Dissertations / Theses on the topic 'Textured silicon'
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Franta, Benjamin Andrew. "Fabrication techniques for femtosecond laser textured and hyperdoped silicon." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493373.
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This thesis presents a range of advances in the fabrication of femtosecond laser textured and hyperdoped silicon, a material platform with potential applications in photovoltaics, photodetectors, light-emitting diodes, lasers, and potentially other optoelectronic devices.
After providing background and a review of the state of hyperdoped black silicon research in Chapter 1, we explore a range of fabrication approaches in Chapter 2, including laser texturing near and below the melting threshold of silicon, laser texturing and hyperdoping using scanned pulses, fabrication with thin films, control of the dopant concentration on textured substrates, and removal of surface material using chemical etching.
In Chapter 3, we review the material microstructure of hyperdoped black silicon, including the morphology, the presence and origin of high-pressure material phases, and the incorporation of dopants from thin films.
In Chapter 4, we explore the use of laser annealing to increase the crystallinity of hyperdoped black silicon, addressing a longstanding challenge in the field. We show that nanosecond laser annealing can be used on a wide variety of textures— from at least 10 micrometers in size to sub-micrometer in size—to produce high crystallinity and high optical absorptance simultaneously. Furthermore, we see that nanosecond laser annealing can reactivate the sub-bandgap absorptance after it has been deactivated by thermal annealing. We close Chapter 4 by exploring the use of fs laser pulses to anneal hyperdoped black silicon.
Finally, in Chapter 5, we discuss advances in the thesis, outstanding challenges in the research field, and an outlook for applications.Engineering and Applied Sciences - Applied Physics
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Lewis, Brian Wellington. "Silica nanosphere textured back reflectors for increased absorption in thin film amorphous silicon solar cells." [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1476317.
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Boesch, Ryan Paul. "SiO₂ nanosphere textured back reflectors for enhanced light trapping in amorphous and nanocrystalline silicon solar cells." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1464182.
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Köppel, Grit [Verfasser], Christiane [Akademischer Betreuer] Becker, Bernd [Akademischer Betreuer] Rech, Bernd [Gutachter] Rech, Christiane [Gutachter] Becker, and Janez [Gutachter] Krč. "Liquid phase crystallized silicon on sinusoidal textured glass substrates : silicon material quality and absorption enhancement / Grit Köppel ; Gutachter: Bernd Rech, Christiane Becker, Janez Krč ; Christiane Becker, Bernd Rech." Berlin : Technische Universität Berlin, 2017. http://d-nb.info/1156177421/34.
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Мадан, Роман Григорович. "Органо-неорганічні гібриди на основі меланіну." Master's thesis, КПІ ім. Ігоря Сікорського, 2020. https://ela.kpi.ua/handle/123456789/38762.
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Актуальність теми – інтерес до створення гібридних органічних та неорганічних тонкоплівкових сонячних елементів, що мають більш низьку вартість, ніж традиційні сонячні елементи.
Метою роботи є визначення оптимальних технологічних умов створення органічно-неорганічних структур для фотовольтаїчного застосування.
Предмет дослідження – органо-неорганічні структури на основі кремнію та меланіну.The relevance of the topic is the interest in creating hybrid organic and inorganic thin-film solar cells, which have a lower cost than traditional solar cells. The aim of the work is to determine the optimal technological conditions for the creation of organic-inorganic structures for photovoltaic applications. The subject of research - organo-inorganic structures based on silicon and melanin.
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Almeida, Andressa da Nobrega. "Estudo da aplicação de um polímero em superfícies têxteis e desenvolvimento de novas texturas." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/100/100133/tde-06072015-212521/.
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O objetivo do presente trabalho foi pesquisar sobre a adequação e viabilização do processo de aplicação de um polímero, comercialmente conhecido como borracha de silicone, com o intuito de criar um novo conceito estético, a partir da vontade de produzir uma nova textura ou nova concepção de estrutura para substratos têxteis aplicados na alta costura. Primeiramente, investigou-se qual a melhor forma de adequação desta borracha e como ela se comporta em diferentes superfícies têxteis. Foram realizados ensaios para avaliar as condições de preparo da borracha de silicone, quanto ao volume de catalisador a ser utilizado de (0,75, 2,5 e 5 mL), temperatura (125oC a 180 oC) e tempo de secagem (30 a 90mim). Os materiais produzidos foram submetidos a testes de secagens a diferentes condições de temperatura para a realização dos trabalhos de moldagem. Além dos processos de secagem, foram realizados ensaios de laboratório como Calorimetria Exploratória Diferencial (DSC), Termogravimetria (TG), Espectroscopia de Absorção na Região do Infravermelho (FTIR) e citotoxicidade e Microscopia Eletrônica de Varredura (MEV) e Espectroscopia de Energia Dispersivo (EDS), a fim de caracterizar e conhecer as características dos materiais produzidos em termos físicos,químicos e biológicos,e ter estes estudos como aliados do processo criativo. Novos ensaios foram realizados ensaios com renda de poliamida, poliéster e algodão com aplicação da borracha e pigmentos preto,azul e amarelo. Os resultados mostraram que a melhor quantidade de catalisador foi entre 3 a 5 mL. A temperatura de secagem 150oC. Por meio da analise de Espectroscopia de Energia Dispersiva (EDS) foi verificado que a diferença da amostra com os controles foi a presença de silício. Foram desenvolvidas seis pecas, dois vestidos, duas saias, um acessório de cabelo e um sapato. Foram trabalhadas algumas possibilidades de utilização da borracha de silicone em materiais têxteis, os resultados foram promissoresThe present work has its aim to investigate on the adaptation and to make it possible the process of application of a polymer, commercially known as a silicone rubber, in the context of creating a new aesthetic concept and the will to bring to textiles a new texture or new conception of structure to substrates. Firstly we investigated how best to adapt this rubber and how it behaves in different textile surfaces. Assays were performed to evaluate the conditions of preparation of the silicone rubber, the volume of the catalyst to be used (0.75, 2.5 and 5 ml), temperature (125°C to 180°C) and drying time (30 to 90 mim). The materials produced were subjected to drying tests at different temperature conditions for carrying out the molding work. Above the drying process, laboratory tests were conducted as Scanning Electron Microscopy-SEM and Analysis by Energy Dispersive Spectroscopy (EDS) in order to characterize and understand the characteristics of the materials on physical, chemical and biological terms, and these studies have as allies of the creative process. New tests were performed tests with income of polyamide, polyester and cotton with application of rubber and black pigments, blue and yellow. The results showed that the optimal amount of catalyst was from 3 to 5 ml. The drying temperature of 150°C. Through spectral analysis Energy Dispersive (EDS) it was found that the difference of the sample with the controls was the presence of silicon. Six pieces were developed, two dresses, two skirts, a hair accessory and a shoe. It was reached possibilities making use of silicone rubber textile materials, the results were promising
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Krzma, Adnan. "Comparative laboratory performance characterisation of silicone rubber textured insulators." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/91934/.
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Silicone rubber (SiR) outdoor insulators are increasingly being deployed in new AC and DC high voltage transmission systems thanks to their superior performance in wet-polluted conditions compared to traditional porcelain and glass insulators. However, in severely polluted environments, sustained discharge activities and dry band arcing due to surface contamination cause tracking, erosion, and the loss of hydrophobicity on the SiR insulator surface. This degradation can accelerate damage to the insulator surfaces, increasing the probability of a flashover and enduring insulator failure. This thesis presents an experimental study on the electric performance of polluted and aged outdoor SiR polymeric insulators using AC and DC voltages. The research involved an extensive review of the published literature and an investigation of the performance of SiR insulators subjected to different ambient conditions and identifies the modes where most failure and degradation occurred on SiR surfaces. Experimental investigations were carried out to compare the aging performance of two 11kV SiR insulator designs using a rotating wheel dip test under AC and positive DC excitations. A standard polymeric insulator design was used and compared with insulators that had a textured surface. Both insulator designs were fabricated in-house using a vacuum casting machine. Several electrical parameters were measured during the test to characterise the performance of each insulator. Dry band arcing activities were mainly observed on the trunk surface of the conventional profile. A decrease in hydrophobicity was measured on the tested surfaces, and tracking and erosion defects were also observed on both insulator designs. Leakage current measurements showed that drying and discharge activity was greater for a conventional insulator compared with the textured insulator, and more severe degradation appeared under positive DC tests than under AC. These studies showed that insulators with a textured design can improve the performance of SiR insulators against tracking and erosion under AC and positive DC excitations. The electric field and potential distributions along the leakage surface of the 11 kV SiR insulators under dry clean and wet polluted conditions were studied using finite element method COMSOL Multiphysics. The critical of high field regions on SiR surfaces were identified and the power dissipated in the pollution layer along insulator surface was calculated. This study showed useful information about surface heating, which could be used to predict of the formation of dry bands. An investigation of the pollution layer characterisation on conventional and textured pattern designs is described. Several tests were conducted to evaluate the behaviour of the insulator surfaces under different conditions. ESDD and NSDD parameters were measured for different materials, and evaluations for each design were also performed. Leakage conductance measurements on surface designs were determined, and the distribution trends of surface conductance were also characterised. Different rectangular SiR samples were assessed, and an improvement for reducing the pollutant deposition on textured surfaces was observed. In 4-shed insulators, the textured design showed comparable ESDD value with conventional profile. Textured designs also showed slower growth of the leakage current than the conventional design. Clean fog tests (based on a high voltage ramp test) were carried out to investigate the flashover performance of conventional and textured insulator designs. For different ranges of wetting and pollution severity conditions, the textured design showed an improvement in the flashover performance that could reach 16 % compared to the conventional surface. This indicates that the textured surface seems to be more effective under severe ambient conditions. It was also observed that the textured insulator design can improve the electrical performance of SiR insulators under AC and DC voltages.
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Ximello, Quiebras Jose Nestor [Verfasser]. "Wet chemical textures for crystalline silicon solar cells / Jose Nestor Ximello Quiebras." Konstanz : Bibliothek der Universität Konstanz, 2013. http://d-nb.info/1045840572/34.
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Damiani, Benjamin Mark. "Investigation of Light Induced Degradation in Promising Photovoltaic Grade Si and Development of Porous Silicon Anti-Reflection Coatings for Silicon Solar Cells." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5203.
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Cast multi-crystalline silicon substrates are used in more than 50% of the photovoltaic modules produced today. The random grain orientations of multi-crystalline silicon wafers inhibit the formation of an effective surface texturing using conventional techniques. The other main substrate used is single crystalline Czochralski wafers (~30% of the market share). Czochralski silicon material is known to suffer from the formation of a metastable defect under carrier injection, sometimes referred to as light induced degradation (LID). Light induced degradation in low-cost photovoltaic grade silicon is studied. Trap formation is shown to occur at temperatures above 200oC. Efficiency degradation reduced from 0.75% to 0.24% when the cell thickness was reduced from 378 to 157m. The presence of light induced degradation in ribbon silicon solar cells is documented for the first time in this thesis. Trap generation and annihilation are observed in high lifetime regions of multi-crystalline silicon samples. No degradation was observed over a 24-hour period at 25oC in high efficiency ribbon solar cells (>16%), but at an elevated temperature of ~75oC, appreciable efficiency degradation was observed. Czochralski silicon solar cells showed full degradation within 24 hours at 25o C. Part two of this thesis involves the development of a surface texturing suitable for all crystalline silicon. Only 6 to 10 seconds in a 200:1 HF to HNO3 solution at room temperature allows for the formation of an effective porous silicon anti-reflection coating. This resulted in a porous silicon anti-reflection coated solar cell efficiency of 15.3% on a float zone Si sample with an excellent fill factor (78.7%). The typical process used in the literature involves porous silicon etching as the final step in the solar cell fabrication sequence. The major problem associated with this process sequence is fill factor degradation. This problem was overcome in this research by porous silicon etching prior to cell processing. It is shown that incorporating an acid texture prior to porous silicon etching can improve the surface reflectance for cast multi-crystalline and Czochralski silicon samples. Solar cell efficiencies of 14.8% for Cz Si and 13.6% for cast mc-Si were achieved.
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Dewan, Rahul [Verfasser]. "Optics in thin-film silicon solar cells with periodic surface texture / Rahul Dewan." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2012. http://d-nb.info/1035209608/34.
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Gan, Weimin. "Texture and microstructure development of the silicon containing magnesium alloys after equal channel angular pressing." Clausthal [Univ.-Bibliothek], 2008. http://d-nb.info/990980464/34.
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LIMA, LIANA M. F. G. de. "Estudo da evolução da textura, da microtextura e da mesotextura de recristalização, após baixos graus de deformação a frio, em dois aços ferríticos com baixo teor de carbono." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11269.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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GOMES, Allysson Antônio Ribeiro. "Estudo comparativo das propriedades físicas, químicas e biológicas de próteses mamárias de silicone." Universidade Federal de Campina Grande, 2015. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1157.
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Os implantes mamários são dispositivos médicos, empregados para aumentar, reconstrutir ou corrigir anomalis congênitas mamárias. Normalmente, são preenchidas por gel de silicone e/ou solução salina. Atualmente, têm sido utilizados com frequência implantes mamários com a superfície externa da membrana texturizada, por apresentar maior seguraça e reduzir complicações pós-operatórias como as contraturas capsulares. Desta forma, este trabalho teve como objetivo avaliar as propriedades físicas, químicas e biológicas de implantes mamários com membrana texturizada e preenchidas com gel de silicone. Portanto foram analisados quatro implantes mamários, de dois diferentes fabricantes, sendo uma marca nacional e outra importada. Os ensaios de caracterização foram realizados no lado da membrana interno que fica em contado com o gel e no lado externo que fica em contato com o meio biológico, através das seguintes técnicas: Microscopia Óptica – MO, Microscopia Eletrônica de Varredura – MEV, Espectroscopia por Energia Dispersiva de Raios X - EDS, Retilineidade, Ensaios Dimensionais - Espessura, Ensaio Mecânico - Tração, Citotoxicidade e Coesividade do Gel. Nos resultados do ensaio de avaliação morfológica (MO e MEV) foi observado que a superfície das membranas em contato com o gel apresenta-se com textura lisa e uniforme já o lado externo da membrana observou-se presença de poros com tamanhos e formas bastante distintas. Em relação aos ensaios mecânicos, todas as amostras atenderam aos requisitos normativos, porém uma das amostras apresentou valor muito próximo do limite de aprovação. Observou-se que a texturização das superfícies influencia nos desempenhos mecânicos das membranas. Os resultados do ensaio de coesividade do gel de preenchimento, citotoxicidade e de elementos químicos contaminantes foram semelhantes em todas as amostras e estão de acordo com as normas de certificação, sendo X2 muito próximo ao limite de aprovação.
Silicone breast implants are medical devices used to increase, reconstruct or correct mammary congenital deformities. Typically, they are filled with silicone gel and / or saline solutions. Currently, there is often used breast implants with the outer surface of the textured membrane to present maximum security and reduce post-operative complications such as capsular contracture. Thus, this study aimed to evaluate the physical, chemical and biological properties of textured silicone gel breast implants. Four breast implants were analyzed, two different manufacturers. The characterization tests were performed on the inner side of the membrane which is in contact with the gel, and the external side, in contact with the biological environment, through the following techniques: optical microscopy - MO, Scanning Electron Microscopy - SEM, Spectroscopy Energy Dispersive X-ray - EDS, Straightness, Dimensional Testing - Thickness, Mechanical Testing - Traction, Cytotoxicity and cohesiveness gel. The results of the morphological evaluation test (OM and SEM) it was observed that the surface of the membrane in contact with the gel appears with smooth and uniform texture, however, the external side of the membrane was observed pores with very different sizes and shapes . Regarding the mechanical tests, all samples met the regulatory requirements, but one of the samples showed a value close to approval limit. It was observed that the texturing of suferfícies influences the mechanical performances of the membranes. The cohesiveness filling gel test, cytotoxicity and chemical contaminants were similar in all samples and comply with certification regulations.
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Kozina, Thomas. "Using the mean field model to analyze the influence of texture on the hysteresis behaviour of silicon steels." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59284.
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A critical study of the Jiles and Atherton Mean Field Model was done to determine the validity of the model, a tool in describing and understanding the magnetization process in textured silicon steels.Hysteresis loops were generated using an Epstein apparatus in various directions with respect to the rolling direction and for various external magnetic fields. Techniques were then used to obtain the model parameters, namely a$ sp prime,$ $ alpha sp prime,$ and k$ sp prime.$ After creating a new version of the model, M$ sb{ rm s}$ was also obtained from the data hysteresis loops.
The model gives a close description of the influence of texture on hysteresis behaviour and predicts the variation of the parameter k$ sp prime,$ which agrees with our understanding of the role of texture in changing the parameter. We have observed that the highest value of this parameter coincides with the angles at which it is most difficult to magnetize the specimen.
The proposal of the model's creators that the main drawback of the model that the pinning parameter $k sp prime$ is not constant, is not justified by them and not supported by our analysis of experimental data.
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Chu, Qingli. "Texture, proprietes de surface et comportement en suspension des fumees de silice." Orléans, 1995. http://www.theses.fr/1995ORLE2037.
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Les fumees de silice (fs) sont des sous-produits formes lors de la fabrication du silicium et de silico-alliages. Leurs caracteres particulaires et cristallochimiques en font un bon additif pour les betons en ameliorant les proprietes rheologiques et mecaniques de ces derniers. Cependant, ces ameliorations ne sont obtenues que si la desagglomeration et la dispersion des fs est complete. L'objectif de ce travail vise a une meilleure comprehension des phenomenes et parametres conduisant a une amelioration de l'etat de dispersion des fs afin d'ameliorer encore la microstructure et les proprietes des beton. Dans ce but, en fonction de la composition initiale des fs, leurs caracteristiques physico-chimiques a l'etat de poudre et leurs proprietes colloidales en milieu aqueux ont ete etudiees et reliees a leurs proprietes structurales et rheologiques. A l'etat de poudre, les fs contiennent en majorite de la silice sous forme quasi-amorphe de cristobalite mal-cristallisee (pseudo-cristallites d'une dizaine d'angstrom), ainsi qu'une faible quantite de quartz, de cristobalite ii cristallisee et de carbure de silicium. L'observation par meb a montre que le traitement de densification influence fortement la morphologie des grains. L'analyse des images de met nous a permis d'obtenir la distribution de taille des particules elementaires pour les fs etudiees, dont les diametres varient de 0,007 a 0,54 m. En milieu aqueux, le traitement de densification modifie la dispersabilite des fs. Les fs densifiees sont plus difficiles a disperser que les fs non-densifiees. Pour les suspensions de fs, les mesures de la vitesse et du volume de sedimentation, les mesures de la charge de surface des particules ainsi que l'analyse granulometrique ont montre que la dispersabilite et la presence de cations, comme ca#+#2, jouent un role tres important dans l'agglomeration des fs. Il n'est donc pas judicieux de former des coulis avec des fs riches en calcium qui engendrent la formation d'agglomerats mecaniquement stables. Le mecanisme d'agglomeration est lie a l'evolution de la charge de surface des particules. Il a ete etudie quantitativement par la methode d'electrophorese et de titrage d'electrolyte. L'etude rheologique des suspensions de fs (viscosite, seuil d'ecoulement et thixotropie) a montre l'importance de la dispersabilite des fs et de leur teneur en impuretes. L'intervention chimique des impuretes est responsable des augmentations de viscosite et de ph au cours du temps, ainsi que de l'evolution de l'agglomeration et de la charge de surface. Une relation quantitative entre la viscosite apparente et la fraction en solide a pu etre demontree en utilisant l'equation de krieger-doupherty et en introduisant un coefficient qui traduit l'influence de l'agglomeration sur la viscosite
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Cardoso, Laura. "Assemblage colloïdal pour l'élaboration de matériaux hybrides polysaccharide-silice. Interactions, interfaces et textures." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2015. http://www.theses.fr/2015ENCM0010.
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L'objectif principal de ce travail de thèse est l'étude de la formation de matériaux hybrides polysaccharides – oxydes métalliques par assemblage colloïdal. Il concerne à la fois la compréhension des mécanismes et l'obtention de nouveaux matériaux et textures. Pour ce faire, nous avons étudié dans un premier temps les suspensions formées par les précurseurs colloïdaux (nano-bâtonnets de chitine, oligomères siloxane). Grâce à la détermination des diagrammes de phases, nous avons montré que ces co-suspensions dans l'éthanol présentent, comme en milieu aqueux, des propriétés d'auto-assemblage conduisant à la formation de mésophases nématiques chirales. Par ailleurs, l'étude rhéologique de ces fluides complexes a montré une forte influence des proportions relatives des deux précurseurs sur la viscosité, mettant en évidence le rôle déterminant des interactions entre colloïdes. Au-delà, la caractérisation par microscopie électronique nous a permis de confirmer la formation de colloïdes hybrides au sein des co-suspensions. Dans un deuxième temps, nous avons élaboré de nouveaux matériaux composites soit en modifiant le précurseur polysaccharide (cellulose vs. chitine), soit en introduisant de nouveaux précurseurs de phases inorganiques (Al2O3, TiO2, ZnS). La caractérisation de ces matériaux nous a permis d'évaluer le rôle de la chimie de surface, de la nature et de la taille des précurseurs sur les interactions colloïdales et les propriétés texturales finales. Enfin, nous avons étudié l'effet des procédés de mise en forme – microsphères par atomisation-séchage, fibres par électro-filage, films minces – et de l'application de champs externes – champ électrique, cisaillement – sur les caractéristiques des matériaux. A partir de ces nouveaux résultats, nous proposons un mécanisme de formation qui permet d'envisager la synthèse de matériaux fonctionnels dont les propriétés seraient ajustées selon les applications visées (catalyse, propriétés mécaniques…)The major aim of this PhD thesis has been to study the formation of polysaccharides metal oxides hybrid materials through colloidal assembly. It concerns both the understanding of the mechanisms and the obtention of new materials and textures. To that purpose, we first studied suspensions of the colloidal precursors (chitin nanorods and siloxane oligomers). By mapping out the phase diagrams, we demonstrated that co-suspensions in ethanol exhibit self-assembly properties, similar to those obtained with chitin in aqueous medium, leading to the formation of chiral nematic mesophases. Besides, the rheological study of these complex fluids showed a great influence of the relative proportions of the precursors upon viscosity, hence revealing the major role played by colloidal interactions. Moreover, electron microscopy observations allowed us to confirm the formation of hybrid nanorods colloids made of chitin and silica within the co-suspensions. Then, we elaborated new composite materials either by changing the polysaccharide precursor (cellulose vs. chitin) or by introducing new precursors of inorganic phases (Al2O3, TiO2, ZnS). The characterization of these materials allowed us to estimate the impact of precursors' characteristics (surface chemistry, nature and size) on colloidal interactions and final textural properties. Lastly, we investigated the influence of the materials morphology and processing method – microspheres by spray-drying, fibers by electrospinning, thin films – and application of external fields – electric field, shearing – on the obtained materials characteristics. Based on these new results, we propose a mechanism of formation which enables us to envision the synthesis of functional materials with properties adjusted to intended applications (catalysis, mechanical properties…)
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Gan, Weimin [Verfasser]. "Texture and microstructure development of the silicon containing magnesium alloys after equal channel angular pressing / vorgelegt von Weimin Gan." Clausthal : [Univ.-Bibliothek], 2008. http://d-nb.info/990980464/34.
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Lockau, Daniel Verfasser], and Bernd [Akademischer Betreuer] [Rech. "Optical modeling of thin film silicon solar cells with random and periodic light management textures / Daniel Lockau. Betreuer: Bernd Rech." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2013. http://d-nb.info/1031756663/34.
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Plassais, Arnaud. "Nanoporosité, texture et propriétés mécaniques de pâtes de ciments." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2003. http://tel.archives-ouvertes.fr/tel-00007576.
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Des silicates de calcium hydratés (C-S-H) forment le liant des matériaux cimentaires et sont responsables de sa cohésion. Mais la structure du C-S-H est encore mal décrite. Nous proposons une description de la porosité basée sur une caractérisation par la relaxation RMN des protons contenus dans les pâtes de C3S. Des courbes de relaxation longitudinale sont extraites des distributions de cinq temps de relaxation (T1). La spectroscopie RMN puis la relaxométrie permettent l'interprétation de ces T1 : le dernier correspond à la portlandite, chacun des quatre premiers correspond à une taille de pore, allant de l'interfeuillet à la plus grande dimension de l'empilement. Dans chacun de ces cas, la relaxation est due à l'association de deux mécanismes impliquant des interactions avec des impuretés paramagnétiques à la surface des C-S-H, ces surfaces comportant des groupements SiOH, CaOH et HOH. La texturation d'une pâte comporte trois étapes. Après une période de latence, l'hydratation s'accélère. La formation des C-S-H implique le développement de la surface associée : ce phénomène est lié à la décroissance progressive de la valeur du T1. Ensuite se dissocient quatre grandes familles de porosité dont trois sont extra-lamellaires. Alors que la réaction d'hydratation est terminée, ces trois familles évoluent vers la formation d'une distribution en loi de puissance. La modification des paramètres de cure influence essentiellement les proportions des deux plus grandes échelles de porosité. La perte de l'organisation en loi d'échelle ou du moins la diminution de son coefficient sont associées à une diminution des modules d'élasticité. C'est le cas lorsque le rapport e/c est supérieur à 0,4 ou quand la température de cure dépasse 50°C. L'ajout de fumée de silice ou l'augmentation de la température de cure, entre 20 et 50°C, accélère la cinétique de texturation. La présence de fumée de silice fait également apparaître une famille de pores supplémentaire aux échelles supérieures.
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Nguebdob, Tchipkam. "Etude et caractérisation de textures amorphes obtenues par la méthode sol-gel (silice-titane-zircone)." Lyon 1, 1988. http://www.theses.fr/1988LYO10108.
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L'etude et la caracterisation des gels humides monolithiques de silice, de dioxyde de titane et de zircone, prepares par un procede sol-gel sont possibles a l'aide de techniques adaptees: la thermoporometrie et la microscopie
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Nguebdob, Tchipkam. "Etude et caractérisation de textures amorphes obtenues par la méthode sol-sel (Silice-titane-zircone)." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb376014659.
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Heimdal, Carl Philip J. "Pulsed Laser Deposition of Zinc Sulfide Thin Films on Silicon : The influence of substrate orientation and preparation on thin film morphology and texture." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25097.
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The effect of orientation and preparation of silicon substrates on the growth morphology and crystalline structure of ZnS thin films deposited by pulsed laser deposition (PLD) has been investigated through scanning electron microscopy (SEM) and grazing incidence x-ray diffraction (GIXRD). ZnS thin films were grown on silicon (100) and (111), on HF-treated and untreated silicon (100) as well as substrates coated with Al, Ge and Au. The ZnS films showed entirely different morphologies for ZnS films grown on silicon (100) and (111) substrates, but a preferred orientation largely independent of substrate orientation, preparation or coating. The films are either wurtzite (W) or a mixture of wurtzite or zinc blende (ZB). The preferred orientation is suggested to be related to the lower surface energies of the W(001) surface, and the ZB(111) surface in a Zn-poor environment. A technique for in-situ removal of native oxide from silicon by laser ablation of a ZnS target was tested and found to remove a significant amount of the surface of the substrates. The reoxidation in air of silicon (100) surfaces was monitored by ellipsometry, and HF-treated substrates were examined by RHEED. The results revealed that HF-treated Si(100) showed signs of rapid reoxidation in air, but this had no visible effect on ZnS film growth compared to untreated substrates.
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Moncada, de la Rosa Jorge Daniel. "Application of Fluid Inclusions and Mineral Textures in Exploration for Epithermal Precious Metals Deposits." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/36164.
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Fluid inclusion and mineralogical features indicative of boiling have been characterized in 855 samples from epithermal precious metals deposits along the Veta Madre at Guanajuato, Mexico. Features associated with boiling that have been identified at Guanajuato include colloform texture silica, plumose texture silica, moss texture silica, ghost-sphere texture silica, lattice-bladed calcite, lattice-bladed calcite replaced by quartz and pseudo-acicular quartz after calcite and coexisting liquid-rich and vapor-rich fluid inclusions. Most samples were assayed for Au, Ag, Cu, Pb, Zn, As and Sb, and were divided into high-grade and low-grade samples based on the gold and silver concentrations. For silver, the cutoff for high grade was 100 ppm Ag, and for gold the cutoff was 1 ppm Au. The feature that is most closely associated with high grades of both gold and silver is colloform texture silica, and this feature also shows the largest difference in grade between the presence or absence of that feature (178.8 ppm Ag versus 17.2 ppm Ag, and 1.1 ppm Au versus 0.2 ppm Au). For both Ag and Au, there is no significant difference in average grade as a function of whether or not coexisting liquid-rich and vapor-rich fluid inclusions are present.
The textural and fluid inclusion data obtained in this study were analyzed using the binary classifier within SPSS Clementine. The models that correctly predicted high versus low grade samples most consistently (â 70-75% of the tests) for both Ag and Au were the neural network, the C5 decision tree and Quest decision tree models. For both Au and Ag, the presence of colloform silica texture was the variable with the greatest importance, i.e., the variable that has the greatest predictive power.
Boiling features are absent or rare in samples collected along a traverse perpendicular to the Veta Madre. This suggests that if an explorationist observes these features in samples collected during exploration that an environment favorable to precious metal mineralization is nearby. Similarly, good evidence for boiling is observed in the deepest levels of the Veta Madre that have been sampled in the mines and drill cores, suggesting that additional precious metal reserves are likely beneath the deepest levels sampled.
Master of Science
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Mrazkova, Zuzana. "Modélisation et caractérisation de matériaux et nanostructures pour les applications photovoltaïques." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX121/document.
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La recherche sur le photovoltaïque vise à réduire le prix par watt de puissance électrique générée. Des efforts considérables sont menés pour rechercher de nouveaux matériaux et des conceptions qui repoussent les limites des cellules solaires existantes. Le développement récent de matériaux et nanostructures complexes pour les cellules solaires nécessite des efforts plus importants pour mener à bien leur caractérisation et leur modélisation. Cette thèse porte sur la caractérisation optique, la modélisation et l'optimisation de la conception d'architectures de cellules solaires de pointe.Les mesures optiques sont utilisées pour la caractérisation rapide et non destructive des échantillons texturés pour les applications photovoltaïques. Les textures de surface améliorent le piégeage de la lumière et sont donc souhaitées pour améliorer les performances des cellules solaires. D'autre part, ces textures rendent la caractérisation optique plus difficile et des efforts plus importants sont nécessaires non seulement pour la mesure optique elle-même mais également pour la modélisation et l'interprétation ultérieure des données obtenues. Dans ce travail, nous démontrons que nous sommes en mesure d'utiliser des méthodes optiques pour étudier les textures pyramidales très répandues ainsi que les réseaux de nanofils de silicium à orientation aléatoire dont l'analyse est très difficile.Premièrement, nous nous sommes concentrés sur l'étude optique de diverses surfaces pyramidales et de leur impact sur les performances des cellules silicium à hétérojonction. Nous avons constaté que les angles au sommet des pyramides, préparées à l'aide de différentes conditions de texturation, diffèrent de la valeur théorique de 70.52° attendue pour le silicium cristallin. Cette modification de l'angle au sommet est expliquée par la présence, sur les facettes pyramidales, de terrasses monoatomiques régulières, observées par microscopie électronique à transmission de résolution atomique. L'impact d'une variation de l’angle au sommet sur les épaisseurs des couches minces déposées est étudié et les conséquences sur l'efficacité des cellules solaires résultantes sont discutées. Un modèle optique développé pour le calcul de la réflectance et de l'absorption des couches minces en multicouches sur surfaces pyramidales a permis l’optimisation de la conception de la cellule solaire pour un angle au sommet pyramidal donné.L'ellipsométrie matricielle Mueller a été utilisée in-situ pour caractéiser le processus de croissance - par méthode vapeur-liquide-solide activée par plasma - des nanofils de silicium. Nous avons développé un modèle optique facile à utiliser, qui, à notre connaissance, est le premier modèle utilisant des données ellipsométriques expérimentales pour contrôler le procédé de croissance, en phase vapeur-liquide-solide assisté par plasma, des nanofils. La dépendance linéaire observée du dépôt de matériau de silicium avec le temps de dépôt nous permet de suivre le processus de fabrication in situ et de contrôler la qualité du matériauResearch in photovoltaics aims at lowering the price per watt of generated electrical power. Substantial efforts aim at searching for new materials and designs which can push the limits of existing solar cells. The recent development of complex materials and nanostructures for solar cells requires more effort to be put into their characterization and modeling. This thesis focuses on optical characterization, modeling, and design optimization of advanced solar cell architectures.Optical measurements are used for fast and non-destructive characterization of textured samples for photovoltaic applications. Surface textures enhance light-trapping and are thus desired to improve the solar cell performance. On the other hand, these textures make optical characterization more challenging and more effort is required for both, the optical measurement itself and subsequent modeling and interpretation of obtained data. In this work, we demonstrate that we are able to use optical methods to study the widely used pyramidal textures as well as very challenging randomly oriented silicon nanowire arrays.At first, we focused on the optical study of various pyramidal surfaces and their impact on the silicon heterojunction solar cell performance. We have found that vertex angles of pyramids prepared using various texturing conditions vary from the theoretical value of 70.52° expected from crystalline silicon. This change of the vertex angle is explained by regular monoatomic terraces, which are present on pyramid facets and are observed by atomic resolution transmission electron microscopy. The impact of a vertex angle variation on the thicknesses of deposited thin films is studied and the consequences for resulting solar cell efficiency are discussed. A developed optical model for calculation of the reflectance and absorptance of thin film multi-layers on pyramidal surfaces enabled a solar cell design optimization, with respect to a given pyramid vertex angle.In-situ Mueller matrix ellipsometry has been applied for monitoring the silicon nanowire growth process by plasma-enhanced vapor-liquid-solid method. We have developed an easy-to-use optical model, which is to our knowledge a first model fitting the experimental ellipsometric data for process control of plasma-assisted vapor-liquid-solid grown nanowires. The observed linear dependence of the silicon material deposition on the deposition time enables us to trace the fabrication process in-situ and to control material quality
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Baza, Souheil. "Contribution à l'étude texturale de gels de silice : thermoporométrie. M.E.T. R.M.N." Lyon 1, 1986. http://www.theses.fr/1986LYO19025.
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Hübner, René. "Dünne tantalbasierte Diffusionsbarrieren für die Kupfer-Leitbahntechnologie: Thermische Stabilität, Ausfallmechanismen und Einfluss auf die Mikrostruktur des Metallisierungsmaterials." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1102329038515-23539.
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Aufgrund der höheren elektrischen Leitfähigkeit und des größeren Widerstandes gegen Elektromigration im Vergleich zum Aluminium wird seit einigen Jahren Kupfer als Leitbahnmaterial in der Mikroelektronik eingesetzt. Da Kupfer jedoch eine hohe Beweglichkeit in den für die Halbleitertechnologie relevanten Werkstoffen aufweist, sind zur Verhinderung einer Diffusion effektive Barrieren notwendig. Dabei muss die u. a. geforderte hohe thermische Stabilität der Barrierematerialien auch im Zuge der fortschreitenden Miniaturisierung der mikroelektronischen Bauelemente und damit der Reduzierung der Barriereschichtdicken sichergestellt sein. Im Rahmen der Arbeit wurden mittels Magnetron-Sputtern neben Ta- und TaN-Einfachschichten sowie Ta-TaN-Mehrfachschichten auch Ta-Si-N-Einfachschichten jeweils mit und ohne Cu-Metallisierung sowohl auf blanke als auch auf thermisch oxidierte Si-Scheiben abgeschieden. Die Dicken der Barriereeinzelschichten und die der Cu-Schichten betrugen 10 nm bzw. 50 nm. Die Beurteilung der Barrierestabilität sowie die Charakterisierung der Ausfallmechanismen erfolgten nach Wärmebehandlungen durch den kombinierten Einsatz von Röntgenstreumethoden, spektroskopischen sowie mikroskopischen Analyseverfahren. In Abhängigkeit von ihrer Zusammensetzung und damit von der Mikrostruktur im Ausgangszustand finden für die zwischen Kupfer und SiO2 abgeschiedenen Diffusionsbarrieren unterschiedliche Prozesse während thermischer Belastungen statt. Bei den mehrstufigen Ta-TaN-Barrieren setzt bereits bei T = 300 °C eine Umverteilung von Stickstoff ein, die bei T = 500 °C in der Bildung von Ta2N-Kristalliten resultiert. Im Fall der Ta-Si-N-Barrieren führt die vorhandene Cu-Metallisierung zu einer an der Cu/Barriere-Grenzfläche beginnenden Kristallisation. Dabei hängen sowohl deren Einsatzzeitpunkt während einer bei konstanter Temperatur durchgeführten Wärmebehandlung als auch das entstehende Kristallisationsprodukt von der Barrierezusammensetzung ab. Im Zuge der Kristallisation erfolgt die vollständige Zerstörung der ursprünglichen Schichtintegrität, so dass Kupfer in unmittelbaren Kontakt zum SiO2-Substrat gelangt. Der sensitive Nachweis einer Cu-Diffusion durch die Barriere erfolgte einerseits durch die Charakterisierung von Cu/Barriere/SiO2/Si-Systemen mit Hilfe spurenanalytischer Methoden und andererseits durch die Untersuchung von Proben mit geändertem Aufbau. Durch Abscheidung der Barrieren zwischen Kupfer und Silizium ist mittels Röntgenbeugung die nach Diffusion von Cu-Atomen ins Substrat einsetzende Bildung von Cu3Si detektierbar. Mit den kritischen Temperaturen für die Bildung dieses Kupfersilizids erfolgte die vergleichende Bewertung der thermischen Stabilitäten der Barrieren. Werden die dünnen Ta-basierten Schichten zusätzlich bezüglich ihres spezifischen elektrischen Widerstandes beurteilt, so stellt sich eine Ta56Si19N25-Diffusionsbarriere als am geeignetsten für den Einsatz in Cu-Metallisierungssystemen heraus. Die mikrostrukturellen Untersuchungen gestatten Aussagen zu den Versagensmechanismen der einzelnen Barrieren. Für die Ta-TaN-Mehrfachschichten wird durch die einsetzende Stickstoffumverteilung und die sich anschließende Ta2N-Bildung bereits frühzeitig die stabile Mikrostruktur der TaN-Schicht zerstört. Während für Ta-Si-N-Schichten mit einem N-Gehalt von bis zu 25 at.% eine Cu-Diffusion ins Substrat erst nach vorzeitiger Barrierekristallisation beobachtet wird, erfolgt sie im Fall der stickstoffreichen Ta-Si-N-Barrieren in einem Zustand, für den mittels Röntgenbeugung eine Kristallisation noch nicht nachweisbar ist. Die Untersuchung der Abhängigkeit der sich während des Cu-Schichtwachstums bzw. einer nachträglichen Wärmebehandlung ausbildenden Cu-Texturkomponenten von der chemischen Zusammensetzung der Unterlage erfolgte mittels röntgenographischer Texturanalyse. Zur Diskussion der beobachteten Vorzugsorientierungen wurde das Modell des zweidimensionalen Kornwachstums in dünnen Schichten herangezogen.
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Calas, Sylvie. "Surface et porosité dans les aérogels de silice : étude strcuturale et texturale." Montpellier 2, 1997. http://www.theses.fr/1997MON20178.
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Les aerogels de silice sont des materiaux tres poreux mais de faible permeabilite et developpant une surface specifique tres importante. Ces trois caracteristiques peuvent etre controlees par un traitement de densification. Cette densification peut se faire soit par traitement thermique (frittage), soit par compression isostatique. L'evolution, au cours de la densification, de la surface specifique et de la porosite des aerogels de silice est analysee par trois techniques experimentales. La spectroscopie de transmission infrarouge et proche infrarouge permet de suivre la deshydratation progressive des materiaux puis la liaison des groupements oh a la surface des pores, favorisant la densification. La diffusion de l'argon dans les aerogels de densite superieure a 0,3 est de type knudsen. Celle du co#2 qui interagit de facon plus importante avec la surface, permet de mettre en evidence un flux supplementaire de surface. L'evolution de ces deux types de flux est liee a celle de la surface volumique. L'adsorption/desorption d'azote conduit a l'obtention des surfaces specifiques, volumes poreux et distributions poreuses. L'influence, sur ces parametres, des conditions de synthese et des traitements subis par le materiau est analysee. Le frittage entraine l'augmentation de la taille des particules. Il conduit a une diminution de la surface specifique. La permeabilite diminue et la distribution poreuse se decale vers les tailles de pores plus faibles. La compression, au contraire, entraine des modifications a une echelle plus importante : celle des agregats. Dans ce cas, la surface specifique demeure constante jusqu'a une densite de 0,9. La diminution de la permeabilite et le decalage de la distribution poreuse apparaissent egalement lors de la compression. Cependant, les plus gros pores etant les premiers affectes, ces evolutions sont plus rapides que dans le cas du frittage.
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Eisenhauer, David [Verfasser], Bernd [Akademischer Betreuer] Rech, Christiane [Akademischer Betreuer] Becker, Bernd [Gutachter] Rech, Christiane [Gutachter] Becker, Olindo [Gutachter] Isabella, and Antonín [Gutachter] Fejfar. "Tailor-made light management textures for liquid phase crystallized silicon solar cells : technological and device considerations / David Eisenhauer ; Gutachter: Bernd Rech, Christiane Becker, Olindo Isabella, Antonín Fejfar ; Bernd Rech, Christiane Becker." Berlin : Technische Universität Berlin, 2018. http://d-nb.info/117234986X/34.
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Dabadie, Thierry. "Synthèse et caractérisation de gels de silice dans les milieux amphiphiles organisés. Application à l'élaboration de matériaux à texture anisotrope ou à porosité ordonnée et modulable." Montpellier 2, 1994. http://www.theses.fr/1994MON20132.
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Une nouvelle technique de structuration de materiaux inorganiques par voie sol-gel a ete mise au point. Certains tensio-actifs permettent la preparation de cristaux liquides lyotropes en phase lamellaire ou hexagonale. De telles structures sont susceptibles d'etre figees lors de la gelification et de la formation du reseau inorganique. Dans le cas des gels humides, cette technique peut generer une orientation et une anisotropie du reseau inorganique lors de l'application d'un cisaillement. Dans le cas de gels traites thermiquement, il s'avere possible d'obtenir une porosite ordonnee et modulable apres elimination de la mesophase structurante. Des couches minces sont preparees et appliquees a la realisation de membranes separatives microporeuses. Ces membranes sont testees en pervaporation
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Smeltz, Jonathan Brett. "Dedolomitization and Alkali-Silica Reactions in Ohio-Sourced Dolostone Aggregates." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1522982074568612.
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Chal, Bruno. "Vieillissement thermohygrique de silices nanostructurées, vers une compréhension des mécanismes." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI090.
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La réduction des émissions de gaz à effet de serre et de la consommation énergétique nécessite de promouvoir l’efficacité énergétique des bâtiments, premier secteur de dépense en France (40%). Les objectifs fixés par le récent plan climat prévoient de rénover thermiquement 500 000 logements par an pour réhabiliter l’ensemble du parc immobilier à l’horizon 2050. Les super-isolants thermiques (SIM), avec une conductivité thermique entre 4 et 20 mW.m-1.K-1, permettent une isolation efficace à moindre épaisseur, et offrent plus de liberté architecturale. Toutes les configurations superisolantes (Panneaux isolants sous vides (PIV), superisolants à pression atmosphérique (SIPA)) s’appuient sur des matériaux nanostructurés et majoritairement sur des silices, permettant de réduire drastiquement la conduction gazeuse (loi de Knudsen) et squelettique. Leurs caractéristiques structurelles et texturales (porosité > 92 %, nanopores, 200 m²/g plus petit Surface Spécifique plus petit 850 m²/g) mais aussi chimiques (différents groupes en surface : silanols SiOH, siloxanes SiOSi, hydrophobants SiR) pilotent leur efficacité thermique mais ouvrent aussi la voie à des évolutions en cas d’exposition à des conditions sévères couplées (Température et Humidité relative). La compréhension des phénomènes physico-chimiques mis en jeu dans leur vieillissement est donc nécessaire, c’est l’objet de cette thèse menée sur un ensemble de matériaux commerciaux (pulvérulents ou aerogels). L’approche originale proposée dans ces travaux couple des techniques locales, multi-échelles et globales (sorption de gaz, porosimétrie mercure, MET, tomographie aux électrons, SANS, FTIR, ATG…) et repose sur différentes conditions de vieillissement destinées à discriminer les mécanismes moteurs. L’emploi des diverses techniques a nécessité un travail d’adaptation préliminaire et des études paramétriques afin de répondre aux exigences et aux spécificités propres à la silice amorphe nanostructurée (porosité importante, sensibilité…). Cette démarche permet de démontrer que des modifications dans la chimie de surface (hydrolyse de siloxanes, condensation de silanols…) accompagnent des modifications de texture et de structure (réduction de la surface spécifique, décalage de la distribution de taille de pore…). Selon le type de silice ou d’aérogel étudié, la typologie et l’intensité de ces évolutions varient et des mécanismes plus spécifiques peuvent être mis en jeu. L’un des principaux mécanismes identifiés implique un déplacement de matière en surface, notamment rendu possible par la physisorption d’eau servant de media (dissolution/précipitation), et des forces capillaires. Ce travail de fond sur les mécanismes apporte une base de connaissance permettant de gagner en visibilité, donc en confiance, sur le devenir des superisolant et d’adapter leur formulation à leur utilisation. Les résultats acquis au cours de cette thèse pourront également implémenter des modélisations et des outils de simulationReducing greenhouse gas emissions and energy consumption imply to promote the energetic efficiency of buildings, first share of consumption in France (40%). The goals is to rehabilitate the entire building stock by 2050 with a 500 000 building thermal retrofitting rate per year.Superinsulation materials (SIM), with a thermal conductivity between 4 and 20 mW.m-1.K-1, offer the opportunity to suitably insulate with a low thickness, improving architectural flexibility. All superinsulation products (Vacuum Insulation Pannels (VIP), Superinsulation Materials at Atmospheric Pressure (SIAP)) are based on nanostructured materials and mainly on silica, which drastically lowers the skeletal and gaseous conductivities (Knudsen’s law). Their structural and textural properties (porosity > 92 %, nano-pores, 200 m²/g plus petit Specific Surface Area plus petit850 m²/g), as their chemical characteristics (different chemical groups at the surface), drive their thermal efficiency but also open the way for evolutions in case of exposition to harsh atmospheres (Temperature and Relative Humidity). Comprehension of physico-chemical phenomena taking part in ageing is thus compulsory to ensure efficient and durable materials at affordable price. This is the aim of this PhD thesis carried out a set of commercial products (divided silica or aerogels). The original approach proposed in this work combines local, multi-scale and global techniques (gaz sorption measurement, mercury porosimetry, TEM, electron tomography, SANS, FTIR, TGA…) and rests on several ageing conditions, which are intended to highlight driving mechanisms. Due to the specificities of nanostructured amorphous silica (high porosity, sensibility…), the use of these techniques preliminarily required adaptation work, which includes parametric studies. Ageing is tracked down to the nano particle and neck size within agglomerate and associated to usual engineering values. This approach allows to demonstrate that chemical modifications (siloxane bridges hydrolysis, silanol groups condensation…) come along with textural and structural modifications (reduction of the specific surface area, shifting of the pore size distribution…). According to the type of silica or aerogel analysed, the intensity and the evolution scenario differ, and more specific mechanisms can be involved. The main mechanism identified implies a displacement of matter through water layers adsorbed on the surface (physical adsorption of water, dissolution/precipitation). Capillary forces at the nano scale are evidenced by coupled techniques. Thermal measurements confirmed that thermal efficiency withstands ageing with adequate design This upstream work on mechanisms offers a knowledge base and allows gaining clarity, thus confidence, regarding superinsulation materials future. It also gives hints to adapt the synthesis according to the application. Results acquired during this thesis could also implement modelling and simulation tools
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Bisaro, René. "Etude des proprietes et structure des couches minces de silicium deposees par decomposition thermique de silane." Paris 6, 1987. http://www.theses.fr/1987PA066267.
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La taille des grains, la texture, la morphologie de surface, la conductivite electrique et l'absorption optique sont etudies en fonction des parametres de depot. L'optimum des proprietes de transport des couches polycristallines est lie a un regime de cristallisation en phase solide. Etude du processus de cristallisation, effet d'impuretes dopantes. On met en evidence l'effet des liaisons disponibles et de leur etat de charge sur le mecanisme des cristallisation
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Shi, Xiang. "The Crystalline Structure of Polydimethylsiloxane : Additional Results and Additional Questions." Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASP009.
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L’objectif principal de ce travail est de tenter d’élucider la structure cristalline du poly(diméthylsiloxane) (PDMS). Nous avons d’abord synthétisé des élastomères PDMS chargés en silice soit par mélange physique ou soit par croissance in situ, afin d’obtenir des échantillons pouvant supporter les élongations nécessaires à notre étude. En couplant tests mécaniques et diffraction des rayons X (WAXD) à température ambiante, il a été montré que les échantillons chargés in situ présentaient un facteur d’amplification des déformations anormalement élevé. Des clichés de diffraction obtenus à basse température et sous différentes extensions sur des échantillons cristallisés ont été comparés à des simulations : il a été démontré que les changements observés provenaient d’une évolution de la texture cristalline, la maille restante quadratique. Ceci contredit l’hypothèse d’un polymorphisme. L’augmentation soudaine de la contrainte lors du refroidissement d’un élastomère PDMS pré-étiré est connue. Il est montré que ceci n’apparaît qu’une fois la cristallisation terminée : cet effet serait dû à la contraction thermique et à l’augmentation du module de Young résultant de la présence de cristallites et d’une phase amorphe confinée. Une détermination atomique de la structure cristalline de PDMS a été tentée, basée sur des mesures de diffraction X de poudre à basse température. Les techniques de recuit simulé simulation, l’optimisation de DFT et d’affinement de Rietveld ont été utilisées. Deux groupes d’espace / 4₁ et / 4₁ ⁄ a sont proposés et les positions atomiques calculées pour chaque cas. Toutefois, aucune de ces propositions n’est vraiment satisfaisante en ce qui concerne les intensités calculées. D’autres hypothèses sont formulées. En complément de ce travail, deux organogélateurs à base de cholestérol ont été étudiés par différentes techniques de diffusion des rayons X. Les résultats suggèrent qu’un changement de l’empilement moléculaire est à l’origine des propriétés chromatiques stimulo-sensibles des molécules de TPE-C n-Chol. L’existence d’une phase smectique-A avec bicouche antiparallèle inter-digitée a été également démontrée pour les molécules de TPE-Azobenzene-Cn-CholThe main objective of this work is to elucidate the crystalline structure of poly(dimethylsiloxane) (PDMS). Silica-filled PDMS elastomers are first synthesized by either physical mixing or in-situ sol-gel loading to obtain specimens that can sustain the extensions necessary for our purpose. Coupling tensile tests and X-ray diffraction (WAXD) at room temperature, it was found that the sol-gel silica filled samples exhibited an anomalously high strain amplification factor. Thereafter WAXD patterns of PDMS elastomer under different extensions was collected at low temperature (typically -100 °C) and the comparison between experimental data and simulations unambiguously demonstrated that the impressive pattern changes observed with increasing deformation originated from textures, the crystal unit cell remaining tetragonal unit cell in all cases; this contradicts the hypothesis of a possible polymorphism. A sudden rise in stress has been previously reported during cooling of a pre-stretched silicone rubber. It is presently shown to appear after crystallization is completed and it is to the combined effect of thermal contraction and the increase of Young’s modulus that results from the presence of crystallites and harder confined amorphous phase. Based on low-temperature powder X-ray diffraction and selected area electron diffraction, an atomic determination of the crystal structure of PDMS was attempted by annealing simulation, DFT optimization as well as Rietveld refinement. Two space groups of / 4₁ (No. 80) and / 4₁ ⁄ a:1 (No. 88-1) with a 0.5 occupancy probability are proposed and the atomic positions are computed for each case. However, no one of this proposal is really satisfying as regard to the computed intensities. Further hypothesis is formulated. As a complement to this work, two cholesterol-based organogelators were studied by different X-ray scattering techniques. The results suggest a change in molecular packing is at the origin of stimuli-responsive chromatic properties in TPE-Cn-Chol molecules. A smectic-A phase with inter-digitated antiparallel bilayer was also evidenced in TPE-Azobenzene-Cn-Chol molecules
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Pastol, Yvon. "Etude de la cristallisation en phase solide de couches minces de silicium implantees." Paris 7, 1987. http://www.theses.fr/1987PA077142.
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Etude des effets de dopage par implantation de bore et de phosphore. Etude du role des defauts d'irradiation dans des couches implantees au silicium. Les couches implantees et non implantees sont cristallisees en phase solide par recuit thermique a basse temperature. Etude de la taille des grains, de la texture, de la morphologie de surface et de la conductivite electriques des couches en fonction de la concentration d'ions implantes
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Yildiz, Ridvan. "Étude de la mise en forme de supports de catalyseurs à porosité hiérarchisée." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R025.
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Depuis la découverte des matériaux à mésoporosité ordonnée au début des années 90, leurs synthèses se sont largement développées. Leurs propriétés texturales particulières, facilitant le transport des réactifs et des produits jusqu’aux sites actifs, ont permis un essor rapide de leur utilisation et notamment en catalyse hétérogène (énergie, biomasse, environnement). Cependant, pour certaines applications particulières, des limitations diffusionnelles conséquentes apparaissent. C’est particulièrement le cas lors de réactions sur les biopolymères (glucose, cellulose, lignine, etc.) et les triglycérides issus de la biomasse. Le développement de supports de catalyseurs hiérarchisés, présentant plusieurs échelles de porosité, permet de s’affranchir de ce problème et ainsi améliorer l’activité catalytique du matériau. Dans cette étude, l’objectif est de préparer des supports de catalyseurs monolithiques présentant une porosité hiérarchisée (micro/méso/macro) à partir de poudres de SBA-15, une silice mésoporeuse présentant un réseau poreux 2D. La réplication d’un édifice sacrificiel en billes de PMMA préparé par chimie-formage, à partir d’une suspension aqueuse de SBA-15 de viscosité adaptée, a été la première voie de préparation étudiée. Après optimisation du procédé de mise en forme et des traitements thermiques de consolidation, les résultats ont démontré qu’il est possible d’obtenir des monolithes méso-/macroporeux sans additif de frittage présentant des tenues mécaniques intéressantes mais au détriment des propriétés texturales (jusqu’à 36 kPa de résistance à la compression, pour 290 m²/g de surface spécifique). Une approche modifiée, utilisant une suspension de billes de PMMA dispersées permet d’améliorer les propriétés mécaniques de l’objet final (jusqu’à 86 kPa sans perte notable de propriétés texturales). L’intérêt de cette approche est qu’elle permet d’incorporer, au moment de l’assemblage de l’objet, des liants tels que la bentonite ou des frittes de verre en différentes proportions afin de renforcer la résistance mécanique des monolithes. En particulier, l’ajout de 2%m de bentonite aux suspensions de SBA-15 permet, à 900°C, d’obtenir des monolithes méso-/macroporeux présentant des tenues mécaniques accrues tout en conservant les propriétés texturales (jusqu’à 343 kPa pour 305 m²/g). Tous ces objets présentent une porosité hiérarchisée sur plusieurs échelles : une micro- et mésoporosité intragranulaire associée à la SBA-15, une « petite » macroporosité résultant des espaces interparticulaires dus à l’arrangement des grains de SBA-15 dans les parois du matériau (quelques μm) et une « grande » macroporosité sphérique interconnectée induite par l’empreinte des billes de PMMAOver the last decades, synthesis of ordered mesoporous materials has been widely studied because of their unique structural properties. In heterogeneous catalysis, they provide easier mass transfer of reactants and products to active sites. However, for some specific industrial catalytic processes, they are limited by internal diffusion, especially for reactions involving biopolymers and/or triglycerides from the biomass. The stabilisation of a multiscale porosity in the material can allow the elimination of such constraints during reaction and can have a positive impact on the catalyst activity. In this study, hierarchical monoliths with multiscale porosity (micro/meso/macro) have been produced from a mesoporous silica powder (SBA-15). Strategy of preparation involves the replication of an organised sacrificial polymeric framework, infiltrated with an optimised slurry of mesoporous silica. After thermal treatment, the results indicate that monolithic meso-/macroporous materials showing an interesting mechanical stability can be prepared at the expense of textural properties (compressive strength up to 36 kPa for 290 m²/g of specific surface area). Using a modified approach consisting in dispersing the polymer beads in the aqueous silica slurry, the mechanical strength of the monoliths can be improved up to 86 kPa while keeping similar textural properties. This approach is also interesting since it allows the use of binders such as bentonite or glass frits. In particular, adding 2 wt.% of bentonite to SBA-15 slurries greatly improves the mechanical stability of the final objects after heat treatment at 900°C while having similar specific surface area (up to 343 kPa for 305 m²/g). All the obtained monoliths have a multiscale porosity: a micro- and a mesoporosity brought by the amorphous SBA-15; a micrometer-sized interparticular “small” macroporosity between the silica grains in the walls of the monoliths; and a “large” macroporosity produced by the replication of the polymer beads
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Baroghel-Bouny, Véronique. "Caractérisation microstructurale et hydrique des pâtes de ciment et des bétons ordinaires et à très hautes performances." Phd thesis, Ecole Nationale des Ponts et Chaussées, 1994. http://tel.archives-ouvertes.fr/tel-00523299.
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Ce document présente les résultats obtenus pour différents bétons et pâtes de ciment, en ce qui concerne la microstructure, les propriétés hydriques et les déformations de retrait. En particulier, des matériaux à très hautes performances ont été étudiés (formulations avec un faible rapport eau sur ciment, contenant fumée de silice et fluidifiant). De nombreuses techniques expérimentales ont été utilisées à cet effet. Ainsi, les paramètres texturaux ont été déterminés par des méthodes classiques d'investigation de la structure poreuse (intrusion de mercure, adsorption d'azote, ...). Cependant, ces méthodes sont apparues suivant les cas incomplètes ou inadéquates pour fournir les caractéristiques exactes du réseau poreux des pâtes de ciment ou des bétons durcis, notamment dans le cas des matériaux à très hautes performances. La difficulté d'accès à la porosité fine des hydrates (gel C-S-H) est essentiellement responsable des insuffisances de ces méthodes. De plus, le séchage et le dégazage nécessaires, préalablement à la mesure, rendent l'interprétation des résultats délicate. Aussi, un autre type d'expérimentations plus pertinent a été mis en oeuvre : les expériences de désorption et d'adsorption de vapeur d'eau, à partir desquelles ont été obtenues les isothermes, c'est à dire les courbes "Teneur en Eau en fonction de l'Humidité Relative", à 'équilibre, à température constante (T = 23 °C) et pour chaque chemin de désorption/adsorption. L'analyse de ces courbes n'a pas seulement fourni les paramètres de texture (porosité, surface spécifique B.E.T., distribution poreuse,...) dans le domaine des mésopores, non accessible par beaucoup d'autres méthodes, elle a aussi permis l'étude des interactions eau/solide (épaisseur du film liquide adsorbé sur la surface solide, état d'énergie de l'eau des pores, hystérésis, ...). Les cinétiques de transfert d'humidité sont très lentes dans un tel milieu microporeux et elles sont fonction de l'épaisseur de l'échantillon testé ; l'équilibre hydrique a été établi après plusieurs mois avec nos échantillons de quelques millimètres d'épaisseur. La diffusivité a été calculée à partir des courbes de perte (ou gain) de masse en fonction du temps, pour chaque palier d'humidité relative. Au cours de ces expériences, les déformations hygrométriques ont aussi été mesurées, afin d'évaluer le retrait de dessiccation en fonction de l'humidité relative, et de le comparer au retrait endogène. La caractérisation hydrique a été complétée par la détermination de la répartition de la teneur en eau dans des éprouvettes en cours de séchage. A partir d'une large panoplie expérimentale, nous avons obtenu une description complète de la structure poreuse, depuis les pores relatifs au gel C-S-H, jusqu'à l'échelle des macropores. Nous avons mis en évidence les similarités et les différences, du point de vue microstructural et hydrique, entre les différents matériaux. Nous avons ainsi quantifié l'influence des paramètres de formulation tels que, par exemple, le rapport eau sur ciment ou la présence de fumée de silice.
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Lippold, Marcus. "Beiträge zum Verständnis des sauren nasschemischen Ätzens von Silicium." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-145077.
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Der Siliciumauflöseprozess in HF-HNO3-H2SO4/H2O-Lösungen unterscheidet sich vom Ätzprozess in HF-HNO3-H2O-Standardmischungen in Bezug auf die Reaktivität gegenüber Silicium, erzielte Oberflächenmorpholgien sowie die beim Ätzen entstehenden gelösten und gasförmigen Produkte. Durch die Behandlung in H2SO4-reichen HF-HNO3-H2SO4/H2O-Lösungen werden auf Siliciumwafern Texturen mit hoher Rauigkeit und geringer Reflexion erzeugt. mc-Si-Solarzellen texturiert durch eine H2SO4-reiche Ätzlösung weisen vergleichend zu Solarzellen mit Standardtexturen höhere Wirkungsgrade auf. In HF-HNO3-H2SO4/H2O-Lösungen mit hohen Schwefelsäurekonzentrationen (c(H2SO4) > c(H2O)) wirkt sowohl das Salpetersäuremolekül HNO3 als auch das Nitrylion NO2+ als Oxidationsmittel. Trifluorsilan HSiF3 und Hexafluordisiloxan F3SiOSiF3 wurden erstmalig als gasförmige Produkte des sauren nasschemischen Ätzens identifiziert. Anhand von Modellreaktionen zur Reaktivität von Nitrylionen wurde deren Reduktionssequenz im Siliciumätzprozess aufgeklärt.
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Drezen, Thierry. "Nouveaux oxydes mesoporeux a base de silice modifies par le vanadium et le fer pour la catalyse heterogene. Synthese hydrothermale de nouveaux oxydes de vanadium et de molybdene textures par des diamines : (nh#2(ch#2)#nnh#2) (n 2, 3, 6, 8)." Nantes, 1998. http://www.theses.fr/1998NANT2065.
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A la suite des premiers travaux de kresge et coll. Sur les mesoporeux, si-mcm-41, obtenus par effet template de molecules amphiphiles, nous avons choisi, dans une premiere partie, de preparer des mesoporeux type mcm-41 modifies par le vanadium et le fer pour leur interet potentiel en catalyse d'oxydation heterogene. Les phases ont ete preparees in-situ et par impregnation. De nombreuses techniques de caracterisation : diffraction rx sur poudre, mesures de surface specifique b. E. T. Et de porosite ; spectroscopies ir, raman, rmn (#5#1v, #2#9si, #1h) et mossbauer (#5#7fe) ont permis de preciser le degre d'oxydation du fer et du vanadium, leur geometrie de site et leur repartition au sein du mesoporeux. Des tests catalytiques d'oxydation du toluene par l'eau oxygenee en milieu aqueux sur les phases au fer et d'oxydation deshydrogenante du propane en propene, a faible taux de conversion, effectues a 400c sur les phases au vanadium ont permis de preciser l'effet de dispersion des especes. Dans une seconde partie, des oxydes bronze de vanadium textures par les diamino-hexane et -octane ont ete prepares par voie hydrothermale et caracterises. La structure est formee de clusters v#1#5o#3#6(cl) stabilises par interactions avec les cations alkyldiammonium avec lesquels ils partagent des liaisons hydrogene. L'anion cl est encapsule au centre d'une cage polyoxovanadique. Deux oxydes de molybdene, un bronze et un oxyde non reduit ont ete egalement textures respectivement par l'ethylenediamine et le diaminopropane. Le double role d'agent reducteur et d'espece texturant des diamines a fait l'objet d'une discussion pour les deux systemes hybrides au vanadium et au molybdene.
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Santos, Hamilta de Oliveira. "Caracterização de camisas de cilindro em ligas Al-Si hipereutéticas e investigação do comportamento de corrosão em meio de condensado sintético automotivo." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-18052012-091151/.
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No presente trabalho quatro ligas Al-Si hipereutéticas, três das quais foram produzidas por conformação por \"spray\" e a outra por fundição, foram caracterizadas quanto a textura, dureza, microestrutura e resistência à corrosão em meio de condensado sintético automotivo (CSA). Duas das ligas conformadas por \"spray\" foram retiradas de camisas de cilindro e a outra de um pré-formado obtido em laboratório. A conformação por \"spray\" envolve a atomização de uma liga e a deposição de gotículas em um substrato, antes mesmo que todas se encontrem no estado sólido. Este processo permite a obtenção de materiais que se caracterizam por uma microestrutura livre de macrossegregações e bastante refinada, implicando melhor trabalhabilidade a quente. A caracterização da microestrutura das quatro ligas hipereutéticas revelou a presença de porosidades na liga obtida em laboratório, e microestrutura com distribuição homogênea de precipitados primários nas três ligas conformadas por \"spray\". A microestrutura de uma das ligas apresentou-se muito diferenciada, com a presença de eutético, sugerindo que esta foi fabricada por fundição. Nas camisas de cilindro foram feitas medidas de rugosidade, e em todas as ligas foram realizados ensaios de microdureza. A liga conformada por \"spray\" e obtida em laboratório foi laminada a quente e a frio. Foram realizados também estudos de textura, para tentar estabelecer uma correlação entre todas as ligas quanto ao processo de fabricação. A avaliação da textura indicou que a presença de fases de silício primário, finamente distribuídas impedem o aparecimento de texturas típicas de deformação de ligas de alumínio, mesmo após severas deformações, como as necessárias para a transformação de pré-formados em tubos que originam as camisas de cilindro. As medidas de rugosidade indicaram características próprias do acabamento superficial usado para a produção das camisas, por brunimento ou por ataque químico. Os ensaios de microdureza apresentaram variações de acordo com as rotas de fabricação sendo que a liga eutética apresentou os maiores valores de microdureza em comparação às ligas conformadas por \"spray\". Todas as ligas foram avaliadas quanto a resistência à corrosão por ensaios de espectroscopia de impedância eletroquímica em dois meios, CSA com pH 3,3 e CSA com pH 11. As quatro ligas hipereutéticas estudadas apresentaram mecanismo de corrosão similar em condensado sintético automotivo (CSA) pH 3,3. Em todas ocorreu o ataque intenso da matriz de alumínio e as partículas de silício primário atuaram como regiões catódicas. A liga 2 apresentou maior resistência à corrosão entre todas as ligas ensaiadas, tanto em CSA pH 3,3 como em pH 11. Neste último meio, uma camada de produtos de corrosão formou-se sobre todas as ligas, e os resultados indicaram mecanismos diferentes para o ataque da matriz de Al e para o crescimento da camada depositada na superfície das ligas estudadas. O ataque da matriz da liga 2 neste meio foi aparentemente mais lento do que sobre as demais ligas, com a formação de uma camada mais compacta de produtos de corrosão, estabelecendo um controle por difusão dos processos interfaciais para maiores períodos de ensaio. A camada formada sobre as demais ligas neste meio apresentou-se mais defeituosa, e nestas ocorreu também menor controle da velocidade das reações interfaciais por processos difusionais.In the present study four hypereutectic Al-Si alloys, three produced by spray forming and one by casting, were characterized for microhardness, roughness, microstructure, texture and corrosion resistance in a synthetic automotive condensed solution (SACS). Two of the spray formed alloys tested were obtained from cylinder liners and the other was laboratory made. Spray forming involves alloy atomization and droplets deposition on a substrate, previous to the solidification of all of the droplets. This process favours the production of materials with a fine microstructure free of macrosegregation that is related to improved hot workability. The microstructure characterization of the four alloys revealed the presence of porosities in the laboratory made alloy. All the three alloys produced by spray forming showed a homogeneous distribution of primary precipitates. The microstructure of one of the alloys showed eutectic microstructure, indicating that this alloy was fabricated by casting. In the cylinder liners, the surface roughness was measured and the microhardness of all the alloys was also evaluated. Furthermore, the laboratory made alloy was hot and cold rolled. Texture determinations were carried out to investigate the correlation between the alloy type and their fabrication process. The texture investigation indicated that the fine distribution of primary silicon phase in the alloy hindered the development of texture typical of aluminium alloys deformation, even after severe mechanical work, such as those used in the conversion of pre-formed in cylinder liners. The surface roughness results indicated typical characteristics of the surface finishing used, honing or chemical etching. The microhardness results were dependent on the fabrication process used, with higher microhardness associated to the eutectic alloy comparatively to the spray formed ones. All hypereutectic alloys were tested for corrosion resistance using electrochemical impedance spectroscopy in two electrolytes, SACS with pH 3.3 and SACS with pH 11. The four tested alloys showed similar corrosion mechanisms in the acid electrolyte (SACS pH 3.3). The intense attack of the aluminium matrix occurred in ali tested alloys and the primary silicon phase was unattacked and appeared as emerging from the surface after corrosion immersion test. The primary silicon particles acted as cathodic sites. The alloy 2 showed the highest corrosion resistance among the tested alloys in both electrolytes, SACS pH 3.3 and SACS pH 11. In this last medium, a layer of corrosion products formed on all the alloys, and the results indicated different mechanisms for the aluminium matrix corrosive attack and growth of the deposited layer on the alloys surface. The kinetics of aluminium matrix attack was apparently slower in the alloy 2 than for the other alloys, resulting in the formation of a more compact layer of corrosion products, leading to diffusion controlled interfacial processes for longer test periods. The layer of corrosion products on the other three alloys (1, 3, and 4) had more defects and for these alloys diffusional controlled interfacial processes were not as significant as for alloy 2.
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Chen, Zih-Yang, and 陳子揚. "Surface Textured Hybrid PEDOT:PSS-Silicon Solar Cells Employing Kirigami Graphene." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/64281534250587923520.
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碩士國立交通大學
光電工程研究所
105
Using the thin substrate to decrease the manufacturing cost is the current trend for photovoltaic industry. Therefore, we need to use the surface texture to compensate the optical absorption loss of the thin substrate. Hence, we use metal assisted chemical etching to create nano-wire on the inverted pyramid as our main texture. By using this hierarchical texture, the reflection of inverted pyramid without and with nano-wire structure reduced from 18.1% to 6.4%. The performance of the device increase from 8.3% to 10.53% Furthermore, collection of the carrier must be more efficient to reduce the current recombination probability. We choose the graphene as the transparent electrode to increase the probability of carrier collection. By cutting the correspond pattern on grapheme, the specific pattern made the two-dimensional grapheme can highly increase the conformal coverage on silicon texture, seem like the three-dimensional material. After transferred to three-dimensional and conductive substrate, the sheet resistance measurement showed graphene with pattern has lower values than without pattern. This like kirigami method can be used to increase the carrier extraction. For the performance of the devices, with two layers patterned graphene showed has better result. Because of the good electrical characteristic, fill factor enhanced 3.3% and make the final power conversion efficiency enhanced 9.8%.
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WU, CHIA-JUI, and 吳佳叡. "The study of adhesive properties between RuCo alloy and textured silicon." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/cq2b2h.
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Lin, Yu-Keng, and 林宥庚. "Fabrication of Graphene and Silicon Textured Substrate for Schottky Junction Solar Cells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2vvvcc.
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碩士國立臺灣大學
材料科學與工程學研究所
106
The system consisting of graphene and textured silicon substrate with enhanced light harvesting was studied in the present work. The thesis is divided into two topics. In the first topic, Schottky junction solar cells based on n-type silicon nanowire arrays (SiNWs) and multi-layered graphene with 1–4 layers were assembled. The textured substrates enhanced the light-harvesting compared to planar substrates. Multi-layered graphene films produced by chemical vapor deposition and layer-by-layer stacking mitigated damages and increased the work function of graphene. Thus, both the power conversion efficiency and fill factor of Schottky junction solar cells could be increased with multi-layered graphene. It was found in the present study that the optimum photovoltaics performance of solar cells was achieved when double-layered graphene was used. The performance degraded with the number of graphene layers when it was more than 2 layers. While damages could be mitigated and the work function could be improved using multi-layered graphene in SiNWs Scottky junction solar cells, the optical transmittance of graphene would be reduced with excessive number of graphene layers. In the second topic, a simple and low-cost method using the combination of metal-assisted chemical etching (MacEtch) and anisotropic wet etching was performed to fabricate an anti-reflection inverted pyramidal cavities on dendrite-like textured silicon substrate. To achieve this, a thin Ag film was deposited on a n-type (100) silicon substrate to form agglomerated Ag particles and MacEtch was performed to obtain vertically aligned etching holes on Si substrate. Subsequently, anisotropic wet etching was conducted and the etchant would penetrate the porous structure to form inverted pyramidal cavities on dendrite-like structure. Using this two-step etching, excellent anti-reflection behavior was obtained for our textured substrates and the reflectance was reduced to 1.13% in the present work.
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Chang, Yuang-Wei, and 張元瑋. "Nano-Structured Indium Sulfide on the Textured Silicon Hetero-Structure Solar Cells." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/hjxg7a.
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碩士國立虎尾科技大學
光電與材料科技研究所
100
Indium sulfide is a III-VI compound semiconductor，the indium sulfide are another attention to substitute to CdS buffer layer of thin films materials. Presently，A wide range of process have been applied to development In2S3 buffer layer，and to produce CIGS solar cells. In this treatise are discussing silicon and different texture by dry-etch and structure are Al / ITO /β-In2S3 (n-Type) / Si / Al，Then we will divided into three part to discuss：First part，we will fixed the texture times by the machine of STS. Then we will know which is roughening sample and bester. The 20 minute roughening samples are bester and efficiency. By the second part， According to first part to know 20 minute roughening are bester，So that we will fix on the times，change the different gold thickness be knowing which is bester and efficiency. The structure（AZO /β-In2S3 / Si）is a heterojunction solar cells. by the third part，We will studyed the powders that is photoluminescence by chemical bath deposition method to get that，and add Cerium(III) nitrate hexahydrate， to get a new one photoluminescence on the application.
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Hsieh, Bao Sheng, and 謝寶勝. "A study of tunnel oxide film grown on textured silicon surface for EEPROM's applications." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/43533817407317741276.
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碩士國立交通大學
電子工程學系
85
In this thesis, novel and simple technologies are proposed to fabricate the tunneling dielectric for the flash EEPROM devices. Firstly, a thin polysilicon (about 10nm) layer was deposited on Si substrate by low-pressure chemical vapor deposition (LPCVD) and dry oxide film was grown at 900℃ in O2 ambient. The polysilicon film and Si substrate were both oxidized during thermal oxidation. This oxide film was served as a sacrificial oxide. After stripping this sacrificial oxide, a textured Si surface was obtained. Tunneling oxide grown on this textured Si surface has different roughness degree. The microtips have been found to be at the bottomand top interface of the oxide. These microtips result in the localized fieldenhancement and enhance electron injection into the oxide. Therefore, the operation voltage of EEPROM devices is reduced to satisfy the requirements ofULSI scale-down. Also, the novel tunnel oxide exhibits higher reliability,lower electron trapping rate, stable interface state and higher asymmetric current in comparison with control oxide.
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Lai, Yi-Chen, and 賴奕辰. "Fabrication of Plasmonic Nanostructure and Silicon Textured Substrate for Surface-enhanced Raman Scattering Applications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/pdxrjh.
Full textAbstract:
碩士國立臺灣大學
材料科學與工程學研究所
105
The system consisting of metallic nanostructure and textured silicon substrate with enhanced light harvesting and strong electromagnetic field enhancements was studied in the present work. The thesis is divided into two topics. In the first topic, the effects of plasmonic behavior on a composite system consisting of suspended gold nanoring and silicon nanotube substrate were studied both theoretically and experimentally. The dependence of plasmonic behaviors on outer/inner diameter ratio (D/d ratio) of the gold nanoring and silicon nanotube was systematically studied using finite-difference time-domain method. On the other hand, the composite systems with different D/d ratios were fabricated using electron beam lithography followed by reactive ion etching and studied by both dark-field microscopy as well as Raman microscopy. In addition to the dipole-like resonance modes, the quadrupole-like resonance mode was also excited with the increasing D/d ratio, and both electric field profile and resonant surface charge distribution were studied to characterize the resonance configuration and to clarify the coupling phenomenon. Experimentally, by tailoring the D/d ratio, the dark-field image showed tunable colors and the potential for the color display application. Raman spectra were also obtained and showed good agreement with simulated enhancement factor which, in turn, provided the evidence of the evolution of resonance modes. This work provides the concept and guideline for designing the system consisting of metallic nanostructures and textured substrates for surface-enhanced Raman scattering application. In the second topic, the ZnO nanowires were grown on silicon nanotube substrate through hydrothermal process and the Ag nanoparticles were loaded on the ZnO branched nanowires. With the help of ZnO nanowires, the light harvesting effect could be enhanced and the surface area could be increased. Also, additional electric field enhancements would be induced due to the charge transfer between the heterojunction, which could further enhance the Raman signals. The mechanism behind the additional enhancements was elucidated by the band structure of the heterojunction. In addition, the photocatalyst properties of Ag/ZnO heterostructure were exploited to reuse the substrate through the degradation of probed molecules upon UV-irradiation.
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"A Development of Thin Films and Laser Processes for Patterning of Textured Silicon Solar Cells." Doctoral diss., 2018. http://hdl.handle.net/2286/R.I.49284.
Full textAbstract:
abstract: This work explores the application and optimization of laser patterning of dielectrics on textured crystalline silicon for improving the performance of industrial silicon solar cells. Current direct laser patterning processes introduce defects to the surface of the solar cell as a result of the film transparency and the intensity variation of the laser induced by the textured surface. As a means of overcoming these challenges, a co-deposited protective masking film was developed that is directly patterned with laser light at greatly depreciated light intensities that allows for selective chemical etching of the underlying dielectric films without incurring substantial defects to the surface of the device. Initial defects produced by the process are carefully evaluated with electron microscopy techniques and their mechanism for generation is identified and compensated. Further, an analysis of the opening fraction within the laser spot is evaluated –the area of removed film within the laser spot divided by the area of the laser spot– and residue produced by the laser process within the contact opening is studied. Once identified, this non-damaging laser process is a promising alternative to the standard screen print and fire process currently used by industry for metallization of silicon solar cells. Smaller contacts may be made with the laser process that are as of yet unattainable with screen printing, allowing for a decrease in shading losses. Additionally, the use of patterning allows for silver-free metallization and improved conductivity in the contacts, thereby decreasing parasitic losses in the device.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2018
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DENG, YU JIE, and 鄧宇傑. "Photovoltaic Performance Enhancement of Textured Silicon Solar Cell Using Sub-Micron Europium Doped Silicate Phosphors Film." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/4w34nq.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
104
In this study, the combination of silicate phosphors and silicon dioxide (SiO2) mixing structure was formed on silicon solar cells. To enhance the photovoltaic performance of silicon solar cells by using phosphors particles was demonstrated. Due to a serious surface recombination and high reflective loss on the surface of silicon at short wavelength region, while limited the conversion efficiency of silicon solar cells. So in this study, Luminescent Down-Shifting (LDS) effect of phosphors particles was applied to the surface of silicon solar cells to improve the conversion efficiency, which can absorb high energy photon and emit low energy photon to enhance the contribution of the short wavelength spectrum of solar cell. Otherwise, the large diameter of phosphor had a larger shading and reflecting area to incident lights. This effects will more obvious on the textured solar cell. In this study, we used different dimensions of Eu-doped phosphors mixed with silicate (SiO2) solution and spun on the both type solar cells. Discussing the enhanced contribution of antireflection, scattering and LDS on solar cell was provided. In addition, the textured surfaced with a TiO2 antireflection layer and three different diameter of phosphors mixed with silicate (SiO2) solution spun on the solar cells were proposed and demonstrated. Finally, the photoluminescence (PL), optical microscope (OM), reflectivity, external quantum efficiency (EQE), dark I-V and photovoltaic I-V characteristics of the SiO2-phosphors mixed layer structure solar cells were measured and compared. In planar solar cells, the cells with single SiO2 layer antireflective coating solar cell were measured and compared. The solar cell with single SiO2 layer had an improvement of 12.73 % (26.30 mA/cm2 →29.65 mA/cm2) in short-current density (Jsc) and 14.61% (10.26 % →11.76 %) enhancement in conversion efficiency (ƞ)；The obtained results indicated that the structure with the small phosphors was the best one, which showed a 16.84 % (26.54 mA/cm2 →31.01 mA/cm2) enhancement in short-current density (Jsc) and 18.14% (10.64 % →12.57 %) enhancement in conversion efficiency (ƞ). On the other hand, in textured solar cells, a 5.6 % (30.98 mA/cm2 →32.73 mA/cm2) enhancement in (Jsc) and 6.2% (12.54 % →13.32 %) enhancement in (ƞ) were achieved. The best result showed that the cell with the textured structure and small phosphors exhibited (Jsc) enhancement of 9.2 % (30.62 mA/cm2 →33.43 mA/cm2) and (ƞ) enhancement of 8.9% (12.64 % →13.77 %).
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LI, GUAN-YI, and 李冠毅. "Electrical and Optical Performance Enhancement of Textured Silicon Solar Cell Using Luminescent Down-Shifting Methylammonium Lead Tribromide Perovskite Nanophosphor." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/52xv64.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
105
In this study, the electrical and optical characteristics of the textured crystalline silicon (C-Si) solar cells coated with luminescent down-shifting (LDS) of MAPbBr3 perovskite nanophosphor by spin-on film technique are demonstrated. Due to high reflectance and low spectral response at the ultraviolet (UV) and blue wavelengths (300–450 nm) bands, a higher recombination loss would be exhibited on the surface of photovoltaic devices because the incident photons of higher energy were absorbed within a short distance from the surface. The LDS phosphors materials can absorb high-energy photons and re-emitted lower-energy photons for the applications of solar cells to improve low spectral response at short wavelength band. Otherwise, the large diameter of phosphor had a larger shading and reflecting area to incident lights. The effects will more obvious be presented on the textured solar cell. In this study, the MAPbBr3 nanophosphor layer was appositely deposited by spin-on film technique on the textured C-Si solar cells. The spin methods and the concentration and layer of nanophosphor to achieve high efficiency are also discussed. The samples with nanophosphor concentration of 10 mg/ml and with 1-3 layers of nanophosphor deposited by two-step spinning rate on the textured silicon solar cell with a SiNx anti-reflection coating are prepared for comparing. The SEM analysis, optical reflectance, external quantum efficiency, dark current-voltage and photovoltaic current-voltage measurements of the solar cells with MAPbBr3 nanophosphor layer are measured and compared. The short circuit current density enhancement (ΔJsc) of 3.13% (from 36.48 mA/cm2 to 37.62 mA/cm2) and 4.35% (from 35.83 mA/cm2 to 37.39 mA/cm2), and the conversion efficiency enhancement (Δη) of 3.38% (from 15.08% to 15.59%) and 4.56% (from 15.13% to 15.82%) were obtained for the cells with 1-layer and 2-layer nanophosphor, respectively. However, the performance of current density and conversion efficiency of the textured cells with 3 layers nanophosphor are degraded that ΔJsc of -1.77% (from 37.85 mA/cm2 to 37.18 mA/cm2) and Δη of -1.72% (from 15.13% to 14.87%). The experimental results show that the textured silicon solar cell with 1-2 layer of MAPbBr3 nanophosphor presented a good LDS characteristics. Especially, the efficiency of the cell coated with 2 layers of MAPbBr3 nanophosphor with the concentration of 10 mg/ml is superior to that of the other ones.
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Tsai, Hung-Yao, and 蔡弘堯. "Fabrication of V-grooved and Textured Single-Crystalline Silicon by Wet Chemical Etching for Buried Contact Solar Cell Applications." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/vrxs7h.
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碩士國立虎尾科技大學
機械與機電工程研究所
100
In this work, v-grooved and textured single-crystalline silicon were demonstrated by the tetramethyl ammonium hydroxide/ isopropyl alcohol (TMAH/IPA) and the KOH/IPA mixed wet chemical solutions, respectively, for the buried contact solar cell applications. The silicon dioxide was used as the etching barrier of TMAH. The tuning conditions include TMAH solution concentrations and the treated temperatures. The results suggest that the etching rate increases with increasing TMAH concentration below 15%. However, the etching rate decreases with increasing TMAH concentrations above 15%. Moreover, the etching rate increase with increasing treated temperature of TMAH solutions. The uniformities of textured surfaces were achieved by decreasing etching rate of KOH/IPA solutions. The lower etching rate can be obtained by adding the IPA into KOH solution. Experimental results indicate that the v-groove with texturization provide excellent light trapping and can be used as a promising metal contact for applications in buried contact solar cells.
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LAI, CHIUNG-TI, and 賴炯杕. "Characterizations and analyses of the ZnO and ZnO : B grown on the (100), (111), textured silicon, and ITO glass substrates." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/92287609090414765193.
Full textAbstract:
碩士國立高雄大學
應用物理學系碩士班
105
First, zinc oxides (ZnO) thin films are grown on the planar (100), planar (111), and textured (100) three different silicon substrates. They are characterized and analyzed by various methods, such as cathode luminescence (CL), Raman spectroscopy, scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD). The results show that ZnO grains with the (110) crystal orientation are most favored to grow on Si(100) substrates, while ZnO(002) grains for Si(111) substrates and ZnO(101) for textured Si substrates, respectively. This result is consistent with the theoretical explanations from the constrains of the lattice match between the ZnO and Si crystals. The analyses of the XRD data also show that the average grain sizes of the zinc oxides grown on the different silicon substrates decrease due to the increases of their average strains. The average size of ZnO grains on the Si(100) substrate is slightly larger than that on the (111) substrate, while both of them are much larger than the average size of ZnO grains on the textured Si substrate; whereas, the average ZnO strains on the Si(100) substrate are slightly smaller than those on the Si(111) one, while both of them are much smaller than the strains on the textured surface. These results strongly agree the measurements from the CL, Raman, SEM, and AFM as well. Second, different thickness zinc oxides (ZnO) (0.5 and 2 μm) and boron doped zinc oxides (BZO)(1, 2, and 3 μm) thin films are grown on the ITO glass substrates. They are characterized and analyzed by various methods, such as cathode luminescence (CL), Raman spectroscopy, scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD). The results show that ZnO and BZO grains with the (110) crystal orientation are most favored to grow on ITO glass substrates, respectively. This result is consistent with the theoretical explanations from the constrains of the lattice match between the ZnO and ITO crystals. The analyses of the XRD data also show that the average grain sizes of different thickness ZnO and BZO grown on ITO glass substrates decrease due to the increases of their average strains. The average size of ZnO@2 grains on the ITO glass substrate is slightly larger than that on ZnO@0.5; whereas, the average ZnO strains on the ZnO@2 are slightly smaller than that on the ZnO@0.5. The transmittance spectra of ZnO@0.5 is larger than that on the ZnO@2. On the other hand, the average size of BZO3 grains on the ITO glass substrate is slightly larger than that on BZO2 grains on the ITO glass, both of them are larger than the average size of BZO1; whereas, the average BZO strains on the BZO3 are slightly smaller than that on the BZO2 while both of them are smaller than the strains on the BZO1. The average transmittance spectra of BZO1 is larger than that on the BZO2, while both of them are larger than the average transmittance spectra of BZO3. These results strongly agree the measurements from the CL, Raman, SEM, and AFM as well.