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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Fabrication et étude des propriétés de diodes Schottky sur diamant homoépitaxié p-/p+

WADE, Mamadou 30 September 2005 (has links) (PDF)
Les diodes réalisées avec le diamant comme semi-conducteur comportent de nombreuses potentialités dues à sa bande interdite de 5.45 eV. Parmi les principales, il y a le fonctionnement à des températures très supérieures à celles supportées par les autres semi-conducteurs, ainsi qu'une tension de claquage de plusieurs kV. Le but de ce travail est de réaliser des couches de diamant homoépitaxié faiblement dopées bore et préparées avec ajout d'oxygène, adaptées à ces diodes. Des méthodes de caractérisation telles que la spectroscopie Raman et la cathodoluminescence fournissent des informations sur la qualité cristalline des couches et la nature des défauts présents. Une étude de l'optimisation de la gravure par plasma O2 a permis de réaliser des contacts ohmiques sur la couche p+ et des structures mesa. Les caractéristiques de contacts ohmiques Au/Ti et Si/Al/Si et de contacts Schottky Ag/Ti et Ni/Er sont étudiées. La génération et la passivation des défauts révélés ainsi que leur interaction avec la compensation des accepteurs introduits par le bore sont déterminées par des mesures électriques et transitoires.
82

Chemical, Isotopic, and Textural Characteristics of Diamond Crystals and Their Mineral Inclusions from A154 South (Northwest Territories), Lynx (Quebec), and Kelsey Lake (Colorado): Implications for Growth Histories and Different Mantle Environments

Van Rythoven, Adrian David 31 August 2012 (has links)
Parcels of diamond crystals from the A154 South kimberlite diatreme, Northwest Territories (n=281), and the Lynx kimberlite dyke, Quebec (n=6598) were examined in terms of colour, size, morphology, and UV fluorescence (A154 South samples only). A subset of stones from each parcel (A154 South: n=60, Lynx: n=20) were cut and polished to expose internal zonation and mineral inclusions. Exposed primary mineral inclusions were quantitatively analyzed for major elements by EMPA. Diamond crystals from the Kelsey Lake kimberlite diatreme, Colorado (n=20), were cut into plates and analyzed for nitrogen aggregation states by FTIR. Twelve of these stones were then analyzed with further subsets from A154 South (n=18) and Lynx (n=16) for carbon isotope ratios and nitrogen abundances by SIMS. Every diamond crystal cut and polished had its internal zonation imaged with CL. Mineral inclusion data from A154 South and Lynx show that the mantle keel of the Slave craton is slightly less depleted than that of the Superior craton, and both are less depleted than those of the Kaapvaal and Siberian cratons. Equilibration conditions plot on hotter geothermal gradients (surface heat flows ~42 mW/m2) than for those of typical Archean cratons (≤40 mW/m2). Equilibration temperatures (~1150-1250°C) are ~100-200°C hotter than previously reported from Kelsey Lake (~1020°C). Kelsey Lake and A154 South samples have carbon isotope ratios and nitrogen contents typical of most diamond populations worldwide. Diamond crystals from Lynx are entirely different, consisting of mostly Type II diamond with δ13C (vs. PDB) values from approximately -3.6 ‰ to +1.7 ‰. These 13C-enriched samples are suggested to be the result of extreme Rayleigh fractionation of diamond from a carbonate fluid and possibly input of carbon sourced from subducted abiotic oceanic crust. Also notable is that growth trends (δ13C-[NT]) for most of the samples studied show little or no consistency with published fractionation models.
83

Chemical, Isotopic, and Textural Characteristics of Diamond Crystals and Their Mineral Inclusions from A154 South (Northwest Territories), Lynx (Quebec), and Kelsey Lake (Colorado): Implications for Growth Histories and Different Mantle Environments

Van Rythoven, Adrian David 31 August 2012 (has links)
Parcels of diamond crystals from the A154 South kimberlite diatreme, Northwest Territories (n=281), and the Lynx kimberlite dyke, Quebec (n=6598) were examined in terms of colour, size, morphology, and UV fluorescence (A154 South samples only). A subset of stones from each parcel (A154 South: n=60, Lynx: n=20) were cut and polished to expose internal zonation and mineral inclusions. Exposed primary mineral inclusions were quantitatively analyzed for major elements by EMPA. Diamond crystals from the Kelsey Lake kimberlite diatreme, Colorado (n=20), were cut into plates and analyzed for nitrogen aggregation states by FTIR. Twelve of these stones were then analyzed with further subsets from A154 South (n=18) and Lynx (n=16) for carbon isotope ratios and nitrogen abundances by SIMS. Every diamond crystal cut and polished had its internal zonation imaged with CL. Mineral inclusion data from A154 South and Lynx show that the mantle keel of the Slave craton is slightly less depleted than that of the Superior craton, and both are less depleted than those of the Kaapvaal and Siberian cratons. Equilibration conditions plot on hotter geothermal gradients (surface heat flows ~42 mW/m2) than for those of typical Archean cratons (≤40 mW/m2). Equilibration temperatures (~1150-1250°C) are ~100-200°C hotter than previously reported from Kelsey Lake (~1020°C). Kelsey Lake and A154 South samples have carbon isotope ratios and nitrogen contents typical of most diamond populations worldwide. Diamond crystals from Lynx are entirely different, consisting of mostly Type II diamond with δ13C (vs. PDB) values from approximately -3.6 ‰ to +1.7 ‰. These 13C-enriched samples are suggested to be the result of extreme Rayleigh fractionation of diamond from a carbonate fluid and possibly input of carbon sourced from subducted abiotic oceanic crust. Also notable is that growth trends (δ13C-[NT]) for most of the samples studied show little or no consistency with published fractionation models.
84

Remote sensing, geochemistry, geochronology, and cathodoluminescence imaging of the Egrigoz, Koyunoba, and Alacam plutons, Northern Menderes Massif, Turkey

Jacob, Lauren Rolston 15 July 2011 (has links)
The Egrigoz, Koyunoba, and Alacam plutons are located in the Northern Menderes Massif of western Turkey between the Simav normal fault to the south and the Izmir-Ankara-Erzincan suture to the north. Although much attention has focused on their geochemical and geochronological history, their relationship to each other and other major structures in the region is still debated. Some geologic maps show the Egrigoz and Koyunoba pluton bounded to the west by the low-angle Simav detachment fault. In contrast, other regional maps show no offsets between the plutons and surrounding metamorphic rocks. Yet other studies indicate thrust faults may be present near the Egrigoz pluton, between Menderes metamorphic rocks and a meta-rhyolite unit. To gain a better understanding of the history of the Egrigoz, Koyunoba, and Alacam plutons, ArcGIS digital elevation data from the region, geochronological data, geochemical analyses, and cathodoluminescence (CL) images were acquired to search for effects of micro- to macro-scales of deformation. Numerous ~E-W trending extension lineations that parallel the Simav graben and cut the plutons were observed in relief images. These lineations, likely due to large-scale ~N-S extension, continue across plutons inferring that extension continued after the exhumation of these rocks. The Simav graben and its associated high-angle fault are evident in the elevation data, but no other significant detachment-related basins or structures are shown, including the low-angle Simav detachment. U-Pb zircon ages, ranging from 29.9±3.9 Ma to 14.6±2.6 Ma, suggest the plutons crystallized over a ~15 m.y. time frame. Samples from the plutons are peraluminous S-type granite to granodiorites. The plutons were emplaced in a post-collisional volcanic-arc setting and range from magnesian to ferroan with increasing silica contents. Geochemical analyses show little difference between the three plutons, consistent with the rocks arising from a similar source. To document microstructures that might help explain these heterogeneities, CL images were obtained. CL images document a complicated tectonic history including magma mixing, multiple episodes of brittle deformation, and fluid alteration. The CL images constitute evidence of a complex multi-stage tectonic history for the region that includes water-mediated brittle deformation. / text
85

Cathodoluminescence spectroscopy studies of aluminum gallium nitride and silicon device structures as a function of irradiation and processing

White, Brad Derek, January 2006 (has links)
Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 191-206).
86

Contribui??o da catodoluminesc?ncia para o entendimento da diag?nese da forma??o Janda?ra: ?reas do campo de petr?leo da fazenda Bel?m e Lajedo do Ros?rio

Fernandes Neto, Severino 16 December 2009 (has links)
Made available in DSpace on 2014-12-17T14:08:43Z (GMT). No. of bitstreams: 1 SeverinoFN_DISSERT.pdf: 3869767 bytes, checksum: 945ebd462d1133b15f06af55a2ec4392 (MD5) Previous issue date: 2009-12-16 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The general objective of this study was to contribute to the understanding of the chemical evolution of fluids that percolate through carbonate rocks of the Janda?ra Formation. The oxidation and reduction conditions in which grains, source and cement were formed was investigated using the cathodoluminescence technique (CL). The study area is located in the west part of the Potiguar Basin (Fazenda Bel?m field) and Ros?rio Ledge (Felipe Guerra municipality, State of Rio Grande do Norte, Brazil). The analysis of thin sections of carbonate rocks under CL revealed that grains (allochemical or not) and diagenetic products (micritization, dolomitization, neomorphism and cementation) exhibit since absence of luminescence the various luminescence colors (yellow, orange, red, brown, and blue) in a variety of intensities. As pure calcite shows dark blue luminescence, the occurrence of different luminescence colors in calcite crystals suggest one or more punctual crystal defects such as free electron, free space and impurity. The dyeing of thin sections with alizarin and potassium ferrocyanide revealed the absence of ferrous carbonate in the different lithotypes of Janda?ra Formation. Therefore, the different colors and intensities of CL observed in these rocks are probably caused by the presence of ion activators such as Mn2+ and is not an activator/inhibitor combination. In the same way, the absence of luminescence is very probably caused by the absence of activator ions and not due to the low concentration of inhibitor ions such as Fe2+. The incorporation of Mn2+ in the different members of the Janda?ra Formation must have been controlled by the redox state of the depositional environment and diagenesis. Therefore, it is possible that the luminescent members have been formed (e.g.,ooids) or have been modified (gastropod neomorphism) under reduction conditions in the depositional environments, in subsurface during the burial, or, in the case of Rosario Ledge samples , during the post-burial return to surface conditions. As regards the sudden changes from low to moderate and to strong luminescence, these features should indicate the precipitation of a fluid with chemical fluctuations, which formed the frequent zonations in the block cement of the Rosario Ledge samples. This study suggests that the different intensities and colors of CL should be correlated with the Mn2+ and Fe2+ contents, and stable isotopes of samples to determine the salinity, temperature, pH e Eh conditions during deposition / O objetivo geral deste trabalho foi contribuir para a compreens?o da evolu??o qu?mica dos fluidos percolantes atrav?s das rochas carbon?ticas da Forma??o Janda?ra. As condi??es oxidantes e redutoras nas quais gr?os, matriz e cimento foram formadas foi investigada usando a t?cnica da catodoluminesc?ncia (CL). A ?rea de estudo localiza-se a oeste da Bacia Potiguar (Campo da Fazenda Bel?m) e no Lajedo do Ros?rio (Munic?pio de Felipe Guerra, Estado do Rio Grande do Norte, Brasil). As an?lises das l?minas delgadas das rochas carbon?ticas sob CL revelou que gr?os (aloqu?micos ou n?o) e produtos diagen?ticos (micritiza??o, dolomitiza??o, neomorfismo e cimenta??o) exibiu desde aus?ncia de luminesc?ncia ? v?rias cores de luminesc?ncia (amarela, laranja, vermelha, marrom e azul) numa variedade de intensidades . Como a calcita pura mostrou luminesc?ncia azul escuro, a ocorr?ncia de diferentes cores de luminesc?ncia em cristais de calcita sugere um ou mais defeitos pontuais nos cristais tais como el?trons livres, espa?os livres e impurezas. O tingimento das l?minas delgadas com alizarina e ferrocianeto de pot?ssio revelou aus?ncia de carbonatos ferrosos nos diferentes lit?tipos da Forma??o Janda?ra. Portanto, as diferentes cores e intensidades de CL observada nestas rochas s?o provavelmente causadas pela presen?a de ?ons ativadores tais como Mn2+ e n?o uma combina??o ativador / inibidor. Da mesma forma, a aus?ncia de luminesc?ncia ? muito provavelmente causada pela aus?ncia de ?ons ativadores e n?o devido a uma baixa concentra??o de ?ons inibidores tais como Fe2+. A incorpora??o do Mn2+ nos diferentes constituintes da Forma??o Janda?ra deve ter sido controlada atrav?s do estado redox do meio ambiente deposicional e diagen?tico. Portanto ? poss?vel que os constituintes luminescentes tenham se formados (Ex: o?ides) ou tenham sido modificados (Ex: neomorfismo de gastr?podes) sob condi??es redutoras no meio ambiente deposicional, em subsuperf?cie durante o soterramento, ou, no caso das amostras do Lajedo do Ros?rio, durante o p?s-soterramento, no retorno ?s condi??es superficiais. No que diz respeito ?s mudan?as bruscas de luminesc?ncia baixa para moderada e forte, estas caracter?sticas devem indicar a precipita??o de um fluido com flutua??es qu?micas, nas quais formou freq?entes zona??es no cimento blocoso das amostras do Lajedo do Ros?rio. Este estudo sugere que as diferentes intensidades e cores de CL deve ser correlacionado com o conte?dos de Mn2+ e Fe2+ e is?topos est?veis das amostras para determinar a salinidade, temperatura, pH e Eh durante deposi??o
87

Optische Eigenschaften von Versetzungen in Silizium

Allardt, Matthias 23 April 2015 (has links)
Versetzungen sind linienhafte Störungen in Kristallen und beeinflussen die mechanischen, elektrischen und optischen Eigenschaften des Halbleitermaterials. In dieser Arbeit werden die optischen Eigenschaften von Versetzungen in Silizium anhand des Studiums ihrer charakteristischen Lumineszenz, der sogenannten D-Linien, untersucht. Dabei wurden die Versetzungen in einkristallinen Siliziumproben verschiedener Orientierung in einem einstufigen Prozess mittels plastischer Verformung bei hohen Temperaturen erzeugt und ggf. in einem zweiten Schritt durch Hochlastverformung bei tieferen Temperaturen modifiziert. Als Methoden zur Untersuchung der optischen Eigenschaften der Versetzungen werden Photolumineszenz (PL)- und Kathodolumineszenz (KL)-Spektroskopie verwendet. Gleitstufen an der Probenoberfläche werden mittels Rasterelektronenmikroskopie (REM), die Versetzungsanordnungen im Probenvolumen mittels Transmissionselektronenmikroskopie (TEM) abgebildet. Die Versetzungsstruktur der auf Einfachgleitung orientierten Proben ist durch relaxierte Versetzungen (einstufige Verformung) bzw. gerade Versetzungen (zweistufige Verformung) gekennzeichnet. In der auf Vielfachgleitung orientierten Probe werden mehrere Gleitsysteme gleichartig aktiviert. Es bildet sich ein Zellmuster aus, wobei das Innere der ca. 1 µm großen Zellen im Wesentlichen versetzungsfrei ist und die Zellwände eine hohe Versetzungsdichte aufweisen. Generell sind die mittleren Versetzungsdichten aller Proben hoch. Sie betragen zwischen 5 x 10^7 und 1 x 10^9 cm-2. Die Lumineszenz der einstufig verformten Proben ist durch das Auftreten von vier Linien (D1 bis D4) im Spektrum gekennzeichnet. In den zweistufig verformten Proben dominieren die Linien D5 und D6 die Lumineszenz. Die spektralen Positionen aller D-Linien entsprechen den aus der Literatur bekannten Daten. Die integrale Lumineszenzintensität im Bereich der D-Linien nimmt mit wachsender mittlerer Versetzungsdichte zu. Zusätzlich kann in den zweistufig verformten Proben eine bisher nicht identifizierte Lumineszenzlinie bei einer Energie von 1,090 eV festgestellt werden. Für diese Linie wird in dieser Arbeit die Bezeichnung P^2SD verwendet. In den KL-Abbildungen wird für alle D-Linien und die P^2SD-Linie im Wesentlichen eine örtlich homogene Lumineszenzverteilung festgestellt. Dies wird auf eine im Maßstab des KL-Wechselwirkungsvolumens homogene Versetzungsverteilung zurückgeführt. Die lokalen Schwankungen der KL um die mittlere Intensität betragen maximal 15 %. Diese Schwankungen äußern sich in hellen und dunklen Lumineszenzstreifen, deren Breite deutlich größer als der mittlere Versetzungsabstand ist. Aus dem Vergleich von KL-Bildern mit Rückstreuelektronenbildern der Oberflächengleitstufen ergeben sich folgende Aussagen: Die KL-Intensität der D3- und D4-Linie ist auf markanten Gleitbändern im Vergleich zur Umgebung verringert, wogegen die Intensität der Linien D1 und D2 auf markanten Gleitbändern erhöht ist. Für die D5-Bande, die D6-, und die P^2SD-Linie kann kein allgemeiner Zusammenhang zwischen der Lokalisierung der Lumineszenz und der Gleitaktivität festgestellt werden. Anhand der experimentellen Ergebnisse kann die D3-Linie als TO-Phononenreplik der D4-Linie identifiziert werden. Für die D4-Lumineszenz werden zwei Rekombinationsmodelle diskutiert. Zum einen kann sie durch die exzitonische Rekombination an eindimensionalen Energiebändern erklärt werden, die durch das Verzerrungsfeld der Versetzungen von den jeweiligen Volumenenergiewerten abgespalten sind. Zum anderen kann auch die Rekombination eines tief gebundenen Elektrons mit einem schwach gebundenen Loch für die D4-Lumineszenz verantwortlich sein. In jedem Fall ist das Auftreten der D4-Linie an die Existenz von relaxierten 60 °- und Schraubenversetzungen gebunden. Die D1-Linie wird als OGamma-Phononenreplik der D2-Linie vorgeschlagen. Die D2-Linie selbst kann als ein strahlender Übergang zwischen zwei gebundenen Zuständen eines zweidimensionalen Potentialtopfs endlicher Tiefe modelliert werden. Die Abmessungen dieses Potentialtopfs sind dabei durch die Ausdehnung von Kinken und Jogs auf der Versetzungslinie gegeben. Allerdings könnte auch ein interner Übergang zwischen den Niveaus eines tiefen Defekts innerhalb der Bandlücke als Erklärung herangezogen werden. Wegen der Zunahme der Lumineszenzintensiät der D2-Linie durch thermische Behandlungen sollten Kinken, Jogs, und Punktdefekte im Verzerrungsfeld der Versetzungen als Ursache der D2-Lumineszenz in Frage kommen. Auch die P^2SD-Linie kann mithilfe von zwei unterschiedlichen Rekombinationsmodellen erklärt werden (free-to-bound-Übergang oder exzitonische Rekombination an zweidimensionalen Energiebändern). Punktdefekte, die während des zweistufigen Verformungsprozesses entstehen, könnten die P^2SD -Linie hervorrufen.
88

Integrated subsurface study on lithofacies and diagenetic controls over porosity distribution in the Upper Ordovician Trenton Limestone in Northwestern Ohio

Ahsan, Mustafa 17 May 2019 (has links)
No description available.
89

Growth Parameter Dependence and Correlation of Native Point Defects and Dielectric Properties in Ba<sub>x</sub>Sr<sub>1-x</sub>TiO<sub>3</sub> Grown by Molecular Beam Epitaxy

Rutkowski, Mitchell M. 09 August 2013 (has links)
No description available.
90

Люминесцентный контроль радиационных полей с использованием двуокиси циркония : выпускная квалификационная работа специалиста / Radiation Fields Luminescence Control with the use of zirconium oxide

Казанцева, М. Г., Kazantseva, M. G. January 2015 (has links)
Цель работы – изучение люминесцентных свойств двуокиси циркония при различных видах облучения, и оценка возможности его использования для высокодозной дозиметрии электронных пучков. В результате исследования образцов получен комплекс параметров, характеризующих их фотолюминесцентные и термолюминесцентные свойства, проведено сравнение найденных параметров с известными литературными данными. Обнаружена сублинейная дозовая зависимость интенсивности термолюминесценции моноклинного ZrO2 от дозы облучения, что подтверждает возможность его использования для дозиметрии электронных пучков. Проведен анализ экологических рисков и соблюдения правил безопасности жизнедеятельности при экспериментальных исследованиях. / The purpose of this work is the study of luminescent properties of zirconia excited by different types of radiation, and to assess the possibility of its use for high-current electron beams dosimetry. Obtained set of parameters characterizing their photoluminescence and thermoluminescence properties was compared with the parameters found in literature. Sublinear dose dependence of thermoluminescence intensity of monoclinic ZrO2 confirms the possibility of its use for dosimetry of electron beams. Ecological risks and compliance with the rules of life safety during experimental investigations were analyzed.

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