technique. Again, the ECP stood out in the results, like SAFER as well. Finally, analytical probabilistic models for ECP and SECDED were proposed and an analysis of PAYG technique (based on ECP's analytical model) was performed / Mestrado / Ciência da Computação / Mestre em Ciência da Computação