Dielectric Components Research Articles

Analysis of and increase in working time of electroluminescence panels

Possible reasons for decomposition of the emission layer of working electroluminescence structures that cause a decrease in the working time are considered. Results of a multifactor experiment aimed at a search for the optimal composition of suspensions of the emitting and dielectric layers of the structure are presented. Compositions of dielectric components are proposed. Results of life tests are presented.

Comparison of Ag and Si nanoparticle arrays: mimicking subwavelength plasmonic field concentrations with dielectric components

We present a comparative theoretical study of the optical response of metallic Ag and dielectric Si sphere arrays on top of reflecting substrates. The interaction of particle modes with guided modes of the substrate leads to a rich optical spectrum. We design structures that sustain highly concentrated electromagnetic fields around periodic arrays of Si nanoparticles through the coupling of incident light to waveguide modes of a dielectric spacer. We discuss the origin of the different modes responsible for the reflectivity spectra of particle arrays and propose that all dielectric structures can support strong field enhancement which is similar to nanostructured metallic surfaces.

Nonlinear dielectric properties of paraelectric-dielectric composites described by a 3D Finite Element Method based on Landau-Devonshire theory

The local field inhomogeneity generated by the interfaces between dissimilar phases plays a major role on the electrical properties of ferroelectric-based composites. This aspect was rarely investigated, because it requires advanced modeling tools. In the present work, a 3D Finite Element Method combined with Landau-Devonshire theory was developed for computing local fields in order to describe the role of realistic microstructures on the electrical response. Various combinations of materials and interconnectivities in paraelectric-based di-phase composites (phases randomly mixed, 0–3 connectivity or 1–3 connectivity) were analyzed and some valuable solutions for providing the most promising tunability properties are proposed. A decrease of tunability and permittivity when increasing the concentration of the dielectric component in composites with randomly distributed phases and in ones with 0–3 connectivity (paraelectric inclusions in a dielectric matrix), often reported experimentally, was obtained by this approach. For other configurations like 0–3 and 1–3 connectivity with dielectric inclusions in a paraelectric matrix, the simulations predicted comparable tunability values as in single phase paraelectrics. The best tunability properties are predicted for 1–3 connectivity with dielectric inclusions having the long axis perpendicular to the direction of the applied field, due to a favorable distribution of the local electric field within the system. Therefore, the proposed numerical method allows design composites with tailored permittivity and tunability by local field engineering.

Photonic Applications of Metal-Dielectric Heterostructured Nanomaterials.

Metal materials, supporting plasmon modes on their surface, can confine the optical field at deep subwavelength scale, which is desired for photonic integration. However, their intrinsic high Ohmic losses make it impossible to construct the whole circuit solely with the metal materials. Integrating the plasmonic components with dielectric materials may offer a solution to this dilemma. With outstanding active optical performance, these dielectric components not only can greatly reduce the optical losses of the entire circuits but also offer an efficient way to launch the surface plasmon polaritons through the evanescent field coupling or the direct exciton-plasmon conversion. Furthermore, the cooperative interaction between metal and dielectric materials would bring vast novel optical phenomena and functional photonic devices. In this review, the synergistic effects among metal and dielectric materials in various heterostructures as well as their related applications are highlighted. Comprehensive understanding on their synergistic interactions would offer useful guidance for the design and fabrication of the ultracompact novel optical devices.

Dielectric properties of glassy disaccharides for electromagnetic interference shielding application

Three amorphous disaccharides (sucrose, trehalose, and lactulose) and their mixtures were studied in order to evaluate their ability to absorb a high frequency (>1 MHz) electromagnetic wave. The materials were characterized by a dielectric loss tangent. It was found out that the highest tan(δ) value is observed in pure amorphous sucrose (tan(δ) = 0.17 at f = 1 MHz at T = 293 K). Moreover, the best Tg/tan(δ) ratio is observed in binary mixtures of sucrose and trehalose. A high glass transition temperature is advantageous as it increases operational temperatures of the material. The high tangent delta in microwave frequencies of sugars is connected with the mobility of sugar groups (possibly –CH2OH). The energy of the electromagnetic wave is converted into rotational movements of side groups and in consequence it is dissipated in the form of heat. It was proven that the polar low molecular glasses such as sugars may form dielectric components of composite microwave absorbers.

Piezo-optic tensor of crystals from quantum-mechanical calculations.

An automated computational strategy is devised for the ab initio determination of the full fourth-rank piezo-optic tensor of crystals belonging to any space group of symmetry. Elastic stiffness and compliance constants are obtained as numerical first derivatives of analytical energy gradients with respect to the strain and photo-elastic constants as numerical derivatives of analytical dielectric tensor components, which are in turn computed through a Coupled-Perturbed-Hartree-Fock/Kohn-Sham approach, with respect to the strain. Both point and translation symmetries are exploited at all steps of the calculation, within the framework of periodic boundary conditions. The scheme is applied to the determination of the full set of ten symmetry-independent piezo-optic constants of calcium tungstate CaWO4, which have recently been experimentally reconstructed. Present calculations unambiguously determine the absolute sign (positive) of the π61 constant, confirm the reliability of 6 out of 10 experimentally determined constants and provide new, more accurate values for the remaining 4 constants.

Microwave dielectric properties of novel temperature stable high Q MgZr1+xNb2O8+2x ceramics

Microwave dielectric ceramics with the composition of MgZr1+xNb2O8+2x were prepared by a solid-state reaction route. XRD patterns revealed that the samples consist of monoclinic MgZrNb2O8 and ZrO2, and the content of ZrO2 phase increased with increasing x values. The microwave dielectric properties of samples, such as dielectric constant, Q×f value and temperature coefficient of resonant frequency have been investigated as a function of composition. It showed that the dielectric properties can be improved with the increase of x values. When x=0.32, the temperature coefficient of resonant frequency of MgZr1+xNb2O8+2x ceramic can be adjusted to a near-zero value of 1.4 ppm/°C, the dielectric constant and Q×f values are 28.03 and 68,600GHz, respectively. These results indicate that MgZr1.32Nb2O8.64 ceramic can be a suitable candidate in microwave dielectric components.

Clarifying the origin of third-harmonic generation from film-coupled nanostripes.

The resonance associated with plasmonic nanostructures strongly enhances local optical fields, and can thus dramatically enhance the nonlinear response of the composite structure. However, the origin of the nonlinear signal generated from hybrid nanostructures consisting of both metallic and dielectric components can be ambiguous when all constituents possess nonlinearities. In this paper, we introduce a method for specifically identifying the third harmonic generation (THG) originating from different nonlinear sources in a film-coupled nanostripe. The nanostripe consists of a metallic patch separated from a metallic film by a dielectric spacer. By considering the THG from each nonlinear source separately, we show that the near- and far-field behaviors of the THG generated within the various constituents of the nanostripe are distinguishable due to fundamental differences in the THG radiation properties. The THG signal from the metal is shown to be suppressed by the structure itself, while the THG signal from the spacer is enhanced by the gap plasmon modes supported by the structure. The total THG signal is found to be the sum of all nonlinear sources, with the far-field radiation pattern determined by the ratio between the third-order susceptibilities of the dielectric and the metal.

Transparent conducting oxides for electro-optical plasmonic modulators

Abstract:The ongoing quest for ultra-compact optical devices has reached a bottleneck due to the diffraction limit in conventional photonics. New approaches that provide subwavelength optical elements, and therefore lead to miniaturization of the entire photonic circuit, are urgently required. Plasmonics, which combines nanoscale light confinement and optical-speed processing of signals, has the potential to enable the next generation of hybrid information-processing devices, which are superior to the current photonic dielectric components in terms of speed and compactness. New plasmonic materials (other than metals), or optical materials with metal-like behavior, have recently attracted a lot of attention due to the promise they hold to enable low-loss, tunable, CMOScompatible devices for photonic technologies. In this review, we provide a systematic overview of various compact optical modulator designs that utilize a class of the most promising new materials as the active layer or core— namely, transparent conducting oxides. Such modulators can be made low-loss, compact, and exhibit high tunability while offering low cost and compatibility with existing semiconductor technologies. A detailed analysis of different configurations and their working characteristics, such as their extinction ratio, compactness, bandwidth, and losses, is performed identifying the most promising designs.

Growth, crystalline perfection, optical, thermal, laser damage threshold and electrical characterization of melaminium levulinate monohydrate single crystal

Equimolar amounts of melamine and levulinic acid results an organic crystal of melaminium levulinate monohydrate (MLM) at room temperature. MLM belongs to a monoclinic crystal structure having P21/c space group which was confirmed by single crystal X-ray diffraction study. Functional groups present in the MLM crystal were identified by FT-IR spectral study. HRXRD study dictates the quality of MLM crystal. UV–visble spectrum of MLM reveals the lower cut-off wavelength of 293nm with 55% optical transparency and optical band gap was found to be 4.20eV for the prominent plane (10−1). Refractive indices for the three axes of MLM crystal were found to be nx=2.6, ny=2.4 and nz=2.2 respectively. Further the thermal stability and melting point of MLM crystal were investigated by TG/DTA study. Dielectric permittivity tensor components were estimated for the planes (10−1), (010) and (111) respectively. The thermal conductivity of the crystal by Wiedemann—Franz law was found to be 5.99×10–11W/mK at 70°C. LDT value (2.84GW/cm2) of MLM was estimated for laser optical device applications.

Enhanced Energy Storage of Dielectric Nanocomposites at Elevated Temperatures

Enhancing the performance of dielectric capacitors toward higher energy density and higher operating temperatures has been drawing increased interest. Therefore, in this investigation, research efforts were dedicated to the fabrication and characterization of nanocomposites in order to enhance the energy density at both room temperature and elevated temperature. The dielectric capacitors are fabricated using nanocomposites composed of BaTiO nanoparticles with polyimide (PI) matrix aiming at combining the high relative dielectric permittivity of the ceramic filler and the high breakdown strength of the polymeric matrix. Dielectric energy storage performance is assessed for nanocomposites with volume fractions ranging from 0 to 20% under operating frequency from 20 Hz to 1 MHz and temperatures ranging from 20 to 120C. It is observed that with the increase of temperature, the capacitance increased while the energy density slightly decreased but significantly higher than pure polymer samples. The highest energy density was found for BaTiO/PI nanocomposites with 20% volume fraction, 9.63 J/cm at 20C and 6.79 J/cm at 120C. Overall, testing results indicate that using nanocomposites of BaTiO/PI as a dielectric component shows promise for implementation to preserve high energy density values up to temperatures of 120C.

Directed Assembly of Optoplasmonic Hybrid Materials with Tunable Photonic-Plasmonic Properties.

Optoplasmonic materials are metallo-dielectric hybrid structures that combine metallic and dielectric components in defined geometries in which plasmonic and photonic modes synergistically interact. These beneficial interactions can be harnessed by integrating plasmonic nanoantennas into defined photonic environments generated, for instance, by discrete optical resonators or extended systems of diffractively coupled nanoparticles. Optoplasmonic structures facilitate photonic-plasmonic mode coupling and offer degrees of freedom for creating optical fields with predefined amplitude and phase in space and time that are absent in conventional photonic or plasmonic structures. This Perspective reviews the fundamental electromagnetic mechanisms underlying selected optoplasmonic approaches with an emphasis on materials available through template-guided self-assembly strategies.

First principle investigation of electronic structure, chemical bonding and optical properties of tetrabarium gallium trinitride oxide single crystal

The electronic band structure, valence electron charge density and optical susceptibilities of tetrabarium gallium trinitride (TGT) were calculated via first principle study. The electronic band structure calculation describes TGT as semiconductor having direct band gap of 1.38eV. The valence electronic charge density contour verified the non-polar covalent nature of the bond. The absorption edge and first peak of dielectric tensor components showed electrons transition from N-p state to Ba-d state. The calculated uniaxial anisotropy (0.4842) and birefringence (−0.0061) of present paper is prearranged as follow the spectral components of the dielectric tensor. The first peak in energy loss function (ELOS) shows the energy loss of fast traveling electrons in the material. The first sharp peak produced in ELOS around 10.5eV show plasmon loss having plasma frequencies 0.1536, 0.004 and 0.066 of dielectric tensor components. This plasmon loss also cause decrease in reflectivity spectra.

Pure ferroelectric polarization of lead-free Na0.5K0.5NbO3 thin films by using the double wave method

Na0.5K0.5NbO3 (NKN) thin films were grown on Pt(111)/Ti/SiO2/Si substrates by using RFmagnetron sputtering. We investigated the behavior of the ferroelectric polarization. Well-saturated P-V hysteresis loops were observed, but the P-V hysteresis loops were sometimes distorted and consisted of three roughly parallel components, such as ferroelectric, dielectric and conductive components. Correction methods were proposed to identify the undesirable components and the pure ferroelectric polarization components from the observed P-V hysteresis loops. A new polarization hysteresis loop measurement technique, the double wave method (DWM), was applied to NKN thin films to obtain pure ferroelectric polarization and elucidate the behaviors of the polarization components.

Dual modality ECT–MIT multi-phase flow imaging

Three-phase flow imaging is a very challenging problem in industrial process tomography. A particular interest here is three phase flow including both conductive and non-conductive phases. Currently there is no robust solution to this problem. Electrical capacitance tomography (ECT) has been applied to visualize the permittivity distribution by measuring inter-capacitance between electrodes around sensing area. Magnetic inductance tomography (MIT) is a technique to image the conductivity distribution through the inductance measurements over the coils around the sensing area. In this paper, the three-phase flow is classified into two scenarios: air background and water background. A dual-modality method of ECT and MIT is proposed to image both the conductive and dielectric components under test. As a result of this experiment, the dual-modality method is able to solve air-background three-phase flow imaging, but a problem has been raised in the water-background scenario. The static experiment results are promising for such contactless three phase flow imaging.

Crystal growth, morphology, thermal and spectral studies of an organosulfur nonlinear optical bis(guanidinium) 5-sulfosalicylate (BG5SS) single crystals

Organosulfur nonlinear optical single crystals of orthorhombic bis(guanidinium) 5-sulfosalicylate (2CH6N3 +·C7H4O6S2−·H2O) with dimension 14 mm × 4 mm × 5 mm have been grown from methanol and water solvents in 1:1 ratio by the slow evaporation growth technique. The crystal structure and morphology of the crystals have been studied by single-crystal X-ray diffraction. FTIR spectroscopic studies were carried out to identify the functional groups and vibrational modes present in the grown crystals. The UV–Vis spectrum was studied to analyze the linear optical properties of the grown crystals. The thermal gravimetric analysis was conducted on the grown crystals, and the result revealed that the grown crystal is thermally stable up to 65 °C. The dielectric tensor components e 11, e 22 and e 33 of BG5SS crystal were evaluated as a function of frequency at 40 °C. The surface laser damage threshold for the grown crystal was measured using Nd:YAG laser. Further, Vickers micro-hardness study was carried out to analyze the mechanical strength of the grown crystals for various loads.

Modulation of the Dirac point voltage of graphene by ion-gel dielectrics and its application to soft electronic devices.

We investigated systematic modulation of the Dirac point voltage of graphene transistors by changing the type of ionic liquid used as a main gate dielectric component. Ion gels were formed from ionic liquids and a non-triblock-copolymer-based binder involving UV irradiation. With a fixed cation (anion), the Dirac point voltage shifted to a higher voltage as the size of anion (cation) increased. Mechanisms for modulation of the Dirac point voltage of graphene transistors by designing ionic liquids were fully understood using molecular dynamics simulations, which excellently matched our experimental results. It was found that the ion sizes and molecular structures play an essential role in the modulation of the Dirac point voltage of the graphene. Through control of the position of their Dirac point voltages on the basis of our findings, complementary metal-oxide-semiconductor (CMOS)-like graphene-based inverters using two different ionic liquids worked perfectly even at a very low source voltage (V(DD) = 1 mV), which was not possible for previous works. These results can be broadly applied in the development of low-power-consumption, flexible/stretchable, CMOS-like graphene-based electronic devices in the future.

Visualization of Nanoparticles Behavior Introduced into Gas Flame Spraying

In a newly developed rod feeding gas flame process, solid resin rod including nanoparticles could be fed into a Rokide® flame gun successfully to create fine ceramics layers without micro cracks and pores applying for electric, magnetic and dielectric components. In this investigation, alumina particles of 170 nm in average diameter were dispersed into acrylic liquid resin at 40 % in volume fraction. The paste materials were injected into a brass mold of φ40×200 mm in inner dimension and thermal cured through heating at 120 °C for 60 min. Formed solid rods were fed into oxyacetylene gas flame coaxially by using the Rokide® spraying gun system. Sprayed particles were cached by water bath for microstructure observations by a scanning electron microscope and crystal phase analyses by an X-ray diffraction spectroscopy. Fine ceramics layer formations will be discussed systematically by the feeding speed of solid rods and gas flame condition of air pressure and oxygen pressure.

Preparation and Microwave Absorbing Properties of Hollow Sphere Fe<sub>3</sub>O<sub>4</sub>/Co Composite

In this paper, the hollow sphere Fe3O4 powders pepared by the solvothermal method were mixed with Co nanoparticles (prepared by arc-discharge, the size about 100nm), the quality ratio of Fe3O4 and Co is 4:1. The SEM study shows that the Fe3O4 powders have Hollow sphere structural with the size of about 200nm. As a result, when Co nanoparticles are introduced, Fe3O4/Co composite absorbent is obtained enhanced microwave absorption properties, which is attributed to the improved synergistic effect of dielectric and magnetic components between er and μr. The results show that Fe3O4/Co composite absorbent is great potential microwave absorbents for practical applications.

TEM and EELS Study on TaOx-based Nanoscale Resistive Switching Devices

ABSTRACTResistive switching, a reversible change in electrical resistance of a dielectric layer through the application of a voltage bias, has propelled a field of research to form improved non-volatile memory device. Tantalum oxide has been investigated as the dielectric component of resistive switching devices as a leading candidate for a few years. Presented here is a structural and chemical investigation of TaOx devices with 55nm in diameter in the virgin, forming on, and switched off (reset) states for comparison using cross sectional TEM techniques including HRTEM, and EELS to gain further understanding of this material system. The nanodevices imaged in this study were switched below 100µA. Unique features found in this study are in agreement with previous hypotheses made by various researchers based on X-ray fluorescence microscopy of micron-scale devices, indicating a variation in oxygen concentration around the switching area.