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Keshavarzi, Shervin [Verfasser], Holger [Akademischer Betreuer] Reinecke, and Ulrich [Akademischer Betreuer] Mescheder. "Silicon needle-like surfaces for room temperature si-si bonding applications." Freiburg : Universität, 2019. http://d-nb.info/1202010865/34.
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Camacho-Aguilera, Rodolfo Ernesto. "Ge-on-Si laser for silicon photonics." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82173.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (p. 253-263).<br>Ge-on-Si devices are explored for photonic integration. Importance of Ge in photonics has grown and through techniques developed in our group we demonstrated low density of dislocations (<1x109cm-2) and point defects Ge growth for photonic devices. The focus of this document will be exclusively on Ge light emitters. Ge is an indirect band gap material that has shown the ability to act like a pseudo direct band gap material. Through the use of tensile strain and heavy doping, Ge exhibits properties thought exclusive of direct band gap materials. Dependence on temperature suggests strong interaction between indirect bands, [Delta] and L, and the direct band gap at [Gamma]. The behavior is justified through increase in photoluminescence on Ge. The range of efficient emission is to 120° with the first band interaction, and above 400° on the second band interaction. Low defect concentration in Ge is achieved through chemical vapor deposition at high vacuum (~1x10-8 mbar) in a two-step process. The high temperature growth and low concentration of particles permits epitaxial growth with low defect concentration. Chemical selectivity forbids Ge growth on oxide. Oxide trenches permit the growth on Si for a variety of shapes, without detrimentally affecting the strain of the Ge devices. Dopant concentration above intrinsic growth concentration, ~1x1019cm-3 phosphorus, have been achieved through a series of methods non-CMOS, spin-on dopant; and CMOS, implantation and delta doping. All the techniques explored use enhanced dopant diffusion observed in Ge under heavy n-type doping. A dopant source, or well, is used to distribute the dopants in the Ge without increasing the defect concentration. The approach lead to the development of electrically injected devices, LEDs and LDs. Ge pnn double heterostructure diodes were made under low, ~1x1018cm-3, and heavy n-type doping, >1x1019cm-3. Both devices showed improved performance compared to pin Ge LED. Furthermore, heavy doped Ge diodes exhibit evidence of bleaching or transparency. The techniques described permitted the development of Ge-on-Si laser with a concentration ~1-2x1019cm-3. It is the first demonstration of a Ge laser optically pumped working under the direct band gap assumption like other semiconductors. It represents the evidence of carrier inversion on an indirect band gap semiconductor. With 50cm-1 gain, the material shows Fabry-Perot cavity behavior. Finally, we demonstrated a fully functioning laser diode monolithically integrated on Si. Ge pnn lasers were made exhibiting a gain >1000cm-1 and exhibiting a spectrum range of over 200nm, making Ge the ideal candidate for Si photonics.<br>by Rodolfo E. Camacho-Aguilera.<br>Ph.D.
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Naftel, Steven. "Interactions of transition metals with silicon(100), the Ni-Si, Co-Si and Au/Si(100) systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0008/NQ42546.pdf.
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Richardsen, Sissel. "Refining of Silicon by Solidification of Al-Si Melt." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19365.
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Primary silicon crystals grown from an Al-Si melt has been investigated by solidifying directionally and under electromagnetic field. The goal of this thesis was to increase the size of the primary Si crystals and to agglomerate the crystals to one part of the melt. If achieved, this could simplify the following acid leaching process that is necessary to collect the crystals from the melt. Seven experiments were conducted in a resistance furnace with directional solidification to investigate the agglomeration and size of the Si crystals. A mono-crystalline Si seed was added to the Al-Si melt in three of these experiments as an attempt to increase the crystal growth. The impact of stirring in the melt before solidification was investigated. Al-Si melt was directionally solidified without the aid of seed in three experiments. The silicon content in the alloy and pulling rate during solidification was varied in these experiments to find the appropriate Si crystal growth conditions. The growth of silicon crystals from a mono-crystalline Si seed without aluminium was performed to investigate the impact aluminium had on the seeded growth. One experiment was conducted in an induction furnace to investigate the influence electromagnetic force has on the agglomeration of primary Si crystals. Agglomeration of Si primary crystals was found not to be successful for either directional solidification or electromagnetic force method, as the crystals were not gathered to one part of the melt. The size of the primary Si crystals was not as large as expected and addition of mono-crystalline Si seed did not improve the crystal size. A single Si crystal was successfully grown from a mono-crystalline Si seed when there was no aluminium in the melt.
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Verwijs, Johan P. "The modification of silicon in Zn-Al-Si alloys." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ31654.pdf.
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Venezia, Vincent C. "Evolution of Vacancy Supersaturations in MeV Si Implanted Silicon." Thesis, University of North Texas, 1999. https://digital.library.unt.edu/ark:/67531/metadc277663/.
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High-energy Si implantation into silicon creates a net defect distribution that is characterized by an excess of interstitials near the projected range and a simultaneous excess of vacancies closer to the surface. This defect distribution is due to the spatial separation between the distributions of interstitials and vacancies created by the forward momentum transferred from the implanted ion to the lattice atom. This dissertation investigates the evolution of the near-surface vacancy excess in MeV Si-implanted silicon both during implantation and post-implant annealing. Although previous investigations have identified a vacancy excess in MeV-implanted silicon, the investigations presented in this dissertation are unique in that they are designed to correlate the free-vacancy supersaturation with the vacancies in clusters. Free-vacancy (and interstitial) supersaturations were measured with Sb (B) dopant diffusion markers. Vacancies in clusters were profiled by Au labeling; a new technique based on the observation that Au atoms trap in the presence of open-volume defects. The experiments described in this dissertation are also unique in that they were designed to isolate the deep interstitial excess from interacting with the much shallower vacancy excess during post-implant thermal processing.
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Jeck, Jonathan. "Highly unsaturated dendritic and conjugated systems of silicon by multiple transfer of Si=Si units." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/39337.
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Stable disilenides, silicon analogues of vinyl anions, offer a valuable entry point to unsymmetrically substituted disilenes of the A2 Si=SiAB (substituents A ≠ B) form otherwise impossible to obtain. Disilenes, although kinetically stabilised by bulky substituents, readily react with a broad range of substrates consuming the silicon double bond in a multitude of addition reactions. This makes manipulations in the periphery of the disilene scaffold a challenging task. This thesis concentrates mainly on the synthetic approach to novel functionalised unsymmetrically substituted disilenes by reaction of a disilenide with suitable precursors and transformation of functionality in the presence of Si-Si double bonds. The second major topic is the preparation of extended (conjugated) systems with multiple Si=Si units using a disilenide as transfer reagent. Stable compounds featuring between one and six Si=Si units were obtained and fully characterised including para-(halosilanyl)phenyl disilenes, thiophenyl disilenes, aminophenyl disilenes as well as disilenyl functionalised amine- and silane-centred dendritic molecules. Spectroscopic data for each class of compounds is presented showing the influence of functional groups on the molecular properties, especially the HOMO-LUMO gap.
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Dufauquez, Christophe. "Production de particules chargées légères et multiplicités neutroniques associées dans les réactions p+(nat)Si et alpha+(nat)Si de 20 à 65 MeV." Université catholique de Louvain, 2005. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-06012006-114210/.
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Cette dissertation présente les résultats des mesures des sections efficaces inclusives de production des particules chargées légères (protons, deutons, tritons, 3He, alpha, 6Li, 7Li et 7Be) ainsi que les multiplicités neutroniques associées, relevés lors des réactions nucléaires induites par protons et alpha sur une cible de natSi. Ces mesures ont été réalisées auprès du cyclotron CYCLONE de Louvain-la-Neuve aux énergies de 26.5, 48.5 et 62.9 MeV pour les réactions (p, (nat)Si) et de 25.4, 45.5 et 57.8 MeV pour les réactions (alpha, (nat)Si). Le système de détection, original dans sa conception, a été assuré par 15 télescopes constitués d'un assemblage de jonctions silicium et de scintillateurs inorganiques CsI assurant une couverture angulaire de 0 à 360°. Toutes les particules chargées étudiées dans ce travail ont été identifiées sur base de l'information de leurs pertes d'énergie dans les différentes jonctions et par la technique de l'analyse en forme des signaux lumineux issus des CsI. La détection des neutrons a été assurée par le multi-détecteur à neutrons DEMON constitué de 81 scintillateurs organiques liquides. Ces neutrons ont été identifiés par la technique de l'analyse en forme du signal lumineux. L'énergie des neutrons a été déduite par mesure de leur temps de vol. Les distributions angulaires des pics élastiques et inélastiques de la diffusion des protons et des alpha sur le 28Si ont été confrontées aux prédictions des modèles Optique, DWBA et Canaux Couplés, utilisant différents potentiels optiques. Une comparaison des résultats expérimentaux avec ceux déjà publiés sur des réactions similaires ou comparables a également fait l'objet de ce travail. De plus, les résultats ont été confrontés à ceux des prédictions des codes de simulation GNASH et TALYS. Une attention particulière a été portée aux prédictions du code TALYS. Enfin, ce travail fournit une très large et très complète base de nouvelles données expérimentales qui constitue un atout majeur et bénéfique aussi bien dans l'amélioration des codes théoriques de simulation de ce type de réactions que dans les prédictions des dégâts radiatifs induits par les différents rayonnements ionisants dans les semi-conducteurs, en général, et les composants électroniques, en particulier.
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Bondarenko, Olesya. "IIIV/Si Nanoscale Lasers and Their Integration with Silicon Photonics." Thesis, University of California, San Diego, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3687359.
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<p> The rapidly evolving global information infrastructure requires ever faster data transfer within computer networks and stations. Integrated chip scale photonics can pave the way to accelerated signal manipulation and boost bandwidth capacity of optical interconnects in a compact and ergonomic arrangement. A key building block for integrated photonic circuits is an on-chip laser. In this dissertation we explore ways to reduce the physical footprint of semiconductor lasers and make them suitable for high density integration on silicon, a standard material platform for today's integrated circuits. We demonstrated the first room temperature metalo-dielectric nanolaser, sub-wavelength in all three dimensions. Next, we demonstrated a nanolaser on silicon, showing the feasibility of its integration with this platform. We also designed and realized an ultracompact feedback laser with edge-emitting structure, amenable for in-plane coupling with a standard silicon waveguide. Finally, we discuss the challenges and propose solutions for improvement of the device performance and practicality.</p>
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Matmon, Guy. "Terahertz sources based on silicon impurities and Si/SiGe heterostructures." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611664.
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Römer, Udo [Verfasser]. "Polycrystalline silicon/monocrystalline silicon junctions and their application as passivated contacts for Si solar cells / Udo Römer." Hannover : Technische Informationsbibliothek (TIB), 2016. http://d-nb.info/1096360942/34.
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Paukstis, Sarah Joan. "The spectroscopy of small silicon clusters Si₂X(X = N,O)." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/30309.
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Sun, Xiaochen. "Ge-on-Si light-emitting materials and devices for silicon photonics." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53254.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 202-211).<br>The rapid growing needs for high data transmission bandwidth challenge the metal interconnection technology in every area from chip-level interconnects to long distance communication. Silicon photonics is an ideal platform for the implementation of optical interconnection capable of high bandwidth and low power consumption by integrating electronic and photonic devices on silicon. Many optical components in silicon photonics have been extensively studied, among which a silicon-based laser is arguably the most challenging element. This thesis mainly focuses on using engineered germanium as the optically active material for silicon-based light emitters with many potential benefits: Si-CMOS compatibility (both material and processing), electrical injection capability, and direct gap emission at technologically important 1.55 pm telecommunication band. Tensile-strained n+ germanium is capable of behaving like a direct band gap material owing to the direct band gap shrinkage upon tensile strain and the state-filling in the indirect L valleys with extrinsic electrons from n-type dopants. Our theoretical calculation using a direct band-to-band transition model has shown great benefit of tensile strain and n-type doping on the direct gap optical gain characteristics. By considering free carrier absorption which dominates the optical loss we have proven net gain can be achieved in 0.25% tensile-strained Ge with n-type doping concentration in a range of 1019 to mid-1020 cm-3. The injection threshold of the net gain is about 1018 cm-3 which can readily be achieved with either optical pumping or electrical pumping.<br>(cont.) The net gain is in favor of the raise of temperature in a large injection range (threshold to mid-1019 cm-3) because of the increased number of high energy electrons in the direct F valley contributing to the direct band-to-band radiative recombination. We have successfully grown single crystalline germanium epitaxially on silicon with a two-step approach. Tensile strain between 0.2% and 0.25% is formed in germanium upon cooling from high growth temperature (or post-growth annealing temperature) to room temperature because of the larger thermal expansion coefficient of germanium compared to that of silicon. Phosphorus are in situ doped in germanium as n-type dopants during the epitaxial growth. By carefully adjusting the growth condition, we have obtained active doping concentration as high as 2 x 1019 cm-3. An in situ doping model built by considering the transportation processes and the reactions of phosphorus-containing species well explains the temperature dependence of the doping concentration. The deviation from the model while analyzing the influence of other growth parameters indicates possible compensation of the dopants. We used photoluminescence (PL) measurement to study to the optical properties of tensile-strained n+ germanium. Room temperature PL was observed from the epitaxial Geon-Si films near the direct gap wavelength of 1600nm. The direct gap PL spectrum exhibits Ge direct band-to-band optical transition properties. The direct gap PL intensity increases with n-type doping concentration as a result of the indirect valley state filling effect which increases the Fermi level leading to higher excited electron density in the direct F valley.<br>(cont.) The direct gap PL intensity also increases with temperature because of the increased number of high energy direct F valley electrons thermally activated from the indirect L valleys. This effect make germanium light emission robust to inevitable heating effects during operation in practice. The "unusual" n-type doping and temperature dependences of PL are unique properties of the direct gap emission from indirect bandgap Ge. There effects are predicted by our theory, and the observation of these effect in experiments is a strong evidence of validity of the theory. In order to study the electrical injection in Ge, we fabricated Si/Ge/Si heterojunction light emitting diodes (LEDs). Room temperature direct gap electroluminescence (EL) are observed from these diodes. It is the first observation of EL from Ge. The direct gap EL spectrum matches the PL spectrum underlying the same injection mechanism in both electrical pumping and optical pumping. The direct gap EL intensity increases superlinearly with injection current because of the raised quasi Fermi level leading to the increased fraction of the injected electrons in the direct F valley. The internal quantum efficiency of the LEDs is on the order of 10-3 consistent with the finite-element simulation results. This EL efficiency can be improved to 10-1 if doping germanium active region with n-type. The design of n+Ge based heterojunction diodes has been simulated, and an optimal design has been proposed based on the simulation. We used pump-probe spectroscopy to measure material gain of the tensile-strained n+ germanium.<br>(cont.) We have observed an optical bleaching effect, the reduction of absorption under pumping and the prelude of optical gain, above the direct band gap energy from the engineered Ge. The population inversion factor increases with the n-type doping concentration in Ge, as predicted by the theory. By increasing the injection level using a Ge micro-mesa structure carrier confinement, we have successfully demonstrated the net gain, i.e. population inversion. A peak gain of 50 ± 25 cm-1 at 1605 nm has been obtained from the experiment. It is the first report of observing net gain from germanium.<br>by Xiaochen Sun.<br>Ph.D.
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Lea, Erik. "Photoelastic waveguides in bulk silicon and Si(1-x)Gex heterostructures." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/843947/.
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A theoretical and experimental investigation into the characteristics of photoelastic optical waveguides in bulk silicon and Si1-xGex/Si heterostructures is presented. This is the first experimental demonstration of this type of waveguide in these material structures. The bulk silicon structures are also the first demonstration of channel waveguides defined using only photoelastic confinement. The photoelastic constants of silicon and Si1-xGex, which give the change in refractive index with strain, are calculated from the strain-induced shifts in the energy band structure of silicon and germanium which modifies their extinction coefficient, from which the strain-induced refractive index changes are found from the Kramers-Kronig relations. A finite element model of the waveguide structures is presented which uses the calculated photoelastic constants to determine the refractive index profiles of the waveguides. Subsequently, finite difference calculations are used to calculate the optical mode profiles of the waveguides. Photoelastic waveguides are fabricated by depositing SiNy stressor films onto bulk silicon and Si1-xGex/Si heterostructures which are subsequently cleaved and polished to produce waveguide facets before narrow stressor stripes are defined from the SiNy films using photolithography and wet etching. The characteristics of the waveguides are investigated at wavelengths of 1.15mum and 1.523mum. Measurements show that there is always one guiding region outside each edge of the stressor stripe. The Si1-xGex/Si heterostructures also allow a third mode to be confined under the centre of the stressor stripe, and the relative intensity and the distance between the guided modes is controlled by the stripe width, in good accordance with the modelling results. These structures are interesting in that up to three guiding regions can be defined by the deposition of one stressor stripe on the waveguide surface, which provides a particularly simple and compact way of fabricating waveguide couplers. An interferometer is used to study the force generated by the SiNy stressor layers. It is shown that the as-deposited stressors produce low and poorly defined stresses, although significant forces of up to 2-3.106 dyn/cm are measured after rapid thermal annealing of the structures. Annealing of photoelastic waveguides in bulk silicon show a corresponding increase in photoelastic confinement which produces waveguides with excess losses of down to 4.3dB/cm. Photoelastic waveguides in Si1-xGex/Si heterostructures, due to the additional confinement from the heterojunction, are reported with zero excess losses. At 1.15mum, the band-edge absorption increases the waveguide propagation losses by up to several dB/cm, and the waveguides show multimode behaviour, making these structures unsuitable for applications at this wavelength. At 1.523mum, however, measurements show low excess propagation losses and single-mode behaviour, and they exhibit a low degree of birefringence. The simple fabrication process and compact design of these structures make them appropriate for optoelectronic intragration, and several possible applications for photoelastic waveguides in optical devices are suggested.
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Ke, Jiaxin. "Stress engineering with silicon nitride stressors for Ge-on-Si lasers." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62116.
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Silicon compatible lasers are in great need for applications such as on-chip and short-reach optical interconnects. Although InAs/GaAs quantum dot lasers monolithically grown on Si have been realized and are well-performed, due to material contamination issues, it is time and cost intensive for those III-V materials to enter mainstream Si processing facilities. Germanium(Ge)-on-Silicon(Si) laser is promising as a solution to solve the Si-compatible laser problem as it is compatible with Si processing. So far, the main problems in Ge lasers are that they have a high threshold current density and low efficiency. Laser structure designs with top and side silicon nitride stressors were proposed in this work and shown to be effective in reducing the threshold current (Ith) and improving the wall-plug efficiency (ηwp) of Ge-on-Si lasers. Side stressors turned out to be a more efficient way to increase ηwp than using the top and side stressors together. With the side stressors and geometry optimizations, a maximum ηwp of 34.8% and an Ith of 36 mA (Jth of 27 kA/cm²) were achieved with a defect limited carrier lifetime (𝜏𝑝,𝑛) of 1 ns. With 𝜏𝑝,𝑛 being 10 𝑛𝑠 , an Ith of 4 mA (Jth of 3 kA/cm²) and a ηwp of 43.8% were achieved. These are tremendous improvements from cases without any stressors. Compared to other stress introduction methods, such design is much more suitable for Ge laser structure implementation. These results provide a strong support to the Ge-on-Si laser technology and create an effective way to improve the Ge laser performance.<br>Applied Science, Faculty of<br>Materials Engineering, Department of<br>Graduate
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Valalaki, Aikaterini. "Etude des propriétés thermoélectriques et d’isolation thermique du Si poreux et Si nanocristallin." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT031/document.
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Cette thèse a été consacrée à l’étude du Si poreux comme matériaux à faible conductivité thermique (k) pour application aux dispositifs thermoélectriques à base de Si. D’autres paramètres thermoélectriques, comme par exemple le coefficient Seebeck de ce matériau, ont été également étudiés.Si poreux est un matériau complexe composé de nanostructures de Si séparées de vide. Quand la porosité est élevée, sa conductivité thermique est bien inférieure à celle de Si cristallin. Nous avons étudié la conductivité thermique de Si poreux de différentes morphologies et porosités dans la gamme de températures 4.2-350K. Les mesures à T<20K sont les premières dans la bibliographie et ont montré une saturation de k en fonction de T pour ces températures. A des températures supérieures à 20K, k augmente régulièrement avec la température. La dépendance de température de k de Si poreux a été interprétée en considérant des modèles théoriques, basées sur la nature “fractal” de Si poreux. Nous avons calculé la dimension fractale de Si poreux par des images de microscopie électronique à balayage (SEM) et l’algorithme de “box counting”.Deux méthodes différentes ont été utilisées pour mesurer k: la méthode à courant direct (dc) combinée avec une analyse FEM et la méthode 3ω. Nous avons proposé deux approches améliorées pour extraire k du signal de potentiel 3ω en fonction de la fréquence. La première considère l’accord des résultats expérimentaux avec la solution asymptotique intégrale de la formule de Cahill, et la seconde fait une analyse des résultats expérimentaux en solvant l’équation temporelle de transfert de chaleur par des éléments finis. Plus précise est la méthode 3ω combinée avec des éléments finis. Les résultats correspondants sont en bon accord avec ceux obtenus par la méthode dc.Nous avons aussi étudié le Si poreux comme matériau thermoélectrique. Dans ce cas, le Si poreux peut être intéressant si il a une faible porosité, car le matériau à haute porosité est très résistive. Dans ce but, nous avons déterminé le coefficient Seebeck (S) des membranes de Si poreux de différentes porosités dans la gamme 40-84%, en utilisant un dispositif de mesure spécialement développé à cet effet. Pour des échantillons de porosité 51%, la valeur de coefficient S est de 1mV/K, bien supérieure à celle le Si cristallin. La dépendance de S de la porosité n’est pas monotone, et ceci est attribué à une combinaison des effets de filtrage d’énergie, des collisions des phonons et interactions phonon-porteurs électriques. Les résultats obtenus sont basées sur des mesures de photoluminescence (PL) et observations microscopiques à transmission (TEM). Nous avons enfin conclue que, malgré le coefficient S très élevé, le Si poreux n’est pas adéquat comme matériau thermoélectrique à cause de sa faible conductivité électrique, qui diminue en augmentant la porosité à cause de la résultante déplétion de porteurs.Nous avons aussi étudié des films minces polycristallins dopés avec du Bore. Ces films sont très intéressants comme matériaux thermoélectrique, car ils sont compatibles avec les procédés de fabrication des circuits intégrés de Si. Leur performance thermoélectrique est améliorée par diminution de la taille des grains. Des films minces polycristallins d’épaisseur entre 100 et 500nm ont été étudiés. Tous leurs paramètres thermoélectriques ont été mesurés et nous avons trouvé que le facteur de performance thermoélectrique zT augmente d’un facteur 3 en diminuant l’épaisseur de 500 à 100nm ceci étant attribué à la diminution de la taille des grains dans les films, conduisant à zT = 0.033, qui est la meilleure valeur reporté dans la littérature.Ce résultat compétitif augmente le potentiel d’utilisation des films polycristallins dans des dispositifs thermoélectriques efficaces, compatibles à la technologie de Si<br>This thesis is devoted to the thermal conductivity and other thermoelectric properties of porous silicon (PSi) and thin polycrystalline Si films (thickness: 100-500 nm).PSi is a complex material composed of a Si skeleton of interconnected nanowires and dots, separated by voids. When it is highly porous, its thermal conductivity is very low, even below that of the amorphous Si. This makes it a good material for use as a thermal isolation platform on the Si wafer. In addition, its Seebeck coefficient is much higher than that of bulk c-Si.We studied k of PSi layers with different morphologies and porosities, in the temperature range 4.2-350K. The measurements below 20K are the first reported in the literature. A plateau-like dependence on temperature was observed for T below 20K, while above this temperature a monotonic increase with T is observed. The observed behaviour was interpreted using known theoretical models, based mainly on the fractal nature of PSi. PSi was characterized as a fractal material by calculating its fractal dimension using SEM images and the box counting algorithm.Two different methods were used to determine porous Si thermal conductivity: the DC method combined with FEM analysis and the 3ω method. Concerning the 3ω method, two improved approaches were proposed for extracting k from the 3ω voltage as a function of frequency: the first uses a fitting of the experimental data to the asymptotic solution of the Cahill’s integral formula, and the second is based on the analysis of the experimental data by combining them with a solution of the transient heat transfer equation using FEM analysis. The results in this second case were more accurate and in very good agreement with the DC method.We also measured the Seebeck coefficient (S) of PSi membranes with porosities 40-84% using a home-built setup, which was fabricated, calibrated and tested within this thesis. A value as high as 1mV/K was obtained for the 51% porosity sample. An anomalous porosity dependence of S was obtained, which was attributed to the interplay between energy filtering, phonon scattering and phonon drag effects. The results were explained by combining them with PL and TEM measurements, used for the determination of nanocrystal sizes. We concluded that, despite of the extremely low k and the high S of PSi, the material with the studied high porosities is not adequate for use as a “good thermoelectric” material, because of its significantly low electrical conductivity, which decreases with increasing porosity, resulting from carrier depletion during formation.We also studied the thermoelectric properties of thin, boron-doped, polycrystalline silicon films, which are much more attractive for use as Si-based thermoelectrics than porous Si. Their thermoelectric performance is improved by decreasing film thickness, due to a decrease in polysilicon grain size. Thin films with thickness between 100-500nm were investigated. We measured their thermal conductivity, resistivity and Seebeck coefficient and extracted their thermoelectric figure of merit, which showed threefold increase by reducing film thickness down to 100nm. A value as high as 0.033 was achieved, which is the highest reported in the literature so far for boron-doped polysilicon films at room temperature. This increase is attributed to a decrease in the grain size of the material. The obtained value shows the interest of nanocrystalline Si films for integration in efficient Si-based thermoelectric generators, compatible with CMOS processing
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Peršun, Marijan. "Scaling of the Silicon-on-Insulator Si and Si1-xGex p-MOSFETs." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/4934.
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Two-dimensional numerical simulation was used to study the scaling properties of SOI p-MOSFETs. Based on the design criteria for the threshold voltage and DIBL, a set of design curves for different designs was developed. Data for subthreshold slope, SCE and threshold voltage sensitivity to silicon film thickness are also given. Results show that short-channel effects can be controlled by increasing the doping level or by thinning the silicon film thickness. The first approach is more effective for p+ gate design with high body doping, while the second approach is much more effective for n+ gate design with low body doping. Then+ gate design is more suited for the design of fully depleted (FD) devices since we need to keep the doping low to minimize the threshold adjustment implant dose and to use thin silicon films to control the SCE. The design of both p-MOSFET and Si 1-xGex p-MOSFET requires the implantation for the threshold voltage adjustment. The p+ gate design is more suited for the partially depleted (PD) or near-fully depleted device design since we need to use high doping for the threshold voltage adjustment and this results in large threshold voltage sensitivity to silicon film thickness for FD devices. The design of Si SOI p-MOSFET is done by properly adjusting the body doping. For the Si1-xGex SOI p-MOSFET large reduction in VTH requires large body doping. This increases the parasitic capacitances and slows down the device.
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Delvigne, Camille. "The Archaean silicon cycle insights from silicon isotopes and Ge/Si ratios in banded iron formations, palaeosols and shales." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209652.
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The external silicon cycle during the Precambrian (4.5-0.5 Ga) is not well understood despite its key significance to apprehend ancient dynamics at the surface of the Earth. In the absence of silicifying organisms, external silicon cycle dramatically differs from nowadays. Our current understanding of Precambrian oceans is limited to the assumption that silicon concentrations were close to saturation of amorphous silica. This thesis aims to bring new insights to different processes that controlled the geochemical silicon cycle during the Archaean (3.8-2.5 Ga). Bulk rock Ge/Si ratio and Si isotopes (δ30Si) offer ideal tracers to unravel different processes that control the Si cycle given their sensitivity to fractionation under near-surface conditions. <p>First, this study focuses on Si inputs and outputs to ocean over a limited time period (~2.95 Ga Pongola Supergroup, South Africa) through the study of a palaeosol sequence and a contemporaneous banded iron formation. The palaeosol study offers precious clues in the comprehension of Archaean weathering processes and Si transfer from continent to ocean. Desilication and iron leaching were shown to be the major Archaean weathering processes. The occurrence of weathering residues issued of these processes as major component in fine-grained detrital sedimentary mass (shales) attests that identified weathering processes are widely developed and suggest an important dissolved Si flux from continent to the ocean. In parallel, banded iron formations (BIFs), typically characterised by alternation of iron-rich and silica-rich layers, represent an extraordinary record of the ocean-derived silica precipitation throughout the Precambrian. A detailed study of a 2.95 Ga BIF with excellent stratigraphic constraints identifies a seawater reservoir mixed with significant freshwater and very limited amount of high temperature hydrothermal fluids as the parental water mass from which BIFs precipitated. In addition, the export of silicon promoted by the silicon adsorption onto Fe-oxyhydroxides is evidenced. Then, both Si- and Fe-rich layers of BIFs have a common source water mass and a common siliceous ferric oxyhydroxides precursor. Thus, both palaeosols and BIFs highlight the significance of continental inputs to ocean, generally under- estimated or neglected, as well as the close link between Fe and Si cycles. <p>In a second time, this study explores secular changes in the Si cycle along the Precambrian. During this timespan, the world ocean underwent a progressive decrease in hydrothermal inputs and a long-term cooling. Effects of declining temperature over the oceanic Si cycle are highlighted by increasing δ30Si signatures of both chemically precipitated chert and BIF through time within the 3.8-2.5 Ga time interval. Interestingly, Si isotope compositions of BIF are shown to be kept systematically lighter of about 1.5‰ than contemporaneous cherts suggesting that both depositions occurred through different mechanisms. Along with the progressive increase of δ30Si signature, a decrease in Ge/Si ratios is attributed to a decrease in hydrothermal inputs along with the development of large and widespread desilication during continental weathering.<p><p><p>Le cycle externe du silicium au précambrien (4.5-0.5 Ga) reste mal compris malgré sa position clé dans la compréhension des processus opérant à la surface de la Terre primitive. En l’absence d’organismes sécrétant un squelette externe en silice, le cycle précambrien du silicium était vraisemblablement très différent de celui que nous connaissons à l’heure actuelle. Notre conception de l’océan archéen est limitée à l’hypothèse d’une concentration en silicium proche de la saturation en silice amorphe. Cette thèse vise à une meilleure compréhension des processus qui contrôlaient le cycle géochimique externe du silicium à l’archéen (3.8-2.5 Ga). Dans cette optique, le rapport germanium/silicium (Ge/Si) et les isotopes stables du silicium (δ30Si) représentent des traceurs idéaux pour démêler les différents processus contrôlant le cycle du Si. <p>Dans un premier temps, cette étude se focalise sur les apports et les exports de silicium à l’océan sur une période de temps restreinte (~2.95 Ga Pongola Supergroup, Afrique du Sud) via l’étude d’un paléosol et d’un dépôt sédimentaire de précipitation chimique quasi-contemporain. L’étude du paléosol apporte de précieux indices quant aux processus d’altération archéens et aux transferts de silicium des continents vers l’océan. Ainsi, la désilicification et le lessivage du fer apparaissent comme des processus majeurs de l’altération archéenne. La présence de résidus issus de ces processus d’altération en tant que composants majeurs de dépôts détritiques (shales) atteste de la globalité de ces processus et suggère des flux significatifs en silicium dissout des continents vers l’océan. En parallèle, les « banded iron formations » (BIFs), caractérisés par une alternance de niveaux riches en fer et en silice, représentent un enregistrement extraordinaire et caractéristique du précambrien de précipitation de silice à partir de l’océan. Une étude détaillée d’un dépôt de BIFs permet d’identifier une contribution importante des eaux douces dans la masse d’eau à partir de laquelle ces roches sont précipitées. Par ailleurs, un mécanisme d’export de silicium via absorption sur des oxyhydroxydes de fer est mis en évidence. Ainsi, les niveaux riches en fer et riche en silice constituant les BIFs auraient une même origine, un réservoir d’eau de mer mélangée avec des eaux douces et une contribution minime de fluides hydrothermaux de haute température, et un même précurseur commun. Dès lors, tant les paléosols que les BIFs mettent en évidence l’importance des apports continentaux à l’océan, souvent négligés ou sous estimés, ainsi que le lien étroit entre les cycles du fer et du silicium.<p>Dans un second temps, cette étude explore l’évolution du cycle du silicium au cours du précambrien. Durant cette période, l’océan voit les apports hydrothermaux ainsi que sa température diminuer. Dans l’intervalle de temps 3.8-2.5 Ga, les effets de tels changements sur le cycle du silicium sont marqués par un alourdissement progressif des signatures isotopiques des cherts et des BIFs. Le fort parallélisme entre l’évolution temporelle des compositions isotopiques des deux précipités met en évidence leur origine commune, l’océan. Cependant, les compositions isotopiques des BIFs sont systématiquement plus légères d’environ 1.5‰ que les signatures enregistrées pas les cherts. Cette différence est interprétée comme le reflet de mécanismes de dépôts différents. L’alourdissement progressif des compositions isotopiques concomitant à une diminution des rapports Ge/Si reflètent une diminution des apports hydrothermaux ainsi que la mise en place d’une désilicification de plus en plus importante et/ou généralisée lors de l’altération des continents.<p><br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
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Al-Helal, Kawther. "New approaches to casting hypereutectic Al-Si alloys to achieve simultaneous refinement of primary silicon and modification of eutectic silicon." Thesis, Brunel University, 2013. http://bura.brunel.ac.uk/handle/2438/8167.
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Hypereutectic Al-Si alloys are of increasing interest for applications that require a combination of light weight and high wear resistance, such as pistons, liner-less engine blocks and pumps. The wear resistance of this class of alloys is due to the presence of hard primary Si particles formed during casting. The objective of this work was to develop one or more methods of refining primary silicon in cast hypereutectic Al-Si alloys to compete with the conventional process of adding phosphorous and to achieve the simultaneous modification of silicon in the Al-Si eutectic. A robust sampling/casting technique was developed to minimise macro-segregation of primary silicon during solidification of hypereutectic Al-Si alloys by using water cooled steel mould with cooling rate in excess of 15 K/s. The morphology of silicon phases was found to change with increasing melt temperature and cooling rate. The high cooling rate and superheat temperature produces a good distribution of polyhedral primary silicon particles in a refined lamellar eutectic matrix in solidification of commercial purity Al-Si alloys. Removing Ca by fluxing with K2SiF6 prior to casting can improve the refinement and modification effect of Mg and Sb respectively. Effects of various inoculants were studied. Microstructural analysis showed that Mg and ZnS refined primary Si whereas MgO, CaO and Na2S coarsened the primary Si together with a modification effect on the eutectic Si. Adding Zn had no effect on morphology of Si phases. Refinement of both primary and eutectic silicon phases was observed for the Al-15Si alloy with Mg content ≤ 0.3 wt%. P-doped γ-Al2O3 was found to be a potent substrate to nucleate primary silicon whilst good modification of the eutectic matrix is retained during solidification of hypereutectic Al-Si alloys. On using P-doped γ-Al2O3 could be a perfect and clean source of P without additional impurities. A new solid-liquid duplex casting process was devised to achieve simultaneous refinement and modification of Si phases in hypereutectic Al-Si alloys with improvement in mechanical properties. The static mechanical properties of Al-Si produced by the solid-liquid duplex casting process are significantly better than conventionally cast untreated Al-Si and slightly better than conventionally cast Al-Si treated with P and/or Sr. A novel Al-ZnS master alloy was developed by in situ reaction of Zn and Na2S in the Al melt. The results from this study leave little doubt that this novel Al-ZnS master alloy is a promising refiner in solidification of hypereutectic Al-Si alloys. It refines primary silicon to the same extent as that achieved by adding P via Cu-P following the same refinement mechanism.
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Ding, Kaining Verfasser], Uwe [Akademischer Betreuer] [Rau, and Rainer [Akademischer Betreuer] Waser. "Nanostructured Si-alloys for silicon solar cells / Kaining Ding ; Uwe Rau, Rainer Waser." Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://d-nb.info/1156536499/34.
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Tegegne, Zerihun. "SiGe/Si Microwave Photonic devices and Interconnects towards Silicon-based full Optical Links." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1070/document.
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Avec la croissance forte de ces dernières années des objets connectés les technologies de communication optique et radio voient davantage d’opportunités de s’associer et se combiner dans des technologies bas-couts Photoniques-Microondes (MWP). Les réseaux domestiques en sont un exemple. La bande millimétrique notamment, de 57GHz à 67GHz, est utilisé pour contenir les exigences des communications sans fils très haut-débit, néanmoins, la couverture de ces systèmes wireless est limitée en intérieur (indoor) essentiellement à une seule pièce, à la fois du fait de l’atténuation forte de l’atmosphère dans cette bande de fréquence, mais aussi de fait de l’absorption et de la réflexion des murs. Ainsi il nécessaire de déployer une infrastructure pour diffuser l’information au travers d’un système d’antennes distribuées. Les technologiques optiques et photoniques-microondes sont une des solutions envisagées. Les technologies MWP se sont également étendues et couvrent une gamme très large d’applications incluant les communications mobiles 5G, les analyses biomédicales, les communications courtes-distances (datacom), le traitement de signal par voie optique et les interconnexions dans les véhicules et aéronefs. Beaucoup de ces applications requièrent de la rapidité, de la bande-passante et une grande dynamique à la fois, en même temps de demander des dispositifs compacts, légers et à faible consommation. Le cout d’implémentation est de plus un critère essentiel à leur déploiement, en particulier dans l’environnement domestique ainsi que dans d’autres applications variées des technologies MWP.Ce travail de thèse vise ainsi le développement de composants photonique-microondes (MPW) intégrés en technologie BiCMOS ou Bipolaire SiGe/Si, à très bas coût, incluant les phototransistors bipolaires à hétérojonctions (HPT) SiGe/Si, les Diodes Electro-Luminescentes (LED) Si et SiGe, ainsi que l’intégration combinées des composants optoélectroniques et microondes, pour l’ensemble des applications impliquant des courtes longueurs d’ondes (de 750nm à 950nm typiquement).Ces travaux se concentrent ainsi sur les points suivants :La meilleure compréhension de phototransistors SiGe/Si latéraux et verticaux conçus dans une technologie HBT SiGe 80GHz de Telefunken GmbH. Nous traçons des conclusions sur les performances optimales du phototransistor. Les effets de photodétection du substrat et de la dispersion spatiale des flux de porteurs sont analysés expérimentalement. Cette étude aide à développer des règles de dessin pour améliorer les performances fréquentielles du phototransistor HPT pour les applications visées.Dans l’objectif de développer de futures interconnexions intra- et inter- puces, nous concevons des lignes de transmissions faibles-pertes et des guides d’ondes optiques polymères sur Silicium faible résistivité. Il s’agit d’une étape afin d’envisager des plateformes Silicium dans lesquelles les HPT SiGe pourront potentiellement être intégrés de manière performante à très bas coût avec d’autres structures telles que des lasers à émission par la surface (VCSEL), afin de construire un transpondeur optique complet sur une interface Silicium. Le polymère est utilisé comme une interface diélectrique entre les lignes de transmission et le substrat, pour les interconnexions électriques, et pour définir le gain du guide d’onde optique dans les interconnexions optiques.La conception, la fabrication et la caractérisation du premier lien photonique-microonde sur puce Silicium sont menées en se basant sur la même technologie HBT SiGe 80GHz de Telefunken dans la gamme de longueur d’onde 0,65µm-0,85µm. Ce lien optique complétement intégré combine des LEDS Silicium en régime d’avalanche (Si Av LED), des guides d’ondes optiques Nitrure et Silice ainsi qu’un phototransistor SiGe. Un tel dispositif pourrait permettre d’accueillir à l’avenir des communications sur-puce, de systèmes micro-fluidiques et des applications d’analyse biochimiques<br>With the recent explosive growth of connected objects, for example in Home Area Networks, the wireless and optical communication technologies see more opportunity to merge with low cost MicroWave Photonic (MWP) technologies. Millimeter frequency band from 57GHz to 67GHz is used to accommodate the very high speed wireless data communication requirements. However, the coverage distance of these wireless systems is limited to few meters (10m). The propagation is then limiting to a single room mostly, due to both the high propagation attenuation of signals in this frequency range and to the wall absorption and reflections. Therefore, an infrastructure is needed to lead the signal to the distributed antennas configuration through MWP technology. Moreover, MWP technology has recently extended to address a considerable number of novel applications including 5G mobile communication, biomedical analysis, Datacom, optical signal processing and for interconnection in vehicles and airplanes. Many of these application areas also demand high speed, bandwidth and dynamic range at the same time they require devices that are small, light and low power consuming. Furthermore, implementation cost is a key consideration for the deployment of such MWP systems in home environment and various integrated MWP application.This PhD deals with very cheap, Bipolar or BiCMOS integrated SiGe/Si MWP devices such as SiGe HPTs, Si LEDs and SiGe LEDs, and focused on the combined integration of mm wave and optoelectronic devices for various applications involving short wavelength links (750nm to 950nm).This research focused on the study of the following points:The better understanding of vertical and lateral illuminated SiGe phototransistors designed in a 80 GHz Telefunken GmbH SiGe HBT technology. We draw conclusions on the optimal performances of the phototransistor. The light sensitive Si substrate and two-dimensional carrier flow effects on SiGe phototransistor performance are investigated. This study helps to derive design rules to improve frequency behavior of the HPT for the targeted applications.For future intra /inter chip hybrid interconnections, we design polymer based low loss microwave transmission lines and optical waveguides on low resistive silicon substrate. It is a step to envisage further Silicon based platforms where SiGe HPT could be integrated at ultra-low cost and high performances with other structures such high-speed VCSEL to build up a complete optical transceiver on a Silicon optical interposer. The polymer is used as dielectric interface between the line and the substrate for electrical interconnections and to design the core and cladding of the optical waveguide.The design, fabrication and characterization of the first on-chip microwave photonic links at mid infrared wavelength (0.65-0.85μm) based on 80 GHz Telefunken GmbH SiGe HBT technological processes. The full optical link combines Silicon Avalanche based Light Emitting Devices (Si Av LEDs), silicon nitride based waveguides and SiGe HPT. Such device could permit hosting microfluidic systems, on chip data communication and bio-chemical analysis applications
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Hughes, Harold. "Si isotopes in tropical rivers as a proxy of the continental silicon cycle." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209808.
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Silicon (Si) is one of the most abundant elements in the dissolved phase in rivers and is a key nu-trient in riverine and marine ecosystems. The continental cycle of Si is complex and involves interactions with many secondary reservoirs such as clay minerals and biogenic silica (BSi), making the Si fluxes hard to constrain. Stable isotopes provide a way to trace and describe element cycling. The natural isotopic fractionations that accompany the transfer of the element from one reservoir to another lead to specific isotopic signatures that can be used to reconstruct its source and the pathway during its biogeochemical cycle. The aim of this thesis is therefore to explore the potential of Si isotopes as a tracer of the factors controlling the dissolved Si (DSi) concentration in rivers and more specifically in tropical rivers.<p>Key issues treated in this thesis are the improvement of our understanding of 1° the spatial and seasonal variability of Si isotopic signatures in rivers, 2° the biological influence on the riverine isotopic signatures and on DSi and BSi fluxes, and 3° the impact of the type of weathering on the riverine isotope signatures.<p>The isotopic composition of different tropical basins such as the Congo River (Central Africa), the Tana River (Kenya), the Amazon (South America) and its tributaries, were determined along with other physico-chemical parameters. In order to achieve this, the water sample purification processing, necessary before isotope analyses, required specific improvements that are also pre-sented here. The average of all the riverine δ30Si signatures available so far is +1.11 ‰ (n = 253). The impact of diatom growth on the isotopic signatures of the rivers can be clearly shown in the different systems studied, and especially in the Congo River where the isotopic signature could be used in order to estimate the diatom production. The impact of anthropic perturbations through dam construction is also clearly shown in the Tana River. On a global scale the biological influ-ence on the riverine isotopic signatures is estimated to induce an increase of 0.18 ‰ of the δ30Si signature in rivers. This study also confirms the preponderant influence of weathering and secondary clay formation on dissolved Si isotope signatures in the studied rivers. Finally, isotopic signatures from these rivers are compared to data available for other rivers around the world in order to draw large trends on a global scale. <p>/<p>Le silicium (Si) est l’un des éléments les plus abondants sous forme dissoute dans les rivières et est un nutriment fondamental tant dans les rivières que dans les écosystèmes marins. Le cycle continental du Si est complexe et inclut des interactions avec de nombreux réservoirs secondaires, comme les argiles et la silice biogénique (BSi), rendant les flux de Si difficiles à quantifier. Les isotopes stables fournissent un moyen de tracer et de décrire le cycle d’un élément. Le fractionnement isotopique qui accompagne le transfert de l’élément d’un réservoir à un autre induit des signatures isotopiques spécifiques qui peuvent être utilisées pour retracer la source et la trajectoire suivie par cet élément au cours de son cycle biogéochimique. Le but de cette thèse est d’explorer le potentiel des isotopes du Si en tant qu’indicateur des facteurs contrôlant la concentration en Si dissous (DSi) dans les rivières et plus spécifiquement dans les rivières tropicales.<p>Les questions principales traitées dans cette thèse sont l’amélioration des connaissances de :1° la variabilité spatiale et saisonnière des signatures isotopiques du Si dans les rivières, 2° l’influence biologique sur les signatures isotopiques des rivières et sur les flux de DSi et BSi et 3° l’impacte du type d’altération sur les signatures isotopiques des rivières. <p>Les compositions isotopiques de différents bassins tropicaux tels que le Fleuve Congo (Afrique Centrale), le Fleuve Tana (Kenya), l’Amazone (Amérique du Sud) et ses principaux affluents ont été déterminées en même temps que d’autres paramètres physicochimiques. Pour ce faire, le pro-cédé de purification des échantillons d’eau, préalable aux analyses isotopiques, a nécessité des améliorations spécifiques qui sont également présentées ici. La moyenne de toutes les signatures δ30Si accessibles à l’heure actuelle est de +1.11 ‰ (n = 253). L’impact de la croissance des diatomées sur les signatures isotopiques des rivières est démontré dans les différents systèmes étudiés, spécialement pour le Fleuve Congo où la signature isotopique a pu être utilisée afin de déterminer la production de diatomées. L’influence de perturbations anthropiques telles que la construction de barrages a pu être démontrée pour le Fleuve Tana. À l’échelle globale, on estime que l’influence biologique sur la signature isotopique des rivières mène à une augmentation de 0.18 ‰ de la signature δ30Si moyenne des rivières. Cette étude confirme également l’influence prépondérante de l’altération et de la formation d’argiles secondaires sur les signatures isotopiques du DSi dans les rivières étudiées. Enfin, les signatures isotopiques de ces rivières sont comparées aux données accessibles pour d’autres rivières à travers le monde afin d’en déduire les grandes tendance à l’échelle mondiale.<p><br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
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Ding, Kaining [Verfasser], Uwe [Akademischer Betreuer] Rau, and Rainer [Akademischer Betreuer] Waser. "Nanostructured Si-alloys for silicon solar cells / Kaining Ding ; Uwe Rau, Rainer Waser." Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://nbn-resolving.de/urn:nbn:de:hbz:82-rwth-2015-010651.
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Quinci, Thomas. "Composant photovoltaïque innovant à base d’hétérojonction GaP/Si." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0016/document.
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L’objectif de ce travail de thèse a été d’étudier une alternative à la cellule photovoltaïque à hétérojonction classique de silicium amorphe/cristallin avec un matériau (GaP) qui permettrait une amélioration de rendement grâce à ses propriétés optiques et électriques. L’étude du potentiel des hétérojonctions GaP/Si pour des applications PV nous a amené à étudier chacun des aspects critiques inhérents à leur réalisation. La préparation chimique de la surface des substrats et les mécanismes qui contrôlent la structuration de la surface de Si(100) ont été étudiés afin d’obtenir une surface de silicium mono-domaine (à marches diatomiques) et faiblement rugueuse par homoépitaxie (dépôts par UHV-CVD). Cette étude a été complétée par l’étude de l’influence de la préparation de surface (préparation chimique et homoépitaxie) du substrat sur la qualité cristalline du GaP déposé en deux étapes par MEE et MBE. La croissance de GaP par MEE a par la suite été effectuée sur des substrats de Si(100) ayant uniquement subi une préparation chimique de surface. Les paramètres de la séquence de croissances MEE ont été étudiés et ajustés afin d’optimiser la phase de nucléation du GaP. La qualité structurale des dépôts a été évaluée par des caractérisations par AFM et DRX. Les couches minces de faibles épaisseurs (20nm) présentent une faible rugosité de surface équivalente à une homoépitaxie et une fraction volumique de MTs inférieure à la limite de détection. La croissance MEE permet d’assurer une nucléation 2D. Cependant les caractérisations par TEM et STM révèlent la présence de parois d’antiphase. En parallèle, la simulation de structures HET GaP/Si (effectuée grâce au programme AFORS-HET) et la réalisation de diodes et de démonstrateurs cellules GaP/Si ont permis de démontrer les optimisations apportées par l’utilisation d’un émetteur de GaP. Ces composants ont été étudiés par caractérisations optiques et électriques. Nous avons constaté une limitation des performances due à la présence de pièges à l’interface et dans le volume. Ces différentes études ont donc permis d’identifier les verrous technologiques à lever pour exploiter pleinement les cellules à hétérojonctions GaP sur silicium afin d’obtenir des hauts rendements photovoltaïques<br>The main objective of this thesis is to study an alternative to conventional amorphous/crystalline silicon heterojunction solar cell using gallium phosphide (GaP) as an emitter layer. This would allow a performance improvement because of its optical and electrical properties. The potential of GaP/Si heterojunction solar cells have been evaluated by studying each of the critical issues inherent to their fabrication process. The chemical preparation of the substrates surface and the mechanisms controling the structure of the Si (100) surface have been studied in order to obtain a single domain silicon surface (with diatomic steps) and slightly roughened by homoepitaxy (UHV-CVD). This work was completed by the study of the impact of surface preparation (chemical preparation and homoepitaxy) of the substrate on the crystalline quality of GaP deposited in two steps by MBE and MEE. The growth of GaP by MEE was subsequently carried out on Si(100) substrates having only undergone a chemical surface preparation. MEE growth sequence parameters were studied and adjusted to optimize GaP nucleation. The structural quality of the thin films was evaluated by AFM and XRD characterizations. Thin films of 20 nm have lower surface roughness equivalent to an homoepitaxy and a volume fraction of MTs below the detection limit. The MEE growth ensures a 2D nucleation. However, TEM and STM characterizations reveal the presence of antiphase boundaries. In parallel, simulations of the structure HET GaP/Si (with AFORS-HET) have been performed to evaluate the potential of the structure. First, diodes and demonstrator cells with GaP/Si junction have been fabricated and optically/electrically characterized. Limitations in performance due to the presence of traps at the interface and silicon volume degradation have been observed. All this work has allowed us to identify the technological issues to overcome in order to fully exploit the GaP/Si heterojunction cells to improve solar cell performance
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Ciampi, Simone Chemistry Faculty of Science UNSW. "A versatile and modular approach to modify silicon surfaces for electrochemical applications." Awarded by:University of New South Wales. Chemistry, 2009. http://handle.unsw.edu.au/1959.4/44630.
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The thesis presents the research results obtained while studying novel chemical strategies for preparing Si(100)-based electrochemical platforms suitable for aqueous environments. A primary research aim was the preparation of well-passivated Si(100) surfaces amenable to further chemical derivatization. The preparation and functionalization of alkyne-terminated alkyl monolayers on Si(100) surfaces using the Huisgen 1,3-dipolar ???click??? cycloaddition of azides with surface-bound acetylenes is reported and shown to be a versatile, experimentally simple, chemically unambiguous modular approach to modified silicon surfaces. Covalently immobilized, structurally well-defined acetylenyl organic monolayers are prepared from a commercially available ??,??-diyne (1,8-nonadiyne) species using a one-step thermal hydrosilylation procedure. Subsequent derivatization of the alkyne-terminated monolayers in aqueous environments with representative azide species affords disubstituted surface-bound [1,2,3]-triazole species. Neither activation procedures nor protection/deprotection schemes are required, as is the case with more established grafting approaches for silicon surfaces. The described surface modification scheme has been used in preparing modified Si(100) electrode surfaces, where modular components such as ferrocene derivatives or electrochemically ???switchable??? linker molecules are introduced onto the passivated silicon surface. An implementation study to prepare modified light-addressable ???switchable??? Si(100) electrodes is also reported. Negligible oxidation of the substrate was generally observed after exposure to aqueous systems for extended periods (tens of hours), and the electroactive monolayers showed a robust and reversible behaviour. The proposed concept of modular components and high-yielding coupling procedures has been shown on Si(100) surfaces and also extended to illustrate the functionalization of porous silicon rugate filters.
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Dai, Letian. "Silicon nanowire solar cells with μc-Si˸H absorbers for tandem radial junction devices". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS303.
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Dans cette thèse, nous avons fabriqué des cellules solaires à jonction radiale en nanofils de silicium avec du silicium microcristallin hydrogéné (µc-Si:H) comme absorbeur, par dépôt chimique en phase vapeur assisté par plasma à basse température (PECVD). Pour contrôler la densité de nanofils sur les substrats, nous avons utilisé des nanoparticules (NP) de dioxyde d'étain (SnO₂) d'un diamètre moyen de 55 nm, disponibles dans le commerce, comme précurseur du catalyseur Sn pour la croissance des nanofils de silicium. La distribution des nanoparticules de SnO₂ sur le substrat a été contrôlée par centrifugation et dilution du colloïde de SnO₂, en combinaison avec la fonctionnalisation du substrat. Par la suite, le SnO₂ est réduit en Sn métallique après le traitement par plasma de H₂, suivi de la croissance, par la technique vapeur-liquide-solide (VLS) assistée par plasma, de nanofils de Si sur lesquels sont déposées les couches P, I et N constituant les cellules solaires à jonction radiale. Nous avons atteint un taux de croissance élevé des nanofils de Si, jusqu'à 70%, avec une très large gamme de densité, de 10⁶ à 10⁹ /cm². Comme approche supplémentaire de contrôle de la densité des nanofils, nous avons utilisé du Sn évaporé comme précurseur du catalyseur Sn. Nous avons étudié l'effet de l'épaisseur de Sn évaporé, l'effet de la durée du traitement au plasma de H₂ et l'effet du débit de gaz H₂ dans le dans le mélange de précurseurs, sur la densité des nanofils. L'ellipsométrie spectroscopique in-situ (SE) a été utilisée pour contrôler la croissance des nanofils et le dépôt des couches de µc-Si:H sur les SiNWs. En combinant les résultats de in-situ SE et de microscopie électronique à balayage, une relation entre l'intensité du signal de SE pendant la croissance et la longueur et la densité des nanofils a été démontrée, ce qui permet d'estimer ces paramètres en cours de croissance. Nous avons réalisé une étude systématique des matériaux (couches intrinsèques et dopées de type n ou p de µc-Si:H, couches dopées d'oxyde de silicium microcristallin hydrogéné, µcSiOx:H) et des cellules solaires obtenues dans deux réacteurs à plasma appelés "PLASFIL" et "ARCAM". Les épaisseurs de revêtement sur substrat lisse et sur les nanofils ont été déterminées et nous avons obtenu une relation linéaire entre les deux, ce qui permet de concevoir un revêtement conforme sur les nanofils pour chaque couche avec une épaisseur optimale. Les paramètres des nanofils et des matériaux, affectant la performance des cellules solaires à jonction radiale, ont été systématiquement étudiés, les principaux étant la longueur et la densité des nanofils, l'épaisseur de la couche intrinsèque de µc-Si:H, l'utilisation de µc-SiOx:H et le réflecteur arrière en Ag. Enfin, avec les cellules solaires à jonction radiale en nanofils de silicium optimisées utilisant le µc-Si:H comme absorbeur, nous avons atteint un rendement de conversion de l'énergie de 4,13 % avec Voc = 0,41 V, Jsc = 14,4 mA/cm² et FF = 69,7%. Cette performance est supérieure de plus de 40 % à l'efficacité record de 2,9 % publiée précédemment<br>In this thesis, we have fabricated silicon nanowire (SiNW) radial junction solar cells with hydrogenated microcrystalline silicon (μc-Si:H) as the absorber via low-temperature plasma-enhanced chemical vapor deposition (PECVD). To control the density of NW on the substrates, we have used commercially available tin dioxide (SnO₂) nanoparticles (NPs) with an average diameter of 55 nm as the precursor of Sn catalyst for the growth of SiNWs. The distribution of SnO₂ NPs on the substrate has been controlled by centrifugation and the dilution of the SnO₂ colloid, combined with the functionalization of the substrate. Subsequently, SnO₂ is reduced to metallic Sn after the H₂ plasma treatment, followed by the plasma-assisted vapor-liquid-solid (VLS) growth of SiNWs upon which the P, I and N layers constituting the radial junction solar cells are deposited. We have achieved a high yield growth of SiNWs up to 70% with a very wide range of NW density, from 10⁶ to 10⁹ /cm². As an additional approach of controlling the density of SiNWs we have used evaporated Sn as the precursor of Sn catalyst. We have studied the effect of the thickness of evaporated Sn, the effect of duration of H₂ plasma treatment and the effect of H₂ gas flow rate in the plasma, on the density of SiNWs.In-situ spectroscopic ellipsometry (SE) was used for monitoring the growth of SiNWs and the deposition of the layers of μc-Si:H on SiNWs. Combining in-situ SE and SEM results, a relationship between the intensity of SE signal and the length and the density of SiNWs during the growth was demonstrated, which allows to estimate the density and the length of SiNWs during the growth. We have carried out a systematic study of materials (intrinsic, p-type,n-type µc-Si:H and µcSiOx:H doped layers) and solar cells obtained in two plasma reactors named “PLASFIL” and “ARCAM”. The thicknesses of coating on the flat substrate and on the SiNWs have been determined with a linear relation which helps to design a conformal coating on SiNWs for each layer with an optimal thickness. The parameters of the SiNWs and the materials, affecting the performance of radial junction solar cells, have been systematically studied, the main ones being the length and the density of SiNWs, the thickness of intrinsic layer of μc-Si:H on SiNWs, the use of the hydrogenated microcrystalline silicon oxide (μc-SiOx:H) and the back reflector Ag. Finally, with the optimized silicon nanowire radial junction solar cells using the μc-Si:H as the absorber we have achieved an energy conversion efficiency of 4.13 % with Voc = 0.41 V, Jsc = 14.4 mA/cm² and FF = 69.7%. This performance is more than 40 % better than the previous published record efficiency of 2.9 %
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Gladysz, Gary M. "Remote microwave-enhanced chemical vapor deposition of silicon-nitrogen (Si xN y) thin films." Ohio University / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1183727670.
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Tam, Wai Keung. "Effect of thermal annealing on Si-H bonds and dangling bonds in amorphous silicon." HKBU Institutional Repository, 2006. http://repository.hkbu.edu.hk/etd_ra/717.
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Myers, Rachael L. "CVD Growth of SiC on Novel Si Substrates." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000185.
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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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Chan, Chun Yip. "Friction stir processing of aluminium-silicon alloys." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/friction-stir-processing-of-aluminiumsilicon-alloys(0ffc1328-0a9d-4220-ab31-ee52173ed3a1).html.
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Friction Stir Processing (FSP) has the potential for locally enhancing the properties of Al-Si alloy castings, for demanding applications within the automotive industry. In this thesis, the effect of FSP has been examined on three different cast Al-Si alloys:i) A Hypoeutectic Al-8.9wt%Si Alloyii) A Hypereutectic Al-12.1wt%Si Alloyiii) A Hypereutectic Al-12.1wt%Si-2.4wt%Ni AlloyThe influence of different processing parameters has been investigated at a fundamental level. Image analysis of particle size distributions and growth method of tessellation were used to quantify the level of particle refinement and the homogeneity of the second phase spatial distribution. Stop-action experiments were also carried out, to allow the microstructural changes around the tool during FSP to be studied. Two computer models have been explored, in order to predict the temperature distribution and the material flow behaviour. Furthermore, the stability of the microstructure of the friction stir processed material was studied after being heat treated at elevated temperatures. The changes in particle size and grain structure were examined, hardness measurements were taken across the PZ, and tensile testing were carried out at room and elevated temperatures.After FSP, the microstructure of the cast Al-Si alloys was greatly refined. However, differences in microstructure have been observed throughout the PZ, which tended to be better refined and distributed on the advancing side, than the retreating side of the PZ. Changing the processing parameters also influenced the size and spatial distribution of the second phase particles. By studying the changes in microstructure around the tool from the stop-action experiments, and comparing the results to the thermal distribution and material flow behaviour predicted by the computer models, it has been shown that the flow stress, pitch, and temperature of processing, all needed to be considered, when determining the effects that FSP have on the microstructure. FSP caused very little changes to the hardness of the material, while tensile properties were greatly improved, due to the elimination of porosity and refinement of large flawed particles. In terms of the stability of the microstructure after FSP, particle coarsening and abnormal grain growth has been observed during high temperatures heat treatment. Furthermore, the Al2Cu phase was found to dissolve into solid solution at elevated temperatures, so GPZs and solute clustering can then develop within the alloy during natural ageing.
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BHADRI, PRASHANT R. "IMPLEMENTATION OF A SILICON CONTROL CHIP FOR Si/SiC HYBRID OPTICALLY ACTIVATED HIGH POWER SWITCHING DEVICE." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1021402169.
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Nielsen, Jon F. "Energetically and Kinetically Driven Step Formation and Evolution on Silicon Surfaces." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu998579834.
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Bushra, Sobia. "Investigation of Wafer Level Au-Si Eutectic Bonding of Shape Memory Alloy (SMA) with Silicon." Thesis, KTH, Mikrosystemteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-55483.
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The objective of this research work was to investigate the low temperature gold silicon eutectic bonding of SMA with silicon wafers. The research work was carried out to optimize a bond process with better yield and higher bond strength. The gold layer thickness, processing temperature, diffusion barrier, adhesive layer, and the removal of silicon oxide are the important parameters in determining a reliable and uniform bond. Based on the previous work on Au-Si eutectic bonding, 7 different Si substrates were prepared to investigate the effect of above mentioned parameters. Cantilevers with different bond sizes were prepared from SMA and steel sheets. Afterwards, these cantilevers were bonded to the prepared substrates. The bond yield and bond strength are the two parameters which establish the bond quality. Quantitative analysis was carried out by shear tests. Scanning Electron Microscopy (SEM) and Mapping were used for the analysis of the bond interface and diffusion of elements across the bond. The research has resulted in bonding of SMA cantilevers onto silicon wafers with high yield and bond strength. Steel cantilever can also be bonded by Au-Si eutectic alloy but the processing of the steel sheet is critical. Further research is needed for the fabrication of steel cantilevers and to investigate the stresses across the bond interface. It was found that the amount of gold is the key factor for reliable bonding.
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Gao, Hang. "The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1322551816.
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Favre, Wilfried. "Silicium de type n pour cellules à hétérojonctions : caractérisations et modélisations." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00635222.
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Les cellules à hétérojonctions de silicium fabriquées par croissance de couches minces de silicium amorphe hydrogéné (a-Si :H) à basse température sur des substrats de silicium cristallin (c-Si) peuvent atteindre des rendements de conversion photovoltaïque élevés (η=23 % démontré). Les efforts de recherche ayant principalement été orientés vers le cristallin de type p jusqu'à présent en France, ce travail s'attache à l'étude du type n pour d'une part déterminer les performances auxquelles s'attendre avec cette nouvelle filière et d'autre part les améliorer. Pour cela, nous avons mis en œuvre des techniques de caractérisation des matériaux composant la structure et de l'interface (a-Si :H/c-Si) couplées à des outils de simulations numériques afin mieux comprendre les phénomènes de transport électronique. Nous nous sommes également intéressés aux cellules à hétérojonctions avec substrats de silicium multicristallin de type n, le silicium multicristallin étant le matériau le plus répandu actuellement dans la fabrication des cellules photovoltaïques.
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Cho, Eun Chel Electrical Engineering UNSW. "Optical transitions in SiO2/crystalline Si/SiO2 quantum wells and nanocrystalline silicon (nc-Si)/SiO2 superlattice fabrication (Restricted for 24 months until Feb. 2006)." Awarded by:University of New South Wales. Electrical Engineering, 2003. http://handle.unsw.edu.au/1959.4/22492.
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Innovation in photovoltaic technology may offer cost competitive options to other energy sources and become a viable solution for the energy and environmental challenges of the 21st century. One proposed innovative technology is based on all-silicon tandem cells, which are constructed using superlattices consisting of environmental friendly Si and its compounds. The well and barrier materials in superlattices are restricted to silicon and silicon oxide during the present study. Single crystalline Si/SiO2 quantum wells (QWs) have been fabricated by thermal oxidation of silicon-on-insulator (SOI) wafers. It is found that oxide properties in QWs are important for SOI wafers prepared by the SIMOX (Separation by Implantation of Oxygen) technique. However, QWs fabricated from SOI wafers prepared by the ELTRAN (Epitaxial Layer TRANsfer) approach show the effect of quantum confinement without evidence of strong oxide interfacial transitions. In these wafers, evidence for an apparently ordered silicon oxide was found with 1.92?atomic fringe spacing along the (110) direction of the Si structure and with the thickness about 17?along the (100) direction of the Si structure. Luminescence wavelength ranges are from 700nm to 918nm depending on the Si thickness. The luminescence measurements on other positions of the sample show peak and shoulder spectra, which are explained by monolayer fluctuations in QW thicknesses, previously observed in III-V QWs and II-VI QWs. Si/SiO2 superlattices are fabricated by RF magnetron sputtering. Si density is the key issue in crystallizing the superlattice. High-density Si layers crystallize either under high temperature furnace annealing or rapid thermal process annealing. However, low density Si would not crystallize even at high temperature. Crystallized nanocrystals in the Si layers are observed by high resolution transmission electron microscopy (HRTEM) when the Si layer is thicker than 3nm. When Si layers are thinner than 3nm, the Si layers are discontinuous and finally deteriorate into small nanocrystals. The suitability of such superlattices for surface passivation and antireflection coatings is reviewed. Initial attempts to fabricate heterojunctions between Si wafers and Si/SiO2 superlattices resulted in open circuit voltage of 252mV. However, it is expected that better results would be obtained if Si/SiO2 superlattices were fully crystallized.
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Chiang, Chia-Lin, and 江佳霖. "a-Si/a-Si silicon-based tandem solar cells." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/88093182292251398940.
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碩士<br>國立交通大學<br>光電工程學系<br>99<br>In this article, we used AMPS-1D software to simulate tandem solar cells, and also used high-density plasma chemical vapor deposition (HDPCVD) to deposit a-Si/a-Si tandem solar cells. Comparing the experiment results with the simulation results, they almost have the same trend. Thus, AMPS-1D could be used to predict the experiment results, and reduce the time to try and error.
In the simulation, we successfully added tunneling recombination junction (TRJ) to simulate tandem solar cells. This article discussed the influence of four kinds of different material compositions in the a-Si/a-Si tandem solar cells, including n-a-Si/p-a-Si, n-a-Si/p-μc-Si, n-μc-Si/p-μc-Si and n-μc-Si/p-a-SiC. The results showed that n-μc-Si/p-μc-Si is the best choice for the recombination junction (RJ) of a-Si/a-Si tandem solar cells because its low resistance and low mobility gap. Also, we optimized a-Si/a-Si tandem solar cells. When i-layer thickness of top cell and bottom cell were 75nm and 450nm individually, the efficiency could reach 10.384%.
In the experiment, we used N&K analyzer to analysis a-Si film, and found that the optical gap was around 1.8eV. Also, Raman spectroscopy and X-ray diffraction were used to analyze μc-Si film. After that, these films deposited a-Si/a-Si tandem solar cells. By changing the parameters of the RJ, we found that decreasing the np junction thickness could reduce the resistance, and varying the np junction doping concentration almost didn’t change the resistance. When increasing the np junction doping concentration, the electric field could enhance and the efficiency could reach higher. With varying the i-layer thickness and the mobility gap of top cell and bottom cell and using p1-a-SiC window layer, the efficiency of a-Si/a-Si tandem solar cell could reach about 8.5%.
Finally, we also used AMPS-1D to optimize a-Si/μc-Si tandem solar cells and a-Si/a-SiGe tandem solar cells to predict the experiment trend. By changing i-layer thickness and the mobility gap of top cell and bottom cell, their efficiency could reach 11.198% and 11.777% individually.
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CHEN, Chien-Chou, and 陳建州. "Applications of Anisotropic Etching On Silicon Substrate : Si-molding and Si V-grooves." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/19225699928287201070.
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碩士<br>國立中山大學<br>機械工程學系研究所<br>89<br>The objective of this thesis is to apply semiconductor etching process technologies on 6 inch P-type Si substrate and produce a mold of Light Guiding Plate (LGP). After evaporate chromium (Cr) onto the Si substrate as etch mask, the thin films were then patterned and subsequently etch by plasma. Different powers were used to compare the cross-sections of the patterns. The results would be the references of Si molding process.
Another objective is to fabricate Si-V grooves which can connect the fibers and accurately position fibers. Anisotropic etching of Si-V grooves were formed using EDP solution, and sputtered Ta2O5 was used as the etch mask. At a etching temperature of 1100C, the under cut is 2.5~3mm . Additionally using SiO2 as etch mask by thermo evaporation at 1050℃ .Use EDP solution at 1100C, the under cut is 2.25mm which had a better result.
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Lo, Tzu-Chieh, and 羅子傑. "Si-rich Silicon Carbide Thin-Film Solar Cells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/87479769395152966842.
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碩士<br>臺灣大學<br>光電工程學研究所<br>98<br>The non-stoichiometric silicon carbide (Si1-xCx) film deposited by plasma enhanced chemical vapor deposition (PECVD) system. At the same gaseous flow ratio, chamber pressure and RF power, changing substrate temperature 250 and 450℃ affect the different deposition condition. According to the SIMS analysis, we observe that the substrate plays an important role on the oxygen-exclusive synthesis and stabilized crystallization of SiC material. In s250 sample annealing 850℃ for 10 min, the oxygen content invaded entire film under 250℃ lower substrate temperature deposition condition and the intensity of O rose to 9.7×105 counts. In addition, silicon atoms content decreased to only 0.3×105 counts and carbon atoms content almost vanished in the film. On the contrary, in s450 sample, the oxidation depth is about 20 nm and the O element component intensity from 9.6×105 counts return to 4.0×105 counts. The same tendency illustrate in XPS measurement, the phase transformation of Si-C to relatively strong SiO2 and graphite/diamond related Si(2p3) and C(1s) XPS signals can be obtained from the oxidized SiC with numerous Si-O and C-C bonds formed during annealing. The solution to solve incorporated oxygen deposition and better stacking sequence of crystalline structure is increasing deposition temperature as shown in SIMS analysis. Moreover, we not only purge chamber by Ar gas during vacuum but also make use of Ar gas substitute for N2 as furnace annealing gas. However, the self-assembled Si starts to appear with increase annealing temperature up to 850℃. The volume density of Si-QDs, with an average diameter of 3±1 nm formatted in annealed Si-rich S1-xCx, is controlled at 4.35×1018 cm-3 after 1050℃ annealing temperature by HR-TEM image analysis. The I-V characteristic of SiC thin film solar cells: ITO/n-type SiC/p-type Si/Al, the open current voltage (Voc) increase from 72.5 to 205.8 mV, and the short current density (Jsc) enhance from 0.93 to 3.01 mA/cm2 with rising PH3 doping concentration from 0.47% to 5%. With 5% PH3 doping concentration, the solar cell conversion efficiency of the n-SiC based sample is 0.16%.
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wen-ming, Hsu, and 許文銘. "The characteristics of Si rich silicon nitride/silicon crystal film in SONOS NVM device application." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/13670058102580508770.
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碩士<br>國立清華大學<br>電子工程研究所<br>93<br>In this thesis, we studied the characteristics of Si rich silicon nitride/silicon crystal film in MONOS NVM application. We produced Si rich silicon nitride/silicon crystal film by PECVD and the precursor gas are the mixture of silane diluted to a concentration of 5% in argon and nitrogen gas at purity in excess of 99.9999% under room temperature or 300C ambience. We kept the SiH4 precursor gas flow at 40 sccm and changed the N2 precursor gas flow rates for varying the Si content in SiNx thin film.
In electrical characteristics measurement, we measured the initial threshold voltage, program/erase performance, endurance (program/erase cycle), and data retention. Because of the thick ONO stack film (min. ~800 Å), we used the uniform FN tunneling mechanism for program/erase. We found some characteristics are as follows.
1.The initial Vt is increased with raising N2 precursor gas flow rates. This is due to EOT (equipment gate oxide thickness) increased in less Si content of SiNx thin film.
2.The program/erase window (�幀T) is increased with reducing N2 precursor gas flow rates.
3.The endurance performance is less sensitivity with N2 precursor gas flow rates. This is due to uniform FN program/erase mechanism.
4.The data retention performance is improved with raising N2 precursor gas flow rates.
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YangChi-Chang and 楊啟昌. "The study on thermoelectric property of Silicon-Rich oxide/Silicon oxide and Si/Graphene multilayers." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/35654943803744544248.
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碩士<br>國立成功大學<br>電機工程學系<br>104<br>In our research, the multilayers of silicon rich oxide/silicon dioxide and silicon/graphene were synthesized by reactive magnetron sputtering. The multilayers act as phonon block for the silicon substrate. Our objective is the reduction of thermal conductivity with preservation of electrical conductivity and seebeck coefficient. The structural and physical properties of all multilayers were investigated by TEM, XRD, XPS, TDTR and Harman method. The thermal conductivity successfully drops to accessible range because of phonon scattering in each interface. The variation of proportion and working pressure shows that the existence of silicon nanocrystal might be a key point to preserve power factor. Relation between the formation of multilayers and figure of merit would be discussed. The figure of merit could further increase via replacing the single layer graphene with silicon dioxide. Although the electrical conductivity was still low, it could be further improved after annealing. The result shows the capacity of eco-friendly and low cost Si material with optimized thermoelectric nanostructure.
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Lee, Chiao-Ti, and 李喬荻. "Amorphous Si-rich Silicon Carbide Thin-Film Photovoltaic Solar Cells." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/93012838730710084414.
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碩士<br>國立臺灣大學<br>光電工程學研究所<br>99<br>The non-stoichiometric silicon carbide (Si 1-x C x ) film is prepared by plasmas enhanced chemical vapor deposition with different RF plasmas power from 20 to 100W
and fixed substrate temperature at 500oC. According to SIMS analysis, we effectively decrease the oxygen concentration to 1.1×105 by using three processes Ar purged. However, the carbon content is increased by enhancing the RF plasmas power to 100 W in XPS analysis. Besides, the Si-C signal is significantly observed than others in Si 2p3 and C 1s core level. The C-Si-O signal is decreased with increasing RF plasmas power.
According to FTIR analysis, owing to the insufficient RF plasmas power, the Si-CH 3
signal is significant observed in 20 W sample. However, the Si-CH3 signal transform to Si-C by increasing the RF plasmas power. Moreover, considering the optical
absorption spectra, the optical absorption oefficient is much broadband and over 105 within visible under 20 W deposition condition. Besides, we also simulate the conversion efficiency of SiC photovoltaic solar cell, which demonstrates 2% conversion efficiency.
We optimize the optical absorption spectrum by detuning the fluence ratio, which enhance the optical absorption coefficient within 300 to 500 nm. Afterward, the
resistivity of p-type and n-type SiC is decreased to 2.8 and 0.31 Ω∙cm. The conversion efficiency of ITO/P-SiC/i-SiC/n-SiC/Al is increased by reducing the thickness of intrinsic SiC, which declining the series resistance simultaneously. Finally, the
conversion efficiency of ITO/P-SiC/ n-SiC/Al is promoted by reducing the thickness of n-type SiC, which decreasing the series resistance to 6 Ω.
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Cheng, Chi Cheng, and 鄭吉成. "Low Temperature Si-rich Silicon Nitride based Thin Film Memory." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/88362869791403236734.
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碩士<br>國立清華大學<br>電子工程研究所<br>93<br>Development of the “System-on-glass (SOG)” display with low temperature poly-silicon thin film transistor has rapidly advanced recently due to the advancement of low temperature poly-silicon technology. Low temperature poly-silicon thin film transistor possibly realizes more value-added display. For a system, memory devices seem to be basic and important elements. However, there are various kinds of technology for memory devices. Taking temperature and process into consideration, SONOS-type structure seems the one of the appropriate choice of them.
In the process of depositing silicon nitride, we take different way to deposit it. In conventional process, Silane and NH3 are the precursors to be used to deposit it with low process chemical deposition. And we use Silane and N2 as precursors to deposit si-rich silicon nitride with plasma enhanced chemical vapor deposition at room temperature. Besides, we fix the flow rate of Silane and adjust the rate of N2 flow to change to ratio of silicon in si-rich silicon nitride to observer the influence of silicon content on memory performances.
In the consideration of substrate, we employ low temperature poly silicon as the substrate rather than single crystal silicon substrate. The mobility of the LTPS is 5 cm2/V.S. Therefore, the performance of the current-voltage relation will be affected seriously and the efficiency of the device is not as good as the efficiency of single crystal silicon substrate. Fortunately, there are substantially improvements in the mobility presently to achieve batter performances.
The blocking oxide and tunneling oxide which stacked above and below the silicon nitride have great influences on efficiency and reliability issues. With the restriction of process temperature, the quality of the oxide will be the key issue. Here, we use TEOS and O3 as the precursors with PECVD at 400 oC to deposit blocking and tunneling oxide.
The fabrication temperature is blow 400 oC in the whole memory processes in addition to the temperature for the source and drain activation is 725 oC, 20 second. But this one is still under the tolerance of the glass.
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Tan, Choa-Peng, and 譚兆鵬. "Recovery of Si and SiC from spent silicon sawing slurry." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/45a25m.
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碩士<br>國立臺北科技大學<br>資源工程研究所<br>101<br>In Si-ingot slicing process, a great amount of spent silicon sawing slurry is produced. Several materials in the spent silicon sawing slurry are worthy of recovery, such as glycol liquor, silicon, silicon carbide. Developing a low-cost and simple recycling process will help decrease the amount of waste and reduce the manufacturing cost. The purpose of this study is to recover silicon and silicon carbide from spent silicon sawing slurry by sedimentation and centrifugation using various carriers. The experimental results show the settling velocity of waste powders in carrier-X was faster than in other carriers, and its settling belonged to dispersed form, which was helpful of the separation of Si and SiC. When solid content was 30 wt.% for a 30-min settling using carrier-X, Si content of the upper layer increased from 30.62 wt.% to 70.3 wt.%, Fe content decreased from 7.13 wt.% to 0.87 wt.%, and the recovery percentage of Si was 68.9 wt.%. And Si content of the lower layer decreased to 1.12 wt.%, Fe content decreased 0.37 wt.%, and the recovery percentage of SiC was about 53.7 wt.%. In centrifugation experiments with 300 rpm for 1 hour, when solid content was 10 wt.%, Si content of the upper layer increased to 88.6 wt.%, Fe content was 2.6 wt.%, but the recovery percentage of Si was only 10.4 wt.%. With the operation of magnetic separation, the highest Si content reached 89 wt.% and Fe content was only 0.85 wt.%. Fe removal fraction was 88.1 wt.%, and the recovery percentage of Si was 20.2 wt.%. This study separated and concentrated Si and SiC from spent silicon sawing slurry successfully using low energy consuming, simple and environmental friendly method.
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Pi, Sheng-cheng, and 畢聖成. "Ta2O5 optical waveguide filters on silicon substrates for Si photonics." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/4xjf7j.
Full textAbstract:
碩士<br>國立中山大學<br>光電工程學系研究所<br>104<br>In this thesis, Tantalum pentoxide (Ta2O5) waveguide filter is proposed for Si photonic. Ta2O5 was prepared using the RF-magnetron sputtering system on silicon substrates with 3μm thick thermal oxide.The waveguide filter was obtained by e-beam lithography for patterns definition and reactive ion etching for ridge formation. In addition, we used 3D Lumerical simulation to calculate the Bragg wavelength of the grating structare. On the other hand, we will also discuss reflective coefficient of Ta2O5 waveguide filters.
The transmission spectrum of the Ta2O5 waveguide filter was measured using a home-made optical system with a broadband ligth sourse.The spectrum range of light sourse is from 1480nm to 1600nm. As a result, the fabricated waveguide filter exhibited a Bragg wavelegth of 1528nm and a spectral linewidth of 5.13nm. For a 200μm long waveguide filter, the reflectivity of the device is larger than 75%.
Finally, we used thermoelectric cooler to detect the thermal stability of optical waveguide filters. The temperature change from 10oC to 100oC. The results showed that the temperature change from 10oC to 100 oC, the Bragg wavelength shifted only 22 pm(from 1528.046nm to 1528.068nm). Ta2O5 optical waveguide filters with a high thermal stability were obtained.
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Cho, Eun Chel. "Optical transitions in SiO2/crystalline Si/SiO2 quantum wells and nanocrystalline silicon (nc-Si)/SiO2 superlattice fabrication /." 2003. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20040105.171835/index.html.
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Hung, Yu-Cheng, and 洪有政. "Studies of Si/SiGe and Si/SiGeC Heterojunctions on Porous Silicon Substrates for Infrared Light Detecting Applications." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/39126400043131425307.
Full textAbstract:
碩士<br>國立成功大學<br>微電子工程研究所碩博士班<br>97<br>In this thesis, we used various etching conditions to prepare porous-Si (PS) layers on N-type (100) silicon substrate. The layer with a porous structure can increase photo-absorbing area, and shift the peak of absorbing wavelength, thus improving the flexibility for designing a high performance photo-detecting device. The PS layers were formed on silicon substrates using an electrochemical anodization etching method. To develop Si/SiGe/PS and Si/SiGeC/PS infrared detecting devices, the SiGe、SiGeC films were deposited on the top of the PS layer by a RTCVD system firstly. Then the physical and electrical characteristics of the films were investigated by FE-SEM, AFM, FTIR, Raman spectrum, XRD, and to optimize the depositing parameters.
We measured I-V characteristics and calculated the photo to dark current ratio of the devices with and without the illumination of an infrared light (IR) source with λ=700nm. The Si/SiGe/PS device with porosity 55%, at -12V bias, and under 5mW laser diode illuminated, the maximum photo to dark current ratio is 2.13×105. In contrast, under the same conditions, its counterpart the Si/SiGeC/PS device with porosity 55% has the maximum photo to dark current ratio of 1.75×106, which is 8.23 times higher than that the Si/SiGe/PS device. It is worthy to note, the photo current increases nearly 10 times, which is better than that reported amorphous silicon germanium infrared sensors on crystalline silicon substrates[38], thus evidencing the developed Si/SiGeC/PS device has better potential for IR detecting applications.
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Kashyap, Sanjay. "Studies On Bulk And Multilayer Composites Of Nb-Si Alloys." Thesis, 2011. http://etd.iisc.ernet.in/handle/2005/2179.
Full textAbstract:
The present thesis deals with Nb-Si alloy composites in both bulk and multilayer forms.
The work has been divided into two parts. First part (chapter 4-6) deals with Nb based
silicides binary and ternary alloys with alloying additions like Ga and Al. These alloys are synthesized by vacuum arc melting and suction casting (non-equilibrium processing techniques). The studies on intermetallic coatings of Nb-Si alloys and Nb/Si multilayer synthesized by pulsed laser deposition technique have been presented in the second part (chapter7-8).
Nb-Si alloys are one of the candidate materials for the advanced structural and
microelectronic applications. There are few issues with these materials like poor oxidation resistance, low fracture toughness and brittleness which need to be solved. Microstructure plays a crucial role to control these properties. The main focus of this work is to understand the process of phase transformation and thereby control the microstructure in both bulk alloys and thin films. We have also investigated in a limited manner mechanical and environmental properties of bulk alloys.
This thesis is subdivided into nine chapters. After a brief introduction in the first chapter, a brief overview on Nb-Si phase diagram and literature reviews on Nb-Si based alloys are presented with emphasis on the current work in the second chapter. Literature reviews on the phase formations sequence and stability in Nb-Si alloys thin films and Nb/Si multilayers are also discussed in the same chapter.
In the third chapter different experimental techniques, processing parameters and
characterization tools like XRD, SEM, TEM etc. are briefly discussed. Special emphasis is given on two non-equilibrium techniques: laser deposition technique to deposit the thin film/multilayer and vacuum suction casting to produce the 3 mm diameter rods of different Nb-Si alloys.
The fourth chapter discusses the microstructural aspects of Nb-Si alloys prepared by suction casting and its mechanical behavior. The samples have the compositions hypoeutectic (Nb-10at.%Si and Nb-14at.%Si), eutectic (Nb-18.7at.%Si) and hypereutectic (Nb-22at.% Si and Nb-25at.% Si). SEM microstructural analyses of all the samples clearly show the enhancement in the volume fraction of eutectic and decease in the eutectic spacings in microstructure due to large undercooling. Rod eutectic is observed in most of places with irregular eutectic a few places in all samples. First check of phases has been done by XRD in all samples. Phase confirmation using TEM showed the eutectic between Nbss and Nb3Si phases in all samples. The primary phase for hypoeutectic alloys is Nbss (dendritic structure), Nb3Si phase for eutectic composition and β-Nb5Si3 phase for hypereutectic alloys. Compositional analysis using EDS and EPMA also supported the above results. No signature of eutectoid reaction (Nb3Si→Nb+α-Nb5Si3) is observed. Mechanical properties like hardness, strength, ductility and indentation fracture toughness have been determined for above mention alloy compositions. SEM micrographs showed that silicides fractured by cleavage and Nb phase in a ductile manner during the compression tests carried out at room temperature. We attempt to explain how the above mention mechanical properties change with alloy compositions and processing.
Chapter five deals with the effect of Ga addition on the microstructure and mechanical
properties of the Nb-Si alloy. The composition selected for this study is Nb-20.2at.%Si-2.7at.%Ga. The results of ternary alloy have been compared with the binary alloy composition Nb-18.7at.%Si. Phase analysis has been carried out using TEM and XRD. Ga addition has suppressed the formation of Nb3Si phase and promoted the formation of β-Nb5Si3 phase. Ga addition also established the eutectic between Nbss and β-Nb5Si3, which is a metastable eutectic. Ga added ternary alloy, on suction casting, yields ultrafine eutectic with nanometer length scale (50-100nm). From the compression tests, it is concluded that the combination of ultrafine eutectic (Nbss-β-Nb5Si3) and primary β-Nb5Si3 in ternary alloy results in a high compressive strength ~2.8±0.1 GPa with 4.3% plasticity. In contrast binary alloy under identical conditions shows the compressive strength ~1.35±0.1 GPa and 0.2% plasticity. Ga addition also enhances the indentation fracture toughness from 9.2±0.05 MPa√m (binary) to 24.11±0.5 MPa√m (ternary). Composite hardness values of the ternary and binary alloys are 1064±20 Hv and 1031±20 Hv respectively.
Chapter six deals with Al added Nb-Si ternary alloy. Here we have discussed
microstructural and mechanical properties like in chapter 5 along with oxidation behavior for the alloy composition Nb-12.7at.%Si-9at.%Al. SEM micrograph shows the presence of primary dendrites structure with ultra fine lamellar eutectic (50-100nm). Detailed TEM studies confirm the Nbss as primary phase present in form of dendrites. These dendrites contain the plate shape precipitates of δ-Nb11Si4 (body centered orthorhombic structure) phase in Nb matrix (primary dendrites). Eutectic phases are Nbss and β-Nb5Si3. The analysis of the results indicates that Al addition promote the formation of β-Nb5Si3 phase in the eutectic. The results of this ternary composition were also compared with the binary alloy composition Nb-18.7at.%Si. Compression tests have been carried out at room and elevated temperatures to measure the strength of the material. Al added ternary alloy yields the compressive strength value 1.6±0.01 GPa whereas binary alloy yields the compressive strength value 1.1±0.01 GPa. Enhancement in indentation fractured toughness is observed in Al added ternary alloy (20.4±0.5MPa√m) compare to binary alloy (9.2±0.05 MPa√m). Thermal analysis by TGA and DTA were used to see the oxidation behavior of Al added ternary alloy.
Chapter seven deals with the deposition characteristics and the TEM studies on the laser deposited Nb-Si thin films. Films were deposited on the NaCl crystals and Si single crystal substrates. The compositions chosen in this case are Nb-25at.%Si, Nb-37.5at.%Si and Nb-66.7at.%Si. These compositions correspond to the equilibrium intermetallic compounds Nb3Si, Nb5Si3 and NbSi2 respectively. In this chapter we have briefly discussed the microstructural and phase evolutions in the intermetallic coatings. The smooth films quenched from the vapor and/or plasma state show amorphous structure. The sequence of crystallization was studied by hot stage TEM experiments as well as by cross sectional TEM in the films deposited at the elevated temperatures (600oC and 700oC) on Si substrates. During the hot stage experiment, crystallization is observed in Nb-25at.%Si film around 850oC with nucleation of metastable cubic Nb3Si phase. Occasionally metastable hexagonal Nb3Si3 phase has also been observed (close to Si substrate) along with cubic Nb3Si phase in the films at elevated temperatures. For Nb-37.5at.%Si film, crystallization is observed at 800oC with the nucleation of grains of metastable hexagonal Nb5Si3 phase. Cross-sectional TEM shows the presence of hexagonal Nb5Si3 phase along with few grains of NbSi3 (equilibrium) phase in the films deposited at elevated temperatures. Hot stage experiment of Nb-66.3at.%Si film showed the onset of crystallization much earlier at 400oC and complete crystallization at 600oC. This crystallization leads to the nucleation of grains of NbSi2 phase. Films of this composition deposited at elevated temperatures showed the presence of NbSi2 and metastable hexagonal Nb5Si3 phases (occasionally). The laser ablated films, besides the film matrix also contain the micron and submicron sized spherical droplets of different sizes. These droplets travel at very high velocities and impinge on the substrate resulting in a very high rate of heat transfer during solidification from liquid state. Therefore in this work we have also studied the microstructural evolution in the droplets for each composition. The phases observed in the droplets embedded in the matrix of Nb-25 at% Si alloy film are the bcc Nb and the cubic Nb3Si (metastable phase). The droplets in the matrix of Nb-37.5 at% Si alloy showed the bcc Nb and tetragonal β-Nb5Si3 phases. The phases observed in the droplets of in the Nb-66.3at.%Si alloy are the bcc Nb, tetragonal β-Nb5Si3 and the hexagonal NbSi2 (metastable phase).
Chapter eight describes the synthesis and microstructural characterization using TEM of
Nb/Si multilayers. The aim of this work is to check the stability and phase formation
sequence in Nb/Si multilayer. Nb/Si multilayers were first annealed at different time intervals at 600oC and at different temperatures (for 2 hours) and then characterized by the cross-sectional transmission electron microscopy. As-deposited Nb layer is crystalline
while Si layer is amorphous. Microstructural and compositional evidences suggest the
intermixing between the Nb and Si layers at the interfaces. Nb/Si multilayer annealed at
600oC for 1 hour, NbSi2 was identified as the first crystalline nucleating phase. However
amorphous silicide layers were also observed between Nb and NbSi2 layers. Metastable
hexagonal Nb5Si3 was identified as the next crystalline phase that nucleated from the
amorphous silicide layers at the interfaces of Nb and NbSi2 layers. Occasionally few grains of cubic Nb3Si phase were also observed after 8 hours of annealing at 600oC. In the chapter we have compared the results to the other reported works in Nb-Si bulk diffusion couples and also thin film couples.
The final chapter summarizes the major conclusions of the present work and scope of
future work.
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Visnovec, Karl. "Refining of Silicon During its Solidification from a Cu-Si Melt." Thesis, 2011. http://hdl.handle.net/1807/31623.
Full textAbstract:
Current methods of solar-grade silicon (SG-Si) production are energy intensive and costly. The possibility of using metallurgical techniques for refining metallurgical-grade Si (MG-Si) to SG-Si has been investigated. The main steps in the metallurgical refining route include alloying with copper to produce a 50-50wt% Cu-Si alloy, controlled solidification, crushing, and acid leaching. The controlled solidification process involved 5 variations to determine the best process to maximize Si dendrite agglomeration in the sample and produce the purest Si. This was determined by using various techniques, such as: optical imaging, dendrite analysis, EPMA and SEM analysis and ICP analysis. The crushing and acid leaching steps were carried out to remove the unwanted Cu3Si eutectic from the pure Si dendrite phase. Upon completion of the analysis techniques, the optimal cooling method was determined to be the top cooled, 0.5°C/min sample.