Neste trabalho são apresentados os detalhes de projeto e construção de um equipamento de tocha de plasma gerada por uma descarga em arco de baixa potência, 300 - 2000W, para sintetização de filmes de diamantes "CVD", assim como são comentados os resultados da caracterização do arco elétrico, da tocha de plasma e dos filmes produzidos. O sistema foi projetado e construido de acordo com a dinâmica de gases unidimensional, teve como diretriz a necessidade de se utilizar componentes e equipamentos disponíveis no Laboratório Associado de Plasma do INPE. A descarga foi caracterizada eletricamente, ou seja, foram determinadas as curvas características da descarga, tensão em função da corrente, para diversas condições de operação, as quais foram comparadas com as curvas características obtidas por um modelo teórico simples desenvolvido para este sistema apresentando boa concordância. Verificou-se que o sistema de descarga apresenta dois modos de operação, que foram denominados modo luminescente e modo arco. No modo luminescente foram determinados os parâmetros da tocha de plasma: densidade e temperatura eletrônica usando sonda eletrostática dupla e no modo arco foi determinada a freqüência angular de rotação do arco utilizando um anodo dividido em quatro setores independentes. Foi realizado também uma análise da superfície dos eletrodos. Tanto no modo luminescente como no modo arco foram crescidos filmes de diamante que foram caracterizados pelas técnicas de microscopia eletrônica de varredura, dispersão em energia de raio-X, difração de raio-X e espectroscopia Raman. Os filmes produzidos no modo luminescente apresentam uma fase cristalina misturada com uma fase amorfa e pouca uniformidade ao passo que os filmes produzidos no modo "arco" são bem uniformes porém apresentam somente a fase amorfa.

This thesis ‘’An Investigation of Tin Chalcogenide Precursors and Thin Film Materials for Applications in Energy Harvesting Devices’’ encompasses a range of research areas. The report can be divided into two categories: The first is the design of novel heavy tin chalcogenide complexes and compounds that demonstrate the recent advances in main group chemistry and act as potential precursor candidates for CVD processes. The second category follows on from the previous, and focuses on materials deposited and their successive development, characterisation and optimisation for device applications. Subsequently, an array of metal chalcogenide thin films have been deposited and characterised within this project. By designing of a number of the tin chalcogenide precursors and precursor solutions it has been possible to selectively deposit thin films of Sn, α-SnS and cubic-SnS polymorphs, SnS2, SnSe, and SnTe via a low-cost deposition route known as aerosol assisted chemical vapour deposition (AA-CVD). It is proposed that the processes developed in this PhD can be adapted to deposit a wider spectrum of metal chalcogenide materials using cost effective techniques. Even though there is a wide scope of the possible applications for the aforementioned materials, the study has only been extended towards the characterisation of the optoelectronic properties of phase pure α-SnS and cubic-SnS samples, and SnS2 thin films deposited onto FTO, Mo and graphene substrates. The optimum deposition parameters for the application of these materials has been defined. In collaboration with a research group at the Institut de Recerca de Energia de Catalunya (iREC), Barcelona, Spain, an extended study of the photovoltaic properties of the α-SnS and Cubic-SnS samples is also presented, from which a series of SnS based thin film photovoltaic devices have been fabricated and characterised. This study present some of the few reports explicitly comparing the PV properties of the two α-SnS and Cubic-SnS polymorphs.

<i>Double Vision: A practice- led investigation of art and differential perception</i> is a series of five interrelated practice-led research studies into artistic expression controlling perceptual experiences between audiences of varying visual acuities. Significant refinements  occurred between the first and second, and second and third studies. The last four studies were conducted with the aim of understanding vision’s influence on perception. <i>Double Vision’s</i> lead methodological approach was artistic practice. Other methods were employed according to the needs of that practice. They included iteration, collaboration, exhibition and testing. The research questions of <i>Double Vision</i> were refined in response to the results of artistic practice. That evolution resulted in two interrelated questions: <i>Can artwork be intentionally created to be experienced differently dependent on one’s visual abilities? </i>and<i> If so, can those experiences be shared?</i> A further question, <i>‘Can an analogy to colour deficient vision be created that engages both those with colour vision deficiency and the typically sighted?’, </i>concludes the investigations. Artwork was realized through printmaking, animation and multimedia formats. Its context and content derived from many forms, notably the Ishihara <i>Test for Colour Deficiency</i>, writings of William Blake, contemporary music and philosophy. Augmented reality was employed to facilitate the translation of visual perceptions between targeted audiences. A number of exhibitions were held exploring these themes.

O presente trabalho estuda a produção e modificações físico-químicas do grafeno frente a tratamentos térmicos. Em uma primeira etapa, foi investigada a síntese de grafeno pela técnica de Deposição Química a partir da fase Vapor (CVD) sobre fitas de cobre. Nós variamos quatro parâmetros que influenciam no crescimento de grafeno: fluxo de metano (CH4), fluxo de hidrogênio (H2), tempo de crescimento e grau de pureza do cobre. Usando as técnicas de caracterização de espectroscopia Raman e microscopia óptica, observamos que fluxo menor de H2 e fluxo intermediários de CH4 favorecem o crescimento de grafeno de alta qualidade. Além disso, vimos que 15 minutos de crescimento de grafeno é suficiente para cobertura do substrato de cobre com grafeno. Por fim, foi visto que o maior grau de pureza do cobre permite a produção de monocamadas de grafeno mais homogêneas. Numa segunda etapa, foi realizado um estudo com objetivo de entender a interação de hidrogênio com monocamadas de grafeno. Nós usamos amostras de grafeno depositadas em filmes de SiO2 (285 nm)/Si e tratadas termicamente em atmosfera controlada de deutério (99,8%) em temperaturas entre 200 e 800 °C. Nós também investigamos a dessorção de hidrogênio do grafeno usando amostras previamente tratadas em deutério a 600 °C e depois tratadas em atmosfera controlada de nitrogênio em temperaturas entre 200 e 800 °C. Após os tratamentos, análise por reação nuclear (NRA) foi realizada para quantificar o deutério, onde nós observamos uma grande incorporação de deutério no grafeno acima de 400 °C, tendo um aumento moderado até 800 °C. Nós também observamos que a dessorção do deutério do grafeno ocorre apenas em 800 °C, embora a dessorção de deutério do óxido de silício ocorra a partir de 600°C. Espectroscopia Raman também foi realizada após cada tratamento térmico. Os resultados mostram que os defeitos na estrutura do grafeno têm um grande aumento para as etapas de maior temperatura na incorporação de deutério. Análises realizadas com Espectroscopia de Fotoelétrons Induzidos por Raios X (XPS) mostraram que a incorporação de deutério para maiores temperaturas causa o "etching" do grafeno. Por fim, caracterizações usando Espectroscopia de Absorção de Raios X (NEXAFS) mostraram que o deutério liga-se ao grafeno sem orientação preferencial. / The present work studies the production and physical-chemical modifications of the graphene under thermal annealings. In a first study, the graphene synthesis by Chemical Vapor Deposition (CVD) on copper foils was investigated. We varied four parameters that influence the growth of graphene: methane flow (CH4), hydrogen flow (H2), growth time and copper purity. Using Raman spectroscopy and optical microscopy, we observed that lower flux of H2 and intermediate flux of CH4 leads to the growth of high quality graphene. In addition, we observed that 15 minutes growth of graphene is sufficient to cover the copper substrate. A higher copper purity allows the production of homogeneous graphene monolayers. In a second step, a study was carried out to understand the interaction of hydrogen with graphene monolayers. We used graphene samples deposited on SiO2 (285 nm)/Si films and annealed in a controlled atmosphere of deuterium (99.8%) at temperatures between 200 and 800 °C. We also investigated the hydrogen desorption of graphene using samples previously treated in deuterium at 600 °C and then annealed in a controlled atmosphere of nitrogen at temperatures between 200 and 800 °C. After the annealings, nuclear reaction analysis (NRA) was performed to quantify the deuterium, where we observed a large incorporation of deuterium in graphene above 400 °C, with a moderate increase up to 800 °C. We also observed that desorption of deuterium occurs only at 800 °C, although deuterium desorption from silicon oxide occurs at 600 °C. Raman spectroscopy was also performed after each annealing. The results show that defects in the structure of graphene have a large increase for deuterium incorporation. Analyzes carried out with X-ray Photoelectron Spectroscopy (XPS) showed that the deuterium incorporation at higher temperatures leads to graphene etching. Finally, characterizations using X-ray Absorption Spectroscopy (NEXAFS) showed that deuterium binds to graphene without preferential orientation.

Objectives: The central Appalachian region of the United States is disproportionately burdened with cardiovascular diseases (CVD) and associated risk factors; however, research to inform clinical practice and policies and programs is sparse. This study aimed to examine the association between multiple modifiable risk factors for CVD and hypertension in asymptomatic patients in central Appalachia. Methods: Between January 2011 and December 2012, 1629 asymptomatic individuals from central Appalachia participated in screening for subclinical atherosclerosis. Participants were asked to report their hypertension status (yes/no). In addition, data on two nonmodifiable risk factors (sex, age) and five modifiable risk factors (obesity, diabetes mellitus, hypercholesterolemia, smoking, and sedentary lifestyle) were collected. Multivariable logistic regression analyses were conducted to assess association between hypertension and risk factors. Results: Of the 1629 participants, approximately half (49.8%) had hypertension. Among people with hypertension, 31.4% were obese and 62.3% had hypercholesterolemia. After adjusting for sex and age, obesity and diabetes mellitus were associated with a more than twofold increased odds of having hypertension (odds ratio [OR] 2.02, confidence interval [CI] 1.57–2.60 and OR 2.30, CI 1.66–3.18, respectively). Hypercholesterolemia and sedentary lifestyle were associated with higher odds for hypertension (OR 1.26, CI 1.02–1.56 and OR 1.38, CI 1.12–1.70, respectively), compared with referent groups. Having two, three, and four to five modifiable risk factors was associated with increased odds of having hypertension by about twofold (OR 1.72, CI 1.21–2.44), 2.5-fold (OR 2.55, CI 1.74–3.74), and sixfold (OR 5.96, CI 3.42–10.41), respectively. Conclusions: This study suggests that the odds of having hypertension increases with a higher number of modifiable risk factors for CVD. As such, implementing an integrated CVD program for treating and controlling modifiable risk factors for hypertension would likely decrease the future risk of CVD.

Herpes simplex viruses (HSVs), are among the most virulent and widespread pathogens; they affect 60-90% of the population worldwide. Substantial evidence indicates a possible association between pathogens and chronic disease. HSVs, among other viruses, have been associated with increased risk for inflammatory diseases. However, prior findings have been inconsistent on the role of infection in triggering autoimmune response and chronic disease. This study builds on the premise that pathogens can induce an inflammatory response and increase the risk for disease development. A representative U.S. sample from NHANES, a national population-based cross-sectional survey, was used to examine the relationship between HSVs infection and type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). Results from the two-tailed, Pearson chi-square test and multiple logistic regression analyses found no significant association between HSV or multiple herpes virus infections and T2DM or CVD, which suggest rather a secondary phenomenon. However, all the risk factors examined in this study indicated an association with either T2DM, CVD or both. Two inflammatory markers, C-reactive protein (CRP) and serum ferritin, were significantly associated with T2DM and CVD. These findings have potential implications for social change as they support the premise that high levels of CRP and ferritin may be associated with T2DM and CVD. Existing guidelines for primary and secondary prevention of T2DM and CVD could be expanded (a) to include CRP and ferritin as part of the health assessment for T2DM and CVD in high-risk populations, and (b) to explore the effectiveness of CRP and ferritin as predictive biomarkers and prognostic tools for T2DM and CVD.

This dissertation involves the study of epitaxial behavior of one-dimensional nanomaterials like single-walled carbon nanotubes and Indium Arsenide nanowires grown on metallic catalyst surfaces. It has been previously observed in our novel microplasma based CVD growth of SWCNTs on Ni-Fe bimetallic nanoparticles that changes in the metal catalyst composition was accompanied by variations in the average metal-metal bond lengths of the nanoparticle and that in turn, affected nanotube chirality distributions. In this dissertation, we have developed a very simplistic model of the metal catalyst in order to explain the nanotube growth of specific nanotube chiralities on various Ni-Fe catalyst surfaces. The metal catalyst model is a two-dimensional flat surface with varying metal-metal bond lengths and comprising of constituent metal atoms. The effect of the composition change was modeled as a change in the bond length of the model catalyst surface and density functional theory based calculations were used to study specific nanotube caps. Our results indicated that nanotube caps like (8,4) and (6,5) show enhanced binding with increased metal-metal bond lengths in the nanoparticle in excellent agreement with the experimental observations. Later, we used this epitaxial nucleation model and combined with a previously proposed chirality-dependent growth rate model to explore better catalysts that will preferentially grow an enhanced chirality distribution of metallic nanotubes. From our DFT calculations and other geometrical considerations for nanotube growth, we demonstrated that the pure Ni0.5Cu0.5 metal nanoparticles and its lattice-strained surfaces can serve as a promising catalyst for enhanced growth of metallic nanotubes. Finally, we extended this model of epitaxial growth to study the growth of,andoriented nanowires on gold metal nanoparticles where a faster growth rate ofnanowires was previously observed in experiments on shaped nanoparticles than that on spherical nanoparticles. The DFT calculations indicated an enhanced growth selectivity of theoriented nanowires on the Au(111) surfaces. However, the DFT results also show that theandNWs will preferentially grow on the Au(100) surface than on the Au(100) surface. The epitaxial model based DFT calculations of nanotube and nanowire growth on metal catalyst surfaces presented in this dissertation, provide a deep insight into their epitaxial growth mechansims and, can be easily exploited to layout better design principles of synthesizing catalysts that helps in growing these one-dimensional nanomaterials with desired material properties.

L'objectif de cette thèse consiste à développer une nouvelle approche d'élaboration des îlots quantiques de Ge sur substrat de Si(001) par épitaxie sélective et à étudier les propriétés optiques et électriques de ces îlots. Deux méthodes d'épitaxie sélective ont été utilisées. La première est la croissance d'îlots quantiques de Ge dans des ouvertures obtenues par désorption partielle d'une couche de silice native. Cette approche qui ne nécessite pas de procédé technologique préalable permet d'obtenir des ouvertures, dont la dimension latérale varie entre 100 et 300 nm. Nous obtenons un ou plusieurs îlots de Ge par ouverture en fonction de cette dimension. Le silicium épitaxié sélectivement dans ces ouvertures évolue vers une forme de pyramide tronquée. En contrôlant la hauteur de cette couche, nous pouvons obtenir au sommet de celle-ci un seul îlot de Ge, même dans une grande ouverture. La deuxième est la croissance sélective des îlots quantiques de Ge dans des fenêtres obtenues par lithographie. Le nombre d'îlots et leurs positions dépendent de la taille, de la forme des fenêtres, et de la surface de la terrasse de Si. Des couches simples et des multicouches d'îlots de Ge ont été réalisées. Les propriétés optiques des îlots sélectifs sont étudiées par spectroscopie de photoluminescence et Raman. La comparaison avec les îlots auto-assemblés révèle l'absence de signaux provenant de la couche de mouillage et un décalage vers les hautes énergies. Les propriétés électriques des îlots sélectifs sont étudiées à travers des caractéristiques courant-tension de diodes Schottky en fonction de la température et des mesures électriques via une pointe AFM à température ambiante.

L'étape clé pour intégrer des nanotubes de carbone à une échelle industrielle demeure un meilleur contrôle de leur croissance et notamment le contrôle sélectif de leurs chiralités en lien avec leurs propriétés électroniques. Ce travail a pour but de s'intéresser à la synthèse in-situ et à la caractérisation de nanotubes de carbone individuels par émission de champ pour mieux comprendre les mécanismes de nucléation et de croissance qui conditionnent sa chiralité. Nous avons développé un microscope à émission de champ couplé à un réacteur CVD (Chemical Vapor Deposition) pour observer directement la croissance catalytique de nanotubes de carbone individuels sur des pointes émettrices. Nous avons ainsi découvert que les nanotubes tournent souvent axialement pendant leur croissance, soutenant ainsi un modèle de " dislocation de vis ". L'analyse détaillée des résultats obtenus montre que nous observons directement la croissance atome par atome d'un nanotube monofeuillet individuel avec ajout d'un dimère de carbone à la fois à sa base. Parallèlement, des échantillons ont été caractérisés en détail sous émission de champ. Nous avons établi un protocole de collage de nanotubes individuels à l'apex d'une pointe métallique sous microscopies optique et électronique à balayage à l'aide d'un nanomanipulateur. Leur dépendance en température à très bas courant a été mise en évidence avec un compteur d'électrons afin d'identifier les différents domaines d'émission électronique. L'analyse des distributions énergétiques a fait apparaître un phénomène de chauffage induit qui peut mener à des températures de l'ordre de 2000 K à l'extrémité du nanotube lorsqu'il est soumis à un fort champ.

Les nanofils de silicium et de germanium présentent un fort potentiel technologique, d'autant plus important que leur position et leur taille sont contrôlées. Dans le cadre de cette thèse, la croissance de ces nano-objets a été réalisée par dépôt chimique en phase vapeur sous ultravide à l'aide d'un catalyseur d'or via le mécanisme vapeur-liquide-solide.Dans un premier temps, différentes techniques, le démouillage d'un film mince, l'évaporation par faisceau d'électrons et l'épitaxie par jet moléculaire, ont été mises en œuvre pour l'obtention du catalyseur métallique pour la croissance des nanofils.Dans un deuxième temps, la cinétique de croissance des nanofils de silicium a été étudiée en fonction de la pression, de la température de croissance et du diamètre des gouttes. Le gaz précurseur qui a été utilisé est le silane. Cette étude a permis de déterminer un diamètre critique de changement de direction de croissance, au-dessus duquel les nanofils sont épitaxiés sans défauts cristallins et préférentiellement selon la direction <111>. Le diamètre critique a été estimé à 80 nm. La cinétique de croissance en fonction de la pression a pu être interprétée de façon satisfaisante par la relation de Gibbs-Thomson. Ceci a permis la détermination du coefficient de collage des molécules de silane sur la surface de l'or et la pression de vapeur saturante du silicium P∞. Le changement morphologique de la section du nanofil et la distribution de nanoclusters d'or sur les parois ont été aussi détaillé à l'aide d'analyses par microscopie électronique en transmission.L'intégration des nanofils dans un dispositif nécessite de pouvoir les connecter. Pour les localiser et les orienter, un procédé basé sur le procédé d'oxydation localisée du silicium est proposé, pour former des ouvertures Si(111), à partir d'un substrat Si(001). Les gouttes d'or sont alors localisées dans ces ouvertures et vont servir à la croissance de nanofils orientés suivant une seule des directions [111]. Enfin, la cinétique de croissance de nanofils de germanium a été étudié. La limitation de l'utilisation du germane dilué à 10% dans l'hydrogène dans notre système d'épitaxie UHV-CVD a été démontrée. Compte tenu de notre dispositif expérimental, le gaz précurseur a été changé pour du digermane dilué à 10% dans de l'hydrogène afin de favoriser une croissance verticale de nanofils de Ge. Ceci nous a permis d'élaborer des nanofils de Ge avec des vitesses de croissance pouvant atteindre 100 nm/min. Des analyses structurales montrent l'existence d'un évasement des nanofils. Ceci est engendré par la présence d'une croissance latérale qui augmente avec la température. Comme dans le cas des nanofils de Si, nous observons la présence de l'or sur les parois latérales des nanofils. Cependant la présence de l'or est limitée à la partie supérieure des nanofils. Cette diffusion des nanoclusters d'or sur les parois peut être diminuée en augmentant la pression de croissance. En outre, l'étude de la vitesse de croissance des nanofils de Ge en fonction du rayon des gouttes d'or a permis de déterminer un rayon critique de 6 nm en dessous duquel la croissance de nanofil ne peut avoir lieu. Ce résultat a été interprété à l'aide d'un modèle basé sur l'effet Gibbs-Thomson et prenant comme hypothèse que l'étape limitante dans la croissance vapeur-liquide-solide est l'adsorption et l'évaporation du germanium.