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Handbook of Graphene || Modelling of Graphene Nanoribbons Antenna Based on MoM‐GEC Method to Enhance Nanocommunications in Terahertz Range
摘要： In this chapter, we present an electromagnetic modelling formulation of graphene nanoribbon antenna based on moments method combined to the generalized equivalent circuit method (MoM-GEC). The electrical properties of graphene are introduced in the mathematical formulation via a quantum mechanical conductivity deduced from the Kubo formalism. The antenna structure is shielded in a rectangular waveguide with electric boundary walls. Next, the global antenna structure is modelled by an electric equivalent circuit to investigate the antenna parameters. It is proved that, graphene nanoribbon-based antenna presents similar performances as well as conventional one, hence allowing to work at terahertz frequencies range. The high input impedance of a single graphene nanoribbon antenna causes an impedance mismatch problem, which requires the use of an antenna array. So, the coupling phenomena have been well studied in order to optimize the antenna response. Obtained numerical results show that the antenna resonant frequency is very sensitive to the variation of the graphene chemical potential. This leads to a reconfigurable antenna by a simple control of bias voltage. On the other hand, it is showed that, at terahertz frequencies, graphene nanoribbon antenna array allows to enhance the far field communication for short distances, which is beneficial for nanocommunications.
关键词： antenna array,nanocommunications,dynamic conductivity,terahertz range,nanoantenna,MoM-GEC method,Graphene nanoribbon
更新于2025-09-11 14:15:04
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Handbook of Graphene || Graphene Plasmonic: Switching Applications
摘要： This chapter focuses on the graphene plasmonic-based optical switching devices operating in the infrared to terahertz spectrum. Graphene plasmonic due to high strong light–matter interaction and nanoscale size has received significant attention in recent years, as they have found an important role in many areas of optical science and engineering by offering schemes to control electromagnetic fields. Another area of science that has been under the spotlight for the last few years relates to graphene plasmonic metasurface, which is formed of graphene layer packed into a structure. This material exhibits exceptional electronic and optical properties, intriguing many research groups across the world including us. However, our interest is specifically in studying the interaction between electromagnetic waves with surface modes of graphene in multilayer configuration (such as Otto configuration) and switching applications that might follow. In this chapter, relying on theoretical models and numerical simulations, we show that by designing and manipulating optical and electrical properties of graphene such as chemical potential, temperature, scattering rate, as well as incident beam characteristics such as beam width, one can have the structures based on graphene as a good platform for not only infrared optical switching devices but also terahertz switching devices.
关键词： Otto configuration,Graphene plasmonic,graphene conductivity,optical switches,terahertz,metasurface
更新于2025-09-11 14:15:04
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Synthesis, Characterization and Electrical Conductivity of Nano-Crystalline Erbium Sesquioxide by the Precipitation Method and Subsequent Calcination
摘要： Due to its superior properties, erbium sesquioxide, Er2O3, is considered as an important material for applications in various fields such as corrosion-resistant coating, electrical insulating coating, in sensing membranes, semiconductor devices, as catalyst, and for applications in nuclear engineering. In the open literature there is a lack of information about the preparation of Er2O3 nanoparticles using the homogenous precipitation and subsequent calcination route. In this paper a facile method for the synthesis of Er2O3 nanoparticles is suggested. The fabrication was carried out by using the homogeneous precipitation of an erbium ions using sodium hydroxide followed by the calcination process. The influence of: (i) the pH value (9-12) during precipitation process, and (ii) the calcination temperature 300-700 °C on the structural and textural properties of the solids obtained will be addressed. The thermal events accompanying the heat treatment of the dried parent was monitored using thermogravimetric analysis (TGA). Various physicochemical techniques were used for investigating the structure and morphology of Er2O3 nanoparticles. These include X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, filed emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Moreover, the electrical conductivity of the calcined samples with temperature was measured.
关键词： precipitation method,nanocrystalline erbium oxide,Er2O3,electrical conductivity,erbium sesquioxide,Er2O3 nanoparticles
更新于2025-09-11 14:15:04
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Light-Induced Current Oscillations in the Charge-Ordered State of (TMTTF)2SbF6
摘要： Below TCO = 157 K the quasi-one-dimensional charge-transfer salt (TMTTF)2SbF6 undergoes a pronounced phase transition to a charge-ordered ground state. We have explored the non-linear and photoconductive behavior as a function of applied voltage, laser pulse energy and temperature. Besides a decay of the photoconductive signal in a double exponential fashion in the millisecond range, we discover current oscillations in the kHz range induced by the application of short laser pulses. While the resonance frequencies do not depend on voltage or laser intensity and vary only slightly with temperature, the amplitude changes linearly with the laser intensity and voltage. We suggest that photo-induced fluctuations of the charge-ordered state alter the current flow of the single particles and hence, the photocurrent. The findings are discussed and compared to comparable phenomena in other low-dimensional electron systems.
关键词： TMTTF,non-linear transport,calculations of band structure and optical conductivity,charge-transfer salts,photoconductivity,current oscillations,charge-order phase transition
更新于2025-09-11 14:12:44
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Design strategy for ferroelectric-based polar metals with dimensionality-tunable electronic states
摘要： Since LiOsO3 was discovered, obtaining easy-accessible polar metals for research and applications has been challenging. In this paper, we present a multilayer design strategy, which is configured as ferroelectric layer/carrier reservoir layer/isolation layer/substrate, for obtaining polar metals by electrostatically doping a strained ferroelectric material in a more effective way. In the proposed configuration, both 1 unit-cell thick BaTiO3 and PbTiO3 exhibited considerable Ti off-centering with various strains, which should extend the applicability of ferroelectric-based polar metals in ultra-thin devices. Moreover, engineered by the compressive strain and the BaTiO3 thickness, the design strategy effectively achieved polar metallicity and dimensionality-tunable electronic states associated with the modulation of highly anisotropic properties such as electrical and electronic thermal conductivity, which may be helpful for designing ultra-thin, ultrafast, and low-power switch devices.
关键词： BaTiO3,design strategy,highly anisotropic conductivity,polar metal,electronic thermal conductivity,electrical conductivity
更新于2025-09-10 09:29:36
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A suspended 3-omega technique to measure the anisotropic thermal conductivity of semiconducting polymers
摘要： Anisotropic thermal conductivity can complicate the performance of semiconducting polymer thin-films in applications such as thermoelectrics and photovoltaics. Anisotropic measurements of low thermal conductivity polymers are challenging, and there are a limited number of appropriate measurement techniques. Suspended film 3-omega is an appropriate technique but has often required unfavorable microfabrication. Herein, we report on the utility of the suspended 3-omega technique that uses shadow masking, and no other microfabrication techniques, in performing anisotropic (in-plane and through-plane) thermal conductivity measurements of polymer films. We report on the necessary conditions for the validity of the 1D suspended-film heat transfer model and provide experimental guidelines for in-plane thermal conductivity measurements of polymer thin-films. Furthermore, for the first time, we report the anisotropic thermal conductivities of N2200 and a low molecular weight P3HT, which are two common n-type and p-type semiconducting polymers. Measured thermal conductivities are compared with predictions from the conventional Cahill-Pohl model and a recent empirical model that more accurately predicts the temperature dependence.
关键词： semiconducting polymers,thermal conductivity measurements,3-omega technique,anisotropic thermal conductivity,shadow masking
更新于2025-09-10 09:29:36
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Glasses in the NaPO3-WO3-NaF ternary system: preparation, physical properties and structural studies
摘要： Oxyfluoride glasses with composition x WO3 - 30 NaPO3 - (70-x) NaF, with 30 ≤ x ≤ 70 were prepared by melt-quenching and characterized with respect to their bulk physical properties and ionic conductivities. As the NaF content increases, the glass transition temperature, Tg, decreases systematically. Impedance measurements reveal no clear effect of NaF content upon room temperature electrical conductivities and activation energies. There is, however, a significant decrease of the Arrhenius pre-exponential factor with increasing WO3 content, suggesting that the electrical conductivities measured in this glass series are increasingly influenced by an electronic contribution. This contribution may be related to a W5+ → W6+ electron hopping process detected in the optical absorption spectra. Detailed spectroscopic investigations by Raman scattering and multinuclear one- and two-dimensional solid-state NMR experiments indicate that NaF acts like a network modifier resulting in the formation of W-F bonds via breakage of W-O-W and W-O-P linkages, with the former process being the preferred one. The concomitant decrease in network connectivity caused by these processes accounts for the experimentally observed decrease in glass transition temperatures with increasing NaF contents.
关键词： Tungsten glasses,Glass structure,Ionic conductivity,Phosphate glasses,Mixed conductivity
更新于2025-09-10 09:29:36
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Optical conductivity and transparency in an effective model for graphene
摘要： Motivated by experiments confirming that the optical transparency of graphene is defined through the fine structure constant and that it could be fully explained within the relativistic Dirac fermions in a two-dimensional picture, we investigate in this article how this property is affected by next-to-nearest-neighbor coupling in the low-energy continuum description of graphene. A detailed calculation within the linear response regime allows us to conclude that, somewhat surprisingly, the optical conductivity at zero temperature that determines the transparency remains robust up to this correction.
关键词： graphene,optical conductivity,linear response,transparency,Dirac fermions
更新于2025-09-10 09:29:36
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Au/Ag NPS Decorated PANI For Electrochemical and Biomedical Applications
摘要： Polyaniline (PANI) has number of electronic structure and it depends on the doping. PANI composites containing Fe3O4NPs are regularly studied as the PANI having electrical and magnetic features. Herein, PANI was prepared from aniline and HCl by means of solution mixing using ammonium persulphate as oxidizing agent and catalyst. Composites of polyaniline with calcium carbonate and Au/Ag NPs were prepared. Nanocomposites of PANI were characterized using FTIR, SEM, EDX, electrical conductivity measurement techniques. The incorporation of CaCO3 and Au/Ag NPs in polyaniline matrix was confirmed by SEM, FT-IR and EDX results. CaCO3 act as binder and provide strength to the composite which can be clearly understood by SEM microgram. Electrochemical study of composite has been done which showed that on decorating PANI with gold/silver NPs, the conducting properties increases. We successfully tested the antimicrobial activity of nanocomposite via paper disk diffusion method against Escherichia coli and Staphylococcus aureus.
关键词： Antibacterial,Nanocomposite,Conducting polymer,Conductivity
更新于2025-09-10 09:29:36
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Free-carrier dynamics in Au <sub/>2</sub> Pb probed by optical conductivity measurements
摘要： We measured the optical reflectivity of the Dirac material Au2Pb in a broad frequency range (30–48 000 cm?1) for temperatures between 9 and 300 K. The optical conductivity, computed from the reflectivity, is dominated by free-carrier contributions from topologically trivial bulk bands at all temperatures. The temperature-independent total plasma frequency of these carriers is 3.9 ± 0.2 eV. Overall, optical response of Au2Pb is typically metallic with no signs of localization and bad-metal behavior.
关键词： topological semimetals,optical conductivity,Dirac materials
更新于2025-09-10 09:29:36