Dielectric Configuration Research Articles

Millimeter Wave Characterization of a Catadioptric Lens for Imaging Applications

Characterization of a catadioptric dielectric lens-horn configuration for short-range sensing and imaging is presented. The focusing property is investigated both numerically and experimentally at 108 GHz. The lens-horn provides a focal spot of ~ 0.9 lambda at a distance of ~ 4.5 lambda. An imaging example employing the lens in a CW imaging setup is presented. A test pattern was imaged and a marked improvement in image resolution was observed. With the aid of the lens, features close to the wavelength are resolved, which are absent or indistinguishable otherwise.

Equilibrium long-ranged charge correlations at the interface between media coupled to the electromagnetic radiation

We continue studying long-ranged quantum correlations of surface charge densities on the interface between two media of distinct dielectric functions which are in thermal equilibrium with the radiated electromagnetic field. Two regimes are considered: the nonretarded one with the speed of light c taken to be infinitely large and the retarded one with a finite value of c . The analysis is based on our results obtained by using fluctuational electrodynamics [L. Samaj and B. Jancovici, Phys. Rev. E 78, 051119 (2008)]. Using an integration method in the complex plane and the general analytical properties of dielectric functions in the frequency upper half plane, we derive explicit forms of prefactors to the long-range decay of the surface charge correlation functions for all possible media (conductor, dielectric, and vacuum) configurations. The main result is that the time-dependent quantum prefactor in the retarded regime takes its static classical form for any temperature.

The Dielectric Response of the Tropical Hawaiian Mars Soil Simulant JSC Mars‐1

The observation of low dielectric values <2, consistent with the bright areas of the surface of Mars, is completely counter to expectation for soils dominated by mafic minerals, especially Fe minerals and pyroxenes that tend to have dielectric values two to three times higher than quartz, which has a value of 4.7. To this day, this observation has not been explained. The recent success of the Phoenix lander in locating water on Mars, however, is renewing interest in the use of sensors to determine Martian soil properties. We took measurements on the Hawaiian JSC Mars‐1 soil simulant, considered to reflect the properties of the soils of the bright regions of Mars. Our objective was to determine if soil structure and dielectric phase configuration could account for low dielectric responses. We discovered that low dielectric values can be reconciled with mafic, Fe‐bearing silicate mineralogy due to the presence of a palagonite structure with internal porosity. Furthermore, dielectric response as a function of water content is startlingly lower than standard soil calibration equations from Earth, meaning that the application of these equations may significantly underestimate water content determined from dielectric measurements—not because of “bound water,” but because of the altered dielectric phase configuration due to the palagonite internal pore structure. The implications of this finding for future planetary missions are that all sensors relying on interpreting soil properties from measurements of bulk soil electrical, thermal, or dielectric properties will be similarly affected in the presence of materials with internal porosity.

Negative and positive lateral shifts: a result of beam reshaping caused by interference

The origin of negative and positive lateral shifts of the light beams in a dielectric slab configuration is investigated from the viewpoint of the interference between multiple light beams, due to the multiple reflections and transmissions inside the slab. It is shown that the whole reflected and transmitted beams with negative shifts can be obtained from the successively reflected and transmitted constituents, respectively, with positive displacements predicted from geometrical optics. When the slab's thickness is much smaller in comparison with the width of the beam waist, the reshaping reflected and transmitted beams retain the profile of the incident beam. The physical mechanism presented here could also be applicable in investigating other counterintuitive phenomena, such as the superluminal traversal time in quantum tunneling and dispersive media.

薄介质板结构中有限光束的多次反射及其重构

薄介质板结构中有限光束的多次反射及其重构

Design of multi-frequency microstrip antennas using multiple rings

An electromagnetically coupled feed arrangement is proposed for simultaneously exciting multiple concentric ring antennas for multi-frequency operation. This has a multi-layer dielectric configuration in which a transmission line is embedded below the layer containing radiating rings. Energy coupled to these rings from the line beneath is optimised by suitably adjusting the location and dimensions of stubs on the line. It has been shown that the resonant frequencies of these rings do not change as several of these single-frequency antennas are combined to form a multi-resonant antenna. Furthermore, all radiators are forced to operate at their primary mode and some harmonics of the lower resonant frequency rings appearing within the frequency range are suppressed when combined. The experimental prototype antenna has three resonant frequencies at which it has good radiation characteristics.

Stopping light by an air waveguide with anisotropic metamaterial cladding

We present a detailed study of oscillating modes in a slab waveguide with air core and anisotropic metamaterial cladding. It is shown that, under specific dielectric configurations, slow and even stopped electromagnetic wave can be supported by such an air waveguide. We propose a linearly tapped waveguide structure that could lead the propagating light to a complete standstill. Both the theoretical analysis and the proposed waveguide have been validated by full-wave simulation based on finite-difference time-domain method.

A Fast Frequency-Domain Eigenvalue-Based Approach to Full-Wave Modeling of Large-Scale Three-Dimensional On-Chip Interconnect Structures

As on-chip circuits have scaled into the deep submicron regime, electromagnetics-based analysis has increasingly become essential for high-performance integrated circuit (IC) design. Not only fast, but also high-capacity electromagnetic solutions are demanded to overcome the large problem size facing on-chip design community. In this paper, we present a novel, high-capacity, and fast approach to the full-wave modeling of 3-D on-chip interconnect structures. In this approach, the interconnect structure is decomposed into a number of seeds. In each seed, the original wave propagation problem is represented as a generalized eigenvalue problem. The resulting eigenvalue representation can comprehend both conductor and dielectric losses, arbitrary dielectric and conductor configuration in the transverse cross section, and arbitrary material. A new mode-matching technique applicable to on-chip interconnects is developed to solve large-scale 3-D problems by using 2-D-like CPU time and memory. A junction matrix acceleration technique is proposed to speed up the mode matching process. A fast frequency sweep technique is employed to obtain the response over the entire frequency band by solving at one or a few frequency points only. An extraction technique is developed to obtain S-parameters from the solution of the eigenvalue system. The entire procedure is numerically rigorous without making any theoretical approximation. Experimental and numerical results demonstrate its accuracy and efficiency.

Fuzzy ring from M2-brane giant torus

We construct spinning dual M2 giant gravitons in AdS_4 x S^7, which generically become 1/16 BPS states, and show that their world-volumes become torii. By taking an orbifold, we obtain spinning dielectric D2-brane configurations in AdS_4 x CP^3 dual to specific BPS operators in ABJM theory. This reveals a novel mechanism how to give an angular momentum to a dielectric D2-brane. We also find that when its angular momentum in the AdS_4 becomes large, it approaches to a ring-like object. Our result might suggest an existence of supersymmetric black rings in the AdS_4 background. We will also discuss dual giant gravitons in AdS_4 x CP^3.

Two-Dimensional Tunneling Effects on the Leakage Current of MOSFETs With Single Dielectric and High-$\kappa$ Gate Stacks

The gate leakage currents of single-gate silicon-on- insulator (SOI) n-type MOSFETs are investigated, assuming direct tunneling as the leakage mechanism and using either a 1-D Schrodinger-Poisson-based approach coupled to the conventional drift-diffusion transport model or a full quantum mechanical treatment. The first approach consists of calculating the transmission probability through the dielectric material along straight lines connecting the transistor channel to the gate. The second method is based on a 2-D Schrodinger-Poisson solver, where carriers are injected into the device from the source, drain, and gate contacts. The simulated structures have a physical gate length of 32 nm. The channel is isolated from the gate contact by a dielectric layer with an equivalent oxide thickness of 1.2 nm. This layer is composed of either pure SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> or a high-kappa SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> - HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> stack. Irrespective of the dielectric material, the leakage currents calculated with the 1-D approach are about one order of magnitude smaller at low gate voltages and converge toward the same value as the channel potential barrier decreases. The difference is caused by the diffraction of the electron waves at both edges of the gate contact. This peculiar 2-D behavior of the gate leakage currents, as well as the limit of the 1-D model, is discussed in this paper for various dielectric configurations.

A streamer-like atmospheric pressure plasma jet

The properties of an atmospheric pressure plasma jet (APPJ) are examined in a single-cell dielectric capillary configuration. In contrast to some other flow-driven APPJs, this stable, cold plasma jet is electrically driven, composed of rapidly propagating ionization fronts with speeds of the order of 107cm∕s. Using spatially and temporally resolved optical diagnostics, it is demonstrated that the plasma jet is initiated independent of the dielectric barrier discharge inside the capillary. It is also shown that the properties and dynamics of this APPJ are directly analogous to those of positive corona streamer discharges.

Growth related properties of pentacene thin film transistors with different gate dielectrics

We report a study on the influence of dielectric surface properties on the growth, the morphology and ordering of pentacene layers and associated consequences on the performance of organic field effect transistors (OFETs). This work mainly aims at disentangling the respective influences of surface roughness and surface energy on pentacene growth. A range of inorganic high-k oxides as well as polymer dielectrics were compared: Ta2O5 deposited by e-beam evaporation or grown by anodic oxidation, polymethylmethacrylate (PMMA) single layer or PMMA/Ta2O5 bi-layer. Some complementary results on anodic HfO2 were also added. Atomic force microscopy, X-ray diffraction and infrared absorption evidenced that hydrophobicity and surface roughness drastically influence pentacene growth mechanisms. Transistors realized with the different dielectrics show characteristics well correlated to pentacene structural properties. In particularly, we point out the relationship between the grain size and the field effect mobility with the surface energy of the dielectric substrate. The general trend is that the bigger the grains, the higher the mobility but that best electrical performances of OFETs are obtained with a dielectric surface energy close to that of pentacene. This work also bears out our former results on the benefit of a polymer/high-k oxide bilayer dielectric configuration to improve the field effect mobility while keeping a low operating voltage.

Atmospheric‐Pressure Glow Discharge CVD of Composite Metallic Aluminium Thin Films

AbstractWe present the first reported investigation exploring the deposition of composite metal/metal oxide thin films using APGD CVD. The approach taken employs a parallel‐plate dielectric barrier configuration, and the deposition of such materials is discussed with respect to their influence on discharge conditions. Controlled and variable composition films were produced based on aluminium which showed metallic‐like reflection (up to 60% visible), and were conductive (≈1 Ω per square). The films are analysed by RBS, SEM, AFM and optical spectroscopy. This new class of APGD‐CVD‐derived thin‐film material, when combined with the associated low thermal load and attractions for industrial scaling, offers significant potential for new applications.magnified image

Experimental Observation of Left-Handed Behavior in an Array of Standard Dielectric Resonators

We demonstrate that by utilizing displacement currents in simple dielectric resonators instead of conduction currents in metallic split-ring resonators and by additionally exciting the proper modes, left-handed properties can be observed in an array of high dielectric resonators. Theoretical analysis and experimental measurements show that the modes, as well as the subwavelength resonance, play an important role in the origin of the left-handed properties. The proposed implementation of a left-handed metamaterial, based on a purely dielectric configuration, opens the possibility of realizing media at terahertz frequencies since scaling issues and losses, two major drawbacks of metal-based structures, are avoided.

A Flexible Full-Wave Analysis of Multilayered AMC Using an Aperture Oriented Approach

A full-wave analysis of printed artificial magnetic conductors (AMC), consisting of multilayered array of metal patches in a stratified dielectric medium, is presented. The approach is based on the Method of Moments, using as unknowns the magnetic currents over the apertures. This approach is effective, irrespective of the metallization shapes and of the dielectric slabs configuration. A comparison with results derived from commercial software will assess the procedure.

Single-mode operation in the slow-light regime using oscillatory waves in generalized left-handed heterostructures

The authors present an exact, analytic study of oscillatory modes guided by generalized asymmetric two-dimensional planar heterostructures with negative refractive index in either the core or the cladding. It is shown that, in sharp contrast to normal dielectric configurations, these waveguides always possess a frequency region where the second-order oscillatory mode may exist alone and allow for attaining zero group velocity under weak guidance conditions. In addition the mode has a field distribution that renders it excitable with an end-fire approach, making such structures attractive for applications requiring slow light. Advantages compared to previous methods of slowing or stopping light are discussed.

Study of geometrical and operational parameters controlling the low frequency microjet atmospheric pressure plasma characteristics

Controllability of small size atmospheric pressure plasma generated at low frequency in a pin to dielectric plane electrode configuration was studied. It was shown that the plasma characteristics could be controlled by geometrical and operational parameters of the experiment. Under most circumstances, continuous glow discharges were observed, but both the corona and/or the dielectric barrier discharge characteristics were observed depending on the position of the pin electrode. The plasma size and the rotational temperature were also varied by the parameters. The rotational temperature was between 300 and 490K, being low enough to treat thermally sensitive materials.

Investigation Into the Performance of Proximity Coupled Stacked Patches

We investigate the parameters that control the impedance and radiation performance of proximity coupled stacked microstrip patch radiators. In particular we explore the relationship required between the dielectric layers to achieve broadband behavior and also how the dimensions of the stacked radiators and the relative location of the feed can influence the impedance response. Bandwidths in excess of 20% can be achieved with careful layer design. We also investigate the dielectric layer configurations required to achieve broadband impedance responses when higher dielectric constant feed material is used. This latter study is of particular importance when designing MMIC compatible printed antennas.

Determination of the thermal conductivity of composite low- k dielectrics for advanced interconnect structures

The increasing use of low- k dielectrics as inter/intralevel insulation materials and the aggressive scaling of advanced interconnects generate new challenges for thermal and electromigration (EM) solutions. Accurate specification of design rules and EM reliability modeling for interconnect systems require knowledge of the thermal behavior of the systems. A key parameter that characterizes thermal behavior is the thermal conductivity of the inter/intralevel dielectric (ILD). In practical, very large scale integration (VLSI) applications, the metal interconnects are fully embedded in a stacked, composite ILD media, which present challenges for the accurate determination of thermal conductivity. This article uses the “effective thermal conductivity” concept to model such complicated composite media, and to introduce a simple methodology that accurately measures effective and bulk thermal conductivities of various thin dielectric layers in integrated circuits (IC). We present measured effective conductivities of several composite media, including various Cu/low- k dielectric configurations: Cu/SiCOH, Cu/spin-on organic dielectric (SOD), Cu/fluorinated silicate glass (FSG), and a hybrid stack with Cu lines in SOD and Cu vias in undoped silicate glass (USG). Recorded temperature measurements ranged from 30 to 120 °C using a unique combination of fully embedded Cu lines as heater/thermometers, wafer-level temperature–voltage–power measurements, and the Harmon–Gill (H–G) quasi-analytical heat conduction model. We demonstrated optimal agreement between an experimental method and a finite element simulation, which suggests that this unique technique yields accurate and simple thermal conductivity measurements for complicated systems. Our observations show that thermal conductivities of all films in this study increased with rising substrate temperature.

Multi-resolution iterative inversion of real inhomogeneous targets

This paper presents a review of the reconstruction results obtained from the inversion of experimental data provided by the Institute Fresnel (Marseille, France) and concerned with inhomogeneous dielectric targets and hybrid configurations, where dielectric and metallic cylinders are present in the scenario under test. The iterative multi-scaling approach (IMSA) is applied for addressing the inversion of scattering data in order to effectively exploit the available information through a multi-step reconstruction procedure, which adaptively allocates a set of unknown coefficients, related to the dielectric distribution in the investigation area, on the basis of the information collected during the iterative process. The obtained results confirm the effectiveness of such an iterative multi-resolution strategy in dealing with complex scatterers already demonstrated in synthetic experiments.