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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Self-complementary tessellations as universal design approach for LP-to-CP transforming frequency selective surfaces
摘要： Recently self-complementary frequency-selective surfaces (FSSs) have been shown capable of linear-to-circular polarization transformation. In this work we numerically and experimentally prove generality of this approach showing that similar self-complementary tessellations can be used as FSS patterns in both the microwave and the sub-millimeter wave ranges. Moreover, we simulated two Escher’s tessellations as patterns of microwave FSSs to further demonstrate the polarization transform function of arbitrary self-complementary FSSs.
关键词： linear-to-circular polarization transformation,self-complementary tessellations,microwave,sub-millimeter wave,frequency-selective surfaces
更新于2025-09-10 09:29:36
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Ultra-Miniaturized Low-Profile Angularly-Stable Frequency Selective Surface Design
摘要： In this study, an ultra-miniaturized low-profile angularly-stable frequency selective surface (FSS) based on 2.5-dimension convoluted interwoven element is designed. The dimension of FSS element is 0.014λ0 × 0.014λ0, where the λ0 represents the free-space wavelength of resonance frequency. The thickness is only 0.0015λ0. When the FSS is illuminated by electromagnetic wave, the frequency selective properties perform stable under different incident angles up to 85° for both TE and TM polarization. For better understanding, the operation mechanism, the design procedure, distribution of surface current, and equivalent circuit are presented. A prototype of proposed FSS is fabricated, the measurement results prove the validity of simulated ones. To further improve the performance, using the same design procedure, the size and thickness of designed FSS have been reduced to 0.0053λ0 × 0.0053λ0 and 0.00061λ0, respectively. Since the resonance frequency of proposed FSS is adjustable at any desired frequency, an ultra-miniaturized low-profile angularly-stable FSS for GSM 900 band has been designed. The designed FSS can be applied in GSM shielding effectively.
关键词： frequency selective surfaces (FSSs),spatial filters,Convoluted element,2.5-D structure,miniaturization
更新于2025-09-10 09:29:36
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Structural, vibrational, Hirshfeld surfaces and optical studies of nonlinear optical organic imidazolium L-tartrate single crystal
摘要： Imidazolium L-tartrate (IMLT) single crystal was grown using solution growth technique. The grown crystal belongs to monoclinic crystal structure with space group P21. Intermolecular interactions of IMLT is executed by the Hirshfeld surface analysis. The structure of the grown crystal was stabilized by an extensive network of O–H···O, N–H···O and O–H hydrogen bonds. The vibrational modes are assigned based on potential energy distribution (PED). 13C and 1H NMR spectra were recorded to interpret the environment of the molecular structure. The HOMO-LUMO energy gap shows that the molecular chemical stability is high for the IMLT molecule. The Mulliken charge distribution confirms that the highest value is noted in C17, whereas the lowest value is obtained in C10 atom. The natural bond orbital (NBO) analysis has been computed to find out the electron delocalization and conjugative interactions. The bonding and anti-bonding orbitals are performed using density of states (DOS) spectrum. From photoconductivity measurement, the dark current is seen to be less than photocurrent. The etching analysis was done on (0 0 1) plane of IMLT crystal and rectangular etch pits are observed.
关键词： ICT,Dislocation density,Photosensitivity,OPDOS,Hirshfeld surfaces
更新于2025-09-10 09:29:36
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Evidence for Primal sp <sup>2</sup> Defects at the Diamond Surface: Candidates for Electron Trapping and Noise Sources
摘要： Many advanced applications of diamond materials are now being limited by unknown surface defects, including in the fields of high power/frequency electronics and quantum computing and quantum sensing. Of acute interest to diamond researchers worldwide is the loss of quantum coherence in near-surface nitrogen-vacancy (NV) centers and the generation of associated magnetic noise at the diamond surface. Here for the first time is presented the observation of a family of primal diamond surface defects, which is suggested as the leading cause of band-bending and Fermi-pinning phenomena in diamond devices. A combination of density functional theory and synchrotron-based X-ray absorption spectroscopy is used to show that these defects introduce low-lying electronic trap states. The effect of these states is modeled on band-bending into the diamond bulk and it is shown that the properties of the important NV defect centers are affected by these defects. Due to the paramount importance of near-surface NV center properties in a growing number of fields, the density of these defects is further quantified at the surface of a variety of differently-treated device surfaces, consistent with best-practice processing techniques in the literature. The identification and characterization of these defects has wide-ranging implications for diamond devices across many fields.
关键词： surfaces,Fermi-level pinning,defects,diamond,NEXAFS
更新于2025-09-10 09:29:36
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Control of Resistive Switching Voltage by Nanoparticle-Decorated Wrinkle Interface
摘要： Control of resistive switching voltage in nonvolatile memory devices plays a critical role in building commercial ultra-low power data storage technology. Here, an effective strategy to control the resistive switching voltage in polymer memory devices by interfacial engineering is presented. By creating a wrinkled surface in reduced graphene oxide (rGO) film as the conductive electrode, an electrical bistable phenomenon is observed in polymer diode with this rGO electrode, with the feature of a write-once-read-many-times nonvolatile memory effect. By further employing silver nanoparticles and controlling their density at the wrinkled rGO electrode/polymer interface, the optimized device exhibits a high performance nonvolatile memory effect with an ultra-low switching voltage of 0.9 V, high ON/OFF ratio of 1000, and desirable long retention time over 104 s. To the best knowledge, the value of switching voltage is much lower than that of previous related polymer memory devices. This study paves a new way toward ultra-low power manufacturing of non-volatile polymer memory devices.
关键词： interfacial engineering,resistive switching voltage,wrinkle surfaces,nanoparticle decoration,polymer memory devices
更新于2025-09-10 09:29:36
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Simulating vibronic spectra via Matsubara-like dynamics: Coping with the sign problem
摘要： Measuring vibronic spectra probes dynamical processes in molecular systems. When interpreted via suitable theoretical tools, the experimental data provides comprehensive information about the system in question. For complex many-body problems, such an approach usually requires the formulation of proper classical-like approximations, which is particularly challenging if multiple electronic states are involved. In this work, we express the imaginary-time shifted time correlation function and, thus, the vibronic spectrum in terms of the so-called Matsubara dynamics, which combines quantum statistics and classical-like dynamics. By applying the Matsubara approximation in the adiabatic limit, we derive a formal generalization of the existing Matsubara dynamics formalism to multiple potential energy surfaces (PESs), which, however, does not feature all the defining properties of its single-PES counterpart though suffering equally from the sign problem. The mathematical analysis for two shifted harmonic oscillators suggests a new modified method to practically simulate the standard correlation function via Matsubara-like dynamics. Importantly, this modified method samples the thermal Wigner function without suffering from the sign problem and yields an accurate approximation to the vibronic absorption spectrum, not only for the harmonic system but also for the anharmonic one.
关键词： classical-like dynamics,Matsubara dynamics,vibronic spectra,quantum statistics,potential energy surfaces,thermal Wigner function,sign problem
更新于2025-09-10 09:29:36
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Van de Hulst Essay: Multiple Scattering of Waves by Discrete Scatterers and Rough Surfaces
摘要： This essay is on the theories of multiple scattering of waves by discrete scatterers and rough surfaces. Applications of the theories are illustrated with emphasis on the remote sensing of the earth. A historical background is provided. The basic theories are based on solving Maxwell equations. We describe the physical results, analytical approaches and numerical approaches of the work of the author and his collaborators.
关键词： rough surfaces,remote sensing,waves,Maxwell equations,multiple scattering,discrete scatterers
更新于2025-09-10 09:29:36
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Study of intense photoluminescence from monodispersed β-Ga2O3 ellipsoidal structures
摘要： Monoclinic β-Ga2O3 particles were obtained through the self-assembly mechanism of nanosheets at different temperatures. An ellipsoidal morphology was obtained through precipitation and calcination processes. The influence of synthesis on the structure and morphology of materials was investigated using X-ray diffraction, scanning and transmission electron microscopy, dynamic light scattering, Raman and Fourier-transform infrared (FTIR) spectroscopies. The ellipsoidal morphologies with mesoporous were led by the Ostwald ripening and self-assembly mechanisms. An investigation into their optical properties revealed very broad and intense photoluminescence emission spectra, which were explained by the presence of oxygen vacancies in the structures. The specific surface areas were found to influence emission intensities. Different vibrations of Ga–O bonds in the Raman and FTIR spectra demonstrated two types of Ga3+ ions (GaO6 octahedral and GaO4 tetrahedral chains). The successful synthesis and the high emission intensities in the blue spectral range are representative of the strong potential of β-Ga2O3 particles in the use of optoelectronic devices as light-emitting materials.
关键词： Calcination,Optical properties,Defects,Porosity,Surfaces
更新于2025-09-10 09:29:36
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Optimized preparation of Co-Pi decorated g-C3N4@ZnO shell-core nanorod array for its improved photoelectrochemical performance and stability
摘要： The cobalt-phosphate (Co-Pi) decorated g-C3N4@ZnO shell-core nanorod array (Co-Pi/g-C3N4@ZnO NRA) photoanode with broadened spectral response and optimized photoelectrochemical (PEC) performance was prepared. The g-C3N4@ZnO NRA was prepared via improved urea impregnation and calcination methods in semi enclosed environment. The g-C3N4 flexible slice shell was uniformly wrapped on ZnO nanorods core and the intimately contacted heterojunction was formed between the interface of g-C3N4 and ZnO. The g-C3N4@ZnO NRA promotes the separation and transfer of the photogenerated electron-hole pairs on g-C3N4 and ZnO under either visible light or white light illumination. The prepared g-C3N4@ZnO NRA was further electrodeposited with Co-Pi nanoparticles (NPs). The Co-Pi NPs can assist in the consumption of the photoinduced holes as well as pull the Fermi level potential of g-C3N4@ZnO NRAs towards the positive direction, resulting in the upward band bending at the band-edge position for Co-Pi/g-C3N4@ZnO NRAs and promoting the separation efficiency of the photogenerated electron-hole pairs. Consequently, the Co-Pi/g-C3N4@ZnO NRA exhibits an improved PEC performance under both visible light and white light illumination. In addition, g-C3N4 flexible slice shell decorated with Co-Pi NPs covered on the surface of ZnO NRAs core improved the stability of the ZnO NRA photoanode.
关键词： Heterojunctions,Photoconductivity and photovoltaics,Optical properties,Surfaces and interfaces,Semiconductors,Electrode materials
更新于2025-09-10 09:29:36
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Slippery Surface Based on Photoelectric Responsive Nanoporous Composites with Optimal Wettability Region for Droplets' Multifunctional Manipulation
摘要： The development of responsive slippery surfaces is important because of the high demand for such materials in the fields of liquid manipulation on biochips, microfluidics, microreactions, and liquid-harvesting devices. Although great progress has been achieved, the effect of substrate wettability on slippery surfaces stability is overlooked by scientists. In addition, current responsive slippery surfaces generally function utilizing single external stimuli just for imprecisely controlling liquid motion, while advanced intelligences are always expected to be integrated into one smart interface material for widespread multifunctional applications. Therefore, designing slippery surfaces that collaboratively respond to complex external stimuli and possess sophisticated composite function for expanding applications from controlling droplets motion to patterned writing is urgently needed but remains a challenge. Here, a photoelectric cooperative-responsive slippery surface based on ZnO nanoporous composites is demonstrated. First, the effect of composite surface wettability on slippery surface stability is systematically researched and the optimum wettability region for fabricating stable slippery surfaces is determined. Furthermore, controllable droplet motion and patterned writing are realized on the same slippery surfaces under photoelectric cooperative stimuli, and the related response mechanism is also deeply studied. This kind of material has potential applications in biochips, microfluidics, in situ patterning, and water-harvesting systems.
关键词： droplet motion,slippery surfaces,wettability region,photoelectric cooperative,patterned writing
更新于2025-09-10 09:29:36