Dissertations / Theses on the topic 'CuGaS2'

In this work, the growth and characterisation of the chalcopyrite semiconductor CuGaS2 is presented. The purpose of this study is to gain a better understanding of the defect chemistry of this class of materials through a systematic study relating the structural and optical properties to the composition of thin films grown by metalorganic vapour phase epitaxy. Details associated with the optimisation of the growth process are presented in a format relating the changes in the composition and morphology to variations in the growth process. The structural properties of thin films grown on GaAs(001) substrates are described. A dominance of polycrystalline growth is found to occur for Cu-rich material, whereas near-stoichiometric to Ga-rich material is typified by epitaxial growth. Secondary phases are identified by X-ray diffractometry and Raman spectroscopy for severely non-stoichiometric material. In some cases, the formation of the cubic zincblende and CuPt polytype of CuGaS2 are identified by transmission electron microscopy. It will be shown that changes in the Cu/Ga ratio of the solid strongly influence the photoluminescence response of the layers. Weak excitonic luminescence is observed for both slightly Ga-rich and Cu-rich material. Near stoichiometric layers exhibit luminescence centered at ~2.4 eV. Cu-rich layers are dominated by a line occurring at ~2.1 eV, whereas a different line at ~2.25 eV dominates for Ga-rich layers. A clear picture emerges of the radiative mechanisms dominating for Cu-rich and Ga-rich layers.

Shirin Movaghgharnezhad for the master of science degree in mechanical engineering, presented on November 6, 2017, at Southern Illinois University Carbondale. TITLE: Electrodeposition of CuGaS2 from Aqueous and Non-Aqueous Electrolyte Mixtures MAJOR PROFESSOR: Dr. Ian I. Suni Electrodeposition of CuGaS2 from aqueous and non-aqueous electrolyte mixtures is reported in this work. Acetonitrile complexation is used to shift the reduction potential of Cu (II) in the cathodic direction. With the presence of 50% acetonitrile, the difference between the peak reduction currents of Cu (II) and Ga (III) during cyclic voltammetry is only 140 mV, whereas the standard reduction potentials of the individual components in aqueous electrolytes differ by 870 mV. When all components are present in the electrolyte, a new reduction peak obtained in cyclic voltammograms at −260 mV and pH 2.7 that is anodically shifted relative to the cathodic peaks when only one component is present. According to the composition, and morphology analysis at deposition potential -260 mV vs. Ag/AgCl for 15 minutes from aqueous and non-aqueous solutions of 10 mM Ga(NO3)3, 0.5 CuSO4, 1 mM Na2S, 100 mM LiClO4 and a 50-50 mixture of water and acetonitrile at pH 2.7 was found to be the optimum condition to obtain stoichiometric CuGaS2 thin films. In addition, oxygen incorporation in the electrodeposit is observed, because electrodeposition of stoichiometric CuGaS2 appears to be immediately followed by Ga oxidation. The sample were annealed at temperature 300°C in Ar atmosphere for 2 hours to improve crystallinity and reduce the extent of oxidation. Thin film analysis by EDX, top-view SEM, and also cross-sectional SEM were also performed to determine the elemental ratio of Cu:Ga:S, thin film morphology, and thin film thickness, respectively. This material has potential application in solar cells. The EDX analysis of copper gallium sulfide thin films at different potentials and different gallium solution phase concentration were also performed.

Le travail présente consiste en l'étude d'un semi-conducteur ternaire: CuGaS2. La famille de la chalcopyrite dont fait partie ce compose suscite, à l'heure actuelle, un intérêt grandissant compte tenu des applications possibles dans le domaine de l'optique non linéaire, des détecteurs photovoltaïques et des cellules solaires. En dépit d'une grande similitude structurale entre CuGaS2 et son analogue binaire (ZnS), la largeur de la bande interdite du compose ternaire est notablement plus faible. A partir de mesures de l'absorption optique, nous montrons l'évolution, sous pression hydrostatique, de cette anomalie du gap. Par diffraction des rayons x sur monocristaux, nous avons étudié la structure cristalline, sous pression, du compose ternaire et mis en évidence les différences essentielles qui résident entre les composes binaire et ternaire : (1) la substitution de l'atome de zinc par alternativement du cuivre et du gallium crée des liaisons différentes avec un changement dans l'électronégativité des ions. (2) Du fait de cette disparité des ions, l'atome chalcogène se trouve déplace de sa position spéciale. (3) Enfin, apparaît une distorsion tétragonale. L'origine de l'anomalie du gap a été attribuée principalement à une hybridation p-d entre les électrons p du soufre et les électrons d du cuivre. Une analyse multipolaire de la distribution de la densité électronique nous a permis de comparer les liaisons Ga-S et Cu-S.

Des echantillons en couches minces de cu xga yse z proches de la stchiometrie de valence (x + 3y 2z) ont ete fabriques par mocvd a partir de trois composes organometalliques. Diverses compositions allant des riches en cuivre aux riches en gallium ont pu etre analysees et caracterisees. Quelque soit la composition, une forte orientation preferentielle est observee dans la direction 112. La structure cristalline et la largeur de bande interdite du cu 2se, du cugase 2, du cuga 3se 5 et du ga 2se 3 fabriques ont ete etablies. Les caracterisations electriques revelent une densite de porteurs elevee. La photoluminescence a permis d'identifier les defauts intrinseques les plus couramment observes. Par spectrophotometrie, il a ete possible de determiner l'epaisseur, les indices n et k des couches, ainsi que d'evaluer les seuils des transitions a, b, c et leurs types.

CuInSe₂, CuInS₂ and CuGaSe₂ are I-III-VI₂ compound semiconductors with a chalcopyrite structure. These ternary compounds exhibit favourable properties, such as direct band gaps and high absorption coefficients, for application as absorber layers in thin-film solar cells. Recently Cu(In,Ga)Se₂ based photovoltaic devices have demonstrated conversion efficiencies of 20.3 % which is the highest amongst polycrystalline thin-film solar cell technologies. This thesis describes a study of excitonic recombination processes in high quality CuInSe₂, CuInS₂ and CuGaSe₂ single crystals using photoluminescence (PL) spectroscopy as a function of excitation power, temperature and applied magnetic field. Excitation power dependent measurements confirm the identification of the free excitons in the PL spectra of the three chalcopyrite semiconductor compounds. Additional sharp lines in the PL spectra appear to be due to the radiative recombination of excitons bound to shallow hydrogenic defects. PL lines due to excitons bound to more complex defects with a low concentration of defects are also found in CuInSe₂ and CuInS₂. Analysis of the temperature dependent PL spectra lead to activation energies of the free and bound excitons in CuInSe₂, CuInS₂ and CuGaSe₂. In addition, phonon energies have been obtained from the temperature dependence of the free exciton spectral positions and of the full width at half maximum. PL spectra measured in applied magnetic fields allow estimation of the diamagnetic shift rates for CuInSe₂, CuInS₂ and CuGaSe₂. A first-order perturbation model leads to values for the excitonic reduced masses and the effective hole masses can be estimated. For CuInSe₂ a theoretically predicted anisotropy of the effective hole masses is demonstrated. The study of the excitonic states in CuInSe₂, CuInS₂ and CuGaSe₂ provides a deeper understanding of the electronic material properties which can facilitate further improvements in solar cell efficiencies.

Pour dépasser la barre théorique de 30% de rendement de conversion, les cellules solaires en tandem basées sur des sous cellules en silicium cristallin (c-Si) sont l'une des architectures les plus prometteuses. En outre, une approche monolithique à deux terminaux utilisant des couches minces à grand gap comme cellule supérieure ne nécessiterait pas de modification significative des modules solaires existants. L’absorbeur Cu(In,Ga)(S,Se)₂ (CIGS) est un candidat prometteur grâce à sa haute efficacité (le record de rendement en module est d'environ 19%) et à son énergie de bande interdite accordable. De plus, on peut noter que des cellules solaires CIGS sont déjà produites à l’échelle industrielle. La chalcopyrite pure-gallium et pure-sélénium CuGaSe₂ (CGSe) peut également être utilisée comme absorbeur de cellule supérieure dans un dispositif multijonction grâce à sa valeur optimale de bande interdite (1,68 eV). Néanmoins, le rendement de conversion actuel des cellules solaires à base de CGSe est encore faible (11,9%) et son intégration tandem n’améliorerait pas, en l’état, les performances de la cellule c-Si. L'objectif de cette thèse est d'optimiser l’élaboration d'une cellule solaire mono-jonction à base de CGSe, de développer un processus de dépôt de cellule supérieure sans dégradation ni contamination de la cellule inférieure en c-Si et enfin d'élaborer des cellules photovoltaïques tandem CGSe / c-Si fonctionnelles
To overcome 30% conversion efficiency, tandem solar cells based on crystalline silicon (c-Si) sub-cells are one of the most promising architecture regarding the theoretical predictions. Furthermore, a monolithic two-terminal approach using wide bandgap thin films as top cell does not require significant modification of the existing solar modules. Cu(In,Ga)(S,Se)₂ absorber layer is a promising candidate thanks to its high efficiency (the module record efficiency is around 19%) and to its tunable bandgap energy. In addition, industrial solar cells are currently produced from this material. In-free CuGaSe₂ (CGSe) can also be used as top cell absorber in a multi-junction device thanks to its optimal bandgap value (1.68eV). Nevertheless, the actual conversion efficiency of CGSe based solar cells is still low (11.9%). The objective of this thesis is to optimize the development of a single-junction solar cell based on CGSe, to develop top cell deposition process without degradation nor contamination of the c-Si bottom cell and finally to elaborate functional CGSe / c-Si tandem solar cells

On decrit deux methodes d'analyse des semi-conducteurs de formule generale cumse#2 (m=in?ga ou ub+ga) qui sont utilises dans la fabrication de photopiles solaires en couche mince. La premiere est effectuee apres mise en solution des echantillons. Les metaux sont determines par polarographie a impulsions et le selenium par amperometrie. Pour l'analyse des metaux, une methode originale d'elimination de l'interference du selenium a ete mise au point, qui permet d'operer une analyse complete en environ une heure, a partir de 0,35 mg de materiau. La seconde technique a consiste en une oxydation anodique des films minces. Des conditions ont ete trouvees pour oxyder separement les metaux et le selenium, mais il n'a pas ete possible de separer les deux metaux. Un exces de cu#2se donne cependant lieu a un pic anodique bien separe permettant ainsi de mettre en evidence les quantites de chacune des phases en presence

Les travaux de thèse portaient sur la réalisation de cellules à colorant de type p (DSSCp) avec une photocathode autre que NiO. L’objectif était de remplacer ce semi-conducteur de type p par des matériaux plus transparents, plus conducteurs et présentant une bande de valence plus basse en énergie pour permettre de générer des tensions en circuit ouvert (VOC) plus élevées. Dans ce cadre, les composés CuGaO2, LaOCuS et ZnO:N ont été synthétisés sous la forme de nanoparticules, caractérisés par diffraction des rayons X et leurs potentiels de bandes plates (Vbp) déterminés par spectroscopie d’impédance complexe. Il en résulte que CuGaO2, LaOCuS et ZnO:N présentent respectivement des Vbp nettement supérieur (0,49 V/ECS), similaire (0,26 V/ECS) et inférieure (0,20 V/ECS) à celui de NiO (0,33 V/ECS). Naturellement, des cellules à colorant à base du matériau de la famille des delafossites ont été réalisées et testées avec la dyade PMI-NDI comme colorant et un complexe de cobalt comme médiateur rédox. Une VOC supérieure à celle observée pour NiO dans les mêmes conditions a été mis en évidence. Ce résultat est malheureusement terni par un courant en court-circuit (Jsc) moindre. Pour tenter de remédier à cet inconvénient, des matériaux CuGaO2:Mg avec des surfaces spécifiques supérieures à celle de CuGaO2 ont été réalisés et testés. Parallèlement, nous nous sommes attachés à la réalisation de cellules à base de LaOCuS, autrement plus conducteur que NiO, tandis que la conductivité de type p de ZnO:N a été caractérisée plus en profondeur
These thesis works focused on the realization of p-type dye sensitized solar cells (DSSCp) with a photocathode using an alternative to NiO. The objective was to replace the p-type semiconductor by more transparent and conductive materials and displaying a lower valence band energy to enable the generation of higher open circuit voltages (Voc). In this context, CuGaO2, LaOCuS and ZnO:N compounds were synthesized in nanoparticles form, characterized by X-ray diffraction and their flat band potentials (Vfb) were determined by complex impedance spectroscopy. As a result CuGaO2, LaOCuS and ZnO:N have Vfb significantly higher (0. 49 V/SCE), similar (0. 36 V/SCE) and lower (0. 20 V/SCE) than that of NiO (0. 33 V/SCE). Thus, dye sensitized solar cells based on the delafossite material were made and tested with the PMI-NDI dyad as dye and a cobalt complex as redox mediator. A greater VOC than that observed for NiO under the same conditions is highlighted. This result is unfortunately altered by a lower short circuit current (Jsc). To try to overcome this drawback, CuGaO2:Mg materials with a higher specific surface area than that of CuGaO2 have been prepared and tested. Simultaneously, we have focused on the achievement of cells based on LaOCuS, more conductive material than NiO. In addition, the p-type conductivity of ZnO:N was further characterized

L'etude des echantillons massifs de cuin::(1-x)ga::(x)se::(2) de type p permet de mettre au point la solution electrolytique acide en presence du couple redix v**(2+/3+). Etude des positions energetiques des bandes par mesures capacitives. Etude de la variation de la bande interdite en fonction de x et mesure des longueurs de diffusion par l'evolution du photocourant en fonction du potentiel. Etude des proprietes optiques et electroniques des couches minces cugase::(2) de type p en fonction des ecarts a la stoechiometrie

Le but de ce travail est la synthese et l'etude du materiau photovoltaique cuga(se#xte#1##x)#2. Les materiaux massifs ont ete elabores par refroidissement lent du liquide stchiometrique. Ils ont ete etudies aux rayons x, a la microsonde electronique et en luminescence. Ces etudes ont montre qu'ils forment des solutions solides. L'etude de luminescence, notamment, a permis de determiner le gap en fonction de x, et d'identifier certains defauts de reseau. A partir du materiau massif, des couches minces ont ete realisees par une methode simple utilisant le transport chimique a courte distance en tube ferme, et une etude thermochimique a permis de determiner les equations gouvernant le transport. Les caracterisations des couches minces, faites a l'aide des rayons x, de la microsonde electronique et du microscope electronique a balayage, nous ont permis, en particulier, d'etudier les conditions de depot quasi-stchiometrique. Des transitions de phase ont ete observees et etudiees. Pour interpreter les phenomenes observes, nous avons generalise l'etude des transitions de phase a d'autres materiaux cuxy#2 (x=ga, in; y=se,te)

El mosquito tigre, Aedes albopictus (Skuse, 1894), es una especie invasora que actualmente se encuentra en los cinco continentes, extendiéndose desde su área nativa en el sudeste de Asia a través del comercio internacional de neumáticos usados y del bambú de la suerte. En Cataluña fue detectado por primera vez en el año 2004, en el municipio Sant Cugat del Vallès, y se expandió rápidamente en los últimos cinco años a más de 200 municipios de Cataluña y Alicante. Esta especie es un vector de diferentes arbovirosis, y ha sido asociada con la transmisión del virus del dengue y la chikungunya en varias zonas del mundo, causando una gran preocupación a las personas y las autoridades de salud pública. En Europa, el brote de fiebre chikungunya que ocurrió en Italia en 2007, y los posteriores casos autóctonos de dengue en Francia y Croacia en 2010, acentuaron la necesidad de establecer programas efectivos de vigilancia y control del vector. Los objetivos de este estudio fueron: (1) Evaluar la efectividad de una estrategia de gestión integrada de vectores para el control de la población de Aedes albopictus en Sant Cugat del Vallès (2), determinar algunos factores que afectan las poblaciones de mosquitos en los domicilios inspeccionados durante las campañas "puerta-a-puerta", (3) describir los recipientes preferidos por las larvas de la especie, (4) analizar la percepción y la participación de la población de Sant Cugat en el control de esta especie invasora y (5 ) proponer como estrategia de control un protocolo específico para la localidad. En total se visitaron 3.720 viviendas y se entrevistó a 720 personas. Además durante 2008-2010 se aplicó en seis barrios del área un programa de gestión integrada para controlar al mosquito tigre. La estrategia incluyó la reducción de los focos de cría (con visitas puerta-a-puerta), los tratamientos larvicidas (Bacillus thuringiensis israelensis y diflubenzuron), tratamientos adulticidas (alfa-cipermetrin) y la limpieza de los vertederos incontrolados. En 2010 también se realizó un estudio de las densidades de larvas en los recipientes donde fueron detectadas. La efectividad de la introducción se evaluó con un modelo lineal generalizado donde la variable dependiente fue la abundacia de huevos de mosquitos monitorizados a través de trampas de oviposición. Los resultados mostraron un número significativamente inferior de huevos en las áreas intervenidas en 2008-2009 comparadas con las áreas control. En 2008, las medianas acumuladas de huevos fueron respectivamente de 175 y 272 en las zonas de intervención y control; en 2009, estas medianas fueron de 884 y 1668 huevos. En los tres años estudiados se observó relación entre algunos factores ambientales y una mayor detección de recipientes con crecimiento de larvas destacando: las instalaciones con huertas (15%; IC 95%: 9-20%), materiales apilados (15%; IC 95%: 9-20%), locales comerciales (11%; IC del 95%: 7-15%), gallineros (5%; IC 95%: 2-8%) y obras (3%; IC 95%: 1-6%). En el estudio de la densidad larvaria, destacaron los pequeños contenedores (≤0,5 l) como preferidos para el desarrollo de la especie. Imbornales, bidones, residuos sólidos y cubos fueron frecuentemente detectados con crecimiento de larvas de Aedes albopictus. La cooperación ciudadana, un factor esencial para el éxito, fue elevada gracias a la colaboración de los propietarios de las casas que facilitaron el acceso al interior de sus viviendas privadas. Estos hallazgos sugieren que la estrategia fue efectiva para disminuir el número de huevos. Finalmente, presentamos un protocolo basado en en la estrategia utilizada para controlar esta especie durante estos años. Este trabajo podría utilizarse como modelo para controlar las poblaciones de Ae. albopictus en otros municipios de la región del Mediterráneo.
The Asian tiger mosquito, Aedes albopictus (Skuse, 1894), is an invasive species that is currently found in the five continents, spreading from its native area in Southeast Asia through the international trade of used tires and lucky bamboo. In Catalonia it was first reported in 2004 in the municipality of Sant Cugat del Vallès, and has quickly expanded over the last five years to more than 200 municipalities in Catalonia and Alicante. This species is a vector of several arboviruses, and it has been associated with the transmission of dengue and chikungunya virus in several areas of the world causing serious concerns to people and public health authorities. In Europe, the outbreak of chikungunya fever in Italy during 2007, and subsequent autochthonous cases of dengue fever in France and Croatia in 2010, raised the urgency of establishing effective surveillance and control programs for the vector. The objectives of this study were: (1) To evaluate the effectiveness of an Integrated Vector Management (IVM) control strategy of the Aedes albopictus population in Sant Cugat del Vallès; (2) to determine the several key factors affecting mosquito populations in the premises inspected during the “door-to-door” campaigns; (3) to describe the larval containers preferred by the species; (4) to explore the perception and the involvement of the population of Sant Cugat in the control of this invasive species and (5) to propose a standard protocol towards an IVM control strategy at local level. During 2008-2010 an IVM campaign was performed in six neighbourhoods of Sant Cugat del Vallès. The IVM strategy included source reduction campaign (with door-to-door visits), larvicide treatments (Bacillus thuringiensis israelensis and diflubenzuron), adulticide treatments (alpha-cipermetrin) and cleaning up uncontrolled landfills. The effectiveness of the introduction was evaluated through Generalised Linear Models based on the differences in the abundance of mosquitoes monitored through oviposition traps. In addition in 2010 a larval survey was carried out. In total 3720 dwellings were visited and 820 householders were interviewed. The results showed the number of eggs significantly reduced in the intervened areas in 2008-2009 when compared to the control ones. In 2008, the accumulate median of eggs was 175 and 272 in the intervention and control areas, respectively. In 2009, these medians were 884 and 1668 eggs. In the three study years an association was observed between some environmental factors, such as premises with vegetable garden (15%; CI 95%: 9-20%), stacked materials (15%; CI 95%: 9-20%), coops (5%; CI 95%: 2-8%) as well as commercial premises (11%; CI 95%: 7-15%), and sites with works (3%; CI 95%: 1-6%), with the detection of larval breeding containers. The larval density surveys highlight small containers (≤0.5 l) as preferred breeding sites for this species. In the peridomestic areas of the inspected premises, containers as scuppers, drums, solid waste and buckets were frequently found with Aedes albopictus larval breeding. Citizen cooperation proved to be an essential factor for success. A high level of collaboration by the home onwers, who allowed entry into their private dwellings was attained. These findings suggest that the strategy was effective in reducing the number of eggs. Finally, we propose a protocol building on our practical experience and research on the control of this species over the years of this study. This work might be a model for controlling the populations of Ae. albopictus in other municipalities of the Mediterranean region.

Many cultural heritage sites across the globe consist of masonry structures. To ensure the preservation of such structures, an accurate evaluation of their current structural condition is often of utmost importance. However, recurrent uncertainties regarding material properties and the complex interaction among structural elements often makes this a challenging task. As a consequence, there has been a considerable research effort on the development of methods and tools that can facilitate this task, and experts responsible for the evaluation of unique masonry structures usually need to weigh information from various diagnosis activities before deciding the best course of action for preservation. In a first instance, the research work presented in this thesis contributes to the enhancement of some key methods for the analysis of masonry structures. Specific topics dealing with materials testing, full-scale vibration testing, and static structural health monitoring (SHM) are addressed. Subsequently, this is built upon to develop specific decision support tools that can assist decision-making for risk mitigation. The research in materials testing involved an experimental study on the dynamic elastic properties of brick masonry constituents, which are known to differ from their static counterpart. Despite being a fundamental deformation property, experimentally determining the static elastic moduli of brick masonry constituents remains a challenging task. Following an experimental campaign, this research proposes a robust procedure based on the synergy of two non-destructive testing methods to reliably estimate the dynamic elastic and shear moduli of such materials. In addition, an empirical expression to estimate the static elastic modulus of constituents from its dynamic counterpart is also provided. With respect to vibration testing, the present study deals specifically with masonry bell towers and the operational modal analysis (OMA) techniques used to extract modal parameters from test acquisitions. Despite significant advances in OMA techniques, the accuracy of resulting estimates from vibration tests are still highly dependent on test conditions, acquisition quality, and on the techniques employed for modal parameter estimation. This work first aimed to design a suitable acquisition system and program for the vibration testing of the bell tower of Seu Vella in Lleida, Catalonia. Several system identification and modal analysis techniques were investigated and the most suitable ones for identifying particular modal parameters under varying acquisition conditions are discussed. The SHM research component is particularly focused on data analysis for static SHM systems, which involve the continuous measurement of key slow-varying parameters over long time periods. Although such systems have the potential to identify slow irreversible deterioration mechanisms in masonry structures at a very early stage, the interpretation of acquired data can be difficult, particularly due to the influence of environmental factors. This research proposes a fully automated data analysis procedure able to filter out reversible environmental effects and classify monitored responses in pre-defined evolution states. The procedure has successfully been used to identify vulnerable areas in two important medieval heritage structures in Spain, namely the cathedral of Mallorca and the church of the monastery of Sant Cugat. Finally, all the findings in specific topics are built upon to elaborate multi-criteria decision-making (MCDM) tools meant to improve the objectivity, clarity, and transparency of risk mitigation decisions for masonry heritage. A systematic risk assessment procedure is proposed involving the computation of two MCDM indices: an index related to the estimated risk of damage, and another to the uncertainty behind this estimation. Applications to several case studies are also included to demonstrate the usefulness of the proposed tools.
Muchos sitios de patrimonio cultural en todo el mundo consisten en estructuras de mampostería. Para asegurar la preservación de tales estructuras, la evaluación precisa de su condición estructural es a menudo de suma importancia. Sin embargo, las incertidumbres recurrentes con respecto a las propiedades de los materiales, así como la compleja interacción entre los distintos elementos estructurales a menudo hacen que esta sea una tarea desafiante. Como consecuencia, ha habido un esfuerzo de investigación considerable en el ámbito del desarrollo de métodos y herramientas que puedan facilitar esta tarea, y los expertos responsables de la evaluación de estructuras de mampostería generalmente necesitan sopesar la información de diversos estudios de diagnóstico antes de decidir el mejor curso de acción para su conservación. Las fuentes típicas de información son fuentes históricas, inspecciones in situ, ensayos no destructivos, auscultación estructural (SHM, del inglés Structural Health Monitoring) y el análisis estructural, entre otros. En una primera instancia, el trabajo de investigación presentado en esta tesis contribuye a la mejora de algunos métodos clave para el análisis de estructuras de mampostería. Se abordan temas específicos relacionados con los ensayos de materiales, los ensayos de vibración de estructuras y el SHM. Posteriormente, esto conduce al desarrollo de herramientas específicas de apoyo a la toma de decisiones que pueden ayudar en la toma de decisiones para la mitigación de riesgos. El trabajo de investigación realizado en el campo de los ensayos de materiales ha implicado un estudio experimental sobre las propiedades dinámicas elásticas de los componentes de mampostería de ladrillo, que se sabe que difieren de sus contrapartes estáticas. A pesar de ser una propiedad de deformación fundamental, la determinación experimental del módulo elástico estático en compresión para los componentes de la mampostería de ladrillo sigue siendo una tarea desafiante. Ello se debe principalmente a las dificultades inherentes en la medición precisa de las deformaciones en el rango de deformación elástica de materiales frágiles. Como resultado, las estimaciones del módulo estático muestran generalmente una dispersión mucho mayor que las involucradas en la determinación del módulo elástico dinámico. Aunque se prefiere la propiedad estática para las verificaciones estructurales comunes, la relación entre las dos aún no se comprende bien para los componentes típicos de mampostería de ladrillo. De hecho, existen muy pocos estudios que evalúen la idoneidad de diferentes técnicas para estimar las propiedades dinámicas elásticas de estos materiales. Como tal, actualmente hay muy poca orientación disponible sobre cómo estimar de manera fiable estas propiedades para dichos materiales. Tras una campaña experimental para determinar los módulos dinámicos elásticos y de corte de una variedad de ladrillos y morteros, esta investigación propone un procedimiento robusto basado en la combinación de dos métodos de ensayo no destructivos para estimar de manera fiable estas propiedades dinámicas. Además, también se proporciona una expresión empírica para estimar el módulo de elasticidad estático de los componentes de mampostería de ladrillo a partir de su contraparte dinámica. Con respecto a ensayos de vibración de estructuras, el presente estudio considera específicamente campanarios de mampostería y las técnicas de análisis modal operacional (OMA, del inglés Operational Modal Analysis)) utilizadas para extraer parámetros modales a partir de adquisiciones. A pesar de avances significativos en las técnicas de OMA, la precisión de las estimaciones resultantes de las pruebas de vibración aún depende en gran medida en las condiciones de la prueba, la calidad de la adquisición y las técnicas empleadas para la estimación de parámetros modales. Este trabajo tuvo como objetivo, en primer lugar, diseñar un sistema y programa de adquisición adecuados para ensayos de vibración del campanario de la Seu Vella en Lleida, Cataluña. Se investigaron varias técnicas de identificación de sistemas y de análisis modal y se discuten las más adecuadas para identificar parámetros modales particulares en diferentes condiciones de adquisición. El componente de SHM de esta investigación se ha centrado en el análisis de datos de sistemas de SHM estáticos que implican la medición continua de parámetros clave de variación lenta durante largos períodos de tiempo. Las estructuras patrimoniales de mampostería a menudo se ven afectadas por mecanismos lentos de deterioro irreversible que pueden poner en peligro la estabilidad estructural en un futuro próximo. El SHM estático tiene el potencial de identificar tales mecanismos en etapas tempranas. Ello puede facilitar enormemente la implementación de medidas preventivas y correctivas adecuadas que pueden ser críticas para asegurar que tales estructuras se preserven para las generaciones venideras. Sin embargo, dado que los parámetros monitoreados generalmente experimentan variaciones estacionales reversibles del mismo orden de magnitud que los cambios causados por mecanismos activos, la identificación de estos últimos es a menudo una tarea difícil. El Capítulo 5 de esta tesis presenta un procedimiento de análisis de datos automatizado totalmente integrado para sistemas completos de SHM estáticos que utilizan modelos de regresión lineal dinámica para filtrar los efectos causados por variaciones ambientales. El método no solo produce tasas de evolución estimadas, sino que también clasifica las respuestas monitoreadas en estados predefinidos de evolución. El procedimiento se ha utilizado con éxito para identificar áreas vulnerables en dos importantes estructuras patrimoniales medievales en España, a saber, la catedral de Mallorca y la iglesia del monasterio de Sant Cugat. Finalmente, todos los hallazgos anteriores se utilizan para la elaboración de herramientas de toma de decisiones multicriterio (MCDM, del inglés Muli-Criteria Decision-Making) destinadas a mejorar la objetividad, claridad y transparencia de las decisiones de mitigación de riesgos para estructuras patrimoniales de mampostería. Se propone un procedimiento sistemático de evaluación de riesgos que involucra el cálculo de dos índices MCDM: un índice relacionado con el riesgo estimado de daño y otro con la incertidumbre detrás de esta estimación. También se incluyen aplicaciones a varios casos de estudios para demostrar la utilidad de las herramientas propuestas
Un gran nombre de llocs de patrimoni cultural consisteixen en estructures de maçoneria. La responsabilitat comuna de protegir aquestes estructures és ara àmpliament reconeguda i, sovint, és fonamental una avaluació acurada de la seva condició estructural actual per tal d’assegurar tal protecció. No obstant això, en molts casos, les incerteses recurrents en les propietats dels materials i la complexa interacció entre elements estructurals converteixen l’avaluació de la seguretat estructural en una tasca difícil. Com a conseqüència, hi ha hagut un considerable esforç investigador sobre el desenvolupament de mètodes i eines que puguin facilitar aquesta tasca, i els experts responsables de l’avaluació de la seguretat d’estructures del patrimoni de maçoneria necessiten normalment contrastar informació provinent de diverses activitats de diagnosi abans de decidir les millors actuacions per a la seva preservació. Les fonts típiques d’informació són documents històrics, inspeccions in situ, assajos no destructius, monitorització de l’estructura (SHM, de l’anglès Structural Health Monitoring), i anàlisi estructural, entre altres. En una primera instància, el treball de recerca presentat en aquesta tesi contribueix a la millora d’alguns mètodes clau per a l’anàlisi d’estructures de maçoneria. S’aborden temes específics relacionats amb l’assaig de materials, assajos de vibració d’estructures i SHM. Posteriorment, això condueix al desenvolupament d’eines específiques de suport a la presa de decisions que poden ajudar en la presa de decisions per a la mitigació de riscos. La recerca realitzada en el camp dels assajos de materials va implicar un estudi experimental de les propietats elàstiques dinàmiques de constituents de la fàbrica de maó, de les quals es coneix que difereixen de les estàtiques. Malgrat ser una propietat de deformació fonamental, la determinació experimental del mòdul elàstic estàtic a la compressió per a constituents de maçoneria de maó és encara una tasca desafiant. Això és principalment a causa de les dificultats vinculades a la forma exacta de mesurar tensions en el camp de deformació elàstic dels materials fràgils. Com a resultat, estimacions del mòdul estàtic mostren usualment una major dispersió que les estimacions obtingudes per al mòdul elàstic dinàmic. Tot i que la propietat estàtica és preferida per a verificacions estructurals comunes, encara cal entendre la relació entre la dues per a constituents de maçoneria de maó típics. De fet, hi ha molt pocs estudis que avaluïn la idoneïtat de diferents tècniques per a estimar les propietats elàstiques dinàmiques d’aquests materials. Com a tal, actualment no hi ha gaires orientacions disponibles per a estimar de manera fiable aquestes propietats per a tals materials. Després d’una campanya experimental per a determinar el mòdul elàstic dinàmic i de cisalla d’una varietat de materials constituents de maçoneria de maó, aquest treball proposa un procediment robust basat en la combinació de dos mètodes d’assaig no destructiu per a una estimació fiable d’aquestes propietats dinàmiques. A més a més, també es proporciona una expressió empírica per estimar el mòdul elàstic estàtic de constituents de fàbrica del maó a partir del seu homòleg dinàmic. Respecte als assajos de vibració, el present estudi tracta de campanars de maçoneria i de tècniques d’anàlisi modal operacional (OMA, de l’anglès Operational Modal Analysis) utilitzades per a extreure paràmetres modals (freqüències naturals, modes de vibració, i coeficients d’amortiment) a partir d’assajos d’adquisició. Malgrat avanços significatius en la identificació de sistemes i les tècniques d’anàlisi modal, la precisió d’estimacions de paràmetres modals resultants d’assajos de vibració d’estructures encara són altament dependents de les condicions de l’assaig, la qualitat de l’adquisició i les tècniques emprades per a l’estimació dels paràmetres modals. Per tal d’entendre millor els efectes reals d’aquests factors en la pràctica, aquest treball ha dissenyat un sistema d’adquisició adequat i un programa per a l’assaig de vibració del campanar de la Seu Vella a Lleida, Catalunya. Dues freqüències naturals, incloent la fonamental, van ser clarament identificats a partir de les vibracions adquirides. Aquests resultats es van utilitzar per a calibrar un model d’elements finits de l’estructura i per a estimar el mòdul elàstic dinàmic del material de la torre. Es van investigar diverses tècniques d’identificació de sistema i d’anàlisi modal, i es discuteixen les més adequades en diferents condicions d’assaig. La part relacionada amb la monitorització en aquest treball s’ha enfocat particularment en l’anàlisi de dades obtingudes a partir de sistemes estàtics de SHM que consisteixen en la mesura contínua de paràmetres clau de variació lenta sobre períodes de temps llargs. Les estructures de patrimoni de maçoneria es veuen sovint afectades per mecanismes de deteriorament irreversibles i lents que poden posar en risc l’estabilitat estructural en un futur pròxim. El SHM estàtic té el potencial d’identificar tals mecanismes en etapes primerenques. Això pot facilitar la implementació de mesures preventives i de rehabilitació adequades, les quals poden ser crítiques per assegurar que tals estructures siguin preservades per a futures generacions. Tot i això, donat que els paràmetres controlats experimenten variacions estacionals reversibles del mateix ordre de magnitud com els canvis causats per mecanismes actius, la identificació d’aquests mecanismes és sovint una tasca difícil. Aquesta tesi presenta un procediment plenament automatitzat per a l’anàlisi de dades per a sistemes de SHM estàtics, el qual utilitza models de regressió lineals dinàmics per filtrar els efectes causats per variacions ambientals. El mètode no només produeix una estimació de les taxes d’evolució, sinó que també classifica les respostes monitorejades en diferents estats d’evolució predefinits. El procediment ha estat utilitzat amb èxit per a identificar àrees vulnerables en dos important estructures de patrimoni medieval a Espanya: la catedral de Mallorca i l’església del monestir de Sant Cugat. Finalment, totes les troballes anteriors s’utilitzen per a l’elaboració d’eines de presa de decisió multicriteri (MCDM, de l’anglès Multi-Criteria Decision-Making) destinades a millorar l’objectivitat, claredat i transparència de les decisions de mitigació de riscos per a estructures del patrimoni de maçoneria. Es proposa un procediment sistemàtic d’estimació de risc estructural que implica la computació de dos índexs MCDM: un índex relacionat amb el risc estimat de dany, i un altre relacionat ambla incertesa darrere d’aquesta estimació. Les aplicacions a diversos casos d’estudi també s’inclouen per demostrar la utilitat de les eines proposades.

碩士
國立虎尾科技大學
材料科學與綠色能源工程研究所
99
The thesis is focused on the application of CuGaS2 for solar cell absorber layer materials. In this study, the nanoparticle ink is prepared using wet-ball milling, and then the ink is deposited on a substrate to form a precursor layer by spin coating. The ink consists of two compound powders, CuS and Ga2S3. By adjust Cu/Ga ratio of CuS to Ga2S3. The precursor layer is placed in RTA furnace, and then heated at the temperature between 400℃ and 800℃ to form the compound layer with chalcopyrite structure. Non-vacuum processing is capable of reducing the cost of manufacturing significantly. CGS2 thin film with the full width at half maximum becoming narrow as the Cu content increases. The mean crystallite size also increases when Cu/Ga ratio is increased. Some displacement towards higher diffraction angles is detected when the Cu content increases. According to the original composition of Cu/Ga ratio, the prepared precursor samples can be classified to two types: Cu-rich and Cu-poor samples based. Microstructural studies are carried out using X-ray diffractometer. The analysis result shows that these samples have chalcopyrite structure. We have developed a novel technique for fabricating CuGaS2 thin film without long heat treatment and selenization. Based on the analysis results of this experiment, CuGaS2 thin film with chalcopyrite structure can be obtained by heating at 650℃ for 10 minutes.

碩士
亞洲大學
光電與通訊學系
103
In this study, we prepared CuGaO2 film by using sputtering method and the annealing under controlled nitrogen atmosphere, with the attempt to identify the structure and optoelectronic properties. During the Cu-Ga-O phase change, CuGa2O4 and CuO were the intermediate phases of the reaction for forming CuGaO2, the temperature of CuGaO2 formation is 750°C. CuGaO2 had its structure remaining steady at high temperature, and had its cross-section formed by stacked polygonal microstructure. With the increase of the annealing temperature, the CuGaO2 film had its surface roughness, average grain size and direct band gap increased. The CuGaO2 films had its surface roughness values of 5.70~7.31 nm. The average CuGaO2 grain sizes were 35.59~39.02 nm. When CuGaO2 films were annealed at 750, 800, 850, and 900°C, its direct band gaps were 3.45, 3.50, 3.64, and 3.65eV, respectively. CuGaO2 absorbed mainly the photons with short wavelengths. The CuGaO2 film exhibited transmittance of 68% at a wavelength of 800nm. The positive Hall coefficient proves that the CuGaO2 is a p-type semiconductor.

CuGaSe���/CuInSe��� tandem junction solar cell is currently being pursued to be a low cost and high efficiency renewable energy source. A reported theoretical efficiency of 33.9% solar cells has been the motivation to fabricate CuGaSe��� films in a simple and low cost method. Electrodeposition is a potentially suitable method to obtain the CuGaSe��� films. A better understanding of the electrodeposition process is required to optimize the process. Focusing on the manufacture of CuGaSe��� film, the reaction accompanying the electrodeposition of CuGaSe��� using rotating disk electrode from cupric sulfate, selenious acid and gallium chloride solution in sulphate medium were studied by voltammetry. Cyclic and rotating disk voltammetry in pure and binary systems were performed in order to understand the complexity of Cu + Ga + Se systems. Diffusion coefficients of Cu(II) and Se(IV) were determined using Levich equation to be 6.93x 10������ cm��/s and 9.69x 10������ cm��/s, respectively. The correlations between supporting electrolytes, flux ratios, working electrodes and films were investigated experimentally. The deposited films were characterized by Induced Couple Plasma Spectrometry, X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-Ray. CuGaSe��� is formed via the reaction of CuSe compound reduction and Ga(III) and higher gallium concentration will favor the formation of CGS film. The incorporation of gallium is highly depending on the pH (higher is better). An impinging flow electrochemical reactor was built as an alternative approach for electrochemical deposition method. Preliminary experiments of copper and copper selenide electrodeposition were conducted, and the results were comparable to the rotated disk voltammetry.
Graduation date: 2004

碩士
國立東華大學
電機工程學系
99
The numerical simulation of CuGaSe2/CdS photovoltaic devices was studied by using AMPS. The simulated results of the energy band diagram and performance parameters for the CuGaSe2 (CGS) solar cells were analyzed. The effects of the interface properties, buffer properties, and conduction band offset between CdS and CGS films on the CGS solar cell were investigated. The effects of various buffers including CdS, ZnS, In(OH,S), or ZnMgO films on the performance of CGS solar cells were studied.

碩士
國立中山大學
材料與光電科學學系研究所
104
For the composition control and testing electric properties, polycrystalline CuGaSe2 (CGSe) films with near-stoichiometric compositions were deposited by three-source co-evaporation on glass without the substrate rotation. XRD analysis veried that the film is single phase with the chalcopyrite structure. From Cu-rich to Ga-rich regions for the film grown on a glass substrate,the film resistivities varied from 3.7x10-1 Ω‧cm to 7.4x104 Ω‧cm. Further experiments on the formation of Ohmic contacts onto CGSe films indicated that the remaining Cu-Se phase on the surface of Cu-rich CGSe could improve the contact properties for the film attached with Mo metal electrodes. Since the successful epitaxial growth should be demonstrated prior to device fabrication, Cu-rich CGSe(p-type CGSe) films were grown on (100) n-type Si wafers.XRD analysis reveal that the c-axis of tetragonal unit cell aligned parallel to the substrate surface to lower the strain energy and thus leaded to the formation of orientation domain structure. For the films grown at 550℃, the XRD peak of CGSe was broden and asymmetric indicating an interduffusion at the CGSe/Si interface. Auger depth profiling showed that a conderable amount of Si was diffused into CGSe. Considering in a Cu-rich CGSe that Si might incorporate into the lattice site of Ga and became as a donor, which could compensate the acceptor in p-type CGSe. This would seriously degrade the junction properties of p-CGSe/n-Si device structure. It is strongly suggested that a low-temperature process such as photo-assited MBE should be employed for the film growth. Keywords:Molecular beam deposition,orientation domain structure,CuGaSe2 epitaxy, CuGaSe2/Si heterojunction solar cell

博士
國立中山大學
材料科學研究所
87
CuGaSe2 chalcopyrite compound was grown heteroepitaxially on (001)GaAs substrate by molecular beam epitaxy (MBE) system. Phase identification and crystalline orientation of thin films were examined by X-ray diffraction measurement. Surface morphology and microstructure were observed by electron microscopy. Chemical composition was measured by electron probe microanalyzer (EPMA). Optical and electrical properties were characterized by photoluminescence (PL) measurement, photoreflectance (PR) measurement, and four-point probe method. Epitaxial and second phase free films can be obtained by the control of substrate temperature, growth rate, and film composition. Antiphase domains present in as-grown films. PL spectra were affected obviously by composition. In Cu-rich films, PL showed two remarkable peaks at 1.71 eV and 1.67 eV which were attributed to exciton recombination and conduction band-to-acceptor transition, respectively. In Ga-rich films, an intense peak due to a donor-to-acceptor pair transition was observed at 1.62 eV. Energies of A, B, and C excitons associated with three uppermost valence bands were determined from analysis of PR spectra. Resistivity of CuGaSe2 films could be ranged from 10-1 to 105 -cm by varying Cu/Ga ratio.

碩士
國立東華大學
電子工程研究所
97
In this thesis, we research the impacts of the top cell performance on the efficiency of tandem solar cells by numerical study. The device physics and parameters of the top cells as the input variables for the device simulation tool of AMPS-1D to study the performance of thin-film tandem solar cells. The band gap energy of the absorber layer for the top cells is employed as the variables to improve the conversion efficiencies of the tandem solar cells. In order to understand the effects of device loss, firstly we vary the junction parameters of CdS/CuGaSe2 solar cells by considering the surface-defect-layer model and Cd-diffusion model for the investigation of device performance. Secondly we change the thickness and bandgap energy of the intrinsic amorphous silicon absorber layer of thin-film solar cells, and discuss the relationship between the amorphous silicon material properties and the p-i-n structure for the amorphous silicon solar cells. In this work, we simulate the best efficiencies of thin-film CuGaSe2 solar cells and of thin-film amorphous silicon solar cells are 13.4%, and 8.0%, respectively.

碩士
國立中山大學
材料科學研究所
94
In this experiment,we used the solvothermal method that described by Y.Qian et al,to synthesize nano powder which have different morphology.We had demonstrated it that by controlling and changing the temperature,reaction time and washing agents,to control the size and it leads to the change of the energy gap.In others,we changed the ,and used the same method to synthesize CuGaSe2 powder.It was used to improve the efficirncy of the solar cell devices. The synthetic temperature 180℃ and rection time 48hrs are the best condition in nano spherical powder experiment.The synthetic temperature 180℃ and reaction time 42hrsare the best condition in nano rods experiment.The synthetic temperature 210℃ and reation time 24hrs,we synthesize CuGaSe2.And in the kinetic mechanism of nano powder,we think that the second phase is the important factor that influence the growth of nano poweder,and also influence the size of powder.

碩士
國立中山大學
材料與光電科學學系研究所
106
Current silicon solar cell is developing towards ultra-thin feature for cost lowering, recombination suppressing and potential flexible applications. In this work, we examine the viability of chalcopyrite materials assisting ultra-thin solar cells performance with simulation software AFORS-HET. P type silicon with n type surface doping is support with CISe for light absorption, between them compositional-variated SiGe buffer layer to lower lattice mis-match (SCH-1 layout). Simulation shows Ge induces narrow bandgap and large energy barrier, witch severely reduce Isc. By replacing buffer layer with InSe passivation layer to resolve band structure issues, p-cSi+InSe+CISe design reaches 30% efficiency while remaining under 10μm, being the most promised design, and provided with utmost fabrication value. N type silicon is matched with CGSe, CIGSe, n-type CISe and SiGe buffer layer forming CGSe(CIGSe) +buffer +n-cSi+buffer+CISe heterojunction cell (SCH-2 design), both SiGe buffer layers form energy barrier and greatly hinder hole transportation. Replacing lower buffer with InSe forms reverse field, thus remove CISe, redesigned CIGSe+buffer+150μm cSi structure also failed to reach 20% due to barrier problems from SiGe buffer. CGSe possesses 1.66eV band gap, forming an even higher energy barrier after contacting with SiGe buffer, cancel out the benefit of CISe. After removing CISe and substitute SiGe with amourphous SiGe to bridge band structure between Si and CGSe, CGSe+a-SiGe +150μm n-cSi structure can reach 24.21% efficiency. However, the lack of CISe and ultra thin CGSe of optimized cell does not differ itself from other silicon-based solar cells.

碩士
國立中山大學
材料科學研究所
88
In this paper, we use a room temperature processing system, Liquid Phase Deposition(LPD) method, to grow silicon dioxide. The advantages are cheap equipment, low temperature growth, and no thermal stress. The quality is good enough to be used in IC devices. To inverstigate the properties of silicon Dioxide, we have done different physical and chemical test, including AES,TEM,FTIR,P-etch rate. We used the high frequency C-V curve to study the interface properties. The leakage current help to clarify the film quality. Moreover, we also discuss the growth mechanism in order to more understanding of LPD method.

碩士
國立虎尾科技大學
材料科學與綠色能源工程研究所
97
Copper indium gallium selenide (CuIn(1-x)GaxSe2, CIGS) has attracted much attentions for its applications in thin film solar cells. Copper gallium selenide (CuGaSe2) thin film has been used in Mo/CGS/CIS/CdS/ZnO solar cell fabrication as a absorber layer and it plays an important role in improving efficiency. We propose a method to prepare CuGaSe2 films by using mechanical milling to form a paste or an ink which is suitable for coating on silicon substrates in the form of a thin precursor layer with dual-source precursors, Cu2Se and Ga2Se3. Composition control, or the control of the Cu/Ga metallic mol ratio is an important concern in chalcopyrite film growth. Subsequently, these precursor layers were annealed in a argon atmosphere at a temperature range from 300 to 800℃ for 10 min. Heat treatment steps were used to convert the powdery precursor layers into solar-cell-grade chalcopyrite absorbers. The Cu2Se and Ga2Se3 are the precursors which are deposited form this experimentation and distinguish thin films between Cu-rich and Cu-poor by Cu/Ga ratio. The structure of CuGaSe2/CIGS films was determined by XRD. It is found that the films are at single chalcopyrite phase. The optical bandgap of CIS/CIGS films could be adjusted from 1.04 eV to 1.68 eV by changing the growth conditions. Therefore, the tandem cell of CIGS-based solar cells can be fabricated by using this technique and may improve the conversion efficiency over 25% in the future. In this work, we demonstrate new techniques of growing CuGaSe2 and CIGS films. In our study, Cu2Se and Ga2Se3 powders were mixed with precursor pastes and precursor layers were selenized in a argon atmosphere. No toxic gases were used and produced during the whole testing process. Chalcopyrite CuGaSe2 was formed at 650℃/10 min and the crystalline of this phase was improved as temperature rises. Thus, the development of CIGS-based solar cells and related devices can easily be achieved by using Ball Milling/Printing technique with a single in-line process.