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CATHODOLUMINESCENCE AND LASER-INDUCED FLUORESCENCE OF CALCIUM CARBONATE: A REVIEW OF SCREENING METHODS FOR RADIOCARBON DATING OF ANCIENT LIME MORTARS
摘要： Accurate radiocarbon (14C) dating of lime mortars requires a thorough mineralogical characterization of binders in order to verify the presence of carbon-bearing contaminants. In the last 20 years, cathodoluminescence (CL) has been widely used for the identification of geologic calcium carbonate (CaCO3) aggregates and unreacted lime lumps within the particle size fraction selected for carbon recovery. These components are major sources of older and younger carbon, respectively, and should be removed to obtain accurate age determinations. More recently, laser-induced fluorescence (LIF) has provided another means of investigating the preservation state and composition of CaCO3 binders. Considered the growing interest of the mortar dating community in the latest advancements of these analytical methods, here we review the principles of CL and LIF of CaCO3, their instrument setup, and their application to the characterization of ancient lime mortars used for 14C dating. In addition, we provide examples of SEM-CL and LIF analyses using high-resolution instrumentation, we discuss current issues and propose future lines of research.
关键词： calcium carbonate,fluorescence,plaster,mortar,cathodoluminescence
更新于2025-09-23 15:21:01
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A discrete core-shell-like micro-light-emitting diode array grown on sapphire nano-membranes
摘要： A discrete core-shell-like micro-light-emitting diode (micro-LED) array was grown on a 100 nm-thick sapphire nano-membrane array without harmful plasma etching for chip singulation. Due to proper design for the sapphire nano-membrane array, an array of multi-faceted micro-LEDs with size of 4 μm × 16 μm was grown. threading dislocation density in the micro-LeD formed on sapphire nano-membrane was reduced by 59.6% due to the sapphire nano-membranes, which serve as compliant substrates, compared to GaN formed on a planar substrate. Enhancements in internal quantum efficiency by 44% and 3.3 times higher photoluminescence intensity were also observed from it. Cathodoluminescence emission at 435 nm was measured from c-plane multiple quantum wells (MQWs), whereas negligible emissions were detected from semi-polar sidewall facets. A core-shell-like MQWs were formed on all facets, hopefully lowering concentration of non-radiative surface recombination centers and reducing leakage current paths. This study provides an attractive platform for micro-LEDs by using sapphire nano-membrane.
关键词： internal quantum efficiency,photoluminescence,threading dislocation density,micro-LED,sapphire nano-membrane,core-shell-like,cathodoluminescence
更新于2025-09-23 15:21:01
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Mapping Local Surface Plasmon Modes in a Nanoplasmonic Trimer Using Cathodoluminescence in the Scanning Electron Microscope
摘要： The excitability of local surface plasmon modes in radial trimers composed of gold nanorods was mapped using hyperspectral cathodoluminescence (CL) in the scanning electron microscope. In symmetric trimers, the local plasmon resonances could be excited most effectively at the ends of individual rods. Introducing asymmetry into the structure breaks the degeneracy of the dipole modes and changes the excitability of transverse dipole modes in different directions. CL in the scanning electron microscope has great potential to interrogate individual nanophotonic structures and is a complement to electron energy loss spectroscopy and optical microscopy.
关键词： scanning electron microscope,local surface plasmon mode,nanoplasmonic trimer,cathodoluminescence
更新于2025-09-23 15:21:01
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Complementary cathodoluminescence lifetime imaging configurations in a scanning electron microscope
摘要： Cathodoluminescence (CL) spectroscopy provides a powerful way to characterize optical properties of materials with deep-subwavelength spatial resolution. While CL imaging to obtain optical spectra is a well-developed technology, imaging CL lifetimes with nanoscale resolution has only been explored in a few studies. In this paper we compare three different time-resolved CL techniques and compare their characteristics. Two configurations are based on the acquisition of CL decay traces using a pulsed electron beam that is generated either with an ultra-fast beam blanker, which is placed in the electron column, or by photoemission from a laser-driven electron cathode. The third configuration uses measurements of the autocorrelation function g(2) of the CL signal using either a continuous or a pulsed electron beam. The three techniques are compared in terms of complexity of implementation, spatial and temporal resolution, and measurement accuracy as a function of electron dose. A single sample of InGaN/GaN quantum wells is investigated to enable a direct comparison of lifetime measurement characteristics of the three techniques. The g(2)-based method provides decay measurements at the best spatial resolution, as it leaves the electron column configuration unaffected. The pulsed-beam methods provide better detail on the temporal excitation and decay dynamics. The ultra-fast blanker configuration delivers electron pulses as short as 30 ps at 5 keV and 250 ps at 30 keV. The repetition rate can be chosen arbitrarily up to 80 MHz and requires a conjugate plane geometry in the electron column that reduces the spatial resolution in our microscope. The photoemission configuration, pumped with 250-fs 257-nm pulses at a repetition rate from 10 kHz to 25 MHz, allows creation of electron pulses down to a few ps, with some loss in spatial resolution.
关键词： Electron microscopy,Ultrafast,Cathodoluminescence,Time-resolved,Quantum wells
更新于2025-09-23 15:21:01
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Unveiling Complex Plasmonic Resonances in Archimedean Nanospirals through Cathodoluminescence in a Scanning Transmission Electron Microscope
摘要： Metallic nanostructures with a complex plasmonic response, such as the Archimedean nanospiral (ANS) present novel ways to utilize plasmonics in modern technology [1,2]. The nanospiral can support several resonant modes, with distinct electric field profiles as shown by finite-difference time-domain (FDTD) simulations such as the hourglass (500-650nm) and focusing (650-980nm) modes [2]. In addition to the linear plasmonic response, the ANS exhibits a stronger second-order nonlinearity than seen in other metallic nanostructured systems. A high spatial-resolution picture of the plasmonic modes is critical to understanding the interactions between plasmonic modes that drive the high non-linear efficiencies [3]. Purely optical experiments struggle to observe the near field behavior of the structure due to being diffraction limited. However cathodoluminescence (CL) experiments in a scanning transmission electron microscope (STEM) create a unique opportunity for characterizing plasmonic systems with both the spatial sensitivity of electron optics and the spectral sensitivity of photonics. A significant benefit to the use of STEM-CL, as opposed to other high-resolution spectroscopy techniques such as electron energy loss spectroscopy (EELS), is that the photons generated from radiative decays in the sample are collected for signal instead of the electrons from the probe. As a result, the signal can be manipulated and filtered using standard optical techniques, allowing us to map difficult to observe plasmon modes and even give insight into the polarization of their radiative decay. To experimentally observe the plasmon modes, an Au ANS array is fabricated using electron-beam lithography on a 50 nm silicon nitride film supported by a silicon substrate. A 500μm x500 μm window is then backside-etched beneath the array. STEM-CL is done in a VG-HB601 STEM operated at 60 kV with a home-built CL spectrometer system. Radiative emission is collected with a parabolic mirror and reflected out of a port in the side of the microscope, allowing the signal to be filtered and polarized using standard optical equipment, and ultimately collected in a photomultiplier tube (PMT). First, the focusing mode (650-980nm) is examined. Fig 1a shows a FDTD simulation of the plasmon mode. Fig 1b shows a high angle annular dark field (HAADF) image of the fabricated ANS on the SiN window. The raw CL intensity is shown in Fig 1c with no spectral filtering. Emission from all plasmonic modes, interband transitions, and any other radiative decay pathways are all simultaneously detected. However, by spectrally filtering the CL signal, individual modes can be isolated. The focusing mode is predicted to be strongest in the 650-980 nm region, so by using a 600 nm long-pass spectral filter, the radiative decay from other optical features can be eliminated, and a map of the focusing mode (Figure 1d) can be obtained. For the hourglass mode, however, spectral filters cannot be used to observe the spatial profile of the plasmonic resonance, because unlike the focusing mode, the hourglass mode has a distinct polarization axis that is parallel to the axis of the exciting optical pulse, as shown in the FDTD simulation in Fig 1e. With no polarization selectivity on electron-optics, the hourglass plasmon modes can be excited in all in-plane axes of the ANS simultaneously within the STEM, and no individual plasmon can be isolated and detected. However, since the hourglass mode has a strong polarization dependence on the exciting pulse, it is likely that the resulting emission is similarly polarized. In Fig 1f the HAADF image of an ANS is shown, and Fig 1g shows the unfiltered CL image. Fig 1h shows CL image filtered with a linear polarizer and exhibits a similar spatial profile to the simulation in Fig 1e, demonstrating that the modes that have a have a strong dependence on the polarization of the exciting optical source also exhibit a polarization dependence on their radiative decay. Nanostructures with complex, nonlinear plasmonic responses, such as the ANS, have unique optical attributes not present in simpler geometries. As a result, high spatial-resolution techniques to investigate the near-field profiles are an important avenue of plasmonic investigation. STEM-CL presents a particularly unique opportunity to combine photon and electron optics in order to characterize and map plasmonic modes, such as the hourglass and focusing modes of the ANS, with nanoscale precision.
关键词： nonlinearity,cathodoluminescence,scanning transmission electron microscope,Archimedean nanospiral,plasmonics
更新于2025-09-23 15:19:57
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Plasmonic Emission of Bullseye Nanoemitters on Bi2Te3 Nanoflakes
摘要： Topological insulators, such as Bi2Te3, have been con?rmed to exhibit plasmon radiation over the entire visible spectral range. Herein, we fabricate bullseye nanoemitters, consisting of a central disk and concentric gratings, on the Bi2Te3 nano?ake. Due to the existence of edge plasmon modes, Bi2Te3 bullseye nanostructures are possible to converge light towards the central disk. Taking advantage of the excellent spatial resolution of cathodoluminescence (CL) characterization, it has been observed that plasmonic behaviors depend on the excitation location. A stronger plasmonic intensity and a wider CL spectral linewidth can be obtained at the edge of the central disk. In order to further improve the focusing ability, a cylindrical Pt nanostructure has been deposited on the central disk. Additionally, the ?nite element simulation indicates that the electric-?eld enhancement originates from the coupling process between the plasmonic emission from the Bi2Te3 bullseye and the Pt nanostructure. Finally, we ?nd that enhancement e?ciency depends on the thickness of the Pt nanostructure.
关键词： bullseye nanostructure,Bi2Te3 nano?akes,plasmonic resonance,cathodoluminescence
更新于2025-09-23 15:19:57
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Field localization of hexagonal and short-range ordered plasmonic nanoholes investigated by cathodoluminescence
摘要： Plasmonic nanoholes have attracted significant attention among nanoplasmonic devices, especially as biosensing platforms, where nanohole arrays can efficiently enhance and confine the electromagnetic field through surface plasmon polaritons, providing a sensitive detection. In nanohole arrays, the optical resonances are typically determined by the inter-hole distance or periodicity with respect to the surface plasmon wavelength. However, for short-range ordered (SRO) arrays, the inter-hole distance varies locally, so the plasmon resonance changes. In this study, we investigate the local resonance of SRO nanoholes using a cathodoluminescence technique and compare it with hexagonally ordered nanoholes. The cathodoluminescence photon maps and resonance peak analysis reveal that the electric fields are confined at the edges of holes and that their resonances are determined by inter-hole distances as well as by their distributions. This demonstrates the Anderson localization of the electromagnetic waves showing locally enhanced electromagnetic local density of states in SRO nanoholes.
关键词： Anderson localization,biosensing,cathodoluminescence,Plasmonic nanoholes,surface plasmon polaritons
更新于2025-09-23 15:19:57
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Crystallization processes of quartz in a granitic magma: Cathodoluminescence zonation pattern controlled by temperature and titanium diffusivity
摘要： Quartz from a granitic pluton is found to have formed through sequential growth events under different mechanisms and crystallization temperatures, which can provide new insights into magmatic processes of granitic magmas that were eventually consolidified into plutons. The events were identified using 1) the description of crystal shape and occurrence, 2) the study of the internal structure with cathodoluminescence (CL), and 3) derivation of the crystallization temperatures based on TitaniQ thermometry. The magmatic quartz crystals from the Toki granite, central Japan, are characterized as having the following internal structures: oscillatory zonation, no-oscillatory zonation with luminescence gradation (gradational zonation), and heterogeneous CL. The quartz crystals with oscillatory zonation were formed in the temperature range of about 800 °C to below 700 °C, which is referred to as oscillatory zoning temperature (OZT) conditions. The CL zonation pattern was controlled by the temperature conditions and titanium diffusivity in the melt (magma). The crystallization process of quartz within the Toki granite reveals the cooling processes of the granitic pluton; the lithofacies with a high frequency of oscillatory-zoned quartz underwent slower cooling under the OZT conditions than those in other lithofacies.
关键词： diffusion-controlled growth,Toki granitic pluton,Cathodoluminescence characterization,Oscillatory zonation,Quartz,TitaniQ thermometer
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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Pulsed laser deposition of a ZnO:Eu3+ thin film: study of the luminescence and surface state under electron beam irradiation
摘要： A highly c-axis orientated Eu3+ doped ZnO (ZnO:Eu3+) thin film was successfully deposited by pulsed laser deposition in an oxygen working atmosphere. The structure, morphology, chemical analysis and luminescence properties of the sample were investigated. The effect of electron beam irradiation on the surface state, chemical and luminescence properties of the sample were studied. Successful incorporation of Eu3+ ions in the ZnO matrix was confirmed by X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) analysis. XPS measurements revealed traces of the divalent (Eu2+) on the film surface while the trivalent (Eu3+) oxidation state in the bulk of the film. XPS depth profile confirmed that the film contained excess oxygen throughout the film. The film exhibited exciton and defect emission of ZnO as well as 4f – 4f characteristic emission of Eu3+ ions superimposed on the defect emission when excited at 325 nm using a He-Cd laser. Whereas only 4f – 4f characteristic emission of Eu3+ ions was recorded when the film was excited at 464 nm and also when excited with the electron beam. XPS high resolution spectra of the O 1s peak confirmed the creation of new defects during electron beam irradiation. In general, ZnO:Eu3+ films show potential for applications as a source of red light in optoelectronic devices.
关键词： Degradation,PLD,ZnO thin film,Eu3+ ions,Cathodoluminescence,Red emission,Electron beam irradiation
更新于2025-09-19 17:13:59