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- 实验方案
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Improving Reliability of InAs Quantum Dot Lasers on Silicon Substrates
摘要： Using correlated electron microscopy techniques, we structural properties of characterize optoelectronic and dislocation in InAs quantum dots (QD) structures. Results indicate that although dislocations significantly affect QD luminescence, the rate of recombination enhanced dislocation climb slows noticeably during the aging process from quantum well structures.
关键词： quantum dot laser,STEM,dislocation,silicon photonics,cathodoluminescence,III-V on Si
更新于2025-09-11 14:15:04
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[IEEE 2018 International Conference Laser Optics (ICLO) - Saint Petersburg, Russia (2018.6.4-2018.6.8)] 2018 International Conference Laser Optics (ICLO) - Mid-IR cathodoluminescence of zinc selenide highly-doped with iron
摘要： The intensity integrated of cathodoluminescence in the middle infrared region of the spectra of ZnSe:Fe crystals with varying iron concentration have been studied. Dependence of decay time on iron concentration has been demonstrated. Experiments were carried out at 77 K and room temperature.
关键词： mid-IR,ZnSe:Fe,cathodoluminescence
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Electron-Driven Photon Sources for Spectral Interferometry using Electron Microscopes
摘要： Photon induced near-field electron microscopy has been recently introduced to investigate the dynamics of field distributions in nanostructures, with femtosecond technique a laser beam excites both a photoemission electron gun and the sample inside an electron microscope. The electron beams then probe the laser-induced excitations. Achieving attosecond temporal resolution to probe electron dynamics is however challenging, due to the requirement for a perfect synchronization between the electron waves and laser light. Recently an alternative approach based on cathodoluminescence (CL) has been proposed. In this way, the interaction of swift electrons with a precisely designed electron-driven photon source (EDPHS) causes radiation of ultrashort optical pulses, which are focused onto the sample (Fig. 1a). The sample interacts with both the EDPHS radiation and the electron. The CL emission is controlled by the distance between the sample and the EDPHS. The distance-energy correlation map between the CL radiations from both the sample and EDPHS is then recorded and used to recover the spectral phase and time-resolved responses of the sample. Here, we propose, fabricate, and investigate an EDPHS structure using transformation optics, used for the purpose of spectral interferometry in electron microscopes. The EDPHS structure is composed of a lattice of holes drilled into a gold thin film, using focused ion beam. The distribution of the holes and their dimensions is precisely controlled to facilitate the generation of focused light waves (Fig. 1c). Moreover, the overall structure supports a hyperbolic dispersion for propagating plasmon polaritons, which greatly enhances radiation channels. Furthermore, we perform CL and electron-energy loss spectroscopy experiments which unravel the broadband nature of the fabricated light source as well as its coherent mechanism of radiation and are in excellent agreement with our numerical studies.
关键词： femtosecond technique,spectral interferometry,Photon induced near-field electron microscopy,electron-driven photon source,cathodoluminescence
更新于2025-09-11 14:15:04
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Plasmonic Lenses for Tunable Ultrafast Electron Emitters at the Nanoscale
摘要： Simultaneous spatiotemporal con?nement of energetic electron pulses to femtosecond and nanometer scales is a topic of great interest in the scienti?c community, given the potential impact of such developments across a wide spectrum of scienti?c and industrial applications. For example, in ultrafast electron scattering, nanoscale probes would enable accurate maps of structural dynamics in materials with nanoscale heterogeneity, thereby leading to an understanding of the role of boundaries and defects on macroscopic properties. On the other hand, advances in this ?eld are mostly limited by the brightness and size of the electron source. We present the design, fabrication, and optical characterization of bullseye plasmonic lenses for next-generation ultrafast electron sources. Using electromagnetic simulations, we examine how the interplay between light-plasmon coupling, plasmon propagation, dispersion, and resonance governs the properties of the photoemitted electron pulse. We also illustrate how the pulse duration and strength can be tuned by geometric design and predict that sub-10-fs pulses with nanoscale diameter can be achieved. We then fabricate lenses in gold ?lms and characterize their plasmonic properties using cathodoluminescence spectromicroscopy, demonstrating suitable plasmonic behavior for ultrafast nanoscale photoemission.
关键词： plasmonic lenses,cathodoluminescence spectromicroscopy,nanoscale,ultrafast electron emitters
更新于2025-09-11 14:15:04
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Energy losses and transition radiation in graphene traversed by a fast charged particle under oblique incidence
摘要： We perform fully relativistic calculations of the energy loss channels for a charged particle traversing a single layer of graphene under oblique incidence in a setting pertinent to a scanning transmission electron microscope (STEM), where we distinguish between the energy deposited in graphene in the form of electronic excitations (Ohmic loss) and the energy emitted in the far field in the form of transition radiation (TR). Our formulation of the problem uses a definition of two in-plane, dielectric functions of graphene, which describe the longitudinal and transverse excitation processes that contribute separately to those two energy loss channels. Using several models for the electric conductivity of graphene as the input in those dielectric functions enables us to discuss the effects of oblique incidence on several processes in a broad range of frequencies, from the terahertz (THz) to the ultraviolet (UV). In particular, at the THz frequencies, we demonstrate that the nonlocal effect in the graphene’s conductivity is not important in the retarded regime, and we show that the longitudinal and transverse contributions to the emitted TR spectra exhibit strongly anisotropic angular patterns that are readily distinguishable in a cathodoluminescence measurement in a STEM. Moreover, we explore the possibility of exciting the so-called transverse mode in the optical response of graphene at the mid-infrared (MIR) range of frequencies by means of a fast charged particle under oblique incidence. Finally, we demonstrate that, aside from the usual high-energy peaks in the longitudinal contribution to the Ohmic energy loss in the MIR to the UV frequency range, there may arise strongly directional features in the in-plane distribution of the transverse contribution to the Ohmic energy loss for an oblique trajectory, which could be possibly observed via momentum- and angle-resolved electron energy loss spectroscopy of graphene in STEM.
关键词： MIR,energy loss,STEM,THz,transition radiation,UV,graphene,cathodoluminescence,oblique incidence,Ohmic loss
更新于2025-09-11 14:15:04
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[IEEE 2018 20th International Symposium on High-Current Electronics (ISHCE) - Tomsk, Russia (2018.9.16-2018.9.22)] 2018 20th International Symposium on High-Current Electronics (ISHCE) - Excitation of Diamonds by a Subnanosecond Runaway Electron Beam with an Electron Energy of Up to 200 keV Generated in a Nanosecond Gas Discharge
摘要： The emission spectra of different diamond samples excited by subnanosecond runaway electron beams (REBs) with an electron energy of up to 200 keV have been experimentally studied. Four diamond samples grown by different methods and one natural diamond were used. REBs were produced by two accelerators based on a gas diode. The effect of the REB parameters as well as the diamond growth method on the emission spectra have been established. The radiation of various bands was observed.
关键词： runaway electrons,cathodoluminescence,diamond,Cherenkov radiation
更新于2025-09-11 14:15:04
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Luminescence from AlGaN/GaN HEMT structures by very-low-energy (100 eV) electron beams using beam deceleration technique
摘要： A low-beam-energy cathodoluminescence (CL) system has been developed. This CL system consists of a scanning electron microscope equipped with a beam deceleration (also known as “retarding”) tool and a CL detection system. We employed the system to study an AlGaN/GaN-based high electron mobility transistor structure and observed band-edge emissions even at 100 eV. The band-edge emissions significantly decreased after the plasma irradiation for a few seconds. The low-beam-energy CL is highly sensitive to the surface and can be used for the optimization of the dry process used in the device fabrication.
关键词： HEMT,low-beam-energy,AlGaN/GaN,beam deceleration,cathodoluminescence
更新于2025-09-10 09:29:36
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Direct imaging of Indium-rich triangular nanoprisms self-organized formed at the edges of InGaN/GaN core-shell nanorods
摘要： Higher indium incorporation in self-organized triangular nanoprisms at the edges of InGaN/GaN core-shell nanorods is directly evidenced by spectral cathodoluminescence microscopy in a scanning transmission electron microscope. The nanoprisms are terminated by three 46 nm wide a-plane nanofacets with sharp interfaces forming a well-defined equilateral triangular base in the basal plane. Redshifted InGaN luminescence and brighter Z-contrast are resolved for these structures compared to the InGaN layers on the nanorod sidewalls, which is attributed to at least 4 % higher indium content. Detailed analysis of the inner optical and structural properties reveals luminescence contributions from 417 nm up to 500 nm peak wavelength proving the increasing indium concentration inside the nanoprism towards the nanorod surface.
关键词： cathodoluminescence microscopy,InGaN/GaN core-shell nanorods,nanoprisms,scanning transmission electron microscope,indium incorporation
更新于2025-09-10 09:29:36
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A novel Li <sub/>2</sub> CaSi <sub/>2</sub> N <sub/>4</sub> :Eu <sup>2+</sup> orange-red phosphor for field emission displays
摘要： The exploration of suitable phosphors with high efficiency, low saturation and good stability has always been a key issue for field emission displays (FEDs) development. In this work, a novel Li2CaSi2N4:Eu2+ orange-red phosphors were prepared by solid reaction process and the cathodoluminescence (CL) properties were investigated in detail to explore the potential application for FEDs. Under a low voltage electron-beam excitation, the phosphors show an intense orange-yellow emission in the range of 500-700 nm, which belongs to the 4f65d → 4f7 electron transition of Eu2+ ion. The influences of the Eu2+ doping concentration, filament current, accelerating voltage and bombardment time on the CL emission of Li2CaSi2N4:Eu2+ were investigated in detail. The results indicate that Li2CaSi2N4:Eu2+ phosphors exhibit an intense orange-red emission, no saturation effect, and excellent degradation property, which give the Li2CaSi2N4:Eu2+ phosphors potential application in full color FEDs.
关键词： Li2CaSi2N4:Eu2+,cathodoluminescence,phosphor,FED
更新于2025-09-09 09:28:46
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Mapping “Broken” Dark Modes Using Cathodoluminescence in a Scanning Electron Microscope
摘要： Dark plasmon modes are modes that lack a net dipolar character, and hence do not radiate efficiently. They possess a smaller spectral linewidth and longer lifetimes, making them attractive for many applications in sensing and for high-Q cavities. A focussed high-energy electron beam can be employed as a local, broad-spectrum excitation source, as the evanescent electric field associated with the fast electrons excites resonances in a polarizable material. The light that is radiated to the far-field can be collected in cathodoluminescence (CL), or the energy loss of the electrons can be measured in electron energy loss spectroscopy (EELS). The spatial resolution of these techniques in the scanning electron microscope (SEM) or scanning/transmission electron microscope (S/TEM) is typically limited by the spatial extent of the evanescent field (order of 10~nm depending on beam energy), making them ideal techniques for mapping the spatial distribution of plasmon modes. The energy lost to a dark mode can be detected in EELS, but since these modes are not radiative, in the strictest sense, these modes cannot be detected in CL. However, due to either inherent or introduced asymmetries in the structure, these dark modes acquire a net dipole resonance and do radiate. We performed hyperspectral CL on gold nanorod trimers fabricated using electron beam lithography using a beam energy of 30 keV and current of 500 pA (FEI Nova Nanosem). The CL was collected using a Delmic SPARC system equipped with an Andor Shamrock 303i spectrometer and Andor iVac spectral camera. We show the concurrent SEM images of a symmetric trimer and a trimer with an introduced asymmetry of an inter-trimer angle of 40 degrees. The trimers show two resonances, a high-energy symmetric mode and a low-energy mode composed of two degenerate dipole modes. We mapped these modes by mapping the average intensity between 350-500 nm and 600-700 nm, respectively. While it is clear that the trimer with broken symmetry has a prominent high-energy mode involving all three rods, the symmetric trimer appears to have enough inherent asymmetry to also display this mode. This inherent asymmetry can also be seen in the map of the dipole resonances. Dark modes that are “broken” by asymmetry acquire a dipolar component that allows them to be detected and mapped in CL. Hyperspectral mapping using CL is a powerful method for understanding the effect of nanoscale defects on plasmonic devices.
关键词： cathodoluminescence,plasmonic devices,Dark plasmon modes,scanning electron microscope,hyperspectral mapping
更新于2025-09-09 09:28:46