Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho foram realizadas a cominuição e passivação da liga metálica U-4Zr-2Nb pelo processo de hidretação-desidretação, bem como o estudo da sua cinética. A obtenção deste material pulverizado através das técnicas da metalurgia do pó é uma etapa necessária e chave na fabricação da pastilha, que será empregada na laminação da placa combustível. Foi escolhida a liga com composição U-4Zr-2Nb devido à sua elevada densidade e baixo teor de elementos de liga, além de suas pequenas seções de choque para nêutrons térmicos. Previamente, foi projetado e construído o equipamento tipo Sievert volumétrico para a cominuição da liga metálica de urânio pelo processo de hidretação-desidretação, operacionalizando-o no modo automático, através da aquisição de dados por intermédio de softwares também desenvolvidos neste trabalho. Juntamente com o desenvolvimento deste equipamento, outro software foi desenvolvido para calcular a cinética de hidretração e a porcentagem hidretada. A seguir, com a utilização deste equipamento, amostras da liga U-4Zr-2Nb foram tratadas termicamente, hidretadas, passivadas, moídas e desidretadas. O processo de cominuição desenvolvido foi realizado nas condições de temperaturas de hidretação variando entre 108C e 295C e a pressão variando entre 2,0 bar e 1,5 bar. Todas as amostras foram hidretadas por completo, independentemente da temperatura de processamento. O tempo de hidretação variou entre 550 a 16176 segundos, de acordo com a temperatura utilizada, sendo mais rápido para temperaturas mais altas. Independentemente dos tratamentos térmicos feitos previamente nas amostras, todas apresentaram somente a fase α e, conseqüentemente, todas as hidretações realizadas foram massivas. Foi desenvolvido também um processo de passivação dos pós obtidos, tendo-se conseguido amostras cominuídas estáveis, ou seja, não apresentaram reações pirofóricas quando expostas ao ar, nem uma excessiva oxidação das mesmas. Para isto, foi utilizada uma mistura de gases contendo 90% de argônio e 10% de oxigênio. Após a passivação, os hidretos foram moídos e passivados novamente para obtenção final do pó metálico. A granulometria final dos pós metálicos obtidos não depende dos tratamentos térmicos da amostra nem da temperatura de hidretação. As partículas maiores se revelaram um aglomerado de partículas menores e, portanto, foi utilizado um processo de moagem para desaglomeração parcial destas partículas, tendo-se obtidos partículas com tamanhos na faixa entre 11,2 e 22,4 μm. / In this work the comminution and passivation of U-4Zr-2Nb alloys by hydrading-dehydrading process was carried out and the kinetics of hydride formation was studied. The obtaining of the powdered material through the techniques of powder metallurgy is a key and necessary step in the manufacture of the pellet useful for providing the fabrication of the fuel plate. An alloy with composition U-4Zr-2Nb was chosen due to their high density and low alloying elements, in addition to its low thermal neutrons cross section. A volumetric Sievert equipment for comminuition of uranium alloys by the process of hydriding-dehydriding was designed and constructed. This equipment operates in an automatic mode through the data acquisition software also developed in this work. Along with the development of this equipment, other software was developed to calculate the kinetic of hydriding and the hydriding amount. Then, using this equipment, samples of the U-4Zr-2Nb alloy were heat treated, hydrided, passivated, milled and dehydrided. The developed comminution process was obtained in the temperature range of 108oC to 295oC and in the pressure range of 1.5 Bar to 2 Bar. All samples were completely hydrided, regardless of the hydriding temperature. The hydriding time ranged from 540 to 16176 seconds, according to the temperature used, being faster at higher temperature. Regardless of the previously heat treatments, all samples showed only the α phase and, consequently, all hydridings were massive performed. It was also developed a passivation process of the obtained powder, and the powdered samples were stable, not pyrophoric and no kind of reaction was observed when exposed to air, without an excessive oxidation. In this case, it was used a gas mixture of 90% argon and 10% oxygen. After passivation, the hydride were milled and passivated again to obtain the metallic powder. The final size of the powdered metal did not depend on the heat treatment of the sample or on the hydriding temperature. The larger particles revealed to be an agglomerate of particles and therefore the milling process partially dismantle these agglomerates into primary particles. The particles size ranged from 11.2 up to 22.4 μm.

A indústria cimenteira busca alternativas para economia de recursos no processo produtivo, em especial envolvendo o uso de materiais residuais no cimento, como escórias siderúrgicas. A escória de aciaria, em particular, apresenta composição desfavorável para aplicação in natura, porém há metodologias na literatura de modificação do material para aplicações cimentícias. No entanto, ainda não se encontram avaliações da corrosão de armaduras de aço em compósitos cimentícios com essa adição, seja em meio sólido ou líquido (água de poro). Esse estudo avaliou, através de curvas de polarização e da espectroscopia de impedância eletroquímica (EIE), a resistência à corrosão do aço CA-50 em soluções representativas de águas de poro extraídas por pressão de pastas de cimento com 25 % de escória de aciaria in natura ou modificada por processo pirometalúrgico. Para efeitos comparativos, foi feita também a avaliação do desempenho do aço em meios de águas de poro indicadas na literatura como representativas de cimento Portland comum e de escória de alto forno. O efeito da presença de espécies agressivas na resistência à corrosão do aço foi avaliado adicionando-se 1,0 % de NaCl em massa às soluções estudadas. Nas águas de poro sem 1,0 % de cloreto, o aço CA-50 apresentou-se passivo e não mostrou indícios de corrosão nos ensaios nem de polarização nem de EIE durante 120 h de imersão. Entretanto, os ajustes dos diagramas com circuito elétrico equivalente (CEE) apontaram que as características de proteção da camada passiva formada nas águas de poro de cimento com escória de aciaria foram superiores, resultando em maior resistência à corrosão do aço CA-50 nestes meios. Por sua vez, nos meios com 1,0 % de NaCl, após polarização e EIE até 120 h, o aço sofreu corrosão para as águas de poro de cimento comum e escória de alto forno, porém não corroeu nas águas de poro representativas de cimentos com escórias de aciaria, cujo melhor desempenho foi associado à maior alcalinidade destes meios. A caracterização microestrutural por microscopia eletrônica de varredura após os ensaios de polarização anódica e de imersão mostrou que o principal produto de corrosão formado foi a lepidocrocita (?-FeOOH), comum em ataque do aço por cloretos. / The cement industry seeks alternatives to save resources in production processes, especially involving the use of residual materials in cements, such as slags. Steel slags present unfavorable composition for application as cement additions in natura, but there are methodologies in the literature for modifying this material for commercial application. However, there are no evaluations of the corrosion of steel reinforcements in cementitious composites with steel slags, either in solid or liquid medium (pore water). The present study employed polarization curves and electrochemical impedance spectroscopy (EIS) to evaluate the corrosion resistance of CA-50 steel in pore water solutions representative of cement pastes with 25 % steel slag in natura or modified by a pyrometallurgical process. For comparison purposes, the performance of CA-50 steel in the pore waters indicated in the literature as representatives of Portland cement and blast furnace slag activated with cement were also evaluated. The effect of aggressive species on the corrosion resistance of the steel was assessed by adding 1.0 % NaCl by mass to the pore water solutions. Without 1.0 % chloride addition, CA-50 steel exhibited good performance and showed no evidences of corrosion in all of the investigated media, both in anodic polarization and in EIS tests performed up to 120 h immersion. However, the fitting of the EIS diagrams with equivalent electric circuit (EEC) revealed that the protectiveness of the passive layer formed in pore waters representative of cements with steel slags were superior, indicating better corrosion resistance of CA-50 steel in these media. Conversely, when 1.0 % chloride was added to the pore waters, CA-50 steel presented pitting corrosion, and impedance decreases with immersion in the pore waters representative of pure cement and blast furnace slag, whereas no corrosion was detected by both methodologies in pore waters representatives of cements with steel slags, which superior performance was ascribed to their higher alkalinity. Microstructural characterization by scanning electron microscopy (SEM) after anodic polarization and immersion tests showed that the main corrosion product formed was lepidocrocite (?-FeOOH), usual of chloride attack of steel.

Novel photovoltaic cells receive considerable attention from researchers as evidenced by high numbers of published articles. Different types of materials are currently being examined in order to reduce the cost and improve the efficiency of solar cells. Essentially, solar cells are constructed by placing layers of light absorber between electron and hole transport materials. Electricity generation by solar cells involves multiple processes. These processes require an understanding of the physical properties of the surfaces and interfaces of the materials. In this thesis, materials for novel photovoltaic cells are studied by X ray photoelectron spectroscopy (XPS), a surface and interface characterisation technique. The materials studied in this thesis are colloidal quantum dots (CQDs) of the core/shell systems CdTe/CdSe and PbS/CdS, and CQDs that have been surface passivated using Cl- (CdTe/Cl) and CdS (CdTe/CdSe/CdS and PbS/CdS). Moreover, CsSnI3, a perovskite material, is also studied in both bulk and thin film form. CQDs can be used as light absorbers in solar cells while CsSnI3 can be employed as the hole transport material. The role of the core shell structure and surface passivation treatment is to improve or maintain charge transport as well as acting as a protective layer to the CQDs. Depth profiling synchrotron radiation XPS is used to determine these structures. In the CdTe/CdSe samples, the elemental ratio between Se (shell) and Te (core) increases with decreasing sampling depth, demonstrating the presence of a CdSe shell located at the surface of the CQDs. The shell thicknesses of the core-shell systems are estimated from XPS and show that the addition of the third thin shell (of CdS) protects the CQD during ligand exchange. Cl- passivation is shown to reduce the energy the valence band maximum and the energy gap of CdTe CQDs. This is associated with the passivation of midgap trap states due to the removal of dangling bonds at the surface of CQDs. Surface passivation is shown to improve the stability of CQDs to air exposure. This is indicated by a significant reduction of the surface oxide species in the passivated PbS/CdS samples. In the unpassivated core-only PbS samples, however, oxidation rapidly occurs which affects the electronic states required for charge transport in solar cells. XPS studies of CsSnI3 show that this material is reactive to air exposure. Surface preparation techniques are performed to remove the contamination layer and reveal the physical properties of the perovskite itself. This is confirmed by the elemental ratios from XPS. The metallic character of CsSnI3 is also observed in the valence band spectra as evidenced by the appearance of the Fermi edge.

As estruturas metal-óxido-semicondutor (MOS) são o coração dos transistores de efeito de campo. O estudo e caracterização físico-química desses dispositivos foram a chave para o avanço da tecnologia do Si na indústria microeletrônica. Hoje, a ciência busca novos materiais para a produção de dispositivos de alta mobilidade. Um dos materiais visados é o Ge, pois apresenta mobilidade de cargas superior ao Si (duas vezes para elétrons e quatro vezes para lacunas). Porém, a interface Ge/GeO2 é de natureza reativa, limitando seu uso na construção de tais dispositivos. Muitos esforços têm sido feitos para superar as limitações. Entre eles, encontram-se a passivação da superfície do Ge a partir de solução aquosa de (NH4)2S, previamente a deposição do dielétrico. Outra etapa do processamento desse material na indústria a ser investigada são os tratamentos térmicos posteriores à deposição: a caracterização de estruturas MOS de Pt/HfO2/Ge submetidas a tratamentos térmicos levaram a melhoria das propriedades elétricas. Nesse sentido, o trabalho tem como objetivos investigar o papel da passivação sulfídrica em estruturas dielétrico/Ge e a influência do eletrodo de Pt nas estruturas Pt/HfO2/Ge quando submetidas a tratamentos térmicos. / The heart of field effect transistors is the metal-oxide-semiconductor (MOS) structure. Physico-chemical characterization of the materials employed in such structures enabled the development of Si technology. Nowadays, in order to build high mobility devices, new material are needed. Ge is an alternative material, since its carrier mobilities are higher than those of Si (almost two times for electrons and four times higher for holes). However, the GeO2/Ge interface is not thermally stable, which is a problem for its use on electronic devices. Many attempts to enhance this stability were already investigated. Among them, sulfur passivation of the Ge surface was employed using (NH4)2S aqueous solution prior to the deposition of dielectric layers. Another important step in the fabrication of MOS structures is post-deposition annealing. Pt/HfO2/Ge MOS structures presented improved electrical characteristics following post deposition annealing. The main objectives of this work are to investigate the role of sulfur passivation on dielectric/Ge structures and the influence of Pt electrode in Pt/HfO2/Ge structures submitted to post deposition annealing.

Energy traps at the silicon surface originating from discontinuities in the lattice is detrimental to the performance of solar cells. Acting as recombination centers, they offer a location where the charge carriers may easily return to their original energy band after excitation. Surface passivation is an effective method to combat this and can be done either by suppressing traps (lowering trap density) or by forming an electric field, preventing the carriers from reaching the defect states. Silicon oxide, SiO2, and aluminum oxide, Al2O3, are two materials which have previously been shown to provide good passivating qualities. In this thesis, SiO2 and Al2O3 have been used both as single layers and in a stack configuration to passivate the surface of crystalline silicon (c-Si). Using a response surface methodology approach, temperature optimization with respect to deposition and annealing temperature has been conducted for SiO2/Al2O3 stacks deposited with plasma-enhanced atomic layer deposition, PEALD. It was shown that the same deposition temperature (Tdeposition = 140 °C, Tanneal = 395 °C) could be used for both materials and provide good passivation with an effective surface recombination velocity, Seff, of 5.3 cm/s (1Ωcm n-type Si wafers). From FTIR measurements, an increase in hydroxyl groups was seen as the SiO2 deposition temperature increased while the opposite was observed for Al2O3 which also showed fewer carbon related impurities with increasing temperature. Increasing the SiO2 temperature strongly affected the fixed charge density, causing it to decrease and even switch polarity. The fixed charge density could also be controlled by varying the thickness of the intermediate SiO2 layer. At a thickness of 1-2 nm, a minimum in the effective lifetime was observed and was correlated to Si close to flat-band conditions. N-type wafers showed a larger negative fixed charge density than p-type wafers which results in stronger field-effect passivation. For phosphorous doped emitters (200 Ω/sq on 10 Ωcm p-type wafer), it was seen that SiO2/Al2O3 stacks with a SiNx anti-reflection coating performed better than SiO2 or Al2O3 single layers. By depositing SiO2 at 130 °C in SiO2/Al2O3 stacks and annealing at 450 °C, an implied open circuit voltage (iVoc) of 710 mV was measured (AM1.5G) together with an implied fill factor (iFF) of 84.1% and a recombination parameter (J0) of 19.2 fA/cm2. Al2O3 single layer showed an extremely low J0 of 10 fA/cm2 but suffered from a decreased iFF and strong injection dependent lifetimes which originates from an inversion layer. ALD ozone processes were successfully developed for SiO2 and Al2O3.  The deposition rate per cycle for SiO2 was found to be only ~0.175 Ǻ/cycle (PEALD ~1.1 Ǻ/cycle), making it rather unpractical for use outside of research. Single layer SiO2 deposited with ozone showed, similarly to a plasma process, almost no surface passivation. Al2O3 however proved to be highly passivating on its own with a τeff = 3.8 ms, Seff = 1.2 cm/s (1 Ωcm n-type) after depositing at 250 °C. Studies on the effect of annealing showed that an annealing temperature of 450 °C is necessary to completely activate the passivation. The low Seff values were attributed to a very high negative fixed charge density ~1013 cm-2 together with strong chemical passivation.

[Some symbols cannot be rendered in the following metadata – please see the PDF file for an accurate version of the Abstract] ¶ Recombination within the bulk and at the surfaces of crystalline silicon has been investigated in this thesis. Special attention has been paid to the surface passivation achievable with plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiN) films due to their potential for widespread use in silicon solar cells. The passivation obtained with thermally grown silicon oxide (SiO2) layers has also been extensively investigated for comparison. ¶ Injection-level dependent lifetime measurements have been used throughout this thesis to quantify the different recombination rates in silicon. New techniques for interpreting the effective lifetime in terms of device characteristics have been introduced, based on the physical concept of a net photogeneration rate. The converse relationships for determining the effective lifetime from measurements of the open-circuit voltage (Voc) under arbitrary illumination have also been introduced, thus establishing the equivalency of the photoconductance and voltage techniques, both quasi-static and transient, by allowing similar possibilities for all of them. ¶ The rate of intrinsic recombination in silicon is of fundamental importance. It has been investigated as a function of injection level for both n-type and p-type silicon, for dopant densities up to ~5x1016cm-3. Record high effective lifetimes, up to 32ms for high resistivity silicon, have been measured. Importantly, the wafers where commercially sourced and had undergone significant high temperature processing. A new, general parameterisation has been proposed for the rate of band-to-band Auger recombination in crystalline silicon, which accurately fits the experimental lifetime data for arbitrary injection level and arbitrary dopant density. The limiting efficiency of crystalline silicon solar cells has been re-evaluated using this new parameterisation, with the effects of photon recycling included. ¶ Surface recombination processes in silicon solar cells are becoming progressively more important as industry drives towards thinner substrates and higher cell efficiencies. The surface recombination properties of well-passivating SiN films on p-type and n-type silicon have been comprehensively studied, with Seff values as low as 1cm/s being unambiguously determined. The well-passivating SiN films optimised in this thesis are unique in that they are stoichiometric in composition, rather than being silicon rich, a property which is attributed to the use of dilute silane as a process gas. A simple physical model, based on recombination at the Si/SiN interface being determined by a high fixed charge density within the SiN film (even under illumination), has been proposed to explain the injection-level dependent Seff for a variety of differently doped wafers. The passivation obtained with the optimised SiN films has been compared to that obtained with high temperature thermal oxides (FGA and alnealed) and the limits imposed by surface recombination on the efficiency of SiN passivated solar cells investigated. It is shown that the optimised SiN films show little absorption of UV photons from the solar spectrum and can be easily patterned by photolithography and wet chemical etching. ¶ The recombination properties of n+ and p+ emitters passivated with optimised SiN films and thermal SiO2 have been extensively studied over a large range of emitter sheet resistances. Both planar and random pyramid textured surfaces were studied for n+ emitters, where the optimised SiN films were again found to be stoichiometric in composition. The optimised SiN films provided good passivation of the heavily doped n+-Si/SiN interface, with the surface recombination velocity increasing from 1400cm/s to 25000cm/s as the surface concentration of electrically active phosphorus atoms increased from 7.5x1018cm-3 to 1.8x1020cm-3. The optimised SiN films also provided reasonable passivation of industrial n+ emitters formed in a belt-line furnace. It was found that the surface recombination properties of SiN passivated p+ emitters was poor and was worst for sheet resistances of ~150./ . The hypothesis that recombination at the Si/SiN interface is determined by a high fixed charge density within the SiN films was extended to explain this dependence on sheet resistance. The efficiency potential of SiN passivated n+p cells has been investigated, with a sheet resistance of 80-100./ and a base resistivity of 1-2.cm found to be optimal. Open-circuit voltages of 670-680mV and efficiencies up to ~20% and ~23% appear possible for SiN passivated planar and textured cells respectively. The recombination properties measured for emitters passivated with SiO2, both n+ and p+, were consistent with other studies and found to be superior to those obtained with SiN passivation. ¶ Stoichiometric SiN films were used to passivate the front and rear surfaces of various solar cell structures. Simplified PERC cells fabricated on 0.3.cm p-type silicon, with either a planar or random pyramid textured front surface, produced high Voc’s of 665-670mV and conversion efficiencies up to 19.7%, which are amongst the highest obtained for SiN passivated solar cells. Bifacial solar cells fabricated on planar, high resistivity n-type substrates (20.cm) demonstrated Voc’s up to 675mV, the highest ever reported for an all-SiN passivated cell, and excellent bifaciality factors. Planar PERC cells fabricated on gettered 0.2.cm multicrystalline silicon have also demonstrated very high Voc’s of 655-659mV and conversion efficiencies up to 17.3% using a single layer anti-reflection coating. Short-wavelength internal quantum efficiency measurements confirmed the excellent passivation achieved with the optimised stoichiometric SiN films on n+ emitters, while long-wavelength measurements show that there is a loss of short-circuit current at the rear surface of SiN passivated p-type cells. The latter loss is attributed to parasitic shunting, which arises from an inversion layer at the rear surface due to the high fixed charge (positive) density in the SiN layers. It has been demonstrated that that a simple way to reduce the impact of the parasitic shunt is to etch away some of the silicon from the rear contact dots. An alternative is to have locally diffused p+ regions under the rear contacts, and a novel method to form a rear structure consisting of a local Al-BSF with SiN passivation elsewhere, without using photolithography, has been demonstrated.

La gravure plasma de structures à fort rapport d'aspect dans le silicium est une étape clé dans la fabrication de microsystèmes et de composants de microélectronique de puissance. L'objectif de ce travail est de développer un procédé de gravure profonde du silicium, qui fonctionne à plus haute température de substrat que le procédé cryogénique en chimie plasma SF6/O2 et qui présente une meilleure stabilité en température et en concentration de gaz passivant(s). Dans ce but, de nouvelles voies de passivation non polymérisante ont été explorées. Nous avons évalué les possibilités de passivation par l'apport de SO2 en remplacement de O2. A température cryogénique, les propriétés de gravure sont semblables en plasma SF6/SO2 et SF6/O2 ; elles sont corrélées aux densités de neutres mesurées par spectrométrie de masse et actinométrie. La majeure partie des recherches a été consacrée à l'étude de la molécule SiCl4 comme précurseur de passivation. Nous avons au préalable analysé les interactions entre espèces générées en plasma SF6/SiCl4. Les expériences de caractérisation du plasma montrent que les réactions aux parois entre atomes F et espèces SiClx contrôlent la chimie du plasma et donc les propriétés de gravure du silicium. En mélange SF6/O2/SiCl4, ces réactions influent également sur la vitesse de gravure du substrat, mais l'ajout de SiCl4 à SF6/O2 a surtout pour effet de favoriser l'attaque chimique latérale. Nous avons finalement étudié la possibilité de former une couche de passivation par plasma SiCl4/O2 à température de substrat de -20 °C. Les résultats de cette étude permettent de proposer un nouveau procédé, basé sur l'alternance d'étapes de gravure par plasma SF6 et d'étapes de passivation par plasma SiCl4/O2.

L'objectif de cette étude est d'évaluer les potentialités du polyimide pour la passivation des composants de puissance en carbure de silicium (SiC), laquelle sera soumise à des températures et des champs électriques nettement supérieurs à ceux rencontrés dans l'environnement des puces en silicium (jusqu'à 350°C et 3 MV/cm respectivement).<br />Pour quantifier les propriétés ‘intrinsèques' du polyimide, des caractérisations électriques ont été réalisées dans une gamme de température étendue jusqu'à 260 °C, sur des structures MIM (Métal Isolant Métal), avec des films de polyimide élaborés selon le procédé de fabrication standard préconisé par le fabricant. Les résultats ont montré de bonnes propriétés électriques à température ambiante et jusqu'à 180 °C. Cependant, des valeurs de facteur de pertes et de permittivité diélectrique trop élevées pour satisfaire l'application visée ont été montrées au-delà de 180°C. Une amélioration des propriétés diélectriques et d'isolation a été cependant observée après la réalisation d'un traitement thermique additionnel, dans lequel les échantillons sont exposés longuement à des températures élevées, indiquant que la stabilité des propriétés du matériau n'est pas atteinte à l'issue du recuit d'imidisation du film polyimide.<br />L'analyse des caractérisations électriques et physico-chimiques montrent que cette instabilité est liée à l'évolution du taux d'imidisation de l'acide polyamique en polyimide, et de la concentration d'impuretés résiduelles (eau, solvant) lesquels dépendent des paramètres (durée, température) du recuit final d'élaboration du polyimide. Cette étude a permis de mettre en évidence la nécessité d'optimiser le recuit d'imidisation du procédé d'élaboration du film de polyimide afin d'obtenir des propriétés électriques adaptées au cahier des charges de l'application visée, dans une gamme de température étendue jusqu'à 350 °C.

Les batteries à électrode lithium métal ont des capacités théoriques élevées, une différence de potentiel importante, des géométries adaptables. Leur développement à l'échelle industrielle est pourtant compromis par l'électrodépôt d'agrégats irréguliers de lithium (dendrites) lors de la recharge de la batterie. La croissance dendritique à faible densité de courant est mal comprise, et semble liée à une mauvaise distribution de la densité de courant locale du fait des inhomogénéités à l'interface lithium/électrolyte. Ce manuscrit présente nos résultats sur des cellules symétriques Li/Electrolyte/Li qui permettent d'étudier simultanément le dépôt et la dissolution du lithium. Ces cellules sont basées sur des systèmes à base de POE+LiTFSI fonctionnant à 80°C, et sur des systèmes à base de PVdF-HFP/POE imbibé en EC:PC+LiTFSI et fonctionnant à température ambiante. Nous avons étudié ces cellules par visualisation in situ de l'espace inter-électrodes, et par spectroscopie d'impédance. Sur des cellules de visualisation à base d'électrolyte polymère fondu chargé en sel coloré, nous avons observé l'évolution des profils d'absorption optique directement liés aux profils de concentration dans l'électrolyte. Sur le système à base d'électrolyte gélifié nous avons constaté des variations locales de densité de courant en cours de polarisation. Par impédance, nous mettons en évidence la présence de deux couches de passivation à l'interface lithium/électrolyte qui évoluent différemment en vieillissement. Lorsqu'on polarise une cellule à courant constant, sa réponse en tension met en évidence la présence d'un milieu peu diffusif à l'interface entre le lithium et l'électrolyte.

Fabrication techniques and process integration considerations for amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) constitute the central theme of this dissertation. Within this theme three primary areas of focus are pursued. The first focus involves formulating a general framework for assessing passivation. Avoiding formation of an undesirable backside accumulation layer in an AOS bottom-gate TFT is accomplished by (i) choosing a passivation layer in which the charge neutrality level is aligned with (ideal case) or higher in energy than that of the semiconductor channel layer charge neutrality level, and (ii) depositing the passivation layer in such a manner that a negligible density of oxygen vacancies are present at the channel-passivation layer interface. Two AOS TFT passivation schemes are explored. Sputter-deposited zinc tin silicon oxide (ZTSO) appears promising for suppressing the effects of negative bias illumination stress (NBIS) with respect to ZTO and IGZO TFTs. Solution-deposited silicon dioxide is used as a barrier layer to subsequent PECVD silicon dioxide deposition, yielding ZTO TFT transfer curves showing that the dual-layer passivation process does not significantly alter ZTO TFT electrical characteristics. The second focus involves creating an adaptable back-end process compatible with flexible substrates. A detailed list of possible via formation techniques is presented with particular focus on non-traditional and adaptable techniques. Two of the discussed methods, "hydrophobic surface treatment" and "printed local insulator," are demonstrated and proven effective. The third focus is printing AOS TFT channel layers in order to create an adaptable and additive front-end integrated circuit fabrication scheme. Printed zinc indium aluminum oxide (ZIAO) and indium gallium zinc oxide (IGZO) channel layers are demonstrated using a SonoPlot piezoelectric printing system. Finally, challenges associated with printing electronic materials are discussed. Organic-based solutions are easier to print due to their ability to "stick" to the substrate and form well-defined patterns, but have poor electrical characteristics due to the weakness of organic bonds. Inorganic aqueous-based solutions demonstrate good electrical performance when deposited by spin coating, but are difficult to print because precise control of a substrate's hydrophillic/hydrophobic nature is required. However, precise control is difficult to achieve, since aqueous-based solutions either spread out or ball up on the substrate surface. Thickness control of any printed solution is always problematic due to surface wetting and the elliptical thickness profile of a dispensed solution. / Graduation date: 2013