Dielectric Properties Of Substrate Research Articles

High Voltages in Sliding Water Drops.

Water drops on insulating hydrophobic substrates can generate electric potentials of kilovolts upon sliding for a few centimeters. We show that the drop saturation voltage corresponds to an amplified value of the solid-liquid surface potential at the substrate. The amplification is given by the substrate geometry, the drop and substrate dielectric properties, and the Debye length within the liquid. Next to enabling an easy and low-cost way to measure surface- and zeta- potentials, the high drop voltages have implications for energy harvesting, droplet microfluidics, and electrostatic discharge protection.

Broadband Characterization of Silicate Materials for Potential 5G/6G Applications

This paper provides a broadband dielectric characterization of different silicate substrates up to 115 GHz, to fill the gap of the properties of different kinds of glasses in a broad part of the mm-wave spectrum. Both the internal structure (crystalline or amorphous) and the chemistry of the substrates has an influence in the permittivity and loss tangent of the material. Quartz and sapphire are crystalline materials that exhibit low loss in the mm-wave frequency range. Amorphous silicates generally have higher loss values than crystalline materials, and within the glasses, the level of impurities added also affects the dielectric loss. Several characterization techniques have been employed to cover a broad frequency band. The limitations of the different characterization techniques are also included. Once the dielectric properties of substrates are characterized, a metasurface has been designed and fabricated at 100 GHz to increase the reflection in window glass and provide coverage on areas that would otherwise be shadowed. The measurement results are in good agreement with the simulations.

Design of rectangular microstrip patch antenna with E-slot

The integration of an E-slot within the conventional microstrip patch antenna structure offers improved radiation characteristics and bandwidth. This research presents the design and analysis of a rectangular microstrip patch antenna with an E-slot. The proposed antenna is designed to operate at a specific frequency in the microwave range. The design process involves determining the dimensions of the rectangular patch, feedline, and E-slot to achieve the desired resonance frequency. The simulation and optimization are carried out using electromagnetic simulation software, considering the dielectric substrate properties and other relevant parameters. The E-slot is strategically placed within the patch structure to enhance the antenna's performance. It acts as an additional resonating element, contributing to increased bandwidth and improved radiation characteristics, such as gain and directivity. The integration of the E-slot modifies the current distribution on the patch, resulting in enhanced radiation properties. The performance of the proposed antenna is evaluated through various parameters, including return loss, radiation pattern, and bandwidth. Overall, the rectangular microstrip patch antenna with an E-slot presents a promising solution for achieving enhanced performance in terms of bandwidth and radiation characteristics. The proposed design opens up possibilities for further advancements in microstrip antenna technology, facilitating the development of an efficient and compact antenna structure for modern wireless applications.

Phonon and Exciton Properties between WS2 and MoS2 Layers via Inversion Heterostructure Engineering.

Recently, two-dimensional (2D) van der Waals heterostructures (vdWHs) have exhibited emergent electronic and optical properties due to their peculiar phonons and excitons, which lay the foundation for the development of photoelectronic devices. The dielectric environment plays an important role in the interlayer coupling of vdWHs. Here, we studied the interlayer and extra-layer dielectric effects on phonon and exciton properties in WS2/MoS2 and MoS2/WS2 vdWHs by Raman and photoluminescence (PL) spectroscopy. The ultralow frequency (ULF) Raman modes are insensitive to atomic arrangement at the interface between 1LW and 1LM and dielectric environments of neighboring materials, and the layer breathing mode (LBM) frequency follows that of WS2. The shift of high-frequency (HF) Raman modes is attributable to interlayer dielectric screening and charge transfer effects. Furthermore, the energy of interlayer coupling exciton peak I is insensitive to atomic arrangement at the interface between 1LW and 1LM and its energy follows that of MoS2, but the slight intensity difference in inversion vdWHs means that the substrate's dielectric properties may induce doping on the bottom layer. This paper provides fundamental understanding of phonon and exciton properties of such artificially formed vdWHs structures, which is important for new insights into manipulating the performances of potential devices.

On comparison of recycled LDPE and LDPE–bakelite composite based 3D printed patch antenna

In the past two decades number of studies have been reported on the use of thermoplastics as a substrate for 3D printed patch antennas. However, no work has been reported on the thermoplastic-thermosetting composite-based substrate for 3D printed patch antennas and their mechanical, morphological, rheological, and radiofrequency (RF) characterization for sensing applications. In this study low-density polyethylene (LDPE) and LDPE-5% bakelite (BAK) composite-based patch antenna (resonating frequency 2.45 GHz) were printed (for secondary recycling) on fused deposition modeling (FDM) setup. The RF characteristics were measured using a vector network analyzer (VNA). Ring resonator test was used for measuring the dielectric properties of substrates (which suggests that the dielectric constant ([Formula: see text]) and loss tangent ([Formula: see text]) for LDPE was 2.282 and 0.0045, whereas for LDPE-5%BAK the calculated [Formula: see text] and [Formula: see text] was 2.0663, 0.0051 respectively). This study highlights that for the LDPE-5%BAK composite there was a marginal increase in the size of the patch antenna; but this resulted in improved transmittance, gain, and return loss for typical sensor applications. As regards to printability of substrate, 5% BAK resulted in a melt flow index (MFI) of 9.96 g/10 min in contrast to 12.208 g/10 min for a neat LDPE sample. The selected LDPE-5%BAK composite resulted in peak strength (PS) and break strength (BS) of 16.08 MPa and 14.47 MPa (at 180 °C screw temperature, 110 rpm, and 11 kg load) while processing with a twin-screw extruder (TSE), which was observed better than the neat LDPE (PS 11.98 MPa, BS 10.79 MPa). The results were supported with porosity (%), surface roughness (Ra) analysis based upon scanning electron microscopy (SEM) and bond strength using attenuated total reflection (ATR) based Fourier transformed infrared (FTIR) analysis.

Determination of Salinity and Sugar Concentration by Means of a Circular-Ring Monopole Textile Antenna-Based Sensor

This paper presents a monopole antenna-based sensor for measuring different amounts and concentrations of salt and sugar in water. The proposed antenna sensor consists of a textile monopole antenna with circular-ring and partial ground plane. It is implemented by means of embroidery on a felt textile substrate and it resonates at 2.4 GHz. The textile substrate can absorb liquids through the sensing area incorporated within the monopole antenna structure. Therefore, the substrate dielectric properties are changed according to the liquid properties of the absorbed solution. The proposed antenna sensor uses microwave signals to track different amount and concentrations of salt and sugar in terms of the magnitude of the return loss and resonance frequency shift. The measurements are recorded and compared before and after applying different solutions. The rinsing reliability of the proposed antenna sensor has been also studied. The proposed antenna sensor demonstrates a high sensitivity of 800 MHz/mL with a good correlation with the linear fit ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{2}= 0.9737$ </tex-math></inline-formula> ) and 550 MHz/mL with linear response ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{2}= 0.9135$ </tex-math></inline-formula> ) for 5% salt and sugar concentration solutions, respectively. To the best of our knowledge, this article demonstrates for the first time the capability of a fully-textile antenna sensor to detect different amounts and concentrations of salt and sugar using microwave signals.

Extracting the Infrared Permittivity of SiO2 Substrates Locally by Near-Field Imaging of Phonon Polaritons in a van der Waals Crystal.

Layered materials in which individual atomic layers are bonded by weak van der Waals forces (vdW materials) constitute one of the most prominent platforms for materials research. Particularly, polar vdW crystals, such as hexagonal boron nitride (h-BN), alpha-molybdenum trioxide (α-MoO3) or alpha-vanadium pentoxide (α-V2O5), have received significant attention in nano-optics, since they support phonon polaritons (PhPs)―light coupled to lattice vibrations― with strong electromagnetic confinement and low optical losses. Recently, correlative far- and near-field studies of α-MoO3 have been demonstrated as an effective strategy to accurately extract the permittivity of this material. Here, we use this accurately characterized and low-loss polaritonic material to sense its local dielectric environment, namely silica (SiO2), one of the most widespread substrates in nanotechnology. By studying the propagation of PhPs on α-MoO3 flakes with different thicknesses laying on SiO2 substrates via near-field microscopy (s-SNOM), we extract locally the infrared permittivity of SiO2. Our work reveals PhPs nanoimaging as a versatile method for the quantitative characterization of the local optical properties of dielectric substrates, crucial for understanding and predicting the response of nanomaterials and for the future scalability of integrated nanophotonic devices.

Comparison of Basic Frequency Selective Surface Design Methods for Optical Windows

Methods for designing frequency selective surface for optical windows are analyzed and experimentally verified. Four methods; ITO coatings, graphene, metallic nano-coatings and metallic meshes; are compared in terms of optical transmission and shielding effectiveness (SE) characteristics. ITO is the most common method for increasing SE performance in the visible band. However, in the infrared band, transmission of ITO is limited. Metallic nano-coating is an alternative for ITO with underperformance from the SE and optical transmission point. Graphene is an emerging method and needs further development. SE performance of the graphene prevents it from being a single material for shielding applications. On the other hand, it might be involved in applications where back reflection is critical because of the electromagnetic absorption characteristic. Metallic mesh is a successful candidate for applications requiring high level SE and optical transmission. However, dielectric properties of substrate the mesh applied, and diffraction effects should be carefully analyzed.

Determination of dielectric properties of unknown substrates using hybrid approach

Unknown dielectric properties of RF/microwave substrates cause headaches for microwave circuit and antenna designers. Most commercial reinforced dielectric substrates made from layers of woven-glass and/or ceramic fillings lead to dielectric anisotropy. Often, re-optimization and even re-fabrication of designed prototypes are required when measuring results are found to be departed from the prediction. These are time consuming and costly. In order to determine the unknown complex permittivity of any substrates, this paper describes a hybrid approach composed of two measurement stages. The first stage is the coaxial-probe method for predicting an initial complex permittivity of unknown dielectric substrates, which is known as the perpendicular permittivity. The second stage is the microstrip open-circuit stub (OCS) method that regulates the complex permittivity of the dielectric laminate by mapping the input impedance curves of OCS via electromagnetic simulation and actual measurement. Three dielectric substrates without prior dielectric properties were selected to validate the proposed method. The equivalent dielectric constants, dissipation factors and dielectric anisotropies were determined and compared. The proposed method is found to be reliable for determining the unknown properties of dielectric substrates.

Customizing 3D-Printing for Electromagnetics to Design Enhanced RFID Antennas

This document discusses some of the advances in additive manufacturing 3D-printing for electromagnetic applications that have been investigated in the literature in the last few years. Starting from the research activity of the authors on this topic, this work summarizes and showcases the effectiveness of the 3D-printing technology in electromagnetics, with reference to UHF RFID technology. Specifically, the first part of the work deals with Fused Deposition Modeling (FDM) printing technique and faces the problem of the characterization of 3D-printable materials using a made-in-lab instrument based on the T-Resonator theory, which has been purposely designed to be 3D-printed. Once verified the dielectric properties of substrates realized with common 3D-printable materials, two techniques to improve their electrical permittivity are explained. Moreover, the possibility to realize fully 3D-printed RFID devices based on the use of novel 3D-printable materials with noteworthy conductive properties is discussed. Then, two new 3D-printed antennas are presented and discussed highlighting some of the advantages of 3D-printing in electromagnetics. Finally, the application in RFID of another promising 3D-printing technology called Digital Light Processing (DLP) and based on the photopolymerization of liquid resins is discussed as well.

Dielectric Properties of Substrates for InkJet Technology in GHz Area

This paper is focused on investigation of dielectric properties of various substrates for InkJet printing technology. In addition this paper included investigation of dielectric properties' homogeneity. Dielectric constant and loss tangent of polymeric flexible substrates (Polyimide DuPont Kapton HN, PET Mylar A, PEN Teonex Q51) and insulation paper (Nomex 410) were measured in GHz frequency area. Measurements were done by combination of vector network analyzer and split cylinder resonator. This measuring method provides dielectric properties at frequency around 10 GHz, the exact value of frequency may vary depends on specific material and its resonant frequency. Experiments included two types of samples, 6 x 6 cm which is recommended area for measurements of dielectric properties by split cylinder resonator and 12 x 12 cm for measurements of dielectric properties' homogeneity (one sheet contains 9 overlapping measuring areas 6 x 6 cm). All measured values of dielectric constant and dielectric losses were statistically processed and depicted by SigmaPlot software. The paper shows values of dielectric properties at GHz frequency area as they are lacking in datasheets from manufacturers and evaluate homogeneity of measured substrates.

Conformal and Disposable Antenna-Based Sensor for Non-Invasive Sweat Monitoring.

This paper presents a feasibility study for a non-wearable, conformal, low cost, and disposable antenna-based sensor for non-invasive hydration monitoring using sweat. It is composed of a patch antenna implemented on a cellulose filter paper substrate and operating in the range 2–4 GHz. The paper substrate can absorb liquids, such as sweat on the skin, through two slots incorporated within the antenna structure. Thus, the substrate dielectric properties are altered according to the properties of the absorbed liquid. Changes in reflection-based measurements are used to analyze salt solutions and artificial sweat, specifically the amount of sampled solution and the sodium chloride (NaCl) concentration. Using the shift in resonant frequency and magnitude of the reflection coefficient, NaCl concentrations in the range of 8.5–200 mmol/L, representing different hydration states, are detected. The measurements demonstrate the feasibility of using microwave based measurements for hydration monitoring using sweat.

Carbon films as perfect electromagnetic wave absorbers and anti‐reflectors

It is shown that thin carbon coating with thicknesses, depending on its structure and porosity, ranging from tens of nanometres to tens of microns can absorb almost all incident microwave radiation without reflection. Special conditions on dielectric properties of substrate and conductivity of carbon material, which are necessary for the realisation of such a perfect absorber, are derived. The conductance of the carbon coating can then be controlled by proper porosity.

Surface Dielectric Resonators for X-band EPR Spectroscopy

A new resonator for X-band electron paramagnetic resonance (EPR) spectroscopy, which utilizes the unique resonance properties of dielectric substrates, has been developed using a single crystal of titanium dioxide. As a result of the dielectric properties of the crystal(s) chosen, this novel resonator provides the ability to make in vivo EPR spectroscopy surface measurements in the presence of lossy tissues at X-band frequencies (up to 10 GHz). A double-loop coupling device is used to transmit and receive microwave power to/from the resonator. This coupler has been developed and optimized for coupling to the resonator in the presence of lossy tissues to further enable in vivo measurements, such as in vivo EPR spectroscopy of human fingernails or teeth to measure the dose of ionizing radiation that a given individual has been exposed to. An advantage of this resonator for surface measurements is that the magnetic fields generated by the resonator are inherently shallow, which is desirable for in vivo nail dosimetry.

Understanding the plasmonic properties of dewetting formed Ag nanoparticles for large area solar cell applications

The effects of substrates with technological interest for solar cell industry are examined on the plasmonic properties of Ag nanoparticles fabricated by dewetting technique. Both surface matching (boundary element) and propagator (finite difference time domain) methods are used in numerical simulations to describe plasmonic properties and to interpret experimental data. The uncertainty on the locations of nanoparticles by the substrate in experiment is explained by the simulations of various Ag nanoparticle configurations. The change in plasmon resonance due to the location of nanoparticles with respect to the substrate, interactions among them, their shapes, and sizes as well as dielectric properties of substrate are discussed theoretically and implications of these for the experiment are deliberated.

The correlation between gate dielectric, film growth, and charge transport in organic thin film transistors: the case of vacuum-sublimed tetracene thin films

The complex interplay of dielectric substrate properties, semiconducting film growth, crystal structure, texture, and charge carrier transport is investigated for the case of tetracene films deposited on different dielectrics (polystyrene, parylene C, polymethylmethacrylate, hexamethyldisilazane-treated SiO2, and untreated SiO2). The tetracene hole mobility, measured in the bottom-gate organic thin film transistor (OTFT) configuration, varies over more than one order of magnitude depending upon the dielectric layer used. Atomic force microscopy and synchrotron grazing incidence X-ray diffraction measurements, analyzed with the extended Rietveld method, were used to investigate the influence of film connectivity, crystalline phase, polymorphism, and texture on charge transport. The role of the surface polarity and the processing conditions of the gate dielectric layer are also discussed. Based on our results, we propose guidelines for the selection of a gate dielectric material favorable for charge transport in tetracene films.

Effects of dielectric substrate properties for optical phenomena in a nanoscale ridge aperture

In this paper, we show that the increase in power throughput is dependent on the thickness and the relative permittivity of the dielectric substrate in the aperture-on-dielectric-substrate configuration. We also show that, similar to a metal nanoparticle, an increase in the medium dielectric constant results in a red-shift in the plasmon resonance of a nanoscale ridge aperture. These results, which are verified by a numerical analysis, provide a new understanding of the phenomenon of surface-plasmon-enhanced transmission. We demonstrate that the red-shifted wavelength and dielectric properties can compensate for the optical loss due to plasmon red-shift. In addition, the dielectric substrate layer behaves like a Fabry–Pérot optical resonator, resulting in coherent constructive interference. The simulation results show that the |E|2 intensity of the triangular aperture is ∼200% greater when this dielectric effect and red-shift resonance are considered.

Effect of the Dielectric Properties of Substrates on the Scattering Patterns of Gold Nanorods

Understanding the electromagnetic interactions between plasmonic noble metal nanocrystals and different substrates is very important because a number of plasmon-based devices and applications, such as chemical and biological sensing, metamaterials, subwavelength waveguides, plasmon-enhanced photovoltaic cells, plasmon-enhanced spectroscopy, and photoswitches, require the attachment of metal nanocrystals onto various substrates. In this study, we focused on the effect of the dielectric properties of substrates on the far-field scattering patterns of supported Au nanorods. Seven types of substrates, including metals, semiconductors, and insulators, were examined. The far-field scattering patterns from individual Au nanorods were found to exhibit a doughnut shape when the modulus of the dielectric constant of the substrate is above ∼7, while they appear as solid bright spots when the modulus is below ∼7. This finding was validated by numerical electrodynamic calculations. Moreover, the doughnut-shaped scattering patterns are very sensitive to the spacing between the nanorod and substrate. For the nanorods supported on silicon wafers, when the spacing is increased above ∼14 nm, the scattering patterns change from the doughnut shape to the solid bright spot. These results will be useful for the understanding of the plasmonic properties of noble metal nanocrystals supported on substrates and the development of a number of plasmon-based optical and optoelectronic devices at different size scales.

Influence of substrate dielectric permittivity on local capacitive behavior in graphene

Graphene deposited on silicon dioxide (DG-SiO2) and high-κ dielectric strontium titanate (DG-STO) are investigated for electrostatic properties by local capacitance measurements carried out with Scanning Capacitance Spectroscopy (SCS). The quantum capacitance associated with 2DEG in graphene showed significant increase for DG-STO as a function of Fermi level (EF) as compared to that for DG-SiO2. The quantum capacitance, being a fundamental property of graphene 2DEG, is not expected to vary with substrate dielectric properties in the absence of any interaction. However, the observed increase in quantum capacitance in our case is predominantly due to the enhanced effectively biased area in DG-STO. We suggest that this effect is a consequence of better dielectric screening of commonly observed charged impurities, on graphene and/or at the graphene/substrate interface, by the use of high permittivity substrate.

Piezoelectric films for 100-MHz ultrasonic transducers

Piezoelectric aluminum nitride (AlN) and zinc oxide (ZnO) thin films were deposited by reactive magnetron sputtering for use in ultrasonic transducers in the 100- to 300-MHz regime. Pulse-echo ultrasonic transducers are being developed to image subsurface microstructure in metal and non-metal (ceramic) materials and components. A Krimholtz, Leedom, Matthaei (KLM) model was used to aid in the design of the ultrasonic transducer. Design criteria included piezoelectric material properties and thickness, electrode material and thickness, substrate dielectric properties, active area diameter and bandwidth and sensitivity requirements. The preliminary designs consisted of Ni/AlN/Ni and Ni/ZnO/Ni on BK-7 glass and fused silica substrates. AlN was chosen because of its a high longitudinal wave velocity of 10 700 m/s and high dielectric strength of 20 MV/cm. Strongly oriented (002) AlN and ZnO coatings, up to 50 μm thick, were deposited onto transducer substrates. Transducers with strongly oriented (002) crystal orientation displayed the highest longitudinal/shear (L/S) wave ratio of 19.6 dB. Crystalline structure was found to depend primarily on substrate temperature, substrate placement, and substrate material. Substrate temperatures ranged between 100 and 400°C. Strongly (002) oriented AlN films were deposited at substrate temperatures as low as 100°C. The L/S ratio decreased with the onset of the (103) and other crystal orientations, which resulted from off-normal adatom flux incidence during deposition. Near normal incidence flux angles were needed to obtain the (002) crystal orientation. Substoichiometric ZnO films were obtained at substrate temperatures below 300°C. The transducers operated at frequencies between 50 and 100 MHz, with performance very close to that of the design.