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Surface plasmon induced atom localization in a tripod-type four level atomic system
摘要： We demonstrate the phenomenon of atom localization using surface plasmon polariton absorption/dispersion spectrums. A single and double localized peaks are measured on the absorption/dispersion spectrums of surface plasmon polariton at di?erent parameters and directions of propagation of the control ?elds. We show localized peaks with ～ 80% probability on dispersion spectrum and 50 % probability on the absorption spectrum. The localized peaks observed are shown to depend on strength of the control ?eld and the electrical conductivity.
关键词： surface plasmon polariton,atom localization,electrical conductivity,control ?elds,absorption/dispersion spectrums
更新于2025-09-09 09:28:46
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Influence of Yttrium Dopant on the Structure and Electrical Conductivity of Potassium Sodium Niobate Thin Films
摘要： KNN thin films with diverse yttrium concentration (mol % = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) were fabricated using sol-gel spin coating technique. Doped KNN revealed that Y3+ was successfully doped into the ABO3 perovskite lattice without changing the phase formation of KNN. The thickness of the deposited layer of KNN produced with increasing dopant concentration was determined to be 200 nm with dense and well-defined grains. Afterwards, the vibrational bonding and conductivity of KNN films with diverse yttrium concentration were identified according to the charge compensation mechanism. At high dopant concentration of > 0.5 mol %, O-Nb-O bonding was asymmetric and became distorted due to B-site occupancy by yttrium dopant. Further investigation revealed that charge compensation mechanism was shifted by increasing doping concentration. As a result, yttrium-doped KNN became semi-conductive at low yttrium concentration. Meanwhile, at high concentration, yttrium-doped KNN became an insulator and underwent ionic compensation.
关键词： yttrium,thin film,doped,structural,KNN,conductivity
更新于2025-09-09 09:28:46
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First-principles investigation of the electronic band structures and optical properties of quaternary <i>A</i> Ba <i>MQ</i> <sub/>4</sub> ( <i>A</i> = Rb, Cs; <i>M</i> = P, V; and <i>Q</i> = S) metal chalcogenides
摘要： In this paper, we study the optoelectronic properties of quaternary metal chalcogenide semiconductor ABaM Q4 (A = Rb, Cs; M = P, V; and Q = S) compounds using state-of-the-art density functional theory (DFT) with TB-mBJ approximation for the treatment of exchange-correlation energy. In particular, the electronic and optical properties of the relaxed geometries of these compounds are investigated. Our first-principles ab-initio calculations show that the CsBaPS4 and RbBaPS4 compounds have direct bandgaps whereas the CsBaVS4 compound exhibits indirect bandgap nature. Importantly, the theoretically calculated values of the bandgaps of the compounds are consistent with experiment. Furthermore, our analysis of the electronic charge densities of these compounds indicates that the above quaternary chalcogenides have mixed covalent and ionic bonding characters. The effective masses of these compounds are also calculated which provide very useful information about the band structure and transport characteristics of the investigated compounds. Similarly, high absorptivity in the visible and ultraviolet regions of the electromagnetic spectrum possibly predicts and indicates the importance of these materials for potential optoelectronic applications in this range.
关键词： energy band structure,electronic charge densities,optical conductivity,Chalcogenides,refractive index,dielectric constants,optical reflectivity
更新于2025-09-09 09:28:46
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Temperature and frequency effect on the electrical properties of bulk nickel phthalocyanine octacarboxylic acid (Ni-Pc(COOH)8)
摘要： The AC conductivity of nickel phthalocyanine octacarboxylic acid was investigated from 100 Hz to 1 MHz and temperature from 290 to 423 K. The AC conductivity was found to vary with frequency (σ(f)) and form two dispersion regions; the associated exponent factor “s” values were found to vary from 1.17 to 1.34 and from 0.42 to 0.67 (< 1). The value and temperature dependent of s are found in agreement with conduction mechanism models of large-polaron tunneling and the correlated barrier hopping, at the first and the second regions, respectively. The real and the imaginary parts of the dielectric constant were observed to decrease as the frequency increases indicating the pronounce contribution of low-frequency polarization mechanisms. Furthermore, the activation free energy ?F, enthalpy ?H, and entropy ?S of the sample were calculated as well.
关键词： enthalpy,polarization mechanisms,AC conductivity,activation free energy,dielectric constant,nickel phthalocyanine octacarboxylic acid,entropy
更新于2025-09-09 09:28:46
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Investigation on Structural and Dielectric Properties of Silica Nanoparticles Incorporated Poly(Ethylene Oxide)/Poly(Vinyl Pyrrolidone) Blend Matrix Based Nanocomposites
摘要： Inorganic and organic materials based polymer nanocomposite (PNC) films, comprising silica (SiO2) nanoparticles as inorganic filler and the polymer blend of poly(ethylene oxide) (PEO) and poly(vinyl pyrrolidone) (PVP) as organic matrix (i.e., (PEO–PVP)-x wt% SiO2; x = 0, 1, 3 and 5) have been prepared by the solution-casting method. These PNC films are characterized by employing the scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscopy, and the dielectric relaxation spectroscopy (DRS). The effect of SiO2 nanofiller on the spherulite and porous morphology, miscibility of the polymers, PEO crystallite size, the degree of crystallinity, polymer–polymer and polymer-nanoparticle interactions, and from 20 Hz to 1 MHz range dielectric and electrical dispersion behaviour and also the structural dynamics of these PNC materials have been investigated. The porous morphology, structures of miscible phases, and the PEO crystallite length greatly alter with the incorporation of merely 1 wt% SiO2 in the polymer blend matrix which further changes with the increase of nanofiller concentration up to 5 wt%. The real part of complex permittivity over the radio frequency range (20 kHz–1 MHz) for these PNC films is found about 2 and their dielectric loss tangent values below 0.03, at the room temperature, which are significantly low. The contribution of interfacial polarization effect at lower audio frequencies enhances the complex permittivity of these materials linearly in the range 2 to 4 with the decrease of frequency from 1 kHz to 20 Hz confirming their frequency tunable dielectric behaviour. The dielectric study of 3 wt% SiO2 containing PNC film in the temperature range 30–60 °C reveals its thermally activated dielectric characteristics, and the temperature dependent values of dielectric relaxation time and dc electrical conductivity obey the Arrhenius behaviour with activation energies in the range 0.2–0.3 eV. The dielectric and electrical parameters ascertain the promising applications of these PNC films in the development of novel electroactive functional materials, and also their use as the dielectric substrate and electrical insulating polymeric nanodielectrics for the fabrication of flexible-type naturally degradable organoelectronic devices.
关键词： Electrical conductivity,FTIR,XRD,Dielectric properties,Polymer nanocomposite
更新于2025-09-09 09:28:46
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Thermal conductivity of silicon nanomaterials measured using the photoacoustic technique in a piezoelectric configuration
摘要： In this study, we investigated the thermal transport in porous silicon nanostructures and silicon nanowires fabricated by electrochemical and metal-assisted chemical etching processes, respectively. In particular, the thermal conductivity values for the silicon-based nanomaterials were estimated based on photoacoustic measurements obtained from piezoelectric recordings. The amplitude–frequency and phase–frequency dependencies of the photoacoustic responses of the nanostructured silicon samples were obtained, and simulated successfully with a theoretical model. Correlations were established between the thermal conductivities and etching parameters.
关键词： Silicon nanomaterial,Piezoelectric recording,Thermal conductivity,Photoacoustic technique
更新于2025-09-09 09:28:46
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Effect of Environmental Humidity in the Electrical Properties of Lead Halide Perovskites
摘要： In large quantities, water is detrimental to lead halide perovskite solar cells, mainly because of the decomposition of the perovskite layer. On the contrary, the presence of small quantities of water has been observed to play a key role in the crystallization of the perovskite and in the performance of the corresponding devices. However, it is still under debate the exact role of water during the operation of perovskite solar cells. In this paper, impedance spectroscopy is used to analyze the changes produced by environmental humidity in the electronic properties of methylammonium lead triiodide perovskite. Our results show that water absorbed from environmental humidity induces a huge increase in the capacitance of this material. This capacitance can reach values as large as the accumulation capacitance found in devices based in perovskite, which is the responsible of the characteristic large hysteresis observed between forward and reverse J-V curves. In parallel to this outstanding rise of the capacitance, water absorption produces a significant rise of the conductivity, in agreement with previous reports in the literature. Activation energy of 0.52 eV is found for electronic transport, a value in line with activation energy of ionic transport found in literature, what suggests ambipolar diffusion as the transport mechanism that links these two phenomena.
关键词： impedance spectroscopy,environmental humidity,electrical properties,lead halide perovskites,capacitance,conductivity
更新于2025-09-09 09:28:46
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Direct probing of cross-plane thermal properties of ALD Al <sub/>2</sub> O <sub/>3</sub> /ZnO superlattice films with improved figure of merit and their cross-plane thermoelectric generating performance
摘要： There is a recent interest in semiconducting superlattice films because their low dimensionality can increase the thermal power and phonon scattering at the interface in superlattice films. However, experimental studies in all cross-plane thermoelectric (TE) properties, including thermal conductivity, Seebeck coefficient, and electrical conductivity, has not been performed from these semiconducting superlattice films, because of substantial difficulties in the direct measurement of the Seebeck coefficient and electrical conductivity. Unlike the conventional measurement method, we present technique using a structure of sandwiched superlattice films between two embedded heaters as heating source, and electrodes with two Cu plates, which directly enables the investigation of the Seebeck coefficient and electrical conductivity across the Al2O3/ZnO superlattice films, prepared by atomic layer deposition (ALD) method. Used in combination with the promising cross-plane four-point-probe 3-ω method, our measurements and analysis demonstrate all cross-plane TE properties of Al2O3/ZnO superlattice films in the temperature range from 80 to 500 K. Our experimental methodology and the obtaining results represent a significant advancement in the understating of phonon and electrical transports in nanostructured materials, especially in semiconducting superlattice films in various temperature ranges.
关键词： Thermal conductivity,Cross-plane thermoelectric properties,Seebeck coefficient,Phonon transport,Superlattice films,3-omega measurement,Phonon scattering
更新于2025-09-09 09:28:46
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Optical signatures of Dirac nodal lines in NbAs <sub/>2</sub>
摘要： Using polarized optical and magneto-optical spectroscopy, we have demonstrated universal aspects of electrodynamics associated with Dirac nodal lines that are found in several classes of unconventional intermetallic compounds. We investigated anisotropic electrodynamics of NbAs2 where the spin-orbit coupling (SOC) triggers energy gaps along the nodal lines. These gaps manifest as sharp steps in the optical conductivity spectra σ1(ω). This behavior is followed by the linear power-law scaling of σ1(ω) at higher frequencies, consistent with our theoretical analysis for dispersive Dirac nodal lines. Magneto-optics data affirm the dominant role of nodal lines in the electrodynamics of NbAs2.
关键词： Dirac fermions,nodal-line semimetal,optical conductivity,magneto-optics
更新于2025-09-09 09:28:46
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High–pressure electrical conductivity and Raman spectroscopy of chalcanthite
摘要： The phase transitions and dehydration of chalcanthite were investigated by electrical conductivity and Raman spectroscopy at 1.0–24.0 GPa and 293–673 K in a diamond anvil cell. At ambient temperature, two secondary phase transitions were observed according to discontinuous changes in the slope of Raman shifts, full width at half maximum and electrical conductivities at (cid:1)7.3 and (cid:1)10.3 GPa. The dehydration temperatures were determined by the splitting of Raman peaks and changes in electrical conductivity as (cid:1)350 and (cid:1)500 K at respective (cid:1)3.0 and (cid:1)6.0 GPa. A positive relationship for chalcanthite between dehydration temperature and pressure is established.
关键词： dehydration,chalcanthite,phase transition,Raman spectroscopy,electrical conductivity
更新于2025-09-09 09:28:46