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Geochemical and geochronological relationships between granitoid plutons of the Biga Peninsula, NW TurkeyBlack, Karen Naomi 20 July 2012 (has links)
The Aegean Sea is considered to be a classic back-arc basin. Back-arc basins may develop by active processes including retreat of the overriding plate or upwelling from the subducting slab. Alternatively, back-arc basins may develop as passive responses to regional tensional stresses. The Biga Peninsula of western Turkey provides an opportunity to explore and test these models. The Biga region is characterized by granitoid plutons of Cretaceous to Miocene age that may provide insight into the nature of extension. This study focuses on understanding the evolution of three of these plutons, the Kozak, Eybek, and Kestanbolu.
Geochemical and geochronological data and cathodoluminescence (CL) images of the rocks and zircons were acquired. The first in situ (in thin section) ion microprobe U-Pb ages of zircon, and the first zircon ages ever reported from the Kozak and Eybek plutons are presented. Zircon ages range from 36.5±6.6 Ma to 17.1±0.7 Ma (238U/206Pb, ±1) with two ages from a single grain of 280±18 Ma and 259±14 Ma. Samples from the Kozak and Eybek plutons are magnesian, calc-alkalic, and metaluminous, whereas the Kestanbolu rocks are magnesian, alkali-calcic, and metaluminous with one ferroan sample. The Rb vs. (Y+Nb) diagram suggests the Kozak and Kestanbolu plutons have a volcanic arc source, whereas the Eybek pluton records a within plate setting. CL imagery documents magma mixing, brittle deformation, and fluid- rock interactions based upon cracked plagioclase cores, cross-cutting microcracks, and fluid reaction textures of myrmekite and red rims on alkali feldspar.
The plutons were generated following the collision of the Sakarya continent with the Anatolide-Tauride block. Geochemical data suggest the Kozak and Kestanbolu granitoids were generated by fluid flux melting from dehydration of the subducting slab of the Anatolide-Tauride block. The Kestanbolu granitoid intruded into the Vardar Suture north of this collision, whereas the Eybek pluton was created within the lithosphere during exhumation of the Kazdağ Massif. The Eocene - Oligocene zircon ages indicate emplacement and initial crystallization of the plutons. Early Miocene ages indicate ongoing extension in the region at this time and are consistent with earlier interpretations that subduction slab roll-back along the Hellenic arc formed the extensional environment in the region at this time. / text
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An experimental and theoretical study of new phosphors for full color field emission displaysZhang, Fu-Li 05 1900 (has links)
No description available.
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Structural defects in CdTe and related materialsWatson, C. C. R. January 1993 (has links)
This work is concerned with the characterisation and observation of structural defects in bulk crystals of CdTe and Cd(_0.96)Zn(_0.04)Te and epitaxial layers of Cd(_0.24)Hg(_0.76)Te, and the validation of appropriate characterisation techniques. The driving force behind this project being the use of Cd(_x)Hg(_1-x)Te as an infra-red detector material. The cathodoluminescence technique has been shown to be an excellent technique for both the qualitative and quantitative identification of structural defects in bulk CdTe and (Cd,Zn)Te. The temperature dependent CL contrast technique is developed and is used to quantitatively distinguish dislocations and precipitates which are represented by a qualitatively similar contrast in CL micrographs. The contrast variations at both type of defect are discussed, and the temperature dependence of the contrast at dislocations is compared with contrast theories derived for the complementary electron beam induced current (EBIC) technique. The action of a saturated ferric chloride solution as a defect revealing etch for CdTe has also been investigated. The etch was found to reliably develop pits on a range of crystal orientations including the technologically important (iii)3 face of both CdTe and Cd(_0.96)Zn(_0.04)Te. Direct correlations with CL and infra-red microscopy has shown the etch to successfully reveal twin boundaries, dislocations and precipitates. The etchant is also shown to reliably develop pits in (Cd,Hg)Te epilayers. The structural quality of boules of CdTe grown by the vertical Bridgman technique with and without the accelerated crucible rotation technique (ACRT) have been assessed by CL microscopy, ferric chloride defect etching and triple axis X-ray diffraction. The use of the ACRT modification is shown to decrease die dislocation and precipitate content, and the mosaic tilt, within CdTe boules. ACRT CdTe is also shown to contain a comparable dislocation density, and a lower precipitate density, to that observed in boules of non-ACRT Cd(_0.96)Zn(_0.04)Te. The lowest mosaic tilt however is seen to occur in (_0.96)Zn(_0.04)Te. Dislocation rosettes observed in ACRT CdTe grown from a Cd rich source are shown to be a result of Cd precipitates and the crystal quality of melt grown CdTe is compared with the quality of boules of CdTe grown from the vapour using the 'Durham' technique. Defect etching and triple axis X-ray studies on epitaxial films of LPE (_0.24)Zn(_0.76)Te have indicated a reduction in the dislocation density with increasing thickness, for layer thicknesses < 6µm. In thicker regions the film dislocation density is observed to maintain a constant (or background) level, the magnitude of which varies from layer to layer. For growth on CdTe and (_0.96)Zn(_0.04)Te substrates, both containing a similar dislocation density (i.e < 5 x 10(^4) cm(^2)), the constant (thick film) dislocation density is seen to be higher than the dislocation density in the corresponding substrate, with its magnitude being dependent on the lattice misfit in the system. These observations are discussed with reference to Mattthews-Blakeslee, and dislocation half-loop, strain relief mechanisms. The fall in the dislocation density from the interface value to the constant (thick layer) value is seen to show a good fit to a strain relief model which predicts the depth dependence of dislocation densities within epitaxial films.
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Application of cathodoluminescence and quantitative color analysis to the study of glass for forensic purposesNawrocki, Heidi D. January 2008 (has links)
Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains ix, 85 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 63-65).
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ZnGa₂O₄ and ZnGa₂O₄:Mn²⁺ for potential use in vacuum fluorescent displaysShea, Lauren Elizabeth 10 January 2009 (has links)
Zinc gallate and Mn²⁺-activated zinc gallate were identified as potential low-voltage cathodoluminescent phosphors for use in vacuum fluorescent displays. The stability of these oxide phosphors in high-vacuum and absence of corrosive gas emission under electron bombardment, offer advantages over commonly used sulfide phosphors.
A low-voltage cathodoluminescence spectrophotometer was developed for phosphor characterization. Sample brightness was measured as a function of anode voltage (10-300 VDC). The effects of activator concentration, phosphor layer thickness, deposition process, and internal pressure were examined. From photoluminescence measurements, absorption and emission centers were identified, the role of composition in the luminescence process explained, and host-to-activator, non-radiative energy transfer identified for ZnGa₂0₄:Mn²⁺.
Samples of the general composition Zn<sub>1-x</sub>Mn<sub>x</sub>Ga₂O₄, with x ranging from 0 to 0.03, were synthesized by solid-state reaction techniques using oxide precursors fired in air, followed by reduction firing in 98%N₂, 2%H₂. The phase-pure ZnGa₂O₄ spinel structure of all the compositions was characterized by X-ray diffraction. / Master of Science
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Contribution à l'étude des larges bandes d'émission du cinabre (HgS alpha).Aicardi, Jean-Pierre, January 1900 (has links)
Th.--Sci. phys.--Perpignan, 1977.
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Maîtrise des propriétés optiques de céramiques transparentes par le contrôle des paramètres physicochimiques des précurseurs et des techniques d'élaboration. Cas du YAG. / Control of ceramics optical properties through mastering precursors phisico-chemical parameters and elaboration technics. Case of YAG.Lachaud, Etienne 05 March 2019 (has links)
Ces travaux ciblent l’étude de la relation entre la microstructure et les propriétés optiques découlant d’une céramique de YAG:Ce. Les propriétés microstructurales d’une céramique luminescente définissent sa capacité à transmettre et émettre la lumière. En considérant l’ensemble des étapes d’élaboration, de la mise en forme de la poudre jusqu’à la densification maximale du matériau final, nous cherchons à déterminer les facteurs régissant l’activité de luminescence. Les céramiques ont été élaborées à partir de poudres commerciales produites par l’entreprise Baikowski. Les caractérisations réalisées sur les particules de poudres ont mis en évidences de défauts internes à l’échelle nanométrique. Une mise en forme par atomisation, pressage uni-axial et pressage isostatique a précédé une densification par pressage isostatique à chaud (HIP). Afin de conservé une bonne finesse granulaire, nous n’avons pas utilisé d’additif de frittage. La maitrise des conditions d’élaborations nous a permis de réaliser des céramiques à microstructures variables. Certaines de ces céramiques présentent de bonnes propriétés de transparence. Les caractérisations optiques confirment l’influence des facteurs expérimentaux considérés. Nous notons l’impact significatif de la quantité et de la dimension des phases diffusantes sur les propriétés optiques du matériau à travers les mécanismes de diffusion optique. De plus, ces phases diffusantes affectent le spectre d’émission du matériau. Un rendement de luminescence maximal a été observé pour une taille de grain sub-micronique. La corrélation des caractérisations optiques et microscopiques mettent en évidence l’influence de l’absorption non radiative sur l’efficacité globale. Grace à la technique de cathodoluminescence couplé à la microscopie électronique à balayage, nous avons observé la répartition spatiale de la luminescence ou sein de l’ensemble des matériaux élaborés / This work aims to study the relationship between microstructure and optical properties of a Ce:YAG ceramic. The microstructural properties of a luminescent ceramic define its capacity to transmit and emit light. Considering the integrally of the elaboration process, from powder shaping to maximal densification, our goal is to identify the factors ruling the luminescence activity. Ceramics were elaborated from Baikowski’s commercial powders. The characterizations on powders particules put in evidence internal defects at the nano scale. The shaping steps (granulation, pressing and isostatic pressing) were followed by densification through hot isostatic pressing (HIP). In order to keep a thin microstructure, we did not used any sintering additives. The mastering of elaboration allowed us to fabricate ceramics with different microstructures. Some of those ceramics present good transparency. Optical characterizations confirm the influence of the investigated parameters. We note the significant impact of both quantity and dimension of secondary phases on optical properties through scattering processes. Thus, scattering affects the emission spectra of the material. A maximal luminescence yield has been observed for a submicronic grain size. Linking optical and microscopic observations, we put in evidence the influence of un-radiative absorption mechanisms on efficiency. Thanks to cathodo-luminescence scanning electron microscopy, we observed the spatial repartition of luminescence on the full range of the elaborated materials
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Ultrathin and nanowire-based GaAs solar cells / Cellules solaires en GaAs ultra-minces et à base de nanofilsChen, Hung-Ling 16 October 2018 (has links)
Confiner la lumière dans un volume réduit d'absorbeur photovoltaïque offre de nouvelles voies pour les cellules solaires à haute rendement. Ceci peut être réalisé en utilisant des nanostructures pour le piégeage optique ou des nanofils de semi-conducteurs. Dans une première partie, nous présentons la conception et la fabrication de cellules solaires ultra-minces (205 nm) en GaAs. Nous obtenons des résonances multiples grâce à un miroir arrière nanostructuré en TiO2/Ag fabriqué par nanoimpression, résultant en un courant de court-circuit élevé de 24,6 mA/cm². Nous obtenons le record d’efficacité de 19,9%. Nous analysons les mécanismes des pertes et nous proposons une voie réaliste vers un rendement de 25% en utilisant un absorbeur de GaAs de 200 nm d'épaisseur seulement. Dans une deuxième partie, nous étudions les propriétés de nanofils en GaAs crûs sur substrats Si et nous explorons leur potentiel comme absorbeur photovoltaïque. Un dopage élevé est souhaité dans les cellules solaires à nanofils en jonction coeur-coquille, mais la caractérisation à l'échelle d'un nanofil unique reste difficile. Nous montrons que la cathodoluminescence (CL) peut être utilisée pour déterminer les niveaux de dopage de GaAs de type n et p avec une résolution nanométrique. Les semi-conducteurs III-V de type n présentent une émission décalée vers le bleu, à cause du remplissage de la bande de conduction, tandis que les semi-conducteurs de type p présentent une émission décalée vers le rouge due à la réduction du gap. La loi de Planck généralisée est utilisée pour fitter tout le spectre et ainsi évaluer quantitativement le niveau de dopage. Nous utilisons également la polarimétrie de CL pour déterminer sélectivement les propriétés de phases wurtzite/zinc-blende d'un nanofil unique. Nous montrons enfin des cellules solaires fonctionnelles à nanofils de GaAs. Ces travaux ouvrent des perspectives vers une nouvelle génération de cellules photovoltaïques. / Confining sunlight in a reduced volume of photovoltaic absorber offers new directions for high-efficiency solar cells. This can be achieved using nanophotonic structures for light trapping, or semiconductor nanowires. First, we have designed and fabricated ultrathin (205 nm) GaAs solar cells. Multi-resonant light trapping is achieved with a nanostructured TiO2/Ag back mirror fabricated using nanoimprint lithography, resulting in a high short-circuit current of 24.6 mA/cm². We obtain the record 1 sun efficiency of 19.9%. A detailed loss analysis is carried out and we provide a realistic pathway toward 25% efficiency using only 200 nm-thick GaAs absorber. Second, we investigate the properties of GaAs nanowires grown on Si substrates and we explore their potential as active absorber. High doping is desired in core-shell nanowire solar cells, but the characterization of single nanowires remains challenging. We show that cathodoluminescence (CL) mapping can be used to determine both n-type and p-type doping levels of GaAs with nanometer scale resolution. n-type III-V semiconductor shows characteristic blueshift emission due to the conduction band filling, while p-type semiconductor exhibits redshift emission due to the dominant bandgap narrowing. The generalized Planck’s law is used to fit the whole spectra and allows for quantitative doping assessment. We also use CL polarimetry to determine selectively the properties of wurtzite and zincblende phases of single nanowires. Finally, we demonstrate successful GaAs nanowire solar cells. These works open new perspectives for next-generation photovoltaics.
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Croissance de nanofilaments d'oxyde d'aluminium et d'oxyde de gallium dans un arc électrique étude microstructurale et propriétés optiques /Arnoult, Claire Scherrer, Hubert. January 2005 (has links) (PDF)
Thèse de doctorat : Sciences et ingénierie des matériaux : Vandoeuvre-les-Nancy, INPL : 2005. / Titre provenant de l'écran-titre. Bibliogr.
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Defect studies of single crystal and thin film zinc oxide by positron annihilation spectroscopy and cathodoluminescenceTo, Chun-kit., 杜俊傑. January 2010 (has links)
published_or_final_version / Physics / Master / Master of Philosophy
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