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Vibrational electron energy loss spectroscopy in truncated dielectric slabs
摘要： Specially designed instrumentation for electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope makes it possible to probe very low-loss excitations in matter with a focused electron beam. Here we study the nanoscale interaction of fast electrons with optical phonon modes in silica. In particular, we analyze the spatial dependence of EEL spectra in two geometrical arrangements: a free-standing truncated slab of silica and a slab with a junction between silica and silicon. In both cases, we identify different loss channels, involving polaritonic and nonpolaritonic contributions to the total electron energy loss, and we obtain the corresponding energy-filtered maps. Furthermore, we present a comparison of the theoretical simulations for a silica-silicon junction with experimental results, and we discuss the spatial resolution attainable from the energy-filtered map considering optical phonon excitations in a conventional experimental arrangement.
关键词： optical phonon modes,nonpolaritonic,polaritonic,silica,electron energy loss spectroscopy,EELS,silicon
更新于2025-09-23 15:21:21
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Plasmonics || Plasmonic Modes in Au and AuAg Nanowires and Nanowire Dimers Studied by Electron Energy Loss Spectroscopy
摘要： In this chapter, we review our recent work on the investigation of surface plasmon modes in metallic nanowires and nanowire dimers by means of electron energy loss spectroscopy combined with scanning transmission electron microscopy (STEM-EELS). Due to the very high spatial resolution, STEM-EELS is a powerful technique to visualize multipole order surface plasmon modes in nanowires and study the dependency of their resonance energies on different parameters such as nanowire dimensions or nanowire porosity. In addition, we investigate surface plasmon hybridization in nanowires separated by gaps of less than 10 nm or connected by small metallic bridges. In such structures new modes arise, which depend strongly on gap or bridge sizes. Experimental results are supported by finite element simulations. The investigated nanowires and dimers are fabricated by electrodeposition in etched ion-track templates, combined with a selective dissolution processes. The synthesis techniques and their advantages for the fabrication of plasmonic nanostructures are also discussed.
关键词： nanowire dimers,scanning transmission electron microscopy,ion-track technology,electron energy loss spectroscopy,nanogaps,nanowires,electrodeposition,plasmon hybridization,etched ion-track membranes,surface plasmons,gold
更新于2025-09-23 15:21:01
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Synthesis of yttrium iron garnet/bismuth quantum dot heterostructures with localized plasmon enhanced magneto-optical performance
摘要： Interactions between light and magnetic matter attracted great attention lately due to their potential applications in nanophotonics, spintronics, and high-accuracy sensing. Here, we grew bismuth quantum dots (Bi–QDs) with strong spin–orbit coupling on a magnetic insulator yttrium iron garnet (YIG) via molecular beam epitaxy. The YIG/Bi–QDs material shows an enhanced magneto-optical Kerr rotation up to 130 % compared with that of a bare YIG film. The Bi–QDs were also introduced onto a lutetium–bismuth co-doped YIG film to form a hybrid system with remarkably enhanced Kerr rotation (from 1626 to 2341 mdeg). Ferromagnetic resonance measurements showed an increased effective magnetization as well as interfacial spin–orbit field in the YIG/Bi–QD heterostructures. Localized plasmons were mapped using electron energy loss spectroscopy with high spatial resolution, revealing enhanced plasmon intensity at both the Bi–QD surface and YIG/Bi–QD interface. Introducing Bi-QDs onto the YIG film enhanced Kerr rotation owing to the attenuated optical reflection and increased effective magnetization. The Bi–QD-enhanced magneto-optical effect enables development of efficient nanoscale light switching, spintronics, and even plasmonic nano-antennas.
关键词： Electron energy loss spectroscopy,Surface plasmon resonance,Bismuth quantum dot,Ferromagnetic resonance,Magneto-optical materials
更新于2025-09-23 15:21:01
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European Microscopy Congress 2016: Proceedings || Characterizing Localized Surface Plasmons using Electron Energy-Loss Spectroscopy
摘要： Localized surface plasmon resonances (LSPRs) are the coherent and collective oscillations of conduction band electrons at the surface of metallic nanoparticles. LSPRs are known to localize far-field light to a sub-diffraction-limited length scale, yielding an intense electric field at the particle surface. This effect has been harnessed to dramatically enhance light-matter interactions, leading to a variety of applications such as surface-enhanced Raman spectroscopy (SERS), photothermal cancer therapy and solar energy harvesting. Though a variety of near- and far-field optical methods are used to probe LSPRs, the spatial resolution of these methods is on the order of tens of nanometers, limiting their effectiveness. In contrast, electron energy loss spectroscopy (EELS) performed in a scanning transmission electron microscope (STEM) combines sub-nanometer resolving power with the capability to excite both optical-accessible and –inaccessible plasmon modes and therefore has emerged as one of the leading techniques (Figure 1). In this presentation, I will briefly introduce the STEM/EELS technique and demonstrate the power of STEM/EELS in the characterization of LSPRs. In addition to the traditional use of STEM/EELS for LSPR imaging, we have recently demonstrated that STEM/EELS can also be used to spatially map LSP-semiconductor energy transfer at the nanoscale. The future of STEM/EELS as a window into the nanoscopic world is especially promising, and we expect continued advances in the molecular, optical, materials, information, and energy sciences as a result.
关键词： Localized Surface Plasmon,Hot Electrons,Scanning Transmission Electron Microscopy,Energy Transfer,Electron Energy-Loss Spectroscopy
更新于2025-09-23 15:19:57
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Monitoring strong coupling in nonlocal plasmonics with electron spectroscopies
摘要： Plasmon-exciton polaritons provide exciting possibilities to control light-matter interactions at the nanoscale by enabling closer investigation of quantum optical effects and facilitating novel technologies based, for instance, on Bose-Einstein condensation and polaritonic lasing. Nevertheless, observing and visualizing polaritons is challenging, and traditional optical microscopy techniques often lead to ambiguities regarding the emergence and strength of the plasmon-exciton coupling. Electron microscopy offers a more robust means to study and verify the nature of plexcitons, but it is still hindered by instrument limitations and resolution. A simple theoretical description of electron beam-excited plexcitons is therefore vital to complement ongoing experimental efforts. Here we apply analytic solutions for the electron-loss and photon-emission probabilities to evaluate plasmon-exciton coupling studied either with the recently adopted technique of electron energy-loss spectroscopy, or with the so-far unexplored in this context cathodoluminescence spectroscopy. Foreseeing the necessity to account for quantum corrections in the plasmonic response, we extend these solutions within the framework of general nonlocal hydrodynamic descriptions. As a specific example, we study core-shell spherical plasmon-molecule hybrids, going beyond the standard local-response approximation through the hydrodynamic Drude model for screening and the generalized nonlocal optical response theory for nonlocal damping. We show that electron microscopies are extremely powerful in describing the interaction of emitters with the otherwise weakly excited by optical means higher-order plasmonic multipoles, a response that survives when quantum-informed models are considered. Our work provides, therefore, both a robust theoretical background and supporting argumentation to the open quest for improving and further utilizing electron microscopies in strong-coupling nanophotonics.
关键词： electron energy-loss spectroscopy,nonlocal hydrodynamic descriptions,cathodoluminescence spectroscopy,quantum plasmonics,Plasmon-exciton polaritons
更新于2025-09-23 15:19:57
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Localized Surface Plasmon Resonance-Induced Welding of Gold Nanotriangles and the Local Plasmonic Properties for Multicolor Sensing and Light-Harvesting Applications
摘要： The excitation of localized surface plasmon resonance in gold nanotriangles by continuous light illumination triggered the welding of two adjacent nanotriangles into one nanoparticle. The facing localized surface plasmon resonance generated at the corners of the gold nanotriangles facilitated welding of the nanotriangles, in which electromagnetically seamless bonding was formed. We examined the scanning transmission electron microscopy-electron energy loss spectra of the obtained nanostructure and confirmed the generation of a localized plasmon mode at the bonding spot with an energy of 2.3 eV, which did not appear in the two adjacent gold nanotriangles without bonding. The experimental electron energy loss spectra and maps were supported by the simulation data calculated using the boundary element method. An electromagnetically continuous nanostructure was successfully constructed by a site-selective welding method in this work, resulting in modulation of the localized surface plasmon resonance in nanoparticles, including the localized spots, resonant wavelength and enhancement factor. The generation of a localized surface plasmon resonance mode by welding of nanoparticles can enable multicolor sensing and light harvesting applications.
关键词： plasmon mode,site-selective welding,nanoparticle,electron energy loss spectroscopy,localized surface plasmon resonance,gold nanotriangle
更新于2025-09-23 15:19:57
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Tents, Chairs, Tacos, Kites, and Rods: Shapes and Plasmonic Properties of Singly Twinned Magnesium Nanoparticles
摘要： Nanostructures of some metals can sustain light-driven electron oscillations called localized surface plasmon resonances, or LSPRs, that give rise to absorption, scattering, and local electric field enhancement. Their resonant frequency is dictated by the nanoparticle (NP) shape and size, fueling much research geared towards discovery and control of new structures. LSPR properties also depend on composition; traditional, rare and expensive noble metals (Ag, Au) are increasingly eclipsed by earth-abundant alternatives, with Mg being an exciting candidate capable of sustaining resonances across the ultraviolet, visible, and near-infrared spectral ranges. Here, we report numerical predictions and experimental verifications of a set of shapes based on Mg NPs displaying various twinning patterns including (10 1), (10 2), (10 3) and (11 1), that create tent, chair, taco and kite-shaped NPs, respectively. These are strikingly different from what is obtained for typical plasmonic metals because Mg crystallizes in a hexagonal close packed structure, as opposed to the cubic Al, Cu, Ag, and Au. A numerical survey of the optical response of the various structures, as well as the effect of size and aspect ratio, reveals their rich array of resonances, which are supported by single particle optical scattering experiments. Further, corresponding numerical and experimental studies of the near-field plasmon distribution via scanning transmission electron microscopy electron-energy loss spectroscopy unravels a mode nature and distribution that are unlike those of either hexagonal plates or cylindrical rods. These NPs, made from earth-abundant Mg, provide interesting ways to control light at the nanoscale across the ultraviolet, visible, and near-infrared spectral ranges.
关键词： nanoplasmonics,nanoparticle shape,magnesium nanoparticles,localized surface plasmon resonance,electron-energy loss spectroscopy,Wulff construction
更新于2025-09-23 15:19:57
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Structure and transport properties of titanium oxide (Ti2O, TiO1+, and Ti3O5) thin films
摘要： Titanium oxides have partially filled or empty d orbital and are stable at various oxidation states with different structures and unique properties. Here, three kinds of titanium oxide thin films of hexagonal Ti2O metal, cubic TiO1+d superconductor, and monoclinic g-Ti3O5 semiconductor, were successfully grown on a-Al2O3 substrates by a pulsed laser deposition technique, through ablating a pure titanium target under different oxygen pressures. The electrical resistivities of these films increase with increasing oxygen content. The metallic behaviors of Ti bulk and Ti2O film can be described by the Bloch-Grüneisen formula, and the semiconducting behaviors of TiO1+d films in normal state and g-Ti3O5 film obey the variable range hopping and the small polaron hopping conduction mechanisms, respectively. For titanium monoxide TiO1+d (1.05 ≤ 1+d ≤ 1.17) films, increasing oxygen content is accompanied by an increase of disorder, a decrease of electron density of states at the Fermi level, and an enhancement of carrier localization, leading to a suppression of superconductivity.
关键词： Electron energy-loss spectroscopy,Oxygen content,Superconductivity,Transport properties,Titanium oxide thin films,Pulsed laser deposition
更新于2025-09-19 17:15:36
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High Resolution Characterization of Plasmonic Hybridization in Silver Nanostructures
摘要： Surface plasmon resonances (SPR) in metallic nanostructures arise from the collective oscillation of conduction electrons, which create strong confined electric fields around the nanostructures. This confinement of electromagnetic (EM) energy at nanoscale dimensions holds potential towards the miniaturization of photonic devices [1]. Tremendous effort has been devoted towards optimization and design of nanostructures for several applications [2,3,4]. Most of these applications involve arrays of closely-spaced nanostructures: the plasmonic properties of the array differ from those of its isolated parts due to the interaction of evanescent fields. The study of SPR in these arrays, in particular the coupling of resonant modes, requires a characterization technique with both high spatial and energy resolution. Electron energy loss spectroscopy (EELS) meets these requirements, but has previously been limited to energies in the range of visible light or higher, mainly because of the relative intensities of the zero loss peak (ZLP) and low energy loss signal.
关键词： electron energy loss spectroscopy,metallic nanostructures,Surface plasmon resonances,hybridization,silver nanostructures
更新于2025-09-19 17:13:59
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Nitrogen plasma treatment of ZnO and TiO2 nanowire arrays for polymer photovoltaic applications
摘要： This work reports on a simple, yet unique approach to improving the opto-electronic properties of vertically-aligned arrays of rutile TiO2 and Wurzite ZnO nanowires by means of controlled nitrogen doping during exposure to highly kinetic radio-frequency generated N2 plasma radicals. Morphologically, the plasma treatment causes a distortion of the vertical alignment of the nanowires due to a dissociation of the weak Van der Waals force clustering the nanowires. Optical spectroscopy show that plasma treatment increases the light transmission of TiO2 arrays from 48% to 90%, with the ZnO arrays exhibiting an increase from 70% to 90% in the visible to UV range. The as-synthesized TiO2 array has an indirect band gap of 3.13 eV, which reduces to 3.03 eV after N2 treatment, with the ZnO equivalent decreasing from 3.20 to 3.17 eV post plasma exposure. A study of the 3d transition metal near edge fine structure of both Ti and Zn show that the N2 plasma treatment of the nanowires results in nitrogen doping of both TiO2 and ZnO lattices; this is confirmed by scanning transmission electron microscopy coupled with energy dispersive spectroscopy x-ray maps collected of single nanowires, which show a clear distribution of nitrogen throughout the metal-oxide. Application of these structures in P3HT:PCBM polymer blends shows progressive improvement in the photoluminescence quenching of the photoactive layer when incorporating both undoped and nitrogen-doped nanowires.
关键词： Electron energy loss spectroscopy,RF plasma nitrogen doping,One-dimensional nanowire arrays,Hydrothermal synthesis
更新于2025-09-16 10:30:52