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Probing the light hole / heavy hole switching with correlated magneto-optical spectroscopy and chemical analysis on a single quantum dot
摘要： A whole series of complementary studies have been performed on the same, single nanowire containing a quantum dot: cathodoluminescence spectroscopy and imaging, micro-photoluminescence spectroscopy under magnetic field and as a function of temperature, and energy-dispersive X-ray spectrometry and imaging. The ZnTe nanowire was deposited on a Si3N4 membrane with Ti/Al patterns. The complete set of data shows that the CdTe quantum dot features the heavy-hole state as a ground state, although the compressive mismatch strain promotes a light-hole ground state as soon as the aspect ratio is larger than unity (elongated dot). A numerical calculation of the whole structure shows that the transition from the heavy-hole to the light-hole configuration is pushed toward values of the aspect ratio much larger than unity by the presence of a (Zn,Mg)Te shell, and that the effect is further enhanced by a small valence band offset between the semiconductors in the dot and around it.
关键词： molecular beam epitaxy,optical spectroscopy,EDX,semiconductors,cathodoluminescence,quantum dot,nanowires
更新于2025-11-21 11:20:48
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Composition-gradient ZnO/Zn(S,O) heterostructure nanorod arrays and their cathodoluminescence
摘要： Well-aligned ZnO/Zn(S,O) heterostructure nanorods have been synthesized through a well-designed chemical vapor deposition synthesis process. The as-synthesized ZnO/Zn(S,O) heterostructures exhibit a single crystal characteristic and a transitive interface with obvious composition gradient. X-ray Energy dispersive spectrometer (EDS) analysis demonstrates that ZnS-phase is rich in the nanorod bottom during the initial nucleation process and the S element content has a drastic decrease along the heterostructure nanorod from the bottom to the top, while O element is spatially detected in the whole rod. Room-temperature cathodoluminescence measurements verify two UV emissions at 330 nm and 385 nm for respective Zn(S,O) and ZnO phases with a strong defect-related emission band in visible range. Finally, the growth mechanism and optical emissions of ZnO/Zn(S,O) heterostructure nanorods are discussed.
关键词： ZnS,Heterostructures,ZnO,Synthesis,Cathodoluminescence
更新于2025-11-14 17:15:25
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Cathodoluminescent lamp for general lighting using carbon fiber field emission cathode
摘要： The prototype of cathodoluminescent bulb for general lighting with field emission cathode on the basis of carbon fiber is manufactured. The bulb comprises a high-voltage built-in AC-DC converter of the electric line voltage and a standard E27 cap. A high frequency converter is used to obtain high voltage. The anode voltage relative to the modulator is up to +20 kV; the cathode voltage is up to –4 kV; the current value is of the order of 1 mA. The voltage converter is located in the bulb cap and around the neck of the glass envelope.
关键词： cathode-ray-tube phosphor,carbon fiber,light sources,field emission cathodes,cathodoluminescence
更新于2025-09-23 15:22:29
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Prospective scintillation electron detectors for S(T)EM based on garnet film scintillators
摘要： The performance of a scintillation electron detector for a scanning electron microscope and/or a scanning transmission electron microscope (S(T)EM) based on new epitaxial garnet film scintillators was explored. The LuGAGG:Ce and LuGAGG:Ce,Mg film scintillators with chemical formula (Ce0.01Lu0.27Gd0.74)3–wMgw(Ga2.48Al2.46)O12 were prepared and their cathodoluminescence (CL) and optical properties were studied and compared with the properties of current standard bulk single crystal YAG:Ce and YAP:Ce scintillators. More specifically, CL decay characteristics, CL emission spectra, CL intensities, optical absorption coefficients, and the refractive indices of the mentioned scintillators were measured. Furthermore, electron interaction volumes with absorbed energy distributions, photomultiplier (PMT) photocathode matchings, modulation transfer functions (MTF), and the photon transport efficiencies of scintillation detectors with the mentioned scintillators were calculated. A CL decay time for the LuGAGG:Ce,Mg film scintillator as low as 28 ns with an afterglow of only 0.02% at 1 μs after the e-beam excitation was observed. As determined from calculated MTFs, the scintillation detectors with the new film scintillators lose contrast transfer ability above 0.6 lp/pixel, while the currently commonly used YAG:Ce single crystal scintillators already do so above 0.1 lp/pixel. It was also calculated that the new studied film scintillators have an 8% higher photon transfer efficiency, even for a simple disk shape compared with the standard bulk single crystal YAG:Ce scintillator. The studied LuGAGG:Ce,Mg epitaxial garnet film scintillators were evaluated as prospective fast scintillators for electron detectors, not only in S(T)EM but also in other e-beam devices.
关键词： electron detector,multicomponent garnet film,scintillator,STEM,SEM,LuGAGG:Ce,Mg,cathodoluminescence
更新于2025-09-23 15:22:29
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Effective SEM Analytical Techniques for the Cathodoluminescence Visualization of Intergranular Cements in Saint Peter Sandstone: A Round Robin Exercise
摘要： The use of Cathodoluminescence (CL) as an analytical tool for geoscience and materials research is well established. Many minerals exhibit CL when activated by the high-energy electron beam bombardment of the Scanning Electron Microscope (SEM) [1]. CL imaging capabilities vary among laboratories due to the differences in detector type, sample preparation (epoxy, polish, coating), SEM type (W, LaB6, FE) and analytical conditions (kV, pA/nA, sample temperature). An interlaboratory comparison was initiated to assess the optimal conditions for obtaining high resolution CL imagery [2]. Quartz (and its polymorphs) are often difficult to image by CL due to low CL response and thus it was chosen as a test material. Composed of fine to medium-grained silicon dioxide, St. Peter Sandstone is used extensively as a proppant in hydraulic formation fracture (fracking) [3]. Appropriate sample preparation is necessary for optimal CL imaging results, varying from lab to lab. In the case of the porous St. Peter Sandstone with incomplete and fragile intergranular cement structures, producing a polished sample surface without plucking grains and removing the cements is imperative. For this interlaboratory comparison, polished samples were prepared from a single St. Peter Sandstone sample that was cored perpendicular to the bedding. Samples were imbedded in Epoxy and polished to a sub micron finish. Six of these samples were shared with other SEM-EPMA laboratories with the goal of refining SEM-CL conventions for cement study and imagery. As of abstract deadline time, we have 3 examples of CL images to present, and expect to have others by the M&M conference.
关键词： intergranular cements,SEM,quartz,St. Peter Sandstone,Cathodoluminescence
更新于2025-09-23 15:21:21
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Selected mode mixing and interference visualized within a single optical nanoantenna
摘要： Interference-based directional antennas typically consist of multiple dipoles with properly set distances and phases, which cause constructive interferences towards certain directions in radiation or reception. For nano optical antennas, the directionality can be realized by superposition of multiple eigen modes in a single structure. Such mode mixing creates locally strong field enhancement, which should be properly controlled for energy-conversion or sensing applications. However, experimental verification of the nano optical field, or especially the hot-spots, created by interference of selected eigen modes is not trivial. We here visualize how optical fields are distributed when multiple modes interfere within a silver disk nano antenna. We use angle- and polarization-resolved cathodoluminescence based on scanning transmission electron microscopy to select specific modes and visualize the field distribution at the nanoscale. The interfered field distribution significantly changes depending on the detection angles even when the detection geometry is symmetric, which can be explained by the phase difference of the excited mode. The cathodoluminescence signals are also modeled as superpositions of analytical eigen mode functions consisting of multipoles in space and complex Lorentzians in frequency to reproduce the experimentally obtained photon maps.
关键词： Scanning Transmission Electron Microscopy,Surface Plasmon,Multipole,Cathodoluminescence,Nanodisk
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Structure and cathodoluminescent properties of ultraviolet emitting Zn(Al<inf>1-x</inf> Ga<inf>x</inf>)<inf>2</inf> O<inf>4</inf> alloy phosphor
摘要： The goal is to control the band gap by replacing the Al site of zinc aluminate having a spinel structure with Ga, and to control the emission wavelength, and aim for application as a light source in sterilization, skin treatment and the like. Zn(Al1-xGax)2O4 phosphor was prepared by a solid phase synthesis method. A plurality of samples with different Al/Ga ratio were prepared, and their crystal structures and luminescent properties were evaluated. In X-ray diffraction, formation of a single phase was confirmed in the sample fired at 1300 oC. It was confirmed that the diffraction peak shifted to the lower angle side by increasing the Ga ratio. In the cathode luminescence method, it was confirmed that ultraviolet emission of ZnAl2O4 was confirmed at about 250 nm, and it was confirmed that the emission wavelength shifted to the long wavelength side by increasing the Ga ratio. It is suggested that substituting Ga for the Al site of ZnAl2O4 is useful for shifting the emission wavelength although the emission intensity is unstable.
关键词： Cathodoluminescence,Zn(Al,Ga)2O4,Alloy phosphor,Ultra-Violet emission
更新于2025-09-23 15:21:21
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Cathodoluminescence and thermoluminescence of ZnB2O4:Eu3+ phosphors prepared via wet-chemical synthesis
摘要： In present work, a series of Eu doped zinc borate, ZnB2O4, phosphors prepared via wet chemical synthesis and their structural, surface morphology, cathodoluminescence (CL) and thermoluminescence (TL) properties have been studied. Phase purity and crystal structure of as-prepared samples are con?rmed by X-ray di?raction measurements (XRD) and they were well consistent with PDF card No. 39-1126, indicating the formation of pure phase. The thermoluminescence (TL) behaviors of Eu activated ZnB2O4 host lattice are studied for various beta doses ranging from 0.1 to 10 Gy. The high-temperature peak of Eu activated sample located at 192 °C exhibited a linear dose response in the range of 0.1–10 Gy. Initial rise (IR) and peak shape (PS) methods were used to determine the activation energies of the trapping centres. The e?ects of the variable heating rate on TL behaviour of Eu activated ZnB2O4 were also studied. When excited using an electron beam induced light emission (i.e cathodoluminescence, CL) at room temperature (RT), the as-prepared phosphors generate reddish-orange color due to predominant emission peaks of Eu3+ ions located at 576–710 nm assigned to the 5D0→7FJ (J=1,2,3, and 4) transitions. The maximum CL intensity for Eu3+ ions at 614 nm with transition 5D0→7F2 was reached Eu3+ concentration of 5 mol%; quenching occurred at higher concentrations. Strong emission peak for Eu3+ ions at 614 nm with transition 5D0→7F2 is observed. The CL experimental data indicate that ZnB2O4:Eu3+ phosphor as an orange-red emitting phosphor may be promising luminescence materials for the optoelectronic applications.
关键词： Thermoluminescence,Zinc borates,XRD,Cathodoluminescence,Rare earth
更新于2025-09-23 15:21:21
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Schottky Contacts on Polarity-Controlled Vertical ZnO Nanorods
摘要： Polarity-controlled growth of ZnO by chemical bath deposition provides a method for controlling the crystal orientation of vertical arrays of nanorods. The ability to define the morphology and structure of the nanorods is essential to maximising the performance of optical and electrical devices such as piezoelectric nanogenerators; however, well-defined Schottky contacts to the polar facets of the structures have yet to be explored. In this work, we demonstrate a process to fabricate metal-semiconductor-metal device structures from vertical arrays with Au contacts on the uppermost polar facets of the nanorods and show the O-polar nanorods (~0.44 eV) have a greater effective barrier height than the Zn-polar nanorods (~0.37 eV). Oxygen plasma treatment is shown by Cathodoluminescence (CL) spectroscopy to reduce mid-gap defects associated with radiative emissions that improves the Schottky contacts from weakly-rectifying to strongly-rectifying. Interestingly, the plasma treatment was shown to have a much greater effect in reducing the number of carriers in O-polar nanorods through quenching of the donor-type substitutional hydrogen on oxygen sites (HO) when compared to the zinc vacancy related hydrogen defect complexes (VZn, Hn) in Zn-polar nanorods that evolve to lower coordinated complexes. The effect on HO in the O-polar nanorods coincided with a large reduction in the visible range defects producing a lower conductivity and creating the larger effective barrier heights. This combination can allow radiative losses and charge leakage to be controlled enhancing devices such as dynamic photodetectors, strain sensors, and LEDs while showing the O-polar nanorods can outperform Zn-polar nanorods in such applications.
关键词： ZnO,Cathodoluminescence,Electrical Transport,Polarity,Schottky Contacts,Nanorods,Defects
更新于2025-09-23 15:21:01
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YAG:Ce <sup>3+</sup> Transparent Ceramic Phosphors Brighten the Next-Generation Laser-Driven Lighting
摘要： Y3Al5O12: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.
关键词： cathodoluminescence,laser-driven lighting,transparent ceramic phosphors,Mg2+–Si4+,YAG:Ce3+
更新于2025-09-23 15:21:01