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[en] Spatially and spectrally resolved low-energy cathodoluminescence (CL) microscopy was applied to the characterization of nanostructures. CL has the advantage of revealing not only the presence of luminescence centers but also their spatial distribution. The use of electrons as an excitation source allows a direct comparison with other electron-beam techniques. Thus, CL is a powerful method to correlate luminescence with the sample structure and to clarify the origin of the luminescence. However, caution is needed in the quantitative analysis of CL measurements. In this review, the advantages of cathodoluminescence for qualitative analysis and disadvantages for quantitative analysis are presented on the example of nanostructures. (topical review)
[en] Assignment of the broad emission band in the visible light (VIS) region was examined by measuring the temperature dependence of the cathodoluminescence (CL) intensity of Cu-doped and annealed ZnO. The CL intensity of Cu-doped ZnO showed a peculiar temperature dependence, i.e., a maximum intensity at 230 K and a minimum intensity at 150 K. The yellow emission was enhanced by annealing, and its intensity simply increased with the decreasing temperature. The broad VIS emission band in nominally pure ZnO is explained by overlapping of the Cu-related green emission and the yellow emission related to intrinsic defects
[en] Highlights: • CNTs and GPNs were simultaneously introduced to improve the conductivity of phosphor. • There are cooperating effects between CNTs and GPNs in improving the conductivity of phosphor. • Improved performances were achieved in the low voltage cathodoluminescence. The saturation behavior in low voltage cathodoluminescence is originated from the low conductivity of the phosphor material. Based on the electrical percolation theory, carbon nano-tubes (CNTs) and graphenes (GPNs) were simultaneously introduced into the phosphor material to achieve a higher conductivity. Owing to the cooperating effects originated from the morphorlogical complementarities between CNTs and GPNs, the electrical percolation threshold of three-dimensional conductive network in the phosphor material was significantly decreased when the CNT/GPN mass ratio was properly set. With the introduction of CNT/GPN cooperating conductive component in the phosphor material, distinctly improved performances were achieved in low voltage cathodoluminescence.
[en] Thermoluminescence (TL), radioluminescence (RL) and cathodoluminescence (CL) spectra are presented for a range of alkali feldspar samples. These show that the spectra are complex, but contain a number of distinct emission bands. Intercomparison of the TL, RL and CL data for the ca 400 nm band shows that the peak wavelength may vary with type of stimulation. Activation energy data calculated over the temperature range 80-110oC, which are sample-dependent, indicate that the trapped charge population at 550 nm has a lower thermal stability than those associated with 290 and 400 nm centres. (author)
[en] Cathodoluminescence (CL) technique, as a special petrologic tool, has been applied to the studies of uranium hosted sandstone from No. 512 uranium deposit located in Xinjiang Autonomous Region, Northwest China. The detrital grains including quartz, feldspar, debris and cements display distinguishing CL properties. The quartz grains mainly demonstrate brown and dark blue CL, feldspar grains demonstrate blue and bright blue CL, calcite cement displays bright yellow-orange and orange-red CL with significant CL zoning, while the debris, mud and sand cements have dark red CL, multicolor CL or non-luminescence. The characteristics of overgrowth, fracture healing, and the original contact relations of detrital grains appear much more significant with CL than that with conventional visual methods. Much more information can be contributed by CL technique to decipher the provenance area, to explain the cementation, consolidation and other diagenesis processes of sandstone. The CL technique also provides and efficient tool for identifying detrital grains and cements, and for more precisely estimating the proportions of various detrital grains and cement components in sandstone. The CL emission of uranium hosted sandstone revealed the existence of radiation-damage rims of quartz grains at the places with a little or no uranium minerals nearby, which may imply a uranium-leaching episode during the diagenesis of sandstone
[en] The current understanding of reliability issues for InP HEMTs is reviewed. To date, the origin of some instability and degradation phenomena have been identified and the solutions to eliminate or mitigate them have been found. On the other hand, some degradation phenomena are quite complicated and are still under investigation. The increase of drain resistance is one of them. This might be related to the hot electron effect, but it is still an open question as to where and how it happens. Some efforts at solving this mystery, including cathodoluminescence studies, are presented
[en] This thesis is concerned with the study of fundamental and defect induced optical properties of synthetic diamond grown using high pressure, high temperature (HPHT) synthesis or chemical vapour deposition (CVD). The primary technique used for investigation is cathodoluminescence (including imaging and decay-time measurements) in addition to other forms of optical spectroscopy. This thesis is timely in that the crystallinity and purity of synthetic diamond has increased ten fold over the last few years. The diamond exciton emission, which is easily quenched by the presence of defects, is studied in high quality samples in detail. In addition the ability now exists to engineer the isotopic content of synthetic diamond to a high degree of accuracy. The experimental chapters are divided as follows: Chapter 2: High resolution, low temperature spectra reveal a splitting of the free-exciton phonon recombination emission peaks and the bound-exciton zero phonon line. Included are measurements of the variation in intensity and decay-time as a function of temperature. Chapter 3: The shift in energy of the phonon-assisted free-exciton phonon replicas with isotopic content has been measured. The shift is in agreement with the results of interatomic force model for phonon scattering due to isotope disorder. Chapter 4: A study of the shift in energy with isotopic content of the diamond of the GR1 band due to the neutral vacancy has allowed a verification of the theoretical predictions due to the Jahn Teller effect. Chapter 5: The spatial distribution of the free-exciton luminescence is studied in HPHT synthetic and CVD diamond. A variation in intensity with distance from the surface is interpreted as a significant non-radiative loss of excitons to the surface. Chapter 6: The decay-times of all known self-interstitial related centres have been measured in order to calculate the concentration of these centres present in electron irradiated diamond. (author)
[en] The marble of the Samaná complex presents a widespread foliation formed during its exhumation following a general decompressive strain path from high pressure (2.0>P>0.7 GPa) and low temperature (<500 ºC) conditions. The foliation is plano-linear and blastomylonitic. Deformation distribution is highly heterogeneous. Calcite preferred orientation is poor, even though the marble has a well-defined tectonic fabric. The blastomylonitic fabric is masking an earlier tectonic fabric. Cathodoluminiscence images reveal that intense fracturing formed prior to foliation development in the marbles. The thermodynamic modelling of mineral phase transformations during prograde metamorphism indicate an increase in water content (1.2%< w.t. H2O<1.8%) that may have involved an increase in fluid pressure and triggered rock embrittlement and subsequent exhumation. Stress drops after a cataclastic event, as well as grain-size reduction by abrasion, may have activated dissolution-precipitation processes along cataclastic bands. Differential stress |s1-s3| increased as exhumation progressed after the cataclastic event. Estimates of paleostress based on calcite mechanical twinning indicate values of |s1-s3| >350 MPa during deformation. In contrast, mean flow stress during grain-boundary migration is estimated in |s1-s3| <150 MPa. The high paleostress record and microstructures of the marble are consistent with the high exhumation rate calculated (>110 MPa Ma-1). All of these data suggest that exhumation always occurred near the brittle-ductile regime of deformation.
[es]Los mármoles del complejo de Samaná presentan una foliación generalizada producida en condiciones de deformación descompresiva (2.0>P>0.7 GPa) y a temperatura <500º C. La foliación es de tipo plano-linear y blastomilonítica. La distribución de la deformación es muy heterogénea. Aunque la fábrica tectónica está bien desarrollada, la orientación cristalográfica preferente de calcita es débil porque la fábrica blastomilonítica enmascara una fábrica tectónica previa. Imágenes de catodolumiscencia fría revelan que la foliación de los mármoles comenzó a desarrollarse por flujo friccional. Los modelos termodinámicos indican que sólo un leve aumento del contenido en agua derivado de reacciones metamórficas progradas (1.2%< w.t.H2O<1.8%) pudo producir una sobrepresión de fluidos que desencadenó la cataclasis y la exhumación. La caída del esfuerzo tras la cataclasis y la reducción del tamaño de grano activaron el creep de disolución-Precipitación sobre las bandas cataclásticas. Los esfuerzos diferenciales |s1-s3| aumentaron progresivamente con la exhumación después del evento cataclástico. La incidencia de maclado de las calcitas registró |s1-s3| >350 MPa. El esfuerzo de fluencia medio durante la migración de borde de grano fue |s1-s3| <150 MPa. Los altos paleoesfuerzos y las microestructuras de los mármoles son consistentes con las elevadas tasas de exhumación calculadas (>110 MPa Ma-1). Todos estos datos sugieren que la exhumación se produjo siempre próxima al régimen de deformación frágil-dúctil