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Cathodoluminescence
Terms modified by Cathodoluminescence Selected AbstractsCUERDA SECA CERAMICS FROM AL-ANDALUS, ISLAMIC SPAIN AND PORTUGAL (10TH,12TH CENTURIES AD): INVESTIGATION WITH SEM,EDX AND CATHODOLUMINESCENCE*ARCHAEOMETRY, Issue 3 2005R. CHAPOULIE Since little is known about the cuerda seca technique, our aim has been to complete an initial analysis of 11th-century cuerda seca by studying fragments from the 10th century (Pechina, Almería) and the 12th century (Mértola and Almería), so as to establish the diachronic evolution of this technique. Characteristics specific to cuerda seca ceramic glazes were investigated using scanning electron microscopy (SEM) and quantitative chemical analysis with energy-dispersive X-ray spectrometry (EDX). The chemical compositions of the different-coloured glazes (green, black, yellow and white) have given us valuable indications about the evolution of the technique. The opacification mode and the firing process were also investigated. With the help of cathodoluminescence (CL) and the study of modern ,cuerda seca' glazed ceramics, new hypotheses regarding the number of firing stages, taking into account glaze and paste transformations and their interactions, are put forward. [source] Study of the Defects in Sintered SnO2 by High-Resolution Transmission Electron Microscopy and CathodoluminescenceEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2007David Maestre Abstract The defect structure of sintered SnO2 was investigated by high-resolution transmission electron microscopy (HRTEM), cathodoluminescence (CL), and electrical measurements. HRTEM shows the presence of the SnO phase in the sintered samples as well as twinning, stacking faults, and disordered intergrowths. The sintered samples annealed under an oxygen atmosphere show changes in the defect structure and in the CL spectra. In particular, the intensity of a CL band at 1.94 eV, related to oxygen vacancies, decreased as the electrical resistivity increased. The results are discussed by considering the presence of stoichiometric defects such as oxygen vacancies and Sn interstitials in the final structure and their evolution during the annealing process under an oxygen atmosphere. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Morphology-Tunable Micro/Nanostructures: Characterization, Cathodoluminescence, and Field-Emission Properties of Morphology-Tunable CdS Micro/Nanostructures (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Mater. On page 2423, T. Y. Zhai et al. report that high quality and uniform 1D CdS micro/nanostructures with different morphologies can be fabricated through a simple and effective thermal evaporation process. Both cathodoluminescence and field-emission measurements are made and clear correlations between morphology, structure, and optical and field emission performance are established. [source] Characterization, Cathodoluminescence, and Field-Emission Properties of Morphology-Tunable CdS Micro/NanostructuresADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Tianyou Zhai Abstract High-quality, uniform one-dimensional CdS micro/nanostructures with different morphologies,microrods, sub-microwires and nanotips,are fabricated through an easy and effective thermal evaporation process. Their structural, cathodoluminescence and field-emission properties are systematically investigated. Microrods and nanotips exhibit sharp near-band-edge emission and broad deep-level emission, whereas sub-microwires show only the deep-level emission. A significant decrease in a deep-level/near-band-edge intensity ratio is observed along a tapered nanotip towards a smaller diameter part. This behavior is understood by consideration of defect concentrations in the nanotips, as analyzed with high-resolution transmission electron microscopy. Field-emission measurements show that the nanotips possess the best field-emission characteristics among all 1D CdS nanostructures reported to date, with a relatively low turn-on field of 5.28,V µm,1 and the highest field-enhancement factor of 4,819. The field-enhancement factor, turn-on and threshold fields are discussed related to structure morphology and vacuum gap variations under emission. [source] Field Emission and Cathodoluminescence of ZnS Hexagonal Pyramids of Zinc Blende Structured Single CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Zhi-Gang Chen Abstract Single-crystal hexagonal pyramids of zinc blende ZnS are fabricated by facile thermal evaporation in an ammonia atmosphere at 1150,°C. It is found that ZnS pyramids grow along the [111] crystal axis and possess a sharp tip with a diameter of ,10,nm and a micrometer-sized base. The structural model and growth mechanism are proposed based on crystallographic characteristics. This unique ZnS pyramid structure exhibits a low turn-on field (2.81,V µm,1), a high field-enhancement factor (over 3000), a large field-emission current density (20,mA cm,2), and good stability with very small fluctuation (0.9%). These superior field-emission properties are clearly attributed to the pyramid morphology, with micrometer-sized bases and nanotips, and high crystallinity. Moreover, a stable UV emission of 337,nm at room temperature is observed and can be ascribed to the band emission of the zinc blende phase. These results suggest that the ZnS hexagonal pyramids can be expected to find promising applications as field emitters and optoelectronic devices. [source] Solvothermal Synthesis, Cathodoluminescence, and Field-Emission Properties of Pure and N-Doped ZnO NanobulletsADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Ujjal K. Gautam Abstract Homogenous crystallization in solution, in the absence of external influences, is expected to lead to growth that is symmetric at least in two opposite facets. Such was not the case when we attempted to synthesize ZnO nanostructures by employing a solvothermal technique. The reaction product, instead, consisted of bullet-shaped tiny single crystals with an abrupt hexagonal base and a sharp tip. A careful analysis of the product and the intermediate states of the synthesis reveals that one of the reaction intermediates with sheet-like morphology acts as a self-sacrificing template and induces such unexpected and novel growth. The synthesis was further extended to dope the nanobullets with nitrogen as previous studies showed this can induce p-type behavior in ZnO, which is technologically complementary to the naturally occurring n-type ZnO. Herein, a soft-chemical approach is used for the first time for this purpose, which is otherwise accomplished with high-temperature techniques. Cathodoluminesce (CL) investigations reveal stable optical behavior within a pure nanobullet. On the other hand, the CL spectra derived from the surfaces and the cores of the doped samples are different, pointing at a N-rich core. Finally, even though N-doped ZnO is known to have high electrical conductivity, the study now demonstrates that the field-emission properties of ZnO can also be greatly enhanced by means of N doping. [source] New approach to cathodoluminescence studies in application to InGaN/GaN laser diode degradationJOURNAL OF MICROSCOPY, Issue 2 2009USKA Summary Cathodoluminescence (CL) studies are widely applied in semi-conductor science and technology. However, for structures with a p-n junction the CL spatial distribution can be strongly affected by internal current flows of the electron beam induced current generated within the structure. This influence is the investigated in application to CL studies of degradation in aged laser diodes with InGaN multiquantum wells. [source] DEVONIAN CARBONATES OF THE NIGEL PEAK AREA, ROCKY MOUNTAINS, CANADA: A FOSSIL PETROLEUM SYSTEM?JOURNAL OF PETROLEUM GEOLOGY, Issue 3 2008J. Köster In this study we report on Devonian (Frasnian , Famennian) limestones and dolostones exposed near Nigel Peak in the Main Ranges of the Canadian Rocky Mountains. These carbonates are a proximal facies of the Southesk-Cairn Carbonate Complex. The investigated strata are stratigraphically equivalent to the oil- and gas bearing Nisku Formation in the subsurface of the Western Canada Sedimentary Basin, about 300 km to the east. The rocks were investigated by polarisation and cathodoluminescence microscopy, total organic carbon analysis, Rock-Eval pyrolysis, solid bitumen reflectance measurements, gas chromatography and fluid inclusion analysis. Thin section analyses showed that silt-grade quartz and saddle dolomite increase upward from the base of the stratigraphic section, and that porosities are generally low. This is due to reduction of pore space due to early cementation and extensive dolomitization. Cathodoluminescence identified up to four generations of calcite cements. TOC values ranged from 0.2 to 2.4 %. Rock-Eval pyrolysis of carbonate samples resulted in measurable S1 peaks but not S2 peaks, indicating that there was no residual petroleum generation potential. Organic petrographic analyses identified dispersed kerogen and migrabitumen, and calculated vitrinite reflectance values were around 4 % on average which implies peak temperatures of 234,262 °C (due to deep burial) or 309,352 °C (due to short term hydrothermal heating). Fluid inclusion data indicates at least one pulse of hot fluids with elevated homogenization temperatures of > 300 °C, and this may explain the high thermal maturity of the studied rocks. [source] Preparation and Cathodoluminescence of Mg-Doped and Zn-Doped GaN PowdersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2008Hui-Li Li In this paper, undoped, Mg- and Zn-doped gallium nitride powders were prepared by direct nitridation of Ga2O3 under a flowing NH3 gas. The phase purity, morphology and cathodoluminescence spectra were presented. The Ga2O3 powders can be completely nitridized to GaN at 1000°C. The resultant GaN powders agglomerated together with submicron-sized polyhedral crystals. At room temperature, the Mg- and Zn-doped powders exhibit bright blue-violet emission at around 3.05 and 2.81 eV, respectively. This provides clear evidence that magnesium or zinc is incorporated into the GaN powders as an acceptor and suggests that the luminescent materials are promising candidates for optoelectronic applications. [source] Cathodoluminescence as a tool to determine the phosphorus concentration in diamondPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2007J. Barjon Abstract In n-type diamond doped with phosphorus, exciton properties have been investigated by cathodoluminescence as a function of the phosphorus concentration. A series of homoepitaxial diamond layers were grown by microwave plasma-assisted chemical vapor deposition and doped with a liquid organic precursor of phosphorus (tertiarybutylphosphine). Their phosphorus concentration ranges from 5.2 × 1016 cm,3 to 3.3 × 1018 cm,3 as measured by secondary ion mass spectrometry. It is shown that the ratio between the luminescence intensities of the neutral phosphorus-bound exciton and the free exciton recombinations follows the donor concentration. A calibration graph is presented to determine the phosphorus contents in diamond with cathodoluminescence spectroscopy at 102 K. The influence of electrical compensation on the optical spectra is discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Profiling of light emission of GaN-based laser diodes with cathodoluminescencePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006M. Godlewski Abstract Cathodoluminescence is applied for evaluation of in-plane variations of light emission from GaN-based laser diode structures. We demonstrate that potential fluctuations affect significantly emission of laser diodes for e-beam currents above thresholds for a stimulated emission. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cathodoluminescence and electrophysical characterization of AlxGa1,xN epilayersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006V. I. Kozlovsky Abstract Cathodoluminescence (CL) of metalorganic vapor phase epitaxy (MOVPE) grown AlxGa1,xN epilayers on sapphire has been studied with x from 0.23 to 0.38. CL spectra of undoped and Si-doped AlGaN epilayers with the same alloy composition grown on thick GaN buffers have been compared. The free electron concentration in the doped samples has been measured to (1-1.6) × 1017 cm,3 with a mobility of 84-115 cm2/Vs. CL spectra have been compared with deep level transient spectroscopy spectra. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Excitation energy transfer between luminescent centers of microcrystalline InGaNPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Hisashi Kanie Abstract InGaN microcrystals were grown by nitridation of gallium and indium sulfide. Cathodoluminescence (CL) image observation of InGaN microcrystals at room temperature was performed under a scanning electron microscope at 3,5 kV with a beam diameter of 10 nm equipped with a monochromator. High-spatial-resolution monochromatic CL images composited with secondary electron microscope images showed each facet has uniform but different CL spectra, such as single or double peaked spectra at 420 and 460 nm. From the width of a dark zone and bright zone at the fringe of the facet in the monochromatic CL images taken at the two wavelengths the length of the excitation energy transfer was estimated as the diffusion length of the excited carriers. The ratios of the lifetimes of the radiative and nonradiative process of the excited carriers are calculated from the estimated diffusion lengths. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cathodoluminescence, High-Resolution X-Ray Diffraction and Transmission-Electron-Microscopy Investigations of Cubic AlGaN/GaN Quantum WellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003D.J. As Abstract The structural and optical properties of cubic Al0.25Ga0.75N/GaN multi quantum well structures grown on GaAs (001) substrates by radio-frequency plasma-assisted molecular beam epitaxy (MBE) are reported. Transmission electron microscopy (TEM), high resolution X-ray diffraction (HRXRD), and cathodoluminescence (CL) measurements are used to characterize the cubic Al0.25Ga0.75N/GaN quantum wells. The interfaces between the quantum-well and barrier layers are well resolved, abrupt and the entire structure shows an excellent periodicity. Due to the high dislocation density of about 1010 cm,2 a severe broadening of the XRD-reflection is observed and superlattice satellite peaks are only weakly indicated. Further, a wavy structure is seen in TEM at the coalescence of submicron-size grains. Nevertheless, CL at room temperature shows a strong emission of quantized states at 3.352 eV. [source] Study of the Defects in Sintered SnO2 by High-Resolution Transmission Electron Microscopy and CathodoluminescenceEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2007David Maestre Abstract The defect structure of sintered SnO2 was investigated by high-resolution transmission electron microscopy (HRTEM), cathodoluminescence (CL), and electrical measurements. HRTEM shows the presence of the SnO phase in the sintered samples as well as twinning, stacking faults, and disordered intergrowths. The sintered samples annealed under an oxygen atmosphere show changes in the defect structure and in the CL spectra. In particular, the intensity of a CL band at 1.94 eV, related to oxygen vacancies, decreased as the electrical resistivity increased. The results are discussed by considering the presence of stoichiometric defects such as oxygen vacancies and Sn interstitials in the final structure and their evolution during the annealing process under an oxygen atmosphere. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Silica Supported Submicron SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ Spherical Particles with a Core,Shell Structure: Sol,Gel Synthesis and CharacterizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2006Cuikun Lin Abstract X1 -Y2SiO5:Eu3+ and X1 -Y2SiO5:Ce3+ and/or Tb3+ phosphor layers have been coated on nonaggregated, monodisperse, submicron spherical SiO2 particles by a sol,gel process, followed by surface reaction at high temperature (1000 °C), to give core/shell structured SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), TEM, photoluminescence (PL), low voltage cathodoluminescence (CL), and time-resolved PL spectra and lifetimes are used to characterize these materials. The XRD results indicate that X1 -Y2SiO5 layers have been successfully coated on the surface of SiO2 particles, as further verified by the FESEM and TEM images. The PL and CL studies suggest that SiO2@Y2SiO5:Eu3+, SiO2@Y2SiO5:Tb3+ (or Ce3+/Tb3+), and SiO2@Y2SiO5:Ce3+ core/shell particles exhibit red (Eu3+, 613 nm: 5D0,7F2), green (Tb3+, 542 nm: 5D4,7F5), or blue (Ce3+, 450 nm: 5d-4f) luminescence, respectively. PL excitation, emission, and time-resolved spectra demonstrate that there is an energy transfer from Ce3+ to Tb3+ in the SiO2@Y2SiO5:Ce3+,Tb3+ core/shell particles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Morphology-Tunable Micro/Nanostructures: Characterization, Cathodoluminescence, and Field-Emission Properties of Morphology-Tunable CdS Micro/Nanostructures (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Mater. On page 2423, T. Y. Zhai et al. report that high quality and uniform 1D CdS micro/nanostructures with different morphologies can be fabricated through a simple and effective thermal evaporation process. Both cathodoluminescence and field-emission measurements are made and clear correlations between morphology, structure, and optical and field emission performance are established. [source] Characterization, Cathodoluminescence, and Field-Emission Properties of Morphology-Tunable CdS Micro/NanostructuresADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Tianyou Zhai Abstract High-quality, uniform one-dimensional CdS micro/nanostructures with different morphologies,microrods, sub-microwires and nanotips,are fabricated through an easy and effective thermal evaporation process. Their structural, cathodoluminescence and field-emission properties are systematically investigated. Microrods and nanotips exhibit sharp near-band-edge emission and broad deep-level emission, whereas sub-microwires show only the deep-level emission. A significant decrease in a deep-level/near-band-edge intensity ratio is observed along a tapered nanotip towards a smaller diameter part. This behavior is understood by consideration of defect concentrations in the nanotips, as analyzed with high-resolution transmission electron microscopy. Field-emission measurements show that the nanotips possess the best field-emission characteristics among all 1D CdS nanostructures reported to date, with a relatively low turn-on field of 5.28,V µm,1 and the highest field-enhancement factor of 4,819. The field-enhancement factor, turn-on and threshold fields are discussed related to structure morphology and vacuum gap variations under emission. [source] Further Characterisation of the 91500 Zircon CrystalGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2004Michael Wiedenbeck zircon 91500; matériau de référence; intercomparaison entre techniques; valeurs de travail This paper reports the results from a second characterisation of the 91500 zircon, including data from electron probe microanalysis, laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), secondary ion mass spectrometry (SIMS) and laser fluorination analyses. The focus of this initiative was to establish the suitability of this large single zircon crystal for calibrating in situ analyses of the rare earth elements and oxygen isotopes, as well as to provide working values for key geochemical systems. In addition to extensive testing of the chemical and structural homogeneity of this sample, the occurrence of banding in 91500 in both backscattered electron and cathodoluminescence images is described in detail. Blind intercomparison data reported by both LA-ICP-MS and SIMS laboratories indicate that only small systematic differences exist between the data sets provided by these two techniques. Furthermore, the use of NIST SRM 610 glass as the calibrant for SIMS analyses was found to introduce little or no systematic error into the results for zircon. Based on both laser fluorination and SIMS data, zircon 91500 seems to be very well suited for calibrating in situ oxygen isotopic analyses. Cet article présente les résultats d'une nouvelle caractérisation du zircon 91500, dont des données de microanalyse par sonde électronique, d'analyse par ablation laser en couplage à un ICP-MS, d'analyse par sonde ionique (SIMS) et d'analyse par fluorination laser. Le but de cette étude etait de démontrer que ce large monocristal de zircon pouvait être utilisé pour la calibration d'analyses in situ de Terres Rares et des isotopes de I'Oxygène, et en même temps de fournir des valeurs "de travail" pour un certain nombre de systémes géochimiques cruciaux. En complément des tests systématiques d'homogénéité de I'échantillon, tant chimiquement que structurellement, /'ex/sfence, dans le zircon 91500, de zonages visibles en électrons retro diffusés et en cathodoluminescence, est décrite en détail, line comparaison en aveugle des résultats obtenus par LA-ICP-MS et par SIMS, dans des laboratoires différents, montre que les différences systématiques entre les ensembles de données obtenues par ces deux techniques sont très faibles. De plus, I'utilisation du verre NIST SRM 610 comme calibrant lors de I'analyse par SIMS n'introduit qu'une erreur systématique très faible si ce n'est inexistante sur les résultats du zircon. Sur la base des analyses par fluorination laser et par SIMS, le zircon 91500 semble être parfaitement adapte a son utilisation pour la calibration d'analyses isotopiques in situ d'oxygène. [source] Luminescence of Nanocrystalline Erbium-Doped YttriaADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Yuanbing Mao Abstract In this paper, the luminescence, including photoluminescence, upconversion and cathodoluminescence, from single-crystalline erbium-doped yttria nanoparticles with an average diameter of 80,nm, synthesized by a molten salt method, is reported. Outstanding luminescent properties, including sharp and well-resolved photoluminescent lines in the infrared region, outstanding green and red upconversion emissions, and excellent cathodoluminescence, are observed from the nanocrystalline erbium-doped yttria. Moreover, annealing by the high power laser results in a relatively large increase in photoluminescent emission intensity without causing spectral line shift. These desirable properties make these nanocrystals promising for applications in display, bioanalysis and telecommunications. [source] Electronic and Mechanical Coupling in Bent ZnO NanowiresADVANCED MATERIALS, Issue 48 2009Xiaobing Han A red shift of the exciton of ZnO nanowires is efficiently produced by bending strain, as demonstrated by a low-temperature (81,K) cathodoluminescence (CL) study of ZnO nanowires bent into L- or S-shapes. The figure shows a nanowire (Fig. a) with the positions of CL measurements marked. The corresponding CL spectra,revealing a peak shift and broadening in the region of the bend,are shown in Figure b. [source] Synthesis and Optical Properties of Tetrapod-Like ZnSSe Alloy Nanostructures,ADVANCED MATERIALS, Issue 17 2008Haiyang Xu Tetrapod-like ZnS1,xSex alloy nanostructures (T-ZnS1,xSex) of different compositions (0,,,x,,,1) are synthesized by chemical vapor deposition. Their composition-dependent Raman scattering and cathodoluminescence are studied. The single-crystal T-ZnS1,xSex nanostructures exhibit strong and narrow near-band-edge emissions that can be continuously tuned from 330,459,nm (see figure). [source] Isotopic alteration of mammalian tooth enamelINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1-2 2003M. J. Schoeninger Abstract Mammalian tooth enamel carbonates from a Pliocene site at Allia Bay in northern Kenya show variable carbon and oxygen isotopic alteration. Sample screening by cathodoluminescence, prior to isotopic analysis, identified areas of extensive chemical alteration and others that were minimally altered. The luminescent patterns were used to guide sampling for the isotope study. Carbon stable isotope ratios of the apatite carbonate from luminescent enamel exteriors differ from the ratios in the enamel interiors and the magnitude of difference varies widely. The interior of the enamel usually retains the carbon isotope ratios expected based on faunal identification, but in a minority of cases, all of the enamel appears to be altered isotopically. Among fauna with an apparent mixed feeding signal, it is particularly difficult to determine whether the ,13C value is due to an actual mixed feeding strategy during life or to alteration toward sediment values. Palaeoecological reconstructions based on the ,13C values of enamel carbonate in browsing fauna would be affected, in many cases, since differences of 1, are significant for such reconstructions. Even so, careful selection of unaltered enamel sections should avoid this problem. Palaeodiet reconstruction would be less affected except in those cases where the alteration approaches 5,. In such cases, a mixed feeding strategy would be the erroneous interpretation of the data. Oxygen isotope ratios in the enamel carbonates show no pattern and the retention of biogenic values is unlikely. For this reason, palaeotemperature reconstructions, based on the ,18O values of the enamel carbonate, would not be possible at this site. Copyright © 2003 John Wiley & Sons, Ltd. [source] SHRIMP U-Pb zircon dating from Sulu-Dabie dolomitic marble, eastern China: constraints on prograde, ultrahigh-pressure and retrograde metamorphic agesJOURNAL OF METAMORPHIC GEOLOGY, Issue 7 2006F. L. LIU Abstract Laser Raman spectroscopy and cathodoluminescence (CL) images show that zircon from Sulu-Dabie dolomitic marbles is characterized by distinctive domains of inherited (detrital), prograde, ultrahigh-pressure (UHP) and retrograde metamorphic growths. The inherited zircon domains are dark-luminescent in CL images and contain mineral inclusions of Qtz + Cal + Ap. The prograde metamorphic domains are white-luminescent in CL images and preserve a quartz eclogite facies assemblage of Qtz + Dol + Grt + Omp + Phe + Ap, formed at 542,693 °C and 1.8,2.1 GPa. In contrast, the UHP metamorphic domains are grey-luminescent in CL images, retain the UHP assemblage of Coe + Grt + Omp + Arg + Mgs + Ap, and record UHP conditions of 739,866 °C and >5.5 GPa. The outermost retrograde rims have dark-luminescent CL images, and contain low- P minerals such as calcite, related to the regional amphibolite facies retrogression. Laser ablation ICP-MS trace-element data show striking difference between the inherited cores of mostly magmatic origin and zircon domains grown in response to prograde, UHP and retrograde metamorphism. SHRIMP U-Pb dating on these zoned zircon identified four discrete 206Pb/238U age groups: 1823,503 Ma is recorded in the inherited (detrital) zircon derived from various Proterozoic protoliths, the prograde domains record the quartz eclogite facies metamorphism at 254,239 Ma, the UHP growth domains occurred at 238,230 Ma, and the late amphibolite facies retrogressive overprint in the outermost rims was restricted to 218,206 Ma. Thus, Proterozoic continental materials of the Yangtze craton were subducted to 55,60 km depth during the Early Triassic and recrystallized at quartz eclogite facies conditions. Then these metamorphic rocks were further subducted to depths of 165,175 km in the Middle Triassic and experienced UHP metamorphism, and finally these UHP metamorphic rocks were exhumed to mid-crustal levels (about 30 km) in the Late Triassic and overprinted by regional amphibolite facies metamorphism. The subduction and exhumation rates deduced from the SHRIMP data and metamorphic P,T conditions are 9,10 km Myr,1 and 6.4 km Myr,1, respectively, and these rapid subduction,exhumation rates may explain the obtained P,T,t path. Such a fast exhumation suggests that Sulu-Dabie UHP rocks that returned towards crustal depths were driven by buoyant forces, caused as a consequence of slab breakoff at mantle depth. [source] Silica as a shock index in shergottites: A cathodoluminescence studyMETEORITICS & PLANETARY SCIENCE, Issue 7 2005Hasnaa CHENNAOUI AOUDJEHANE Determining its structural state as either silica glass, quartz, cristobalite, tridymite, coesite, stishovite, or post-stishovite could provide informations about their shock history. The purpose of this work is to assess the shock intensity in shergottites using two spectroscopic methods. On a conventional polished section, a scanning electron microscope (SEM) enables us to study the cathodoluminescence (CL) of silica at variable magnification. The results were crosschecked by systematic Raman spectroscopy of the selected areas. CL spectra differ substantially from one another and enable separating stishovite, high and low pressure silica glass, quartz, and cristobalite. We studied a set of five shergottites: Northwest Africa (NWA) 480, NWA 856, Zagami, Shergotty, and Los Angeles. Stishovite is common in Shergotty, Zagami, NWA 856, and NWA 480 and absent in the studied section of Los Angeles. High-pressure glass is very common, particularly in close association with stishovite. According to the textural relationship, it may be a product of the retromorphosis (amorphization during decompression) of stishovite. Large stishovite areas result from the transformation of preexisting low-pressure silica crystals, while needles result from the high-pressure transformation of pyroxene to glass (melt) and silica. In the latter case, they are found in melt pockets and represent a small fraction of areas of overall pyroxene composition. Needles exhibit square sections of about 1 ,m. Silica spots identical to those described previously as post-stishovite are found in Shergotty, Zagami, NWA 480, and NWA 856. At present, the spectroscopic distinction of post-stishovite from stishovite is difficult. Post-stishovite is destroyed under the Raman beam, and CL spectra are possible mixtures of several phases (e.g., glass and post-stishovite). It is concluded that the shock intensity is highly heterogeneous, and the pressure probably exceeded 60 GPa in all shergottites studied here. [source] Identification of shocked quartz by scanning cathodoluminescence imagingMETEORITICS & PLANETARY SCIENCE, Issue 6 2001Sam Boggs Jr. These lamellae appear as remarkably straight, thin, planar features (microstructures) in sets within which lamellae are essentially parallel to each other and spaced , 20 ,m apart. Two or more intersecting sets are typically present. Shock lamellae are commonly recognized and identified by optical methods, by use of the transmission electron microscope (TEM), and by etching polished sections and subsequent examination with a scanning electron microscope (SEM) operated in the secondary electron mode. We present here a method for observing planar microstructures in shocked quartz by using a cathodoluminescence (CL) detector attached to a SEM. The method relies on the fact that planar microstructures in quartz arising as a result of shock display no CL whatever; thus, they show up as distinct, thin, black lines on otherwise luminescent quartz grains. We used scanning CL imaging to study shocked quartz from the Ries Crater, Germany, a well-known impact crater of Miocene age. We demonstrate that shock-produced planar microstructures are clearly displayed in SEM-CL images and can be distinguished from microfractures generated by tectonism, and subsequently filled with quartz, and other similar features not related to impact events. The SEM-CL method provides a powerful supplement to other methods of identifying shocked quartz. It commonly provides better spatial resolution than does standard optical methods, and does not require etching of quartz grains. Further, it is easier and faster to use than are TEM methods, although it is not capable of the fine-scale defect analysis possible with TEM. [source] Phosphorus incorporation and activity in (100)-oriented homoepitaxial diamond layersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009G. Frangieh Abstract In this work, we present a study about the homoepitaxial growth of phosphorus-doped diamond on (100) substrates. The growth was performed by microwave plasma assisted chemical vapor deposition (MPCVD) adding an organic precursor for phosphorus (tertiarybutylphosphine: TBP) in the gaseous phase. We show that phosphorus is incorporated in (100) chemical vapor deposition (CVD) diamond as proved by secondary ion mass spectrometry (SIMS). The recombination of excitons bound to phosphorus donors is observed by cathodoluminescence (CL) spectroscopy. The influence of the growth parameters on the phosphorus donor activity is investigated. We show that the [C*]/[H2] ratio is a key parameter for controlling the P-donor activity when diamond is grown on (100) surfaces. [source] Three-dimensionally structured silicon as a substrate for the MOVPE growth of GaN nanoLEDsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2009Sönke Fündling Abstract Three-dimensionally patterned Si(111) substrates are used to grow GaN based heterostructures by metalorganic vapour phase epitaxy, with the goal of fabricating well controlled, defect reduced GaN-based nanoLEDs. In contrast to other approaches to achieve GaN nanorods, we employed silicon substrates with deep etched nanopillars to control the GaN nanorods growth by varying the size and distance of the Si pillars. The small footprint of GaN nanorods grown on Si pillars minimise the influence of the lattice mismatched substrate and improve the material quality. For the Si pillars an inductively coupled plasma dry-etching process at cryogenic temperature has been developed. An InGaN/GaN multi quantum well (MQW) structure has been incorporated into the GaN nanorods. We found GaN nanostructures grown on top of the silicon pillars with a pyramidal shape. This shape results from a competitive growth on different facets as well as from surface diffusion of the growth species. Spatially resolved optical properties of the structures are analysed by cathodoluminescence. Strongly spatial-dependent MQW emission spectra indicate the growth rate differences on top of the rods. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Preparation and luminescent properties of Eu2+ -activated glass ceramic phosphor precipitated with ,-Ca2SiO4 and Ca3Si2O7PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009Takayuki Nakanishi Abstract Eu2+: calcium silicate glass ceramics (GC) containing ,-Ca2SiO4 and Ca3Si2O7 crystal phosphors were fabricated by cerammization process from a GC that were prepared by a novel GC preparation; frozen sorbet method. The GC obtained (as-made GC) consisted of glass and spherical ,-Ca2SiO4 crystal phases with size of about 20,40 ,m. After post-ceramization, Ca3Si2O7 crystals were also precipitated. Judging from the cathodoluminescence (CL) mapping images, two emission bands peaked at 515 nm and 600 nm were observed from different parts in the GC. The observed photoluminescence (PL) have two broad emission bands at 515 nm from Eu2+: ,-Ca2SiO4 and at 600 nm from Eu2+:Ca3Si2O7. With increasing heat-treatment temperature, the color coordinates shifted from green range to center region, which corresponds to pure white in the CIE chromaticity diagram. Eu2+ doped calcium silicate GC containing ,-Ca2SiO4 and Ca3Si2O7 are suitable phosphor as the use of phosphor converting white light emitting diode (pc-wLED) with high color rendering. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cathodoluminescence as a tool to determine the phosphorus concentration in diamondPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2007J. Barjon Abstract In n-type diamond doped with phosphorus, exciton properties have been investigated by cathodoluminescence as a function of the phosphorus concentration. A series of homoepitaxial diamond layers were grown by microwave plasma-assisted chemical vapor deposition and doped with a liquid organic precursor of phosphorus (tertiarybutylphosphine). Their phosphorus concentration ranges from 5.2 × 1016 cm,3 to 3.3 × 1018 cm,3 as measured by secondary ion mass spectrometry. It is shown that the ratio between the luminescence intensities of the neutral phosphorus-bound exciton and the free exciton recombinations follows the donor concentration. A calibration graph is presented to determine the phosphorus contents in diamond with cathodoluminescence spectroscopy at 102 K. The influence of electrical compensation on the optical spectra is discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||