Multilayer Resonator Research Articles

Enhanced electrical transport properties of Cr-substituted Mg2–Y-type hexaferrites for power applications

The impact of Cr3+ substitution on the electrical and dielectric properties of Y-type hexaferrites with composition Ba2Mg2CrxFe12-xO22 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) was synthesized by the sol-gel auto combustion technique. The lattice parameters 'a' and 'c' slightly increase with the substitution content of Cr3+, and some other physical parameters, including porosity, microstrain, dislocation density, specific surface area, and stacking fault coefficient, were determined from XRD data. FTIR spectra confirm the formation of iron oxide base material by the appearance of three signature bands at precisely 429, 474, and 499 cm-1 due to Fe–O vibrations at octahedral and tetrahedral sites. Substituting Cr3+ at the octahedral site enhanced the room temperature DC electrical resistivity from 6.89 × 109 to 2.27 × 1010 Ω-cm. Temperature-dependent DC electrical resistivity exhibits semiconducting behavior. There is a direct relation between resistivity and activation energy. The dielectric behavior of Cr3+ substituted samples in the frequency range of 1 MHz–6 GHz was understood based on the conduction mechanism through the hopping of electrons between Fe3+ and Fe2+ ions and the Maxwell-Wagner Model. In impedance spectroscopy studied using Cole-Cole plots, most dielectric response arises from the contribution of the grain boundary effect. With the substitution of Cr3+, dielectric losses decreased. A very high Q-value around 1 GHz was observed, suggesting that these hexaferrites are efficient materials for many high-frequency applications, such as multi-layer chip inductors (MLCI), dielectric resonators, and power applications.

Advancing Raman spectroscopy of erythrocytes with 3D-printed acoustofluidic devices

Acoustofluidics is a technique that utilizes the forces produced by ultrasonic waves and fluid flows to manipulate cells or nano-/microparticles within microfluidic systems. In this study, we demonstrate the feasibility of performing the Raman analysis of living human erythrocytes (Erys) within a 3D-printed acoustofluidic device designed as a half-wavelength multilayer resonator. Experiments show that a stable and orderly Ery aggregate can be formed in the pressure nodal plane at the resonator's mid-height. This has a significant potential for improving the applicability of Raman spectroscopy in single Ery analysis, as evidenced by the acquisition of the spectrum of healthy and pre-heated Erys without substrate interference. Moreover, principal component analysis applied on the obtained spectra confirms the correct Ery group identification. Our study demonstrates that 3D-printed acoustofluidic devices can improve the accuracy and sensitivity of Raman spectroscopy in blood investigations, with potential clinical applications for noninvasive disease diagnosis and treatment monitoring.

Material dissipation of graphene resonators

Graphene resonators hold a promising potential to be integrated into nanoscale sensors and electronic devices. Therefore, understanding the physics underlying their dissipation mechanisms is essential. Here we investigate the dissipation of graphene through a study of graphene foam (GF) resonators. We show that intrinsic material dissipation, related to interlayer friction, is a primary source of energy dissipation in graphene. We fabricated GFs with varying wall thicknesses and characterized their frequency responses under ambient and vacuum conditions. Additionally, we investigated their atomic structure by using Raman analysis, high-resolution scanning electron microscopy, and transmission electron microscopy. While air losses are considered the primary dissipation source of micro- and nano-electromechanical systems (M/NEMS) operating under ambient conditions, we show that friction between graphene layers is a comparable source for energy dissipation and, thus, it limits the dynamic amplification of multilayer graphene resonators even when they are operated under high-vacuum conditions. We show that the friction between the layers is enhanced when multiple layers exist and that dissipation is further amplified by microscopic defects, such as cracks and grain boundaries, or by the existence of amorphous carbon. Thus, we uncover the fundamental physical behavior of graphene.

An analysis of nonlinear thickness vibration frequencies of multi-layered film bulk acoustic resonators

The fast reduction of the physical size of film bulk acoustic wave resonators as a layered structure implies the intensification of the electric field which can induce large deformation in the functioning state of devices as a circuit element. Consequently, the nonlinear behavior of the resonator and accompanying properties are to be included and evaluated in the development and optimization for performance improvement. With this objective, the nonlinear formulation of a multilayered film bulk acoustic resonator is presented for the analysis of vibration frequencies and mode shapes with the consideration of larger mechanical deformation. The dominantly linear relationship between the voltage or deformation and frequency is obtained to understand the nonlinear behavior and properties which have been subjected to extensive research analytically and experimentally to satisfy the application needs in all modes of communications and network technology.

Surface plasmon optical sensor based on multilayer metal-coated nanorods resonator

Surface plasmon optical sensor based on multilayer metal-coated nanorods resonator

Investigation of crystal structure, electrical and dielectric response of Ga3+ substituted Sr–Ni Y-type hexaferrites as a suitable material for high frequency applications

Technology important ferrites ceramic Sr2Ni2GaxFe12-xO22 (x = 0.00, 0.2, 0.4, 0.6, and 0.8) samples were produced using sol-gel auto combustion route. Structural, electrical, dielectric, and magnetic parameters were identified by substituting Ga3+ at the Fe3+ site. It was recognized that an increase of Ga3+ content in (Sr2Ni2GaxFe12-xO22) ceramic samples first decreased, then increased lattice parameters, and the density of samples was observed. This is because of the ionic radii and atomic weight of Ga3+ and Fe3+ cations. FTIR spectra show two characteristic absorption bands at 444-513 cm−1 caused by metal-oxygen vibrations. Due to the contribution of smaller grains of samples, the higher values of resistivity were observed, which vary from 3.78 × 1010 (Ω cm) to 1.13 × 1011 (Ω cm) by the substitution of Ga3+ ions at the octahedral site. The activation energy was measured between 0.20 and 0.61 eV. The dielectric response of Ga3+ substituted ferrite ceramic samples were studied in the 1 MHz-6 GHz frequency region. The Maxwell-Wagner bilayer model studied the effect of polarization with applied frequency on dielectric parameters. With the substitution of Ga3+, minimal losses in the range 0.34–0.44, about 6 GHz, and a high Q-value of about 10,000 were observed for each sample. In impedance spectroscopy analysis Cole-Cole plots confirm that the dielectric response is because of the influence of grain boundaries. The substitution of Ga3+ enhances saturation magnetization (68.20–71.78 emu/g) while coercivity decreases (655.86–507.86 Oe). In the present finding, the low dielectric loss, moderate permittivity, high value of the Quality factor, and very high value of resistivity of about 1.13 × 1011 that reduces the eddy current losses suggested that these materials are appropriate candidates for many high-frequency applications such as multilayer chip inductor, dielectric resonators, power applications, and microwave devices.

High-order mode solid mounted resonators with polarity inverted multilayered GeAlN/AlN films

High frequency bulk acoustic wave (BAW) resonators for beyond 5 G communications have low Q values and electromechanical coupling because of their ultra-thin piezoelectric monolayer films. Polarity inverted multilayered film BAW resonators operating in high-order mode resonance can have thicker piezoelectric layers than monolayer BAW resonators. In this paper, we fabricated and evaluated two- to four-layered polarity inverted GeAlN/AlN film solid mounted resonators (SMRs). They resonated in high-order mode. Their total film thicknesses were approximately two- to four-times thicker than that of a monolayer AlN film SMR. The polarity inverted GeAlN/AlN film SMRs had higher Q values than the monolayer SMR.

Layered piezoelectric structures with arbitrary acoustic termination impedances.

Multilayer piezoelectric transducers and resonators are widely used for generating propagating and standing acoustic waves as well as for sensor devices. More recently, layered piezoelectric structures based on thin film technology became increasingly important for electromechanical filters used in mobile phones. As a consequence, analytical mathematical modeling of such structures is of high interest. In this paper, a general rigorous transfer matrix description for one-dimensional (1D) layered structures consisting of piezoelectric, visco-elastic, and dielectric layers of arbitrary number is introduced to characterize the electrical and mechanical behavior of a general piezoelectric transducer or resonator with two electrodes and arbitrary acoustic termination impedances (Rig-1D-model). This model is the most general 1D analytical description of layered piezoelectric structures available and can be used for the characterization of various composite transducer and resonant sensor applications. Considered in detail are layered structures with the technically important cases of only one electromechanically coupled mode, and the structure at one or both outer surfaces is in contact with semi-infinite media. For such devices, it is shown how the frequency dependence of the total electrical admittance and spatial dependence of the displacements can be calculated.

Numerical Analysis of Coronavirus Detection Using Photonic Crystal Fibre-Based SPR Sensor.

Coronavirus disease (COVID-19) is a worldwide health emergency caused by the coronavirus 2 (severe acute respiratory illness) (SARS-CoV-2). COVID-19 has a wide range of symptoms, making a definitive diagnosis difficult. The shortage of equipment for testing technology COVID-19 has resulted in long queues for COVID-19 testing, which is a major problem. COVID-19 testing is currently performed using sluggish and costly technology like single-photon emission computed tomography (SPECT), computed tomography (CT), positron emission tomography (PET), and enzyme-linked immunosorbent assay (ELISA). The gold standard test for diagnosing COVID-19 is real-time reverse transcriptase-polymerase chain reaction (RT-PCR), which necessitates highly skilled workers and has a lengthy turnaround time. However, rapid and affordable immunodiagnostic techniques (antigen or antibody tests) are also available with some trade off accuracy. Optical sensors are frequently employed in a variety of applications, because of their increased sensitivity, strong selectivity, rapid reaction times, and outstanding resolution. The use of photonic crystal fibre (PCF) is advantageous for the quick detection of the new coronavirus and is suggested with the use of a PCF-based (Au/BaTiO3/graphene) multilayered surface plasmon resonance (SPR) biosensor. The proposed sensor can quickly detect the COVID-19 virus in two different ligand-analyte environments: (i) the virus spike receptor-binding domain (RBD) as an analyte and monoclonal antibodies (mAbs) as a probe ligand, and (ii) monoclonal antibodies (IgG or IgM) as an analyte and the virus spike RBD as a probe ligand. The finite element method (FEM) is used to quantitatively examine the performance of the PCF-based multilayered SPR sensor.

Effect of 2-D nanomaterials on sensitivity of plasmonic biosensor for efficient urine glucose detection

This paper presents a multi-layered Kretschmann configuration-based Surface Plasmon Resonance (SPR) biosensor for the detection of urine glucose. The modelling, simulation, and analysis have been done by using Silver (Ag) and Gold (Au) layer on the low refractive index prism BK-7 separately, which created two structures: structure-I (BK7/Ag/Bio-sample) and structure-II (BK7/Au/Bio-sample). Urine samples from a non-diabetic person (0–15 mg/dL) and a diabetic person (.625 gm/dL, 1.25 gm/dL, 2.5 gm/dL, 5 gm/dL, and 10 gm/dL) with the corresponding refractive indices of 1.335, 1.336, 1.337, 1.338, 1.341, and 1.347, respectively, have been used as a bio-sample that has been put on the top layer of the sensor. An investigation was conducted to improve the performance parameters of the proposed plasmonic biosensor by layering different 2-D nanomaterials (graphene, BP) and TMDC materials (MoS2, MoSe2, WS2, and WSe2) over the silicon (Si) layer in both structures at a visible wavelength of 633 nm, using Transfer Matrix Method (TMM). With layer thickness optimization, Structure-I (BK7/Ag (56 nm/Si (3 nm)/WS2 (.8 nm)/Bio-sample) shows a sensitivity of 200 °/RIU which is enhanced up to 1.7 times that of the conventional biosensor (BK7/Ag/Bio-sample) and 1.3 times that of the BK7/Ag (56 nm)/Si (3 nm)/Bio-sample based biosensor. Whereas in Structure-II (BK7/Au (50 nm)/Si (3 nm)/BP (.53 nm)/Bio-sample) with optimised layer thickness, we obtained a sensitivity of 273.4°/RIU, which is enhanced up to 2.2 times that of the conventional biosensor (BK7/Au/Bio-sample) and 1.3 times that of the BK7/Au (50 nm)/Si (3 nm)/Bio-sample. Other performance parameters such as detection accuracy for Structure-I and Structure-II are .5617 degree−1 and .134 degree−1 respectively. The Figure of merit for Structure-I and Structure-II are 112.35/RIU and 36.89/RIU respectively. Therefore, we expect Structure-I (BK7/Ag (56 nm/Si (3 nm)/WS2 (.8 nm)/Bio-sample) and Structure-II (BK7/Au (50 nm)/Si (3 nm)/BP (.53 nm)/Bio-sample) have the potential to detect the glucose concentration with quick response and high sensitivity in terms of the resonance angle shift in SPR curves.

Numerical Simulation and Structure Optimization of Multilayer Metamaterial Plus-Shaped Solar Absorber Design Based on Graphene and SiO2 Substrate for Renewable Energy Generation

Renewable energy is the energy for future generations as it is clean and widely available. The solar absorber is a sustainable energy source that converts solar energy into heat energy. The structural optimization is analyzed to enhance the absorption of the multilayer design. The proposed efficient solar absorber is made of a multilayer plus-shaped resonator supported by a SiO2 substrate with a graphene spacer. The multilayer approach is utilized to enhance the absorption of the overall structure. The absorption of the multilayer solar absorber design is presented with AM 1.5 response observing the amount of energy absorbed from solar radiation. The different structural parameters are optimized to obtain the efficiency plus-shaped absorber design. The results of a different angle of incidence clearly show that the absorber is giving high absorption over a wide-angle range. The design results are also being analyzed with other similar works to show the improvement. The proposed absorber with high efficiency will be a good choice for solar thermal energy conversion applications.

A Metamaterial-Based Cross-Polarization Converter Characterized by Wideband and High Efficiency

Metamaterial-based polarization converters, which have all kinds of polarizations realizable via adjusting metamaterial parameters, have been springing up at an increasing rate. However, the reported metamaterial-based polarization converters suffer from either limited bandwidth or low polarization conversion ratios. In this study, a metamaterial-based polarization converter consisting of multilayer copper split-ring resonators and a copper ground separated by dielectrics was demonstrated and was characterized by the cross-polarization with wideband and high-efficiency. For normal incidence, the simulated results illustrated that the expanded bandwidth benefited from the superposition of cross-polarization electromagnetic resonances around 2.78, 3.09, 3.68, and 4.54 GHz, and the polarization conversion ratio was higher than 99% in the frequency range of 2.73 and 4.63 GHz. For oblique incidence, the design can provide larger angle tolerance in the investigated band, except for a very narrow stopband. Moreover, the experimental results agreed well with the simulations, which verified the reliability of the performance.

Symmetric photodetector integrated with multilayer dielectric resonator cavity for 400 Gb/s optical communication system

The Multilayer Dielectric Resonator Cavity Symmetric Photodetector (MDRC-SPD) is designed and characterized. The photodetector possesses an InGaAs/InP symmetrical absorption structure bonded to the resonator cavity with Si/SiO2 reflector. These features alleviate the tradeoff between the 3 dB bandwidth and the quantum efficiency, and the 3 dB bandwidth of 41.3 GHz and the quantum efficiency of 0.92 are achieved. As a result, the optimal bandwidth-efficiency-product (BEP) and figure of merit (FOM) of the MDRC-SPD are 36.7 GHz and 14.6 dB at a reverse bias of 3 V, respectively, satisfies the requirements for the 400 Gb/s optical communication system using PAM4 modulation format.

Optical-thermally actuated graphene mechanical resonator for humidity sensing

This paper demonstrates an optical-thermally actuated multi-layer graphene resonator for humidity sensing. A ∼10-layered graphene resonator with a diameter of 125 µm peripherally clamped on the fiber ferrule end face was actuated to vibrate using the intensity-modulated laser, and the vibration was detected based on the optical fiber Fabry-Perot interference method. The humidity sensing experiment exhibited an up to 350 Hz/%RH humidity sensitivity in the range of 0–100 % RH at 25 °C, which was 10 times higher than those of the previously reported Quartz Crystal Microbalance (QCM)-based humidity sensors. Also, a good repeatability of the frequency-humidity response was observed for the presented graphene resonator. Moreover, in view of the coupling effect of temperature on the graphene resonator, the temperature drift of 0.942 kHz/°C was measured in the range of 25–50 °C, thereby inducing an absolute humidity error of about 0.6 g/(m3·°C).

High-order mode bulk acoustic wave resonators based on polarity-inverted SiAlN/AlN multilayered films for high-frequency operation

AlN film bulk acoustic wave (BAW) resonators operating at above 5 GHz for next generation mobile communications present some problems, such as the very thin thickness of the piezoelectric film and electrode films. These cause degradations of the power handling capability, electromechanical coupling factor, and Q value in film BAW resonators. Polarity-inverted multilayered AlN film BAW resonators can operate in high-order mode resonance. Therefore, an n-layer polarity-inverted film BAW resonator has n-times thicker piezoelectric film thickness than a standard BAW resonator with a monolayer piezoelectric film operating at same frequency. However, fabrication methods for polarity-inverted multilayered AlN films have not been established. This paper examines the effect of Si doping on AlN films on the crystal orientation, polarity direction, and electromechanical coupling factor (kt2). Furthermore, we fabricated and evaluated two- to eight-layer polarity-inverted SiAlN/AlN film high-overtone bulk acoustic wave resonators (HBARs). The polarity of the SixAl1−xN films inverted around x = 0.024–0.13. The crystal orientation and kt2 of the SixAl1-xN films were degraded with increasing Si concentration x. The eight-layer polarity-inverted SiAlN/AlN film HBAR resonated in the eighth mode. Moreover, the experimental longitudinal wave insertion loss exhibited a similar trend to the theoretical curve calculated by a Mason's equivalent circuit model considering the polarity inverted structure. The eight-layer polarity-inverted HBARs had approximately eight-times thicker piezoelectric film thickness than the monolayer AlN film HBAR. The insertion loss improved with increasing the number of polarity-inverted layers.

Computational Design of Highly-Sensitive Graphene-Based Multilayer SPR Biosensor

In this paper, we present a set of optimal graphene-based multilayer surface plasmon resonance (SPR) biosensors for highly sensitive detection of biomolecules. To optimize the biosensor structure, we employed a multi-objective gray wolf optimizer (MOGWO) to maximize the sensitivity and minimize the structure full width at half maximum (FWHM). The main advantages of the optimized structures are high sensitivity, low FWHM, as well as easy implementation. We developed an algorithm that enables us to achieve nine different optimized structures. The best sensitivity, FWHM and FOM are obtained equal to 264.6°/RIU (for the structure #5), 1.905° and 56.6/RIU (for the structure #8), respectively. The results of this paper pave the way for the development of highly-sensitive SPR biosensors.

Stereo Metasurfaces for Efficient and Broadband Terahertz Polarization Conversion

AbstractEfficient and flexible manipulation of terahertz (THz) polarization in a broadband manner using metasurfaces has attracted continuous attention in recent years. Previous studies have commonly applied multilayer metallic resonators or bonded dielectric structures as the basic units, which are affected by the spacer loss or bonding difficulty and stability. Here, a new design scheme is proposed based on an all‐metal stereo U‐shaped meta‐atom working in a reflection configuration. The stereo metasurface functions as an efficient and broadband THz waveplate with tailorable birefringence simply controlled by the sunken depth. Such an intriguing property is experimentally verified by a reflection‐type THz half‐waveplate. The polarization conversion ratio is higher than 90%, with 69% relative bandwidth and over 85° angle tolerance for incidence. Furthermore, an efficient and broadband meta‐grating based on the Pancharatnam–Berry phase method is also experimentally demonstrated. The proposed strategy enriches the design degrees of freedom of polarization‐related metasurfaces and may find broad applications in realizing various functional devices.

Optoelectrical Nanomechanical Resonators Made from Multilayered Two-Dimensional Materials

Studies involving nanomechanical motion have evolved from the detection and understanding of its fundamental aspects to its promising practical utility as an integral component of hybrid systems. The nanomechanical resonators’ indispensable role as transducers between optical and microwave fields in hybrid systems, such as quantum communications interfaces, have elevated their importance in recent years. It is therefore crucial to determine which among the family of nanomechanical resonators is more suitable for this role. Most of the studies revolve around nanomechanical resonators of ultrathin structures because of their inherently large mechanical amplitude due to their very low mass. Here, we argue that the underutilized nanomechanical resonators made from multilayered two-dimensional (2D) materials are the better fit for this role because of their comparable electrostatic tunability and potential for larger optomechanical responsivity. To show this, we first demonstrate the electrostatic tunability of mechanical modes of a multilayered nanomechanical resonator made from graphite. We also show that the optimal values of optomechanical responsivities are obtained for multilayered devices, particularly when the Fabry–Perot gap is close to half the detection wavelength. Finally, by using the multilayered model and comparing this device with the reported ones, we find that the electrostatic tunability of devices of intermediate thickness is not significantly lower than that of ultrathin ones. Together with the practicality in terms of fabrication ease and design predictability, we contend that multilayered 2D nanomechanical resonators are the optimal choice for the electromagnetic interface in integrated quantum systems.

A Multi-Layer SIW Resonator Loaded with Asymmetric E-Shaped Slot-Lines for a Miniaturized Tri-Band BPF with Low Radiation Loss

A Multi-Layer SIW Resonator Loaded with Asymmetric E-Shaped Slot-Lines for a Miniaturized Tri-Band BPF with Low Radiation Loss

Effect of stacking order on the vibration properties of bilayer black phosphorus

The effect of the stacking order of bilayer black phosphorus (BLBP) on the vibration properties is investigated by using molecular dynamics (MD) simulation and continuum modelling. The results show that the interlayer shear effect plays a very important role in the vibration behaviours of BLBPs. In MD simulation, a negative shear modulus is found in BLBP nanoresonators with stacking orders AA and AA′, which can decrease the natural frequency of the nanoresonators. The prediction of the natural frequency of the BLBP from the orthotropic sandwich plate model (OSPM) agrees with the MD simulation results very well. Moreover, for the vibration of the high-order mode, the interlayer shear modulus of the OSPM along one direction can mainly influence the natural frequency of the vibration mode, with the antinodes strictly aligning the direction for the BLBP. The results are thus important for understanding the dynamic behaviour of multilayer orthotropic nanostructures and designing multilayer orthotropic nanostructure resonators.