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Latent tracks and novel infrared waveguide formation in lithium tantalate irradiated with swift heavy ions
摘要： In this work, the formation mechanisms of latent ion tracks and infrared-light waveguides in ion-irradiated LiTaO3 single crystals were comparatively studied using 200 MeV Kr17+ irradiation at a fluence of 1 × 1012 cm?2 and 247 MeV Ar12+ irradiation at fluences of 1 × 1012 cm?2 and 3 × 1012 cm?2. Because of the intense electronic energy loss, the produced lattice disorder and formed latent track were experimentally determined through complementary techniques, including the analysis of transmission electron microscopy patterns and Rutherford backscattering/channeling spectra. Corresponding to different ions with different irradiation energies and electronic energy losses, the related spatio-temporal evolutions of lattice temperatures in Kr17+- and Ar12+-irradiated LiTaO3 crystals were numerically calculated using the inelastic thermal spike model. The simulation results theoretically describe the experimentally observed lattice disorder and latent track behaviors. The lattice swelling in the latent-ion-track regions was demonstrated using high-resolution x-ray diffraction patterns; the lattice swelling resulted in a decrease in the refractive index, thereby providing a path to tailor the optical properties and fabricate the waveguide structure. Optical measurements and simulations indicated that the formed LiTaO3 waveguide could effectively support the guided modes and confine the light propagation, especially in the infrared region.
关键词： swift heavy ion irradiation,latent ion track,electronic energy loss,infrared waveguide
更新于2025-11-14 17:04:02
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The description of quantum dielectric function for insulators over Bethe surface
摘要： A new expression for the dielectric function is suggested here, which is the Mermin–Belkacem-Sigmund (MBS) model derived from the Belkacem–Sigmund (BS) model based on the conservation of a local particle number in the Mermin model. The energy loss function expressions are reviewed analytically for both models, and these dielectric functions were used to calculate the Bethe sum rule, the energy loss function (ELF), as well as the differential inelastic inverse mean free path (DIIMP) for H2O. The indication from the results is that, compared to the BS dielectric function, the MBS dielectric function is more compatible in its consistency with the exact Bethe sum rule. The ELF for the MBS type is compatible relatively in high and low momentum transfers, while the ELF for the BS type is suitable for high-k. The two models of ELF were also applied to evaluate DIIMP for electron kinetic energy 1 keV, and these were compared with the results predicted in several ways via the SESINIPAC program, using the Mermin dielectric function and the extended Drude and Monte–Carlo method. These predicted results are in reasonable agreement with those estimated from other methods at the range of energy transfer (0–50) eV.
关键词： Bethe surface,differential inelastic inverse mean free path,local particle number,Energy loss function,dielectric function
更新于2025-09-23 15:23:52
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[IEEE 2018 18th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM) - Waterloo, ON (2018.8.19-2018.8.22)] 2018 18th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM) - Excitation of Hyperbolic Plasmons and Transition Radiation in Phosphorene by a Swift Electron
摘要： We analyze the energy loss channels for a fast electron traversing a monolayer phosphorene under oblique incidence taking the retardation effects into account.
关键词： transition radiation,electron energy loss,retardation effects,Phosphorene,hyperbolic plasmon polariton
更新于2025-09-23 15:23:52
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[IEEE 2018 18th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM) - Waterloo, ON (2018.8.19-2018.8.22)] 2018 18th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM) - Plasmon Excitation and Transition Radiation in Graphene Traversed by a Fast Charged Particle
摘要： A progress report is presented on recent theoretical investigations of the interaction of fast charged particles with single and multiple graphene layers. By adopting a fully relativistic formulation of the problem, special focus is placed on retardation effects in the energy loss of a charged particle due to electronic excitations in graphene, which include its plasmon polariton modes, as well as the energy that is emitted from graphene in the form of transition radiation. Using both empirical and ab initio models for the dynamic in-plane conductivity of graphene allows the exploration of energy losses at frequencies ranging from the terahertz to the ultraviolet.
关键词： transition radiation,electron energy loss,graphene,relativistic effects,plasmon polariton
更新于2025-09-23 15:23:52
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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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Phase transitions and critical phenomena of tiny grains carbon films synthesized in microwave-based vapor deposition system
摘要： Different peak trends of tiny grains carbon film have been observed under the investigations of the Raman spectroscopy and energy loss spectroscopy. Carbon films known in nanocrystalline and ultrananocrystalline diamond films are synthesized by employing microwave‐based vapor deposition system. Carbon atoms exhibit several state behaviors depending on the incurred positions of their electrons. Different morphology of tiny grains under different chamber pressure is related to different rate of arriving typical energies at/near substrate surface. Those tiny grains of carbon film, which evolved in graphitic state atoms are converted to structure of smooth elements where elongation of atoms of one‐dimensional arrays is as per exerting surface format forces along opposite poles from their centers. Such tiny grains in the film are the cause of v1 peak under the investigation of the Raman spectrum because of the enhanced propagation of input laser signals through channelized inter‐state electron gaps of elongated graphitic state atoms. Those tiny grains of carbon film, which evolved in fullerene state are the cause of v2 peak. The tiny grains related to v1 peak possess a low intensity as compared with the ones which comprised atoms having state behaviors known in their exceptional hardness. Tiny grains representing v1 peak in the Raman spectrum are also the cause of field emission characteristic of a carbon film. Different peak recordings were made for the Raman at defined positions indicating a different state of carbon atoms for a different phase of deposited tiny grains, which is in line to their energy loss spectroscopy.
关键词： field emission,tiny grains carbon films,Raman spectra,phase transition,heat energy,energy loss spectroscopy
更新于2025-09-23 15:21:01
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Effects of the Isomerized Thiophene-Fused Ending Groups on the Performances of Twisted Non-Fullerene Acceptor-Based Polymer Solar Cells.
摘要： Recently, benefiting from the merits of small molecule acceptors (NFAs), polymer solar cells (PSCs) have achieved tremendous advances. From the perspective of the structural characteristics of the π-conjugated acceptor-donor-acceptor (A-D-A)-type of organic molecules, the backbone’s planarity, as well as the terminal groups and their substituents, have strong influences on the performances of the constructed NFAs. Through enlarging the dihedral angle of the conjugated main-chain of NFAs, a certain degree of enhanced photovoltaic parameters have been achieved. To further probe the influences of ending groups on the performances of nonplanar NFAs, we synthesized two new NFAs of i-cc23 and i-cc34 with isomerized thiophene-fused ending groups and twisted π-conjugated main-chain. Compared to the i-cc23 containing 2-(6-oxo-5,6-dihydro-4H-cyclopenta[b]thiophen-4-ylidene)malononitrile ending group, the 2-(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-ylidene)malononitrile contained acceptor i-cc34 has a relatively higher molar extinction coefficient, bathochromic-shifted absorption spectrum, and deepened energy levels. When mixed with PBDB-T in solar cells, the i-cc23-based device achieved an excellent open-circuit voltage (VOC) of 1.10 V and a moderated power conversion efficiency of 7.34%. Although the VOC of i-cc34 related device was decreased to 0.96 V, the short-circuit current density and fill factor were improved, giving rise to enhanced efficiency of 9.51%. Apart from the distinct photovoltaic performances, the two isomers-based devices exhibit high radiative efficiency of 8×10-4, leading to a very small non-radiative loss of 0.19 V. Our results emphasize the importance of the isomerized thiophene-fused ending groups on the performances of nonplanar NFAs-based PSCs.
关键词： Twisted small molecular electron-acceptors,Thiophene-fused ending groups,Polymer solar cells,Isomerized end-groups,Non-radiative energy loss
更新于2025-09-23 15:21:01
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Decreasing Energy Loss and Optimizing Band Alignment for High Performance CsPbI3 Solar Cells through Guanidine Hydrobromide Post-Treatment
摘要： On account of the superior thermal stability and applicable band gap (~ 1.7 eV), the inorganic halide CsPbI3 perovskite solar cells (PSCs) have aroused intense interest in recent years. Nevertheless, the CsPbI3 PSCs are still facing a problem of high energy loss (Eloss) which leads to low open-circuit voltage (VOC). Herein, we developed efficient CsPbI3 PSCs through guanidine hydrobromide (GABr) post-treatment on the surface of CsPbI3 film. After optimizing, a supreme power conversion-efficiency (PCE) of 18.02% was obtained, which was higher than the original one (16.58%). By further studying, the characterization of passivation was found, which led to the reduced nonradiative recombination rate. Besides, the band alignment between CsPbI3 and interface layer is also optimized, leading to the decreased electron transport barrier for electron collection, and superb hole contact for furnishing a driving force in the hole transferring and forbidding electron to flow in the opposite direction.
关键词： energy loss,GABr,nonradiative recombination,CsPbI3,band alignment
更新于2025-09-23 15:21:01
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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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Reduced Non-radiative Recombination Energy Loss Enabled Efficient Polymer Solar Cells via Tuning Alkyl Chain Positions on Pendent Benzene Units of Polymers
摘要： Non-radiative recombination energy loss (ΔE3) plays a key role in enhancing device efficiencies for polymer solar cells (PSCs). Up to now, there is no clear resolution for reducing ΔE3 via molecular design. Herein, we report two conjugated polymers, PBDB-P-p and PBDB-P-m, which are integrated from benzo[1,2-b:4,5-b′]dithiophene (BDT) with alkylthio chain substituted at para- or meta- position on pendent benzene and benzo[1,2-c:4,5-c′]dithiophene-4,8-dione (BDD). Two polymers have different temperature-dependent aggregation properties, but similar molecular energy levels. When BO-4Cl was used as acceptor to fabricate PSCs, the device of PBDB-P-p:BO-4Cl displayed a maximal power conversion efficiency (PCE) of 13.83%, while the best device of PBDB-P-m:BO-4Cl exhibited a higher PCE of 14.12%. The close JSCs and FFs in both PSCs are attributed to their formation of effective nanoscale phase-separation as confirmed by atomic force microscopy (AFM) measurements. We find that the PBDB-P-m-based device has one order of magnitude higher of electroluminescence quantum efficiency (EQEEL) than that in PBDB-P-p-based one, which could arise from the relatively weak aggregation in PBDB-P-m-based film. Thus, the PBDB-P-m-based device has a remarkably enhanced VOC of 0.86 V in contrast to 0.80 V in PBDB-P-p-based device. This study offers a feasible structural optimization way on the alkylthio side chain substitute position on the conjugated polymer to enhance VOC by reducing non-radiative recombination energy loss in resulting PSCs.
关键词： polymer solar cells,open-circuit voltage,non-radiative recombination energy loss,polymer donor,alkylthio substituted position
更新于2025-09-23 15:21:01