Showing papers on "Cathodoluminescence published in 2020"
TL;DR: YAG:Ce3+ transparent ceramic phosphors (TCPs) are regarded as the most promising luminescent converter for laser-driven (LD) lighting as discussed by the authors.
Abstract: Y3 Al5 O12 :Ce3+ (YAG:Ce3+ ) transparent ceramic phosphors (TCPs) are regarded as the most promising luminescent converter for laser-driven (LD) lighting. High-quality YAG:Ce3+ TCPs are still urgent for high efficiency LD lighting devices. YAG:Ce3+ TCPs in a vacuum ambience by using nano-sized raw materials are prepared. Controlling defects by adding nano-sized MgO and SiO2 simultaneously enables a high transmittance nearly 80%. After annealing in air furthermore, the luminous efficiency is enhanced greatly from 106 to 223 lm W-1 , which is the best result reported now for LD lighting. These results demonstrate that the optimizing YAG:Ce3+ TCPs in a fitting strategy will brighten once again in the next-generation LD lighting. Based on scanning electron microscopy (SEM) coupled with a cathodoluminescence system, defects and Ce3+ distributions in grains are identified directly for the first time.
261 citations
TL;DR: In this paper, the fundamental properties of point defects in monoclinic β-Ga2O3 and the methods employed to study them are discussed and a tutorial is presented.
Abstract: In the field of high-power electronics, gallium oxide (Ga2O3) is attracting attention due to its wide bandgap and ability to be doped n-type. Point defects, including vacancies, impurities, and dopants, play important roles in optimizing device performance. This tutorial discusses the fundamental properties of point defects in monoclinic β-Ga2O3 and the methods employed to study them. Oxygen vacancies are deep donors that do not cause n-type conductivity but may compensate acceptors. Gallium vacancies are deep acceptors that can be partially passivated by hydrogen. Substitutional magnesium is a promising acceptor that produces a semi-insulating material and also forms a complex with hydrogen. Calcium and iron also have deep acceptor levels. Iridium deep donors are introduced into crystals grown from a melt in an Ir crucible. Other defects are introduced by irradiation with energetic particles such as neutrons or protons. In addition to altering the electronic properties, defects give rise to UV/visible emission bands in photoluminescence and cathodoluminescence spectra.
129 citations
TL;DR: In this paper, a combination of optical and electron microscopy helps to distinguish at least four classes of defects and correlate them with local strain, and the results provide a foundation for future atomic-scale optical characterization of colour centres.
Abstract: Defects in hexagonal boron nitride (hBN) exhibit high-brightness, room-temperature quantum emission, but their large spectral variability and unknown local structure challenge their technological utility. Here, we directly correlate hBN quantum emission with local strain using a combination of photoluminescence (PL), cathodoluminescence (CL) and nanobeam electron diffraction. Across 40 emitters, we observe zero phonon lines (ZPLs) in PL and CL ranging from 540 to 720 nm. CL mapping reveals that multiple defects and distinct defect species located within an optically diffraction-limited region can each contribute to the observed PL spectra. Local strain maps indicate that strain is not required to activate the emitters and is not solely responsible for the observed ZPL spectral range. Instead, at least four distinct defect classes are responsible for the observed emission range, and all four classes are stable upon both optical and electron illumination. Our results provide a foundation for future atomic-scale optical characterization of colour centres. Defects in hexagonal boron nitride exhibit room-temperature quantum emission, but their unknown structural origin challenges their technological utility. A combination of optical and electron microscopy helps to distinguish at least four classes of defects and correlate them with local strain.
128 citations
TL;DR: In this paper, a narrow-band blue-emitting garnet-type phosphor of Sr3Lu2Ge3O12: Bi3+ that is available for NUV-LED chips is presented.
82 citations
TL;DR: This concept is based on a recent demonstration of the optical frequency modulation of the free-electron quantum electron wave function by an ultrafast laser beam, and it is asserted that pulses of such QEWs correlated in their modulation phase, interact resonantly with two-level systems, inducing resonant quantum transitions.
Abstract: Here we present a new paradigm of free-electron-bound-electron resonant interaction. This concept is based on a recent demonstration of the optical frequency modulation of the free-electron quantum electron wave function (QEW) by an ultrafast laser beam. We assert that pulses of such QEWs correlated in their modulation phase, interact resonantly with two-level systems, inducing resonant quantum transitions when the transition energy ΔE=ℏω_{21} matches a harmonic of the modulation frequency ω_{21}=nω_{b}. Employing this scheme for resonant cathodoluminescence and resonant EELS combines the atomic level spatial resolution of electron microscopy with the high spectral resolution of lasers.
77 citations
TL;DR: In this paper, a double-perovskite type Ba2GdSbO6:Eu3+ phosphors was successfully demonstrated by the simple high-temperature solid-state reaction at 1400°C.
51 citations
TL;DR: In this paper, the growth of gallium oxide films by halide vapor phase epitaxy (HVPE) on various substrates under the same growth conditions was compared, and most of the films exhibit growth features of hexagonal symmetry.
Abstract: In this study we compare the growth of gallium oxide films by halide vapor phase epitaxy (HVPE) on various substrates under the same growth conditions. Gallium oxide films were deposited at 500 °C–600 °C on basal plane (0001) planar and patterned sapphire substrates, (0001) 2H-GaN, 4H-SiC, and bulk β-Ga2O3 substrates. The layers were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and cathodoluminescence (CL) techniques. Most of the films exhibit growth features of hexagonal symmetry. Sn-doped Ga2O3 films exhibit n-type electrical conductivity. Heterojunctions composed of n-type hexagonal Ga2O3:Sn and p-type GaN:Mg demonstrate diode-like I-V characteristics and emit light under forward bias.
46 citations
TL;DR: The EPC mechanism of Cr3+ in CSSG is revealed for the first time by temperature-dependent photoluminescence measurement from 77 to 573 K and cathodolumineminescence using a scanning electron microscope.
Abstract: Cr3+ in the Ca3Sc2Si3O12 garnet (CSSG) has the ability to convert blue light to broadband near-infrared (NIR) emissions, which is a promising strategy for next-generation smart NIR light sources based on blue LEDs. The Cr3+ luminescence strongly depends on temperature due to electron–phonon coupling (EPC). We reveal the EPC mechanism of Cr3+ in CSSG for the first time by temperature-dependent photoluminescence measurement from 77 to 573 K and cathodoluminescence using a scanning electron microscope. Cr3+ occupies the Sc3+ site and experiences a weak crystal field in CSSG, manifesting a broad NIR emission in the 700–900 nm range that originates from the 4T2g → 4A2g transition. The zero phonon line (ZPL) of the 4T2 state is observed at ∼713 nm with a vibrational energy of ∼310 cm−1. A strong EPC leads to a large Stokes shift (∼2900 cm−1). The Huang–Rhys parameter (S = 4), crystal field strength (Dq/B), and Racah parameters (B and C) are estimated.
32 citations
TL;DR: Experimental visualization of the phase associated with the plasmonic field of metallic particle-surface composites through nanoscopically and spectroscopically resolved cathodoluminescence using a scanning transmission electron microscope is demonstrated.
Abstract: Nanoscale gaps between metals can strongly confine electromagnetic fields that enable efficient electromagnetic energy conversion and coupling to nanophotonic structures. In particular, the gap formed by depositing a metallic particle on a metallic substrate produces coupling of localized particle plasmons to propagating surface plasmon polaritons (SPPs). Understanding and controlling the phase of such coupling is essential for the design of devices relying on nanoparticles coupled through SPPs. Here we demonstrate the experimental visualization of the phase associated with the plasmonic field of metallic particle-surface composites through nanoscopically and spectroscopically resolved cathodoluminescence using a scanning transmission electron microscope. Specifically, we study the interference between the substrate transition radiation and the field resulting from out-coupling of SPP excitation, therefore giving rise to angle-, polarization-, and energy-dependent photon emission fringe patterns from which we extract phase information. Our methods should be readily applicable to more complex nanostructures, thus providing direct experimental insight into nanoplasmonic near-fields with potential applications in improving plasmon-based devices.
31 citations
TL;DR: In this article, a wide spectrum of doping enabled to control the free electron concentration in semiconducting β-Ga2O3 oxide semiconductor that additionally scintillates under gamma excitation.
27 citations
TL;DR: In this paper, the growth of GaN-based LEDs using metal-organic chemical vapor deposition (MOCVD) on an amorphous glass substrate has been demonstrated, and the InGaN/GaN multiple quantum well shells are conformally grown on semipolar { 11 2 ¯ 2 } growth facet of m-axial GaN core nanowires and resulted in reduced quantum confined Stark effect.
TL;DR: Conversion from NV– to NV0 due to electron-induced carrier generation is shown and new insights are provided into the NV– → NV0 conversion dynamics and into the use of pump–probe cathodoluminescence as a nanoscale NV characterization tool.
Abstract: Nitrogen-vacancy (NV) centers in diamond are reliable single-photon emitters, with applications in quantum technologies and metrology. Two charge states are known for NV centers, NV0 and NV–, with the latter being mostly studied due to its long electron spin coherence time. Therefore, control over the charge state of the NV centers is essential. However, an understanding of the dynamics between the different states still remains challenging. Here, conversion from NV– to NV0 due to electron-induced carrier generation is shown. Ultrafast pump–probe cathodoluminescence spectroscopy is presented for the first time, with electron pulses as pump and laser pulses as probe, to prepare and read out the NV states. The experimental data are explained with a model considering carrier dynamics (0.8 ns), NV0 spontaneous emission (20 ns), and NV0 → NV– back transfer (500 ms). The results provide new insights into the NV– → NV0 conversion dynamics and into the use of pump–probe cathodoluminescence as a nanoscale NV chara...
TL;DR: In this article, single-photon sources based on InGaAs quantum dots (QDs) emitting in the telecom O-band were developed and studied using in situ electron beam lithography in combination with thermocompression bonding to realize a backside gold mirror.
Abstract: In this work, we develop and study single-photon sources based on InGaAs quantum dots (QDs) emitting in the telecom O-band. Quantum devices are fabricated using in situ electron beam lithography in combination with thermocompression bonding to realize a backside gold mirror. Our structures are based on InGaAs/GaAs heterostructures, where the QD emission is redshifted toward the telecom O-band at 1.3 μm via a strain-reducing layer. QDs pre-selected by cathodoluminescence mapping are embedded into mesa structures with a backside gold mirror for enhanced photon-extraction efficiency. Photon-autocorrelation measurements under pulsed non-resonant wetting-layer excitation are performed at temperatures up to 40 K, showing pure single-photon emission, which makes the devices compatible with stand-alone operation using Stirling cryocoolers. Using pulsed p-shell excitation, we realize single-photon emission with a high multi-photon suppression of g(2)(0) = 0.027 ± 0.005, an as-measured two-photon interference visibility of (12 ± 4)%, a post-selected visibility of (96 ± 10)%, and an associated coherence time of (212 ± 25) ps. Moreover, the structures show an extraction efficiency of ∼5%, which is comparable to values expected from numeric simulations of this photonic structure. Further improvements of our devices will enable implementations of quantum communication via optical fibers.
TL;DR: In this article, depth-resolved cathodoluminescence spectroscopy was combined with X-ray diffraction to reveal optical signatures of mid-gap states that can be associated with cation sublattice disorder.
Abstract: III-nitrides have revolutionized lighting technology and power electronics. Expanding the nitride semiconductor family to include heterovalent ternary nitrides opens up new and exciting opportunities for device design that may help overcome some of the limitations of the binary nitrides. However, the more complex cation sublattice also gives rise to new interactions with both native point defects and defect complexes that can introduce disorder on the cation sublattice. Here, depth-resolved cathodoluminescence spectroscopy and surface photovoltage spectroscopy measurements of defect energy levels in ZnGeN2 combined with transmission electron microscopy and x-ray diffraction reveal optical signatures of mid-gap states that can be associated with cation sublattice disorder. The energies of these characteristic optical signatures in ZnGeN2 thin films grown by metal–organic chemical vapor deposition are in good agreement with multiple, closely spaced band-like defect levels predicted by density functional theory. We correlated spatially resolved optical and atomic composition measurements using spatially resolved x-ray photoelectron spectroscopy with systematically varied growth conditions on the same ZnGeN2 films. The resultant elemental maps vs defect spectral energies and intensities suggest that cation antisite complexes (ZnGe–GeZn) form preferentially vs isolated native point defects and introduce a mid-gap band of defect levels that dominate electron–hole pair recombination. Complexing of ZnGe and GeZn antisites manifests as disorder in the cation sub-lattice and leads to the formation of wurtzitic ZnGeN2 as indicated by transmission electron microscopy diffraction patterns and x-ray diffraction reciprocal space maps. These findings emphasize the importance of growth and processing conditions to control cation place exchange.
01 Feb 2020-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, a method for identifying inclusions in steel that has been deoxidized and desulfurized by misch metal using cathodoluminescence (CL) analysis within 1 minute was proposed.
Abstract: The injection of misch metal, which primarily consists of La, Ce, and Nd, into molten steel can reduce the size of nonmetallic inclusions, suppress the formation of harmful nonmetallic inclusions, and reduce the content of oxygen and sulfur in steel. To investigate the impact of misch metal on these effects, we propose a method for identifying inclusions in steel that has been deoxidized and desulfurized by misch metal using cathodoluminescence (CL) analysis within 1 minute. Based on the CL images and spectra of model steel samples that were deoxidized and desulfurized by La, Ce, or Nd metal, we demonstrate that La2O3, La2O2S, CeO2, Ce2O2S, Nd2O3, and Nd2O2S inclusions can be identified by the emitted luminescence color using cameras with sensitivity ranges of 420 to 680 and 350 to 1000 nm. La2O3, La2O2S, CeO2, Ce2O2S, Nd2O3, and Nd2O2S inclusions emitted blue-green, yellow-orange, yellow-orange, violet, blue-violet, and red luminescence, respectively when observed by a camera with a sensitivity range of 420 to 680 nm. CeO2 and Nd2O3 inclusions emitted red-orange and red-violet luminescence, respectively when observed by a camera with a sensitivity range of 350 to 1000 nm.
TL;DR: In this article, the deleterious effect of V-pit density on device performance is demonstrated by evaluating test devices fabricated on two wafers with significantly diverse density of buried V-pits induced by varying growth conditions of the aluminum nitride nucleation layer.
Abstract: Gallium nitride on silicon (GaN/Si) is an important technological approach for power electronic devices exhibiting superior performance compared to devices based on a pure silicon technology. However, the material defect density in GaN/Si is high, and identification of critical defects limiting device reliability is still only partially accomplished because of experimental difficulties. In this work, atomic force microscopy, scanning electron microscopy, secondary ion mass spectrometry, and cathodoluminescence were employed to investigate commonly occurring epitaxial overgrown V-pits and inhomogeneous incorporation of oxygen and carbon across layer stacking in the vertical direction. These experiments identified V-pits as regions with higher n-type carrier concentrations and paths for vertical leakage through the buffer, as directly probed by conductive atomic force microscopy. The deleterious effect of V-pits on device performance is demonstrated by evaluating test devices fabricated on two wafers with significantly diverse density of buried V-pits induced by varying growth conditions of the aluminum nitride nucleation layer. A clear correlation between observed vertical breakdown and density of V-pits within the C-doped GaN layer below the device structures is obtained. Back-gating transient measurements also show that the dynamic device behavior is affected by the V-pit density in terms of the detrapping time constants.Gallium nitride on silicon (GaN/Si) is an important technological approach for power electronic devices exhibiting superior performance compared to devices based on a pure silicon technology. However, the material defect density in GaN/Si is high, and identification of critical defects limiting device reliability is still only partially accomplished because of experimental difficulties. In this work, atomic force microscopy, scanning electron microscopy, secondary ion mass spectrometry, and cathodoluminescence were employed to investigate commonly occurring epitaxial overgrown V-pits and inhomogeneous incorporation of oxygen and carbon across layer stacking in the vertical direction. These experiments identified V-pits as regions with higher n-type carrier concentrations and paths for vertical leakage through the buffer, as directly probed by conductive atomic force microscopy. The deleterious effect of V-pits on device performance is demonstrated by evaluating test devices fabricated on two wafers with s...
TL;DR: In this work, models of Al 0.75 Ga 0.25 N/AlN QWs constructed with variable lattice orientations were used to investigate the orbital intercoupling among atoms between the well and barrier regions and the barrier potential and transition rate at the band edge were enhanced through orbital engineering.
Abstract: AlGaN has attracted considerable interest for ultraviolet (UV) applications With the development of UV optoelectronic devices, abnormal carrier confinement behaviour has been observed for c-plane-oriented AlGaN quantum wells (QWs) with high Al content Because of the dispersive crystal field split-off hole band (CH band) composed of pz orbitals, the abnormal confinement becomes the limiting factor for efficient UV light emission This observation differs from the widely accepted concept that confinement of carriers at the lowest quantum level is more pronounced than that at higher quantum levels, which has been an established conclusion for conventional continuous potential wells In particular, orientational pz orbitals are sensitive to the confinement direction in line with the conducting direction, which affects the orbital intercoupling In this work, models of Al075Ga025N/AlN QWs constructed with variable lattice orientations were used to investigate the orbital intercoupling among atoms between the well and barrier regions Orbital engineering of QWs was implemented by changing the orbital state confinement, with the well plane inclined from 0° to 90° at a step of 30° (referred to the c plane) The barrier potential and transition rate at the band edge were enhanced through this orbital engineering The concept of orbital engineering was also demonstrated through the construction of inclined QW planes on semi- and nonpolar planes implemented in microrods with pyramid-shaped tops The higher emission intensity from the QWs on the nonpolar plane compared with those on the polar plane was confirmed via localized cathodoluminescence (CL) maps
TL;DR: In this paper, a combination of qualitative and quantitative analyses (petrography, CL, EBSD, X-ray CT, LA-ICP-MS) is used to identify the underlying structure and texture interdependencies in igneous quartz.
Abstract: Abstract Textural and chemical heterogeneities in igneous quartz crystals preserve unique records of silicic magma evolution, yet their origins and applications are controversial. To improve our understanding of quartz textures and their formation, we examine those in crystal-laden rhyolites produced by the 74 ka Toba supereruption (>2800 km3) and its post-caldera extrusions. Quartz crystals in these deposits can reach unusually large sizes (10–20 mm) and are rife with imperfections and disequilibrium features, including embayments, melt inclusions, titanomagnetite and apatite inclusions, spongy morphologies, hollow faces, subgrain boundaries, multiple growth centers, and Ti-enriched arborescent zoning. Using a combination of qualitative and quantitative analyses (petrography, CL, EBSD, X‑ray CT, LA-ICP-MS), we determine that those textures commonly thought to signify crystal resorption, crystal deformation, synneusis, or fluctuating P–T conditions are here a consequence of rapid disequilibrium crystal growth. Most importantly, we discover that an overarching process of disequilibrium crystallization is manifested among these crystal features. We propose a model whereby early skeletal to dendritic quartz growth creates a causal sequence of textures derived from lattice mistakes that then proliferate during subsequent stages of slower polyhedral growth. In a reversed sequence, the same structural instabilities and defects form when slow polyhedral growth transitions late to fast skeletal-dendritic growth. Such morphological transitions result in texture interdependencies that become recorded in the textural-chemical stratigraphy of quartz, which may be unique to each crystal. Similar findings in petrologic experimental studies allow us to trace the textural network back to strong degrees of undercooling and supersaturation in the host melt, conditions likely introduced by dynamic magmatic processes acting on short geologic timescales. Because the textural network can manifest in single crystals, the overall morphology and chemistry of erupted quartz can reflect not only its last but its earliest growth behavior in the melt. Thus, our findings imply that thermodynamic disequilibrium crystallization can account for primary textural and chemical heterogeneities preserved in igneous quartz and may impact the application of quartz as a petrologic tool.
TL;DR: Fourier-transform CL holography is used to determine the far-field phase distribution of fields scattered from plasmonic nanoholes, nanocubes, and helical nanoapertures and reconstruct the angle-resolved phase distributions.
Abstract: High-energy (1-100 keV) electrons can coherently couple to plasmonic and dielectric nanostructures, creating cathodoluminescence (CL) of which the spectral features reveal details of the material's resonant modes at a deep-subwavelength spatial resolution. While CL provides fundamental insight in optical modes, detecting its phase has remained elusive. Here, we use Fourier-transform CL holography to determine the far-field phase distribution of fields scattered from plasmonic nanoholes, nanocubes, and helical nanoapertures and reconstruct the angle-resolved phase distributions. From the derived fields, we derive the relative strength and phase of induced scattering dipoles. Fourier-transform CL holography opens up a new world of coherent light scattering and surface wave studies with nanoscale spatial resolution.
01 Mar 2020-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the luminescence and thermal stability of defects formed in α-Al2O3 single crystals after powerful (300-keV) pulsed irradiation with C+/H+ ion beam were investigated.
Abstract: The luminescence and thermal stability of defects formed in α-Al2O3 single crystals after powerful (300 keV) pulsed irradiation with C+/H+ ion beam were investigated. It was found by measuring of optical density, photoluminescence, and pulsed cathodoluminescence that ion irradiation induces both single F-, F+-centers and F2-type aggregate centers. An intense thermoluminescence band with a complex shape was observed in the broad temperature range of 350–700 K, its intensity decreases with increasing of the energy density of the ion beam. The thermal stability of the F-type defects produced in α-Al2O3 after irradiation with a pulsed ion beam is comparable to that in neutron-irradiated samples. The appropriate kinetics of annealing of radiation-induced defects has been analyzed in terms of the diffusion-controlled bimolecular reactions between F-type centers and complementary interstitial oxygen ions. Thus, two important kinetic parameters – the migration energy of mobile interstitials and pre-exponential – have been evaluated and discussed.
TL;DR: In this paper, the growth of gallium nitride pyramids was carried out on few layer graphene substrates with different growth parameters such as growth time and precursor-to-substrate distance.
TL;DR: A significant increase in the sensing response at low operating temperature (100°C) opens the possibility of developing very large-scale integrable (VLSI), low operational cost gas sensors with easy fabrication methods and low-cost materials.
Abstract: In this study, we report a simple method for the fabrication of carbon dots sensitized zinc oxide-porous silicon (ZnO-pSi) hybrid structures for carbon dioxide (CO2) sensing. A micro-/nanostructured layer of ZnO is formed over electrochemically prepared pSi substrates using a simple chemical precipitation method. The hybrid structure was structurally and optically characterized using scanning electron microscopy, X-ray diffraction, fluorescence, and cathodoluminescence after the incorporation of hydrothermally prepared nitrogen-doped carbon dots (NCDs) by drop-casting. With respect to the control sample, although all the devices show an enhancement in the sensing response in the presence of NCDs, the optimal concentration shows an increase of ~37 % at an operating temperature of 200 °C and a response time <30 s. The increment in the CO2 sensing response, upon the addition of NCDs, is attributed to an increase in CO2-oxygen species reactions on the ZnO surface due to an increment in the free electron density at the metal-semiconductor type junction of NCDs clusters and ZnO micro-/nanorods. A significant increase in the sensing response (~24 %) at low operating temperature (100 °C) opens the possibility of developing VLSI integrable, low operational cost gas sensors with easy fabrication methods and low-cost materials.
TL;DR: In this paper, the generation of visible and near-infrared (NIR) luminescence associated with the formation of point defects in hydroxyapatite (HAp) nanobelts was studied.
TL;DR: According to photo- and cathodoluminescence measurements performed at room temperature, an improved efficiency of light emission at 435 nm with internal quantum efficiency > 15 % has been achieved by adding a GaN spacer prior to the growth of QW.
Abstract: Different types of buffer layers such as InGaN underlayer (UL) and InGaN/GaN superlattices are now well-known to significantly improve the efficiency of c-plane InGaN/GaN-based light-emitting diodes (LEDs). The present work investigates the role of two different kinds of pregrowth layers (low In-content InGaN UL and GaN UL namely "GaN spacer") on the emission of the core-shell m-plane InGaN/GaN single quantum well (QW) grown around Si-doped c-GaN microwires obtained by silane-assisted metal organic vapor phase epitaxy. According to photo- and cathodoluminescence measurements performed at room temperature, an improved efficiency of light emission at 435 nm with internal quantum efficiency >15% has been achieved by adding a GaN spacer prior to the growth of QW. As revealed by scanning transmission electron microscopy, an ultrathin residual layer containing Si located at the wire sidewall surfaces favors the formation of high density of extended defects nucleated at the first InGaN QW. This contaminated residual incorporation is buried by the growth of the GaN spacer and avoids the structural defect formation, therefore explaining the improved optical efficiency. No further improvement is observed by adding the InGaN UL to the structure, which is confirmed by comparable values of the effective carrier lifetime estimated from time-resolved experiments. Contrary to the case of planar c-plane QW where the improved efficiency is attributed to a strong decrease of point defects, the addition of an InGaN UL seems to have no influence in the case of radial m-plane QW.
TL;DR: In this paper, a SiNx-masked GaN template grown on a sapphire substrate was used to study spatially resolved Raman scattering mapping and room-temperature cathodoluminescence (CL) mapping of GaN via epitaxial lateral overgrowth.
TL;DR: In this article, a database of the parameters obtained from the main marble quarries used in antiquity is presented, with a total number of 473 marble samples from ten districts of the central and eastern Mediterranean, with the additional advantage of being the same samples that have already characterized by other conventional techniques and available in the literature.
Abstract: Quantitative cathodoluminescence (CL) has rarely been applied for the archaeometric studies concerning marble provenance, despite its potential. This paper develops the method and provides a new database of the parameters obtained from the main marble quarries used in antiquity. With a total number of 473 marble samples from ten districts of the central and eastern Mediterranean, it is the first database on quantitative CL, with the additional advantage of being the same samples that have already characterized by other conventional techniques and that are available in the literature. Focused on the measurements of the intensity peaks at the UV and visible spectra, registered by a spectrometer coupled to a scanning electron microscope (CL-SEM), the representative values are plotted on different useful diagrams to be applied in the identification of marble provenance studies, as a complementary tool of other analyses.
TL;DR: In this paper, the size of nanoparticles in the deposited powders has been estimated by X-ray diffraction and transmission electron microscopy, and it is found that the maxima of the luminescence spectra of nanostructured zinc sulfide are located at about 450nm.
TL;DR: In this paper, the effects of iron content on morphology, crystal structure, optical and magnetic properties of ZnO nanoparticles were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive Xray spectroscopy (EDX), cathodoluminescence (CL), photoluminecence (PL) and magnetic measurements.