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Válek, Lukáš. "Microdefects in Czochralski Silicon." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-234030.
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Disertační práce se zabývá studiem defektů v monokrystalech Czochralskiho křemíku legovaných bórem. Práce studuje vznik kruhových obrazců vrstevných chyb pozorovaných na povrchu křemíkových desek po oxidaci. Hlavním cílem práce je objasnit mechanismy vzniku pozorovaného rozložení vrstevných chyb na studovaných deskách a vyvinout metody pro řízení tohoto jevu. Na základě experimentálních analýz a rozborů obecných mechanismů vzniku defektů jsou objasňovány vazby mezi vznikem defektů různého typu. Tyto jsou pak diskutovány v souvislosti s parametry krystalu i procesu jeho růstu. Takto sestavený model je využit pro vývoj procesu růstu krystalů, kterým je potlačen nadměrný vznik defektů ve studovaných deskách. Za účelem studia defektů jsou zaváděny a vyvíjeny nové analytické metody. Disertační práce byla vytvořena za podpory ON Semiconductor Czech Republic, Rožnov pod Radhoštěm.
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Derby, Jeffrey J. "Analysis of heat transfer, stability, and dynamics of Czochralski and liquid encapsulated Czochralski growth of semiconductor materials." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15048.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 360-367.
by Jeffrey J. Derby.
Ph.D.
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Hicks, T. W. "Hydrodynamics of liquid encapsulation Czochralski crystal growth." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233905.
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Pascoa, Soraia Sofia. "Oxygen and related defects in Czochralski silicon crowns." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27116.
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For the purpose of this thesis work, four n-type CZ silicon ingots with different crown tapered angle and shouldering area were characterized in order to understand the oxygen behavior and related defects on ingot top cuts and its influence on material lifetime. A p-type CZ silicon ingot was also characterized in order to have a reference material for comparison. Differences in lifetime between the crowns were observed and a strong correlation between the crown tapered angle and oxygen concentration and distribution was established. The crown with the higher tapered angle has the highest lifetime. In contrast, the crown with the lower crown tapered angle has the lowest lifetime. The crystal body quality can be influenced by the top ingot quality in what concerns the interstitial oxygen concentration and distribution. Thus, analyzing the early body of each ingot, it might be possible to predict the crystal body quality.
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Kozakevich, Daniel Norberto. "Simulação numerica do fluxo de czochralski não isotermico." [s.n.], 1988. http://repositorio.unicamp.br/jspui/handle/REPOSIP/307528.
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Orientador : Jose Vitorio ZagoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computção Científica
Made available in DSpace on 2018-07-16T04:08:25Z (GMT). No. of bitstreams: 1 Kozakevich_DanielNorberto_M.pdf: 1469044 bytes, checksum: 696736f842cfb0a6aec0d6210c9639fe (MD5) Previous issue date: 1988
Resumo: Na produção de cristais pela solidificação de sais fundidos, a técnica de CZOCHRALSKI é amplamente utilizada. Os cristais obtidos por esta técnica são indicados para a construção de dispositivos de baixa potência. Nesta técnica o sal é fundido num cadinho e mantido a uma temperatura superior a seu ponto de fusão. Uma semente do cristal é mergulhada no liquido e então puxada lentamente. O calor latente do sal que se solidifica na interfase semente-liquido, é eliminado por conducções através do cristal. Os três mecânismos básicos: convecção natural, rotação do cadinho e rotação do cristal e suas combinações foram simuladas numéricamente, para um fluxo de CZOCHRALSKI. Uma solução aproximada foi obtida mediante o metodo dos elementos finitos mistos, utilizando elementos quadrilaterais subparamétricos com aproximações / quadráticas nas componentes da velocidade e a temperatura e lineares na pressão. As integrais são calculadas numéricamente com uma regra gaussiana de nove pontos. As equações discretizadassao resolvidas pelo método de Newton e,os sistemas lineares pelo método frontal. O fluxo é não isotérmico, incompressivel, newtoniano, estacionário, tridimensional axisimétrico com fronteiras fixas. Outras formulações alternativas são colocadas para as equações de Navier-Stokes
Abstract: Not informed
Mestrado
Mestre em Matemática Aplicada
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Brakel, Thomas W. "Mathematical modelling of the Czochralski crystal growth process." Doctoral thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/4868.
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Includes bibliographical references (leaves 142-149).In this document a mathematical model for the Czochralski crystal growth process is developed. The trend in current research involves developing cumbersome numerical simulations that provide little or no understanding of the underlying physics. We attempt to review previous research methods, mainly devoted to silicon, and develop a novel analytical tool for indium antimonide (lnSb) crystal growth. This process can be subdivided into two categories: solidification and fluid mechanics. Thus far, crystal solidification of the Czochralski process has been described in the literature mainly qualitatively. There has been little work in calculating actual solidification dynamics. Czochralski crystal growth is a very sensitive process, particularly for lnSb, so it is crucial to describe the system as accurately as possible. A novel ID quasi-steady method is proposed for the shape and temperature field of an lnSb crystal, incorporating the effects of the melt. The fluid mechanics of the Czochralski melt have been modelled by numerous researchers,with calculations performed using commercial software. However, a descriptionof the buoyancy and rotation interaction in the melt has not been adequatelyperformed. Many authors have presented flow patterns but none have indicated either: melt conditions preferential for crystal growth or at least a description of a typical melt structure. In this work, a scale analysis is performed that implies an idealized flow structure. An asymptotic model is then derived based on this order of magnitude analysis, resulting in a fast and efficient fluid flow calculation. The asymptotic model is validated against a numerical solution to ensure that the macroscopic features of the flow structure are present. The asymptotic model does not show exact agreement, but does provide an estimate of the melt heat flux that is necessary for the solidification calculation. The asymptotic model is also used to predict macroscopic changes in the melt due to rotation.
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Perret, Christian. "Simulation numérique des échanges thermiques et des contraintes thermoélastiques dans un tirage Czochralski." Grenoble 1, 1989. https://theses.hal.science/tel-00335809.
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Hui, David C. W. "Characterization of semi-insulating liquid encapsulated Czochralski gallium arsenide." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/30648.
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This thesis consists of a study of several qualification techniques for SI LEC GaAs and the application of these techniques to various ingots.
For use on the starting material before any doping procedures, the technique of studying the semi-insulating properties by monitoring the activation energy of dark resistivity with temperature was investigated. Experiments were performed on both ring dot as well as cloverleaf samples. Different activation energies for the dark resistivity were observed for temperatures above and below 290 K. Also, ingots with different background impurity concentrations were tested.
Another technique applicable to the undoped starting material is Optical Transient Current Spectroscopy (OTCS). The occurrence of 'negative' peaks was simulated using a depletion layer model. The results showed that under certain conditions a recombination centre can produce a positive peak, a negative peak, or both a positive and a negative peak. Further analysis of the negative peaks led to the formulation of a field enhanced injection model to explain their occurrence. More than one negative peak was observed experimentally. In addition, the effect of different electrode structures on OTCS experiments was investigated. The effect of polarity on negative peaks was studied using ring dot structures and was found to agree with the proposed model.
Some peculiar anomalies which were observed in investigating OTCS led to the discovery of a photocurrent memory effect with decay time constants of the order of minutes at a temperature of 266 K. This memory effect was found to be associated with surface modifications. The effects of surface passivation with Na₂S were investigated. The method of normalizing the OTCS peak height with photocurrent was investigated.
A microscopic spatial analysis tool, scanning OTCS, with a spot size of about 2 µm was developed in order to probe the spatial variation of deep levels and compare with that of dislocations or other defects. An experiment on an abraded surface was performed using the scanning OTCS and showed that the negative peak does indeed correlate with mechanical damage.
Wafer performance during implantation doping is an important qualification test. Comparisons between standard furnace annealing and rapid thermal annealing were performed. A comparison of the estimated percentage activation using C(V) measurements with that from Hall measurements, with and without a correction for the surface depleted region, was performed. The C(V) analysis technique, used in the industry to obtain doping profiles of implanted wafers, was studied. The effect of using serial and parallel measurement modes was investigated. Simulations of C(V) measurements on implanted devices by solving the Poisson-Boltzmann equation for the charge distribution under different biases were performed. The limitation of the C(V) profiling technique in detecting sharp dopant profiles was investigated. A system for quick analysis of the percentage of activation using a mercury probe was designed. The effect of serial and parallel analysis of the impedance measured by the mercury probe on the estimated dopant profile was investigated. The effect of different electrode structures (Schottky to Schottky as compared to Schottky to Ohmic) on estimated doping profiles was studied.
The mobility profile as a tool for qualification was investigated. The effect of surface states on mobility was studied.
A crucial factor in wafer qualification is the uniformity of transistor characteristics across the wafer. In order to test this on a wafer, thousands of transistors have to be measured. A technique of perforating measurements automatically with
consistency is needed. An automatic probing station for measuring large arrays of transistors was engineered. Tests on arrays of transistors were performed to investigate the effect of different fabrication processes, in particular the amount of surface etch, on the uniformity of threshold voltage.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Martinez, André Luiz. "Síntese e crescimento de cristal da fase BiNbO4." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-14012008-170719/.
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Muitos trabalhos científicos têm sido publicados relatando os diferentes métodos de preparação e as propriedades de corpos cerâmicos e filmes finos de niobato de bismuto (BiNbO4 - BN). Provido de características como alta permissividade dielétrica e excelentes propriedades ferroelétricas, esse composto tem despertado o interesse da comunidade científica. No entanto, uma literatura restrita e conflitante é encontrada sobre esse composto na forma de monocristais. A ocorrência de transições de fase estrutural mostrou-se a maior dificuldade na preparação desses compostos como monocristais. A potencial aplicação como material de dispositivos eletrônicos, devido suas propriedades ferroelétricas, assim como o desafio da preparação de materiais que apresentam transição estrutural de fase, serviram de motivação para a realização desse estudo. O objetivo desse trabalho foi a realização do estudo da síntese e do crescimento de cristais de BiNbO4. Para isso foram utilizadas as técnicas de Czochralski (CZ), Laser Heated Pedestal Growth (LHPG) e fluxo. As dificuldades encontradas quando utilizada cada uma das técnicas, assim como suas variações, foram discutidas. A transição estrutural de fase (\'alfa\'-BiNbO4 - \'beta\'-BiNbO4) mostrou-se uma barreira na preparação desse tipo de material com qualidade óptica. O comportamento da permissividade dielétrica (\'épsilon\') e fator de perda (tg\'teta\') em função da temperatura e freqüência foram determinados através de estudos de espectroscopia de impedância.Many scientific works have been published reporting different procedures to the preparation and properties of ceramic bodies and thin films of bismuth niobate (BiNbO4 - BN). Characterized by high dielectric permittivity and excellent ferroelectric properties, this compound has attracted the interest of the scientific community. However, a restricted and conflict literature is found about this compound in the single crystal form. The appearance of structure phase transitions was demonstrated in the most difficulty for the preparation of this compounds as single crystals. The potential applications as electronic device material, due its ferroelectrics properties, as well as the challenge to preparation materials which indicate structural transition were used as motivations to the development of this work. The main purposes of this work were to make synthesis and the crystal growth of BiNbO4. For this propose, techniques as Czochralski (CZ), Laser Heated Pedestal Growth (LHPG) and self-flux were used. The difficulties found when used each one of the techniques and their variations are discussed. The structural phase transition (\'alfa\'-BiNbO4 - \'beta\'-BiNbO4) was the principal barrier in the preparation of this material with optical quality. The behavior of dielectric permittivity (\'épsilon\' ) and lost factor (tg\' teta\') by the temperature and frequency were determined through studies of Impedance Spectroscopy
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Kinney, Thomas Arthur. "Quantitative modelling for optimization of the Czochralski growth of silicon." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13204.
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Furtado, Wagner Wilson. "Efeito do carbono na formação de defeitos em silício Czochralski." Universidade de São Paulo, 1991. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-06082013-103439/.
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Neste trabalho é estudado o efeito do carbono na formação de defeitos em silício Czochralski crescido na direção em amostras submetidas a tratamentos térmicos variados. Medidas de espalhamento difuso de raios-X, espectroscopia de infravermelho, medidas de resistividade, topografia de raios-X e microscopia eletrônica de transmissão mostraram que os defeitos nas amostras \"como crescidas\" podem ser relacionados com os microdefeitos tipo B. Tratamento térmico a 450ºC mostrou a presença de vacâncias nas amostras com baixa concentração de carbono enquanto que nas amostras com alta concentração de carbono ocorre a inibição da formação dos doadores térmicos (\"Thermal Donors - TD\"). Os resultados confirmam os modelos de Newman e Mathiot para a geração dos TD. Para tratamento térmico a 650ºC o carbono promove a formação de Novos Doadores (\"New Donors - ND\"). Os resultados mostram que estes defeitos são de natureza predominante de vacância e concordam com os modelos de geração que envolvem átomos de oxigênio substitucional. Os doadores observados a 550ºC puderam ser relacionados aos Novos Doadores Térmicos (\"New Thermal Donors - NTD\") observados por Kamiura et al..Effect of carbon concentration upon defect formation in oxygen rich Czochralski grown silicon has been investigated by combining various furnace thermal anneals. Diffuse X-ray scattering, infrared spectroscopy, resistivity, x-ray topography, and transmission electron microscopy have shown that defects in as-grown samples could be related to the B swirls. 450ºC anneals have shown the presence of vacancies in low carbon samples while high carbon concentration inhibited Thermal Donor (TD) formation. Our results confirm models by Newman and Mathiot for thermal donors generation. For 650ºC anneals carbon promotes New Donors (ND) formation. Our results show that these defects are mainly vacancy in nature and agrees with the substitutional oxygen models proposed for these donors. Donor formation was observed at 550ºC which could be related to New Thermal Donors (NTD) proposed by Kamiura et al..
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Möckel, Robert. "Growth and properties of GdCa4O(BO3)3 single crystals." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2012. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-90095.
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In der vorliegenden Arbeit wird die Einkristallzüchtung nach dem Czochralskiverfahren von GdCa4O(BO3)3 (GdCOB) beschrieben. Aus insgesamt 18 Zuchtversuchen, bei denen auch die Ziehgeschwindigkeit zwischen 1 und 3mm/h variiert wurde, wurden erfolgreich nahezu perfekte Einkristalle gewonnen. In einigen Kristallen traten jedoch auch Risse oder Einschlüsse auf. Diese enthielten neben Iridium vom Tiegelmaterial auch andere Phasen des Gd2O3–B2O3–CaO-Systems, sowie P und Yb, deren Herkunft unklar ist. Als Hauptziehrichtung wurde die kristallographische b-Achse gewählt, ergänzt durch einige Experimente in der c-Richtung. In den drei kristallographischen Hauptrichtungen wurden die thermischen Ausdehnungskoeffizienten von GdCOB bestimmt. Diese können in zwei nahezu lineare Bereiche unterteilt werden: von Zimmertemperatur bis etwa 850° C und von 850 bis 1200° C, wobei die Koeffizienten im Hochtemperaturbereich deutlich höher sind (unter 850° C: alpha_a=11.1, alpha_b=8.6, alpha_c=13.3 10^-6/K, oberhalb 850° C: alpha_a=14.1, alpha_b=11.7, alpha_c=17.8 10^-6/K). Daraus ergibt sich, dass ein Phasenübergang höherer Ordnung vorliegen muss. Als mögliche Ursache wurde mittels HT-Raman Spektroskopie ein Ordnungs-Unordnungs-Übergang identifiziert, während dessen die BO3-Gruppen in der Struktur leicht rotieren. Weitere Untersuchungen mittels thermodynamischer Methoden führten zu schwachen, aber eindeutigen Signalen, die diesem Effekt ebenfalls zuzuordnen sind. Obwohl das Material ein vielversprechender Kandidat für piezoelektrische Anwendungen im Hochtemperaturbereich ist, wurde dieser Effekt bisher unzureichend beschrieben. Dieses Verhalten, kombiniert mit den anisotropen thermischen Ausdehnungskoeffizienten, könnte eine der Ursachen für das Vorkommen von Rissen in den Kristallen während der Synthese darstellen. Spektroskopische Untersuchungen ergaben einen großen Transparenzbereich von 340 bis 2500nm (29 400–4000 cm^-1), was für optische Anwendungen von großer Bedeutung istIn a series of 18 growth experiments, GdCa4O(BO3)3 (GdCOB) single crystals were successfully grown by the Czochralski method. They have a well-ordered structure, as revealed by single crystal structure analysis. Although the main growth direction was along the crystallographic b-axis, some experiments were conducted using the cdirection. Pulling velocities were varied between 1 and 3mm/h. Except for a few crystals with cracks or elongated "silk-like" inclusions consisting of multiphase impurities, most of the obtained crystals are of good quality. Those inclusions contain iridium, deriving from the crucible, P and Yb with unclear source, and other phases from the system Gd2O3–B2O3–CaO. Thermal expansion coefficients of GdCOB were determined in the directions of the crystallographic axes and found to be approximately linear in two temperature ranges: from 25° C to around 850° C, and from 850 to 1200° C, with the latter range showing significantly higher coefficients (below 850° C: alpha_a=11.1, alpha_b=8.6, alpha_c=13.3 10^-6/K, and above 850° C: alpha_a=14.1, alpha_b=11.7, alpha_c=17.8 x10^-6/K). This sudden increase of thermal expansion coefficients indicates a phase transition of higher order. An order-disorder transition in form of the rotation of BO3-triangles in the structure was made tentatively responsible for this transition, as revealed by HT-Raman spectroscopy. This transition was also detected by DSC-methods but appeared to result in very weak effects. Although the material is thought to represent a promising candidate for high temperature piezoelectric applications (noncentrosymmetric space group Cm), this effect of change in specification has not been described and it is unknown whether it has influence on the piezoelectric properties. Furthermore, this characteristic behaviour in combination with anisotropic coefficients may be the reason for the development of cracks during cooling of crystals, making the growth difficult. Spectroscopic investigation revealed a wide transparency range from 340 to 2500nm (29 400–4000 cm^-1) of GdCOB, which is a very important property for optical applications
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Shah, Dhaval. "DELAY MODELING AND LONG-RANGE PREDICTIVE CONTROL OF CZOCHRALSKI GROWTH PROCESS." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2118.
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This work presents the Czochralski growth dynamics as time-varying delay based model, applied to the growth of La3Ga5.5Ta0.5O14 (LGT) piezoelectric crystals. The growth of high-quality large-diameter oxides by Czochralski technique requires the theoretical understanding and optimization of all relevant process parameters, growth conditions, and melts chemistry. Presently, proportional-integral- derivative (PID) type controllers are widely accepted for constant-diameter crystal growth by Czochralski. Such control systems, however, do not account for aspects such as the transportation delay of the heat from crucible wall to the crystal solidification front, heat radiated from the crucible wall above the melt surface, and varying melt level. During crystal growth, these time delays play a dominant role, and pose a significant challenge to the control design. In this study, a time varying linear delay model was applied to the identification of nonlinearities of the growth dynamics. Initial results reveled the benefits of this model with actual growth results. These results were used to develop a long-range model predictive control system design. Two different control techniques using long range prediction are studied for the comparative study. Development and testing of the new control system on real time growth system are discussed in detail. The results are promising and suggest future work in this direction. Other discussion about the problems during the crystal growth, optimization of crystal growth parameters are also studied along with the control system design.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
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Kearns, Joel K. "Origin Of Growth Twins During Czochralski Growth Of Heavily Doped, Dislocation-Free Single Crystal Silicon." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/514.
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Low voltage power electronics are made from dislocation free silicon heavily doped with arsenic or antimony to provide low electrical resistivity. Attempts to grow crystals with decreased resistivity have led to a higher probability of twinning during growth, so that the crystal no longer possesses the required crystallographic orientation for device fabrication. The source of the twins must be identified so that crystal growth process conditions can be designed to eliminate this defect mechanism, allowing lower resistivity crystals to be grown reliably. In lightly doped crystals, twinning was ascribed to presence of carbon impurity or a low probability atomic stacking accident, neither of which should be affected by increased concentration of arsenic or antimony. Crystals that twinned during growth were characterized by resistivity, Laue back-reflection x-ray diffraction, optical and scanning electron microscopy, energy dispersive x-ray spectroscopy, spreading resistance, x-ray computed tomography and electron backscatter diffraction. The twin nucleation site of silicon crystals that were grown heavily doped with arsenic or antimony were compared to lightly doped crystals which twinned, and crystals that exhibited other defects. The initial twinning in the <100> orientation heavily doped crystals occurred from small gas bubbles bursting at a {111} facet at the three phase boundary, and forming a twin orientation domain on that facet. The gas bubbles likely consist of argon, the process gas used during solidification to remove silicon monoxide gas from the growth system. The higher levels of arsenic or antimony dopant may have changed the silicon surface tension, or provided additional impurities into the liquid silicon. Either effect may have changed the number or size of argon bubbles in the liquid silicon, leading to a higher incidence of gas bubbles near the {111} facet during solidification. Similar but smaller crater features were observed on two lightly boron-doped silicon crystals that twinned. Two other lightly doped crystals formed twins from carbon inclusions, consistent with carbon as a cause. Some heavily-doped twinned samples also show high concentrations of metals at the twin nucleation site, which could affect surface energy. Measurement of the geometry of crystal surface-to-facet radius eliminated a recently-proposed twin nucleation theory from consideration. Constitutional supercooling was demonstrated to not be a major contributing factor to twin nucleation. It was shown that deliberately introducing additional arsenic dopant during solidification would nucleate twins, but twins did not occur if only elemental carbon was introduced.
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Tavakoli, Mohammad Hossein. "Numerical analysis of seeding process during Czochralski growth of oxide single crystals." [S.l.] : [s.n.], 2006. http://se6.kobv.de:8000/btu/volltexte/2006/14.
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Pawlowicz, Leszek Miroslaw 1957. "Studies of point defect control in liquid-encapsulated czochralski growth of GaAs." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14838.
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Winkler, Jan [Verfasser]. "Beiträge zur Regelung des Czochralski-Kristallzüchtungsprozesses zur Herstellung von Verbindungshalbleitern / Jan Winkler." Aachen : Shaker, 2007. http://d-nb.info/116434157X/34.
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Li, Hui. "Bubbles propagation in undoped and Titanium (Ti3+)-doped sapphire crystals grown by Czochralski (Cz) technique." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10327/document.
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En dépit de leurs simplicités chimiques, de leurs fusion congruente, de leurs performances mécaniques et de leurs propriétés optiques, les monocristaux de saphir contiennent comme défauts des bulles aussi connus sous le nom de micro-vides. Quelle que soit la technologie de croissance, les cristaux obtenus sont caractérisés par la présence de micro-et macro-bulles qui affectent leurs qualités optiques et mécaniques limitant ainsi leurs applications. Ces bulles dégradent les propriétés optiques et l'efficacité des lasers produits par une réduction de la transparence des saphirs; elles induisent également des défauts de surface pendant le processus de polissage. Afin d'améliorer la qualité des cristaux, il est important d'éliminer les bulles, de connaître la raison de leurs formations, les causes de leurs propagations, de leurs constitutions, et de leurs diffusions dans le cristal. Nous avons étudié la distribution des bulles et leurs tailles dans les cristaux de saphir non dopés et dopés titane obtenus par la technique Czochralski (Cz). Les données expérimentales recueillies ont permis de connaître l'effet de différents paramètres de croissance sur la distribution, la densité et la taille des bulles. La propagation des bulles et leurs distributions dans les cristaux ne sont pas influencées par le type de germe. Si les vitesses de tirages augmentent, le diamètre des bulles diminuent et leurs densités augmentent. Les bulles formées dans le cristal de saphir sont influencées par la matière formant la charge de départ. L’utilisation de saphirs craquelés comme charge de départ pourrait être une bonne façon de minimiser la création de bulles et de limiter leurs propagations. Les résultats obtenus dans le cadre de cette thèse décrivent l'ensemble des phénomènes impliqués lors de l'incorporation de bulles dans les cristaux de saphir non dopés et dopés titaneIn spite of the chemical simplicity, the congruent melt behaviour and it’s performed mechanical and optical properties sapphire single crystals contain bubbles defects also known as micro-voids. Whatever the growth technology, the grown crystals are characterized by the presence of micro and macro bubbles which affect the optical and mechanical quality of the crystal limiting their application. They degrade the optical properties and the laser efficiency by reduction of the transparency; they also induce surface defects during substrate polishing process. In order to improve the crystal quality, it is important to eliminate bubbles defects and know the reason of their formation, the causes of their propagation, their incorporation and their distribution in the crystal. We have studied bubbles distribution and their size in undoped and Ti-doped sapphire crystals grown by Czochralski (Cz) technique. The collected experimental data made it possible to know the effect of several growth parameters on the distribution, the density and the size of the bubbles. The bubbles propagation and distribution in the crystal are not influenced by the seed type. If the pulling rate increases, the diameter of bubbles decreases and their density increases. The bubbles formed in sapphire crystal are influenced by the starting charge material. Using sapphire crackle as starting charge could be a good way to minimise bubbles creation and limited their propagation. The obtained results in the frame of this thesis describe the whole phenomena involved during bubbles incorporation in undoped and Ti-doped sapphire crystals
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Scalvi, Luis Vicente de Andrade. "Simulação numérica da fase líquida do crescimento de silício pelo método Czocharalski." Universidade de São Paulo, 1986. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-13102009-111526/.
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Visando compreender os fluxos na fase líquida do crescimento de silício pelo método Czochralski, é feita a Simulação Numérica do silício fundido, resolvendo-se as equações que governam o fenômeno da convecção forçada no fluido: Balanço de Quantidade de Movimento e Balanço de Massa. A técnica numérica escolhida é a de Elementos Finitos, onde é utilizada a formulação de Galerkin, com aproximações quadráticas nas componentes da velocidade e linear na pressão. A partir de várias combinações de rotações cadinho-cristal, os perfis de velocidade obtidos são analisados com relação aos efeitos de incorporação de impurezas e/ou dopantes no cristal em crescimento.In order to visualise the flow conditions during crystal growth of Silicon by the Czochralski technique, a numerical simulation is done. It is used the Finite Element Method with the Galerkin Formulation , and with quadratic approximations on the components of the velocity and linear approximations on the pressure. Many combinations of crystal and crucible rotations are analised and discussed considering optimal growth conditions.
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Bargawi, Ahmad Yousef. "A study of the martensitic phase transition in the shape memory alloy Ni₂MnGa." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/32824.
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A study of the martensitic phase transition in the shape memory alloy Ni2MnGa has been carried out. Ni2MnGa is one of the group of "shape memory effect" alloys which are currently exciting considerable interest. The origin of this effect in the compound is in the phase change which takes place on cooling through T = 200 K from the cubic L21 Heusler structure to a tetragonal phase. Recently the results of band structure calculations have been used to conclude that in Ni2MnGa the structural phase transition is driven by a band Jahn-Teller distortion.
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Abuelgasim, A. "High resistivity Czochralski-silicon using deep level dopant compensation for RF passive devices." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/350849/.
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Combinations of analytical and experimental results indicate that deep level doping of Czochralski grown silicon wafers is capable of providing very high resistivity wafers suitable for silicon-on-insulator (SOI), integrated passive devices (IPD) and 3D integration configurations. Deep level doping involves adding trace elements to silicon that compensate for background free carriers introduced by impurities in the silicon and pin the Fermi level near the mid bandgap intrinsic level. Starting from n-type Czochralski-silicon wafers with a nominal resistivity of 50 Ωcm, gold ion implantation and subsequent annealing were used to increase the resistivity of silicon wafers by up to 3 orders of magnitude, to values as high as 93 kΩcm. Hall measurements performed over a large temperature range show that the increase in resistivity is solely due to a decrease in carrier concentration and not a decrease in mobility. The carrier concentration is only one order of magnitude larger than that of intrinsic silicon over a temperature range of 200-360 K. Hall results also show that the resistivity of the compensated material remains up to two orders of magnitude larger than that of the uncompensated material at near operating temperatures. High frequency attenuation measurements in the 1-67 GHz range for coplanar waveguides show attenuation reductions of up to 76% from 0.76 dB/mm to 0.18 dB/mm at 10 GHz for those fabricated on uncompensated and compensated silicon respectively. Spiral inductors fabricated on both compensated and uncompensated silicon show up to a factor of 10 increase in the maximum quality factor from 0.3 to 3.1 for inductors on uncompensated and compensated silicon respectively. A 70% increase in maximum quality factor from 9 to 15.2 is exhibited by inductors commercially fabricated on compensated silicon when compared to those on float-zone silicon. The coplanar waveguide and spiral inductor results provide clear evidence that deep level dopant compensation is effective in improving the performance of passive devices in the GHz frequency range.
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Moussambi, Membetsi Hermance. "Croissance par la méthode Czochralski de cristaux non linéaires de borate : premières caractérisations." Metz, 2004. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2004/Moussambi_Membetsi.Hermance.SMZ0407.pdf.
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La phase basse température du métaborate de baryum (-BBO) possède des propriétés optiques non linéaires (ONL) avantageuses pour la génération d'U. V. Par doublage de fréquence. Le tétraborate de lithium est actuellement étudié pour l'application aux systèmes non linéaires. Le travail présenté est destiné à la croissance de ces matériaux et à une première évaluation de leurs potentialités. Nous avons utilisé au laboratoire la méthode Czochralski permettant d'obtenir des cristaux directement à partir d'un bain pur. L'obtention de cristaux de bonne qualité s'est développé autour de différents points : - Le choix des matériaux de départ et particulièrement la synthèse des pourdres de départ de BBO. - La mise au point des paramètres thermiques tels que les gradients de température et la températureà la surface du bain, ainsi que l'adaptation de notre matériel à la technique de croissance Crochralski pour chacun des matériaux. - La mise en forme des échantillons par un technique de polissage respectant l'hygroscopie des cristaux borate et par l'utilisation de techniques d'orientation originales des échantillons BBO par spectroscopie micro-Raman et conoscopie. Des premières caractérisations ont été menées sur des échantillons obtenus. A partir des mesures d'absorption et de coefficients ONL effectifs par Génération de Second harmonique (GSH) nous avons pu non seulement valider le choix de la technique de croissance de -BBO, mais de plus entamer une comparaison avec les cristaux issus de la technique de croissance en solution, celle la plus communénément utilisée dans l'industrie. Les résultats obtenus sont très prometteurs quant à la perspective de génération d'U. V. Par GSH. Les cristaux de LTB ont été mis à la disposition au laboratoire pour des caractérisations par spectroscopie Raman ou par mesures électro-optiquesThe low temperature phase of baryum metaborate possesses non linear optical properties (NLO) that offer advantages regarding the generation of U. V. By frequency doubling. Lithium tetraborate is currently being studied for application to linear systems. The work presented concerns the growth of these materials and a first evaluation of their potential. The Czochralski method was used et lab to obtain crystals directly from a pure melt. The production of good quality crystals resulted from some key points. The initial choice of starting materials and the synthesis of powders from BBO in particular. The setup of thermal parameters such as temperature gradients and the temperature at the surface of the melt, as well as the adaptation of our equipement to the Czochralski growth technique for each material. The preparation of samples using polishing techniques respecting the hygroscopy of borate crystals and using original orientation techniques of BBO samples by micro-Raman spectroscopy and conoscopy. Original characterizations were made from the obtained samples. From absorption measures and effective ONL coefficients from Second Harmonic Generation, (SHG) we were able to not only validate the choice of -BBO crystal growth technique, but also perform a comparison with crystals from the liquid crystal growth technique, the most widely used method in industry. The obtained results are very encouraging regarding the generation of U. V. D by SHG. LTB crystals were available to the laboratory for characterization by Raman spectroscopy or by electro-optical measures
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Perret, Christian Witomski P. "Simulation numérique des échanges thermiques et des contraintes thermoélastiques dans un tirage Czochralski." S.l. : Université Grenoble 1, 2008. http://tel.archives-ouvertes.fr/tel-00335809.
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Moussambi, Membetsi Hermance Kugel Godefroy. "Croissance par la méthode Czochralski de cristaux non linéaires de borate premières caractérisations /." Metz : Université Metz, 2008. ftp://ftp.scd.univ-metz.fr/pub/Theses/2004/Moussambi_Membetsi.Hermance.SMZ0407.pdf.
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Reuther, Christoph. "Züchtung und Charakterisierung von Sr3Gd2[BO3]4-Einkristallen." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-115924.
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Polykristallines Sr3Gd2[BO3]4 (SGB) konnte mithilfe einer stöchiometrischen Mischung aus SrCO3, Gd2O3 und B2O3 durch zweimaliges Sintern bis 1.350 °C phasenrein erzeugt werden. Ein Exzess von 3 Ma% B2O3 musste der Mischung beigesetzt werden, um das an B2O3 gebundene Wasser auszugleichen [125].
Kristalle des SGB ließen sich mit verschiedenen Orientierungen erfolgreich mit dem Czochralski-Verfaren synthetisieren. Unter Einsatz eines arteigenen, b-orientierten Keimes, einer Translation von 1 mm/h und einer Rotation von 4 /min konnten Kristalle mit guter Qualität bei hoher Erfolgsrate produziert werden. Bei den gezüchteten Kristallen waren keine Segregationserscheinungen zwischen Gadolinium und Strontium feststellbar. Jedoch weist das Auftreten von Fremdphasen (vor allem Gd2O3) in wenigen Kristallen auf eine mögliche, geringfügige Bevorzugung des Sr in der Struktur hin.
Die Härte des Materials ist mit ca. 5,5 nach Mohs bestimmt, die Dichte mit 5,15(1) g/cm3. SGB ist nicht hygroskopisch, lässt sich aber in mineralischen Säuren lösen. Die Schmelztemperatur konnte mit 1.461+/-5 °C bestimmt werden.
Einkristallines SGB besitzt ein Transmissionsfenster zwischen 215-3.450 nm. Das entspricht einer Bandlücke von 5,4 eV. In diesem Bereich werden über 80% des eingestrahlten Lichtes transmittiert. Im ultravioletten Spektrum finden sich für Gd charakteristische Absorptionsbanden, die durch Elektronenübergänge erzeugt werden. Im mittleren Infrarotbereich lassen sich um die Absorptionskante mehrere Absorptionsbanden, deren Ursache ungeklärt ist, feststellen. Sie stehen offensichtlich im Zusammenhang mit dem Auftreten von [BO3]3- -Gruppen, da sie auch bei anderen Boraten, wie dem Ca4Gd[O|(BO3)3] [99], vorkommen. Gepulvertes SGB weist im Bereich von 550-1.600 cm-1 zahlreiche Absorptionsbanden, die auf verschiedene Schwingungen innerhalb der [BO3]3- -Gruppe zurückgeführt werden können, auf. Es folgen zu kleineren Wellenzahlen hin vermutlich Sr-O- und Gd-O-Schwingungen.
Die thermische Ausdehnung von SGB-Kristallen ist anisotrop sowohl zwischen den kristallographischen Richtungen a, b und c als auch über die Temperatur innerhalb einer Richtung. Sie kann im Mittel zwischen 150-830 °C mit alpha11=18,1(2)*10-6/K, alpha22=8,9(3)*10-6/K und alpha33=20,3(4)*10-6/K angenommen werden. Die Ausdehnungskurven deuten mehrere Effekte an, wobei ein Effekt im Bereich von 450-700 °C und vermutlich zwei weitere im Bereich von 800-1.000 °C zu beobachten sind. Aufgrund der Stetigkeit der Kurve ist wahrscheinlich von Phasenübergängen höherer Ordnung auszugehen.
Zur Struktur des SGB konnten wichtige Grundverständnisse gewonnen werden. So lässt sich die Struktur bei Raumtemperatur nicht durch eine orthorhombisch zentrische Metrik beschreiben, da die Einzelreflexe bei Einkristallmessungen eine Aufspaltung im Bereich von 0,1 ° zeigen. Dies deutet auf das Vorhandensein von Zwillingen und auch auf eine mögliche monokline Metrik hin. Es fällt dabei besonders auf, dass die Aufspaltung mit zunehmendem Theta-Winkel nicht größer wird, so dass auch andere Phänomene für die Reflexaufspaltung verantwortlich sein könnten. Dennoch ergeben die ermittelte Raumgruppe Pnam, die zugehörigen Gitterparameter (a0=0,7408 nm, b0=0,8757 nm, c0=1,6057 nm) und Atomkoordinaten ein vereinfachtes Modell zur Veranschaulichung der Struktur. Hoch- und Raumtemperaturstruktur sind bis 700 °C unter Annahme des vereinfachten Modells isomorph, wobei die Gitterparameter entsprechend der Ausdehnung vergrößert sind. Die Gd- und Sr-Positionen sind untereinander mischbesetzt. Außerdem deutet sich eine Positionsfehlordnung einer Sauerstoff-Position an, der Ligand eines Borions auf spezieller Lage ist. Hinweise auf die korrekte Struktur liefern die entdeckten Phasenübergänge und Hochtemperatur-Einkristalldaten. Der in der Dilatometrie entdeckte Effekt zwischen 450-700 °C korreliert mit dem Rückgang der Reflexaufspaltung, die bei ca. 700 °C nicht mehr sichtbar ist, wobei sich dieser Rückgang vermutlich von Raumtemperatur bis 700 °C erstreckt. Damit bestätigt sich, dass der erst genannte Effekt als Phasenübergang höherer Ordnung aufgefasst werden kann. Die festgestellte Positionsfehlordnung von Sauerstoff verringert sich mit steigender Temperatur. Die Mischbesetzung ändert sich ebenfalls bis ca. 500 °C. Beide Effekte sowie auch größeren Schwingungsellipsoide der Sauerstopositionen um die allgemeine Borlage sind vermutlich Ausdruck für den stattfindenden Phasenübergang und verstärken die Annahme einer Zwillingsbildung.
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HAUMESSER, PAUL-HENRI. "Elaboration par croissance czochralski, caracterisation spectroscopique et proprietes laser de monocristaux dopes par l'ytterbium." Paris 6, 2000. http://www.theses.fr/2000PA066208.
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Cette etude s'inscrit dans la recherche de nouveaux lasers solides pompes par diodes pour l'emission autour de 1 m. Dans ce cadre, les materiaux actives par l'ytterbium offrent des performances accrues par rapport aux lasers au neodyme. Le choix de nouveaux materiaux repose sur plusieurs criteres. Le premier est leur facilite d'elaboration. La methode de czochralski constitue une technique de choix pour obtenir de gros monocristaux d'excellente qualite optique. Pour cette raison, l'un des aspects de ce travail a ete la mise au point d'une machine d'elaboration de monocristaux. Une attention particuliere a ete portee a la regulation de la croissance. Sur le plan spectroscopique, l'eclatement du niveau fondamental de l'ytterbium par le champ cristallin doit etre suffisant pour obtenir un fonctionnement laser quasi-4-niveaux. De plus, un desordre structural est souhaitable pour elargir les raies de transitions et ameliorer l'efficacite du pompage par diodes. Les composes retenus dans cette etude combinent ces caracteristiques. Ce sont les borates m 3tr(bo 3) 3 (m = ba, sr tr = lu, y) et ca 3tr 2(bo 3) 4 (tr = y, gd), et les silicates y 2sio 5(yso), sry 4(sio 4) 3o (sys) et ca 2al 2si 2o 7 (cas). L'etude de l'influence des conditions de croissance a permis d'obtenir dans la plupart des cas des cristaux de grandes dimensions (plusieurs cm 3) et de bonne qualite optique. Dans tous ces materiaux, les niveaux d'energie de l'ytterbium sont fortement eclates. L'utilisation du modele pcem permet de confirmer les diagrammes de niveaux d'energie experimentaux, et il est montre que ce modele peut etre employe dans une demarche predictive. Cela permettrait d'accelerer la decouverte de nouveaux materiaux potentiellement interessants. Enfin, l'oscillation laser a ete observee pour la plupart de ces composes sous pompage par un laser saphir-titane, avec un seuil generalement faible et des rendements tres prometteurs. De plus, l'emission laser peut etre accordable sur une large gamme de longueur d'onde.
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Pang, Shu Koon. "Investigation of recombination lifetime and defects in magnetic czochralski silicon for high efficiency solar cells." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/13554.
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Letty, Elénore. "Identification and neutralization of lifetime-limiting defects in Czochralski silicon for high efficiency photovoltaic applications." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI094/document.
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Les cellules photovoltaïques à base de silicium cristallin représentent plus de 90% du marché photovoltaïque mondial. Des architectures de cellules à haut rendement de conversion sont actuellement développées. Pour atteindre leurs performances maximales, ces architectures nécessitent néanmoins une amélioration des propriétés électriques des substrats de silicium cristallin. Les objectifs de cette thèse sont d’identifier les défauts limitant les propriétés électriques de ces substrats, de comprendre les mécanismes menant à leur formation et de proposer des moyens permettant leur neutralisation. Les matériaux étudiés sont des plaquettes de silicium Czochralski de type n, généralement utilisé pour les applications à haut rendement. Le four de tirage Czochralski a d’abord été modélisé afin de comprendre comment le passé thermique subi par le lingot de silicium lors de la cristallisation affecte la génération des défauts. Ces travaux ont été confirmés via des confrontations avec des données expérimentales, en utilisant une méthode originale développée dans le cadre de ce travail. Nous avons ensuite étudié l’influence du budget thermique lié aux procédés de fabrication des cellules sur la population de défauts. Nous avons ainsi pu montrer que la nature des défauts limitant les propriétés électriques du silicium était grandement modifiée selon le procédé de fabrication de cellules utilisé. Nous avons en outre mis en évidence une dégradation inattendue des propriétés électriques du silicium Czochralski de type n sous illumination, liée à la formation d’un défaut volumique inconnu. Les conditions de formation et de suppression de ce défaut ont été étudiées en profondeur. Enfin, les principaux défauts limitant les propriétés électriques du silicium ayant été identifiés et les mécanismes menant à leur formation compris, nous proposons dans un dernier chapitre des nouvelles techniques de caractérisation permettant de détecter les plaquettes défectueuses en début de ligne de production de cellules photovoltaïques, et ce à une cadence industriellePhotovoltaic solar cells based on crystalline silicon represent more than 90% of the worldwide photovoltaic market. High efficiency solar cell architectures are currently being developed. In order to allow their maximal performances to be reached, the electronic properties of their crystalline silicon substrate must however be enhanced. The goals of the present work are to identify the defects limiting the electronic properties of the substrate, to understand the mechanisms leading to their formation and to propose routes for their neutralization. The studied materials are n-type Czochralski silicon wafers, usually used as substrates for high efficiency photovoltaic applications. The Czochralski puller was first modeled in order to understand how the thermal history experienced by the silicon ingot during crystallization affects the defects generation. This study were validated through the comparison with experimental data using an original method developed in the frame of this work. We then studied the influence of the thermal budget associated to solar cell fabrication processes on the defects population. We thus showed that the nature of lifetime-limiting defects was completely changed depending on the solar cell fabrication process. Besides, we evidenced an unexpected degradation of the electronic properties of n-type Czochralski silicon under illumination, related to the formation of an unknown bulk defect. The formation and deactivation features of this defect were extensively studied. Finally, the main limiting defects being identified and the mechanisms resulting in their formation understood, we propose in a last chapter new characterization techniques for the detection of defective wafers at the beginning of production lines at an industrial throughput
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SANTOS, IVANILDO A. dos. "Estudo das soluções sólidas de LiGdsub(1-x)Lusub(x)Fsub(4) visando o crescimento de cristais." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11656.
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Made available in DSpace on 2014-10-09T12:54:23Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:15Z (GMT). No. of bitstreams: 0
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP
FAPESP:05/57580-2
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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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Stowe, David John. "An investigation of efficient room temperature luminescence from silicon which contains dislocations." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:9ee073b7-9e3c-4637-9ce1-62e9e4ade69d.
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This thesis presents an investigation of the phenomenon of efficient, room temperature luminescence from dislocation-engineered (DE) silicon. Previous work had demonstrated that the introduction of near-surface dislocation loops to a silicon substrate by boron ion implantation and high temperature annealing produced efficient electroluminescence at room temperature. However, the mechanism by which high efficiency luminescence is produced was not understood. A wide matrix of specimens containing dislocations was fabricated by a variety of methods, including ion implantation, and their luminescence efficiencies were correlated to their physical properties. Transmission electron microscopy was used to characterise the defect structures created by ion implantation. In the majority of specimens a band of dislocation loops in close proximity to the surface was observed. The dislocation loops were shown to be consistent with a mixture of Frank and perfect dislocation loops, the relative proportions of which were dependent upon processing conditions. The thermal evolution of the dislocation loop size distribution was investigated. For the first time, a size distribution displaying a double peak was observed. The size distribution was shown to be consistent with the Gaussian distribution of two defect populations of different mean diameter. The thermal evolution of the size distribution was investigated in silicon implanted samples. A flux of self-interstitials from Frank dislocation loops to perfect dislocation loops was deduced. The evolution of the dislocation loop sizes was found to be consistent with Ostwald ripening. Cathodoluminescence (CL) was used to investigate the luminescent properties of silicon at room temperature for the first time. A new CL system was installed for this work, initially the CL system was characterised and a routine to ensure a high degree of reproducibility was formed. The luminescence mechanism of DE-silicon was shown to be the same as in unprocessed silicon wafers; TO phonon-assisted recombination. The mechanism of enhanced luminescence from DE-silicon was unambiguously shown to be due to the gettering of electrically active impurities from the specimen bulk. A reduction in the bulk transition metal impurity concentration of up to 35 times was inferred. In samples which were implanted with boron the degree of gettering was found to show a logarithmic dependence on the dislocation density. Using a crosssectional mapping technique, implanted samples were shown to contain a lower concentration of transition metal impurities throughout the entire wafer in comparison to as-received, unprocessed specimens. Furthermore, the impurity concentration was found to be lowest in close proximity to the band of dislocation loops. The dislocation loops were found to act as non-radiative recombination centres and their strength was strongly influenced by the local carrier concentration. The high doping levels of samples implanted with boron were found to minimise the non-radiative recombination action of the dislocations. Low temperature annealing was used to improve the luminescence efficiency of DE-silicon further.
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Nawash, Jalal Mohammad. "A study of the crystal growth of select II-VI oxides by Czochralski and Bridgman techniques." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/J_Nawash_121406.pdf.
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Soares, Demetrio Artur Werner. "Estudo de monocristais de silicio czochralski pelos metodos: pseudo kossel e espalhamento difuso de raios x." Universidade de São Paulo, 1988. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-14062012-165956/.
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A determinação do estado de deformação de monocristais planos através da técnica pseudo-Kossel, combinada com o estudo do espalhamento difuso de raios X próximo a uma reflexão de Bragg, permite uma caracterização dos defeitos quanto a sua natureza, tamanho e simetria se houver poucas variedades de defeitos diferentes ou quando ocorrer a predominância de um deles. Estudamos monocristais de silício Czochralski dopados com antimônio ou com boro, e que também continham oxigênio e carbono devido ao processo de crescimento. Estas amostras apresentam aglomerados de defeitos pontuais com dimensões características em torno de 102 - 103 nm. Medidas de espalhamentos interplanares mostram que estas são mais fortemente influenciadas pela direção de crescimento que pela concentração de dopantes, e que as maiores alterações ocorrem à medida que 0 angulo entre a direção de crescimento e os planos diminuem. A partir das medidas dos espalhamentos interplanares podemos levantar 0 estado de deformação dos cristais através do tensor de \"strain\" e foi possível analisar a configuração \"stressstrain\". Desta análise obtivemos, além da variação do parâmetro de rede, 0 tensor de \"stress\" e dele 0 tensor momento de dipolo elástico P. 0 tensor P pode nos dar informações acerca da simetria do defeito &nos permitiu calcular 0 espalhamento difuso de raios X próximo de uma reflexão de Bragg. Vimos que algumas amostras estão deformadas numa configuração muito próxima daquela de cisalhamento simples e que a simetria do tensor P indica que em praticamente todas as amostras tem uma variedade grande de defeitos diferentes. Uma das amostras, Si com Sb (CSb= 8. 1018 dopantes/ Cm3)apresenta um tensor P pr6ximo daquele gerado por defeito que temsimetria ortorrombica e, para ela foram construidas curvas de isso intensidades em torno do ponto (004) da rede recíproca, calculados a partir das componentes de P, e que foram comparadas com as curvas de \"rocking\" experimentais.The accurate determination of strain distributions in single crystals through the pseudo-Kossel technique together with the analysis of the diffuse X-ray scattering near a Bragg reflection permits the characterization (nature, size and shape) of predominant defects. Czochralski silicon single crystals doped by diffusion during growth with antimony and boron were studied. These samples presented clusters of 102 - 103 nm. Interplanar spacings determined by the pseudo- Kossel method showed a significant dependence on growth direction,planes parallel to growth direction were the most affected. From and the dipole tensor P determined. This dipole tensor was employed in the calculation of the diffuse X-ray scattering. For one of the samples Si:Sb P presents an orthorrombic simetry. The results for this sample were compared with experimental rocking.
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Ruther, Ricardo. "Crescimento e caracterização de monocristais do semicondutor GaSb pela técnica do líquido encapsulante no método Czochralski." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1991. http://hdl.handle.net/10183/140843.
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Neste trabalho foram desenvolvidas algumas das etapas de um processo que culmina com a obtenção e caracterização de monocristais do semicondutor GaSb crescidos pela técnica de Czochralski com o uso de um líquido encapsulante. O trabalho constou basicamente de quatro etapas. Na primeira etapa, de obtenção das matérias-primas, procedeu-se à purificação do elemento antimônio (Sb) por fusão zonal horizontal e obteve-se o encapsulante óxido bórico (B2 O3 ) por desidratação do ácido bórico (H 130). A segunda etapa compreendeu a síntese estequiométrica do composto GaSb. A terceira etapa constou no crescimento dos cristais propriamente, em equipamento Czochralski construído no laboratório e na etapa final os cristais obtidos foram caracterizados por análises metalográficas, de composição química (Absorção Atômica e Retroespalhamento Rutherford), de propriedades elétricas (resistividade e efeito Hall) e por difração de raios-X (método de Laue). Os resultados do crescimento de sete cristais a partir de sementes policristalinas são apresentados. Estes cristais foram crescidos sob condições diversas: com o uso de dois encapsulantes distintos (BO23 e NaCl-KCl) sob fluxo de N e sem o uso de encapsulante sob fluxo de H2. As velocidades de rotação e puxamento utilizadas foram da ordem de 30 RPM e 20 mm/h respectivamente e os cristais que tiveram sua orientação determinada cresceram na direção <111>. As propriedades elétricas dos cristais são comparáveis às encontradas na literatura, sendo a sua densidade de discordâncias, no entanto, bastante elevada.In this work some of the stages of a process which leads to the production of GaSb semiconductor single crystals grown by the Czockralski technique utilizing a liquid encapsulant were developed (the process is called LEC Liquid Encapsulated Czochralski). The work consisted of four stages. In the first one, where the source materiais wer-e obtained, antimony (Sb) was puri fied by horizontal zone melting and the encapsulant, boric oxide (B2 O3), was obtained by dehydration 2 3 of boric acid (H l30 ). The second stage comprised the stoichiometric synthesis of the compound GaSb. The third stage consisted in the GaSb crystal growth (encapsulated and unencapsulated) in a 11 home-madell Czochralski growth apparatus, and in the final stage the obtained crystals were characterized by metallographic and chemical composition (Atomic Absorption Spectroscopy and Rutherford Backscattering Spectroscopy) analyses, as well as by X-ray diffraction (Laue's method) and electrical properties (electrical resistivity and Hall effect). Results were presented for seven crystals grown from pollycr-ystalline seeds. Those crystals were grown under diverse conditions: with the use of two distinct encapsulants (B O and the eutectic mixture NaCl-KCl) under N 2 3 2 atmosphere, and at an unencapsulated growth under H2 atmosphere. Rotation and pulling rates were around 30 RP1'1 and 20 mm/h respectively, and the crystals whose orientation was determined grew ln the <111> direction. Electrical properties of the crystals obtained were found to be in good agreement with results of other works, but the dislocation density was found to be excessively high.
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Raufeisen, Alexander [Verfasser], and Antonio [Akademischer Betreuer] Delgado. "Numerical Simulation of the Three-Phase Boundary Movement in the Czochralski Process / Alexander Raufeisen. Gutachter: Antonio Delgado." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2013. http://d-nb.info/1054164843/34.
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Zhou, Xiao. "The behaviour of nitrogen in Czochralski-grown silicon crystrals : its role in oxygen precipitation and intrinsic gettering." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240913.
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Streicher, Morgana. "Crescimento e caracterização de cristais de GaSb e GaInSB obtidos através do método Czochralski com líquido encapsulante." Pontifícia Universidade Católica do Rio Grande do Sul, 2011. http://hdl.handle.net/10923/3343.
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Previous issue date: 2011This work describes the growth and characterization of GaSb and GaInSb crystals, lightly doped with aluminum (Al), cadmium (Cd) and tellurium (Te). The Gallium antimonite is a semiconductor compound of the family III-V, with thermalphotovoltaic and optoelectronics characteristics. This is a preferential candidate on the new generation of low-power, low-consumption and high performance electronic devices. The methodology presents the description of the crystal growth process through Liquid Encapsulated Czochralski Method. The distribution of dopants and Indium, analyzed by Energy Dispersive Spectroscopy, was compared to resistivity, carrier density and mobility throughout the crystals. The n-type conductivity found in some of the crystals suggests that defects like SbGaSb and more likely VGaSb could be present. The uneven distribution of aluminum and tellurium in the analyzed samples are probably linked to a non-uniformity of the radial distribution of dopants due to defects as twins and facets found in the crystals.
Este trabalho descreve a obtenção e caracterização de cristais compostos semicondutores III-V GaSb e GaInSb, levemente dopados com alumínio (Al), cádmio (Cd) e telúrio (Te). O Antimoneto de Gálio é um composto semicondutor da família III-V, com característica optoeletrônica e termofotovoltaica, de aplicação preferencial para uma nova geração de dispositivos de baixo consumo de energia e alto desempenho. A metodologia apresenta a descrição do processo de crescimento dos cristais através do método Czochralski com Líquido Encapsulante. A distribuição dos dopantes e do índio, analisada por Espectroscopia por Dispersão de Energia, foi comparada com a resistividade, densidade de portadores e mobilidade ao longo dos cristais. A condutividade tipo-n encontrada em algum dos cristais sugere que defeitos complexos como VGaGaSb e mais provavelmente gálio no sítio do Sb (GaSb) possam estar presentes. A distribuição não uniforme do alumínio e do telúrio nas amostras analisadas provavelmente esteja vinculada a não uniformidade da distribuição radial dos dopantes em função da presença de defeitos como maclas, contornos de grão e pits encontrados nos cristais.
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Zhang, Xuzhao. "Crystals growth and laser properties of Nd:CNGS and Yb:CNGS." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/670355.
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El mètode Czochralski es va utilitzar per a l'augment de cristalls Nd: CNGS i Yb: CNGS, es van analitzar els fonaments del creixement i els problemes trobats durant el creixement del cristall. S'ha estudiat l'estructura i propietats tèrmiques dels cristalls Nd: CNGS i Yb: CNGS. Es va mesurar l'índex de refracció, l'espectroscòpia òptica dels cristalls Nd: CNGS i Yb: CNGS. Es van demostrar les propietats de duplicació de làser i auto-freqüència de Nd: CNGS i Yb: CNGS.El método de Czochralski se usó para cultivar Nd: cristales de CNGS e Yb: CNGS, se analizaron los fundamentos del crecimiento y los problemas encontrados durante el crecimiento del cristal. Estructura y propiedades térmicas de los cristales Nd: CNGS e Yb: CNGS fueron estudiados. Se midieron el índice de refracción, la espectroscopía óptica de los cristales Nd: CNGS e Yb: CNGS. Se demostraron las propiedades de duplicación láser y de frecuencia propia de los cristales Nd: CNGS e Yb: CNGS.
Czochralski method was used to growing Nd:CNGS and Yb:CNGS crystals,the growth fundamentals and problems encountered during the crystal growth were analyzed. Structure and thermal properties of the Nd:CNGS and Yb:CNGS crystals were studied. The refractive index, optical spectroscopy of the Nd:CNGS and Yb:CNGS crystals were measured. The laser and self-frequency doubling properties of Nd:CNGS and Yb:CNGS crystal were demonstrated.
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Pidol, Ludivine. "Scintillateurs denses et rapides pour la détection de rayonnement gamma : monocristaux à base de silicates de lutécium dopés Ce3+." Phd thesis, Paris 6, 2004. http://pastel.archives-ouvertes.fr/pastel-00001090.
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Ce travail concerne l'étude de cristaux scintllateurs et en particulier, le développement de silicates de lutécium dopés cérium: Lu2Si2O7:Ce3+ (LPS) et Lu2(1-x)Y2xSiO5:Ce3+ (LYSO). Une densité et un numéro atomique effectif élevés ,une reponse rapide, un rendement lumineux élevé sont quelques-unes des propriétés qui rendent les cristaux de LPS et de LYSO intéressants pour la detection de rayonnement gamma. En raison de leur application potentielle en imagerie médicales (TEP° et en géophysique, le développement de ces cristaux est envisagé. Un travail important d'optimisation des conditions d'élaboration par la méthode Czochralski a été effectué afin d'obtenir des cristaux performats de grande taille, et ce, de façon reproductible. Ce développement ne peut se faire sans une bonne compréhension des mécanismes. Dans ce sens, plusieurs approches (XPS, spectroscopie optique résolue en temps...) sont proposées pour localiser les niveaux d'energie des lanthanides par rapport à ceux de la matrice.
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Bahouka, Armel. "Comparaison des propriétés optiques de [bêta]-BBO obtenu par croissance TSSG et par tirage Czochralski en vue d'optimiser la génération de rayonnements UV." Metz, 2006. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2006/Bahouka.Armel.SMZ0601.pdf.
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Bêta-BBO est un cristal non linéaire très utilisé dans la conversion de fréquences vers l'UV. Son mode de fabrication le plus courant est la croissance TSSG (Top Seeded Solution Growth) à partir d'une solution composée de BaB2O4 dans le solvant Na2O. Bien que très répandus les cristaux TSSG contiennent impuretés et inclusions dues essentiellement au solvant et qui limitent leurs performances optiques. La méthode Czochralski (Cz) permet d'éviter l'ajout du solvant. Ainsi, des cristaux plus purs, avec une vitesse de tirage 24 fois supérieure sont obtenus en laboratoire. Cependant cette croissance exige un bain en surfusion hors équilibre thermodynamique et peut générer contraintes et dislocations dont il est intéressant de connaître l'impact sur les performances optiques. Pour qualifier voire distinguer les cristaux Cz et TSSG, des études sur la synthèse, les impuretés, la qualité cristalline du volume et des surfaces ainsi que sur la mise en forma des échantillons ont été menées dans le cadre de cette thèse. Les deux croissances ont des contraintes internes et surfaciques similaires mais les cristaux Cz comportent moins d'impuretés et présentent des densités de dislocation plus faibles. Les mesures des phénomènes d'absorption non linéaire et d'autofocalisation menées d'après la méthode Z-scan conduisent, dans la direction de l'accord de phase IR-visible, à une amélioration de la figure de mérite des échantillons Cz. Le coefficient effectif non linéaire mesuré sur ces cristaux pour la conversion visible-UV indique une meilleure efficacité pour les échantillons Cz qui peut en partie s'expliquer par les résultats d'absorption linéaireBBO is a non linear optical crystal which benefits from two growing methods, the top seeded solution growth (TSSG) and the Czochralski (Cz) growing method. In this PhD thesis, we stidied the impact of each process upon the optical properties of BBO. Crystals grown by the tssg method contain impurities and inclusions essentially due to the Na2O solvent that decrease their optical performances. The Cz grown crystals produced 24 times faster in laboratories should have less impurities since no solvent is used in the Cz technique. Nevertheless, the use of great temperature gradients could induce more dislocations and strains in those crystals which should also decrease the optical performances. In order to evaluate and to distinguish the two growing method and their impact upon the optical properties, numerous investigations on the crystal's crystalline quality and the crystal's chemical composition have been made. The results of these investigations lead to prove that Cz grown crystals and TSSG grown crystals have the same surface and volume strains but, Cz grown crystals have less impurities and less dislocations than the TSSG-grown crystals. The self focalization and non linear absorption figures of merit of Cz grown crystals studied by Z-scan method is better than those of the TSSG grown crystals. The non linear effective coefficient in the second harmonic generation from visible light to UV light is greater for the Cz-grown crystals
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Octaviano, Edson Salvador. "Influencia de campo elétrico na segregação de dopantes durante o processo de crescimento de cristais pelo método Czochralski." Universidade de São Paulo, 1991. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-20082014-111217/.
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Em processos de crescimento de cristais pelo método de Czochralski, é observado que um campo elétrico aplicado ao cristal durante o processo de crescimento modifica a quantidade de dopante incorporada ao cristal. É desenvolvido um modelo, baseado na teoria de Burton, Prim e Slichter, levando-se em consideração as duas classes de material envolvidas, os óxidos e os semicondutores, e os efeitos produzidos pelo campo elétrico, eletromigração, subresfriamento constitucional, Efeito Peltier e efeito Seebeck. Resultados experimentais obtidos em crescimentos de LiNbO3:Cr2O3 e Si:Al são usados para aplicações do modeloIn crystal growth processes through the Czochralski method, it is observed that an electrical field applied to the crystal during the growth process modifies the quatity of the dopant incorporated to the crystal. A model is developed based on Burton, Prim and Slichter´s theory, taking into consideration two classes of materials, the oxides and the semiconductors, and the effects produced by the electrical field, electromigration, constitutional supercooling, Peltier Effect, Seebeck Effect. Experimental results obtained from the growth of the LiNbO3:Cr2O3 e Si:Al singlecrystals are used to the model application
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Marsaud, Françoise. "Croissance par la méthode Czochralski de monocristaux de Bi₁₂GeO₂₀ purs et dopés : caractérisation de ses propriétés photoréfractives." Bordeaux 1, 1987. http://www.theses.fr/1987BOR10610.
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Adaptation d'un systeme de controle par pesee sur l'appareillage de croissance czochralski pour l'obtention de monocristaux purs et dopes de bi::(12)geo::(20). Caracterisations physicochimiques des monocristaux en parallele avec l'etude des performances optiques. Conclusions quant aux consequences d'un dopage controle de la phase. Optimisation des proprietes du materiau au regard de ses conditions d'elaboration
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GONDET, SYLVAIN. "Optimisation des conditions de croissance et réduction des dislocations dans des monocristaux d'InP élaborés par un procédé Czochralski." Grenoble INPG, 1999. http://www.theses.fr/1999INPG0043.
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Les dislocations presentes dans les substrats monocristallins d'inp se propagent dans les couches epitaxiees et entrainent une baisse des performances et de la duree de vie des composants opto et microelectroniques. Ces dislocations sont le resultat des contraintes thermiques subies par les monocristaux en cours de croissance par un procede czochralski encapsule. Pour diminuer la densite de defauts presente dans les plaquettes, les gradients thermiques dans le cristal, sources de contraintes, peuvent etre optimises par l'ajout d'ecrans thermiques. Des outils muneriques ont ete utilises pour tester l'impact des ces ecrans supplementaires sur le champ de temperature dans les differents elements du fours. Ces simulations, effectuees par la methode des elements finis, prennent en compte un grand nombre de phenomenes physiques comme la semitransparence de l'encapsulant ou la convection turbulente dans le bain et le gaz. La qualite structurale des plaquettes a ete caracterisee de deux facons : premierement par la densite surfacique des points d'emergence des dislocations mesuree par analyse d'image, deuxiemement par la largeur a mi hauteur d'un pic de diffraction. Ces deux methodes permettent de quantifier de facon reproductible les ameliorations apportees par les configurations donnant les meilleurs resultats numeriques. Une diminution de 40% des densites de dislocations a ete ainsi obtenue pour des plaquettes de 2 et 3 pouces de diametre. Un modele visco plastique de type haasen-sumino a ete ensuite couple avec les calculs thermiques. Il permet de calculer a partir du champ de temperature la densite de dislocations en chaque point de cristal et a chaque pas de temps. L'annihilation des dislocations, processus critique a haute temperature, a ete pris en compte et permet d'obtenir une tres bonne correlation qualitative et quantitative entre les mesures et les calculs. Il a ainsi ete determine que les dislocations presentes au centre de la plaquette sont produites au niveau de l'interface solide/liquide et que celles presentes a sa peripherie sont multipliees au niveau de la surface de l'encapsulant. Les resultats de cette these sont une meilleure qualite cristalline des plaquettes industrielles, le developpement d'outils numeriques specifiques a la croissance czochralski et une meilleure connaissance des phenomenes conduisant a la formation des dislocations.
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FERRARI, MARCO A. "Laser de Nd:YLF para aplicacoes em lidas." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11745.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Colbaugh, Katherine E. "Czochralski Growth of Doped Yttrium Aluminum Garnet (Y3Al5O12) Crystals and Oxygen Tracer Diffusion Analysis by ToF-SIMS and LEAP." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1429182946.
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Tanay, Florent. "Étude des défauts liés à l'oxygène dans le silicium Czochralski destiné aux cellules solaires photovoltaïques – Influence des impuretés isovalentes." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4353/document.
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Ce travail a pour but de comprendre les effets de deux principaux défauts liés à l’oxygène, les complexes bore-oxygène et les donneurs thermiques, sur les propriétés électriques et photovoltaïques du silicium. Plus particulièrement, les interactions des impuretés isovalentes, connues pour modifier la distribution spatiale de l’oxygène, avec ces défauts ont été étudiées. Deux protocoles expérimentaux ont d’abord été développés pour évaluer la dégradation de la durée de vie des porteurs de charge sous éclairement dans le silicium riche en fer. Ensuite, il a été mis en évidence que l’introduction de germanium et d’étain en très grande quantité dans le silicium n’influence pas de façon significative le rendement de conversion des cellules. Cependant, contrairement à ce qui a été récemment avancé dans la littérature, aucune limitation due au co-dopage au germanium ou à l’étain de la dégradation sous éclairement des performances photovoltaïques n’a été observée. Par contre, il a été montré que le carbone entraîne un ralentissement de la dégradation due aux complexes bore-oxygène. Egalement, contrairement à l’étain qui n’influence pas la génération des donneurs thermiques, le germanium conduit à un ralentissement de la formation de ces défauts. Une expression empirique a été proposée pour rendre compte de cet effet, et ce pour une large gamme de teneurs en germanium. Enfin, dans le silicium très dopé et très compensé, la génération des donneurs thermiques est identique au cas du silicium standard. Ceci constitue un résultat marquant puisqu’il permet de valider par l’expérience le fait que la formation des donneurs thermiques est limitée par la teneur en électronsThis study aims at understanding the effects of two main defects related to oxygen, the boron-oxygen complexes (responsible for light-induced degradation of the carrier lifetime) and the thermal donors (among other things, responsible for variations of the conductivity), on the electric and photovoltaic properties of silicon. More precisely, the interactions of isovalent impurities, known for modifying the oxygen spatial distribution, with these defects were studied. Two experimental protocols were first developed to evaluate the light-induced degradation of the carrier lifetime in iron-rich silicon. Then, the introduction in silicon of germanium and tin in high quantity were shown not to significantly influence the conversion efficiency of the cells. However, contrary to recent studies from the literature, no reduction due to germanium co-doping or to tin co-doping of the light-induced degradation of the photovoltaic performances was observed. However carbon was shown to lead to a slowdown of the degradation due to boron-oxygen complexes. Moreover contrary to tin which has no influence on the thermal donor generation, germanium slows down their formation. An empirical expression has been proposed to take into account this effect for a large range of germanium concentrations. Eventually in highly doped and compensated silicon, the thermal donor generation is identical as in conventional silicon, which experimentally confirms that the thermal donor formation is limited by the electron density
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Aron, Astrid. "Croissance cristalline et caractérisation laser des monocristaux d'oxoborates non linéaires M4R(BO3)3O (M=Sr, Ca et R=Y, La, Gd) dopés par les ions Yb3+ et/ou Er3+." Paris 6, 2002. https://pastel.archives-ouvertes.fr/pastel-00001101.
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Thomas, Paul David. "Optimization of silicon sheet growth and liquid encapsulated Czochralski growth of gallium arsenide by thermal-capillary modeling and stress analysis." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14335.
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Reino, Elisabeth. "Les oxoborates de calcium et de lanthanide, Ca4LnO(BO3) (Ln=Gd, Y, La) : synthèse et recherche d'angles d'accord de phase non critique pour la conversion de fréquence de longueurs d'onde laser spécifiques." Phd thesis, Paris 6, 2002. http://pastel.archives-ouvertes.fr/pastel-00001067.
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Actuellement, les lasers visibles et UV sont étudiés dans de nombreux domaines d'application (médecine, militaire, communication, etc.). Le doublage de fréquence intracavité à l'aide de cristaux non-linéaires apparaît comme une bonne solution pour générer de telles sources de lumière cohérente à partir de lasers solides usuels émettant dans l'IR. Dans ce cadre, la famille non linéaire Ca4LnO(BO3)3 (Ln = lanthanide, LnCOB) présente un intérêt grandissant pour la conception de systèmes lasers visibles compacts. De plus, ces offrent une grande flexibilité en terme de composition permettant d'envisager des substitutions partielles susceptibles de conduire à l'accord de phase non critique (APNC). Ainsi, nous nous sommes intéressés dans ce travail à diverses substitutions cationiques à travers les solutions solides telles que Gd1-xYxCOB, Gd1-xLaxCOB, Gd1-xScxCOB (élaborée pour la première fois), Ln1-xBixCOB (Ln = Gd ou Y) et (Ca1-xSrx)4GdO(BO3)3 dans le but d'étudier leur cristallogenèse et d'ajuster la longueur d'onde en APNC en composition. La plage spectrale visée est directement reliée à l'émission laser issue de la transition 4F3/2-4I9/2 des matrices lasers dopées au néodyme, par exemple YAP:Nd (YAlO3) à 930 nm, YAG:Nd (Y3Al5O12) à 946 nm ou ASL:Nd (Sr1-xNdyLax-yMgxAl11-xO19) à 900 nm. Nous avons également démontré que la composition destinée à l'APNC peut être déterminée en connaissant les indices de réfraction des matrices "mères" M1-xM'xCOB (M, M' = Ln) avec x = 0 ou 1, en utilisant la loi de Clausius-Mosotti. Deux systèmes lasers bleus ont alors été choisis pour générer le second harmonique de type I en APNC: un cristal laser YAG:Nd associé au non-linéaire Gd0.87Y0.13COB à 946 nm, ou à 900 nm en utilisant l'ASL:Nd associé à un cristal Gd0.56Y0.44COB. Par ailleurs, nous avons obtenu pour la première fois l'effet laser à 900 nm du cristal ASL:Nd.
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Li, Zhen [Verfasser], Andreas [Gutachter] Magerl, and Jürgen [Gutachter] Ristein. "In-Situ X-ray Study of Nano SiO_x with Germanium Doping in Czochralski Silicon / Zhen Li ; Gutachter: Andreas Magerl, Jürgen Ristein." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1144619238/34.
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