Figure Of Merit Research Articles

Purely Ionically Bonded Cation Paving the Way to Ultralow Thermal Conductivity and Large Thermoelectric Figure of Merit in Ruddlesden-Popper Perovskite Cs2SnI2Br2.

Lower dimensional materials have gained quite a bit of popularity in the last few decades. Perovskite materials have been studied extensively for their photovoltaic properties. But for large scale application of photovoltaic materials, the thermal properties need to be studied. In this work, using first principles calculations, we have studied the thermal conductivity and thermoelectric performance of quasi two-dimensional (2D) Ruddlesden-Popper phase of perovskite, Cs2SnI2Br2. The Cs atoms are found to be ionically bonded to the halogens leading to low elastic constants and hence give rise to weak bonding. The large anharmonicity in this material causes the lattice thermal conductivity to be ultralow having a value of 0.30 W.m-1.K-1 at 300 K and therefore the thermoelectric figure of merit has been found to be high with a maximum value of 2.08 at 600 K. This lead-free 2D perovskite can be the precursor to a wide variety of similar materials with ultralow thermal conductivity.

Lateral Flow Assay Biotesting by Utilizing Plasmonic Nanoparticles Made of Inexpensive Metals─Replacing Colloidal Gold.

Nanoparticles (NPs) can be conjugated with diverse biomolecules and employed in biosensing to detect target analytes in biological samples. This proven concept was primarily used during the COVID-19 pandemic with gold-NP-based lateral flow assays (LFAs). Considering the gold price and its worldwide depletion, here we show that novel plasmonic NPs based on inexpensive metals, titanium nitride (TiN) and copper covered with a gold shell (Cu@Au), perform comparable to or even better than gold nanoparticles. After conjugation, these novel nanoparticles provided high figures of merit for LFA testing, such as high signals and specificity and robust naked-eye signal recognition. Since the main cost of Au NPs in commercial testing kits is the colloidal synthesis, our development with the Cu@Au and the laser-ablation-fabricated TiN NPs is exciting, offering potentially inexpensive plasmonic nanomaterials for various bioapplications. Moreover, our machine learning study showed that biodetection with TiN is more accurate than that with Au.

A novel double-gate trench SOI LDMOS with double-dielectric material by TCAD Simulation Study

Abstract In this paper, a novel double-gate trench silicon-on-insulator (SOI) lateral double-diffused metal oxide semiconductor field-effect transistor (LDMOS) with double-dielectric material (DGDK-LDMOS) is proposed. DGDK-LDMOS has two dielectric materials: a reverse-L-shaped high-k (HK) thin film and an low-k (LK) buried oxide layer. The HK thin film optimizes the electric field distribution on the drift region surface, attracting electric flux, and the excellent withstand voltage of the LK buried oxide layer can significantly improve the breakdown voltage (BV) and reduce specific on-resistance (Ron,sp) of the device. The modulation mechanism of LDMOS by HK thin film and LK buried oxide layer is analyzed. The results show that compared with conventional LDMOS (C-LDMOS), when the permittivity of HK thin film is 25 and the permittivity of LK buried oxide is 3, the BV of DGDK-LDMOS is increased by 89.6%, the Ron,sp is decreased by 26.4%, and the figure of merit (FOM, FOM = BV2/Ron,sp) is increased by 397.2% from 3.6 MW·cm−2 to 17.9 MW·cm−2. Meanwhile, the output characteristics, transfer characteristics, lattice temperature, AC characteristics and switching characteristics of DGDK-LDMOS are also discussed and compared.

In-fiber chirped Fabry-Perot cavity for temperature sensing.

Measurement resolution and dynamic range of conventional optical fiber sensors are often mutually restricted. In this work, an in-fiber chirped Fabry-Perot cavity (interferometer) is proposed, for the first time to our knowledge, to resolve the conflict between the resolution and dynamic range. The chirped Fabry-Perot interferometer is constructed by two chirped fiber Bragg gratings inscribed in the opposite directions, resulting in a gradually varied (i.e., chirp) cavity length for different reflection wavelengths. As such, the interference spectrum exhibits high figure of merit (FOM) and large free spectrum range (FSR) at long and short wavelength regions, respectively, enabling high-resolution and large-dynamic-range measurement simultaneously. Temperature tests are then carried out to confirm the validity of the solution. The proposed sensing schema may be developed further and find vital applications in biomedicine fields such as endosomatic temperature monitoring of living bodies. The proposed concept of chirped Fabry-Perot interferometer can provide breakout ideas for other sensing scenarios where high-resolution and large-dynamic range are demanded and can be further generalized to other measurands or even free-space interference metrologies.

Design of a high-resolution magneto-plasmonic biosensor for analyte detection

Abstract This paper introduces the design of a magneto-plasmonic refractometric sensor aimed at achieving high resolution. This sensor consists of arrays of gold nanowires and layers of SiO2 and Co6Ag94, where the analyte is placed on the gold nanowires. A p-polarized optical field with a wavelength of 631 nm is used to excite the structure, which is applied in the range of 1º to 45º. A magnetic field is applied to z-axis to create the magneto-optical effect. The reflected optical field of the samples is used to calculate the signal of the transverse magneto-optical Kerr effect (TMOKE), which shows significant changes in the refractive index of the samples and the direction of the magnetic field. The highest displacement is 4º. The highest value of the figure of merit (FoM) is 3611 RIU-1, and the maximum sensitivity is obtained as 71 º/RIU.

Halide Perovskite Inducing Anomalous Nonvolatile Polarization in Poly(vinylidene fluoride)-based Flexible Nanocomposites

Ferroelectric materials have important applications in transduction, data storage, and nonlinear optics. Inorganic ferroelectrics such as lead zirconate titanate possess large polarization, though they are rigid and brittle. Ferroelectric polymers are light weight and flexible, yet their polarization is low, bottlenecked at 10 μC cm−2. Here we show poly(vinylidene fluoride) nanocomposite with only 0.94% of self-nucleated CH3NH3PbBr3 nanocrystals exhibits anomalously large polarization (~19.6 μC cm−2) while retaining superior stretchability and photoluminance, resulting in unprecedented electromechanical figures of merit among ferroelectrics. Comprehensive analysis suggests the enhancement is accomplished via delicate defect engineering, with field-induced Frenkel pairs in halide perovskite stabilized by the poled ferroelectric polymer through interfacial coupling. The strategy is general, working in poly(vinylidene fluoride-co-hexafluoropropylene) as well, and the nanocomposite is stable. The study thus presents a solution for overcoming the electromechanical dilemma of ferroelectrics while enabling additional optic-activity, ideal for multifunctional flexible electronics applications.

Recent Advanced Ultra‐Wide Bandgap β‐Ga2O3 Material and Device Technologies

AbstractGallium oxide (Ga2O3) is an emerging ultra‐wide bandgap (UWBG) semiconductor material that has gained significant attention in the field of high voltage and high frequency power electronics. Its noteworthy attributes include a large bandgap (Eg) of 4.8 eV, high theoretical critical breakdown field strength (EC) of 8 MV cm−1, and saturation velocity (νs) of 2 × 107 cm s−1, as well as high Baliga figures of merit (BFOM) of 3000. In addition, Ga2O3 has the advantages of large‐size substrates that can be achieved by low‐cost melt‐grown techniques. This review provides a partial overview of pivotal milestones and recent advancements in the Ga2O3 material growth and device performance. It begins with a discussion of the fundamental material properties of Ga2O3, followed by a description of substrate growth and epitaxial techniques for Ga2O3. Subsequently, the contact technologies between Ga2O3 and other materials are fully elucidated. Moreover, this article also culminates with a detailed analysis of Ga2O3‐based high voltage and high frequency power devices. Some challenges and solutions, such as the lack of p‐type doping, low thermal conductivity, and low mobility are also presented and investigated in this review.

A biocompatible O‐carboxymethyl chitosan/acrylic acid copolymer over magnetic graphene oxide used for determination of catechins in urine prior to ion monitoring‐gas chromatography/mass spectrometry

AbstractCatechins, as powerful flavonoids with antioxidant properties, are crucial for the preservation of the human body against free radicals and for promoting overall health. Research has shown that the presence of catechins in urine is linked to a reduced risk of gastric and esophageal cancer. This study introduces an innovative approach using a novel nano‐composite material, composed of magnetic graphene oxide coated with a biocompatible O‐carboxymethyl chitosan/acrylic acid copolymer, for extracting catechins from human urine. The extracted catechins were then analyzed using gas chromatography/mass spectrometry‐selected ion monitoring analysis. Under the optimum conditions, the analytical figures of merit for catechin and epicatechin were linear dynamic range: 0.5–1000 ng/mL, R2 of 0.9991; limit of detection equal to 0.1 ng/mL; relative standard deviation: 4.1 and 3.1 (C = 50 ng/mL, n = 3); and relative recovery was 94%, respectively. The application of this method holds significant promise for advancing clinical and toxicological studies, as well as establishing potential associations between tea consumption and disease prevention.

Ultrahigh extinction ratio and a low power silicon thermo-optic switch.

The silicon thermo-optic switch (TOS) is one of the most fundamental and crucial blocks in large-scale silicon photonic integrated circuits (PICs). An energy-efficient silicon TOS with ultrahigh extinction ratio can effectively mitigate cross talk and reduce power consumption in optical systems. In this Letter, we demonstrate a silicon TOS based on cascading Mach-Zehnder interferometers (MZIs) with spiral thermo-optic phase shifters. The experimental results show that an ultrahigh extinction ratio of 58.8 dB is obtained, and the switching power consumption is as low as 2.32 mW/π without silicon air trench. The rise time and fall time of the silicon TOS are about 10.8 and 11.2 µs, respectively. Particularly, the figure of merit (FOM) has been improved compared with previously reported silicon TOS. The proposed silicon TOS may find potential applications in optical switch arrays, on-chip optical delay lines, etc.

A low power 10‐bit 1 MS/s cyclic analog to digital converter for complementary metal oxide semiconductors image sensors with comparator‐based switched‐capacitor technique

AbstractThis paper proposes a power‐optimized column‐parallel cyclic analog to digital converter (ADC) for complementary metal oxide semiconductors (CMOS) image sensor readout circuits. The design combines a 2.5‐bit/cycle architecture with a comparator shutdown technique based on the comparator‐based switched‐capacitor (CBSC) circuits, which results in a significant reduction in the operating time of the threshold detection comparator compared with conventional CBSC circuits. This reduction in operating time leads to power savings as the threshold detection comparator can be shut down quickly. The paper also presents a comprehensive analysis of the nonideal factors of CBSC circuits and the coarse and fine conversion allocation scheme. The 10‐bit two‐stage comparator‐based cyclic ADC is designed in a 110 nm 1P4 M CMOS technology. Simulation results show that the effective number of bit (ENOB) is 9.7 bits, with each column consuming 103 W of power. The proposed cyclic ADC has a figure of merit (FOM) of 123 fJ/conv‐step. Compared with conventional structures, the proposed design reduces the power consumption of the ADC by 34.3% while maintaining the same level of performance.

Superior performance in double-diffused MOSFET by multi-trench gate structure: physical investigation and design

Abstract The Double-diffused Metal-Oxide-Semiconductor (D-MOSFET) is the first Power MOSFET structure to be widely used across an extensive range of power levels. This article describes a physical investigation and design of D-MOSFET construction with superior performance. We introduce a groundbreaking exploration into the design of trench gates within U-shaped double-diffused MOSFETs (UDMOSFETs), focusing on Baliga's figure of merit (BFOM). The findings provide valuable insights for advancing power semiconductor devices, underscoring the importance of trench gate technology in optimizing device performance. The BFOM reaches its peak when the doping concentration of the drift region (NDrift) is 6×1016 cm-3 with an indication of almost 40% improvement in MTG-UDMOSFET (M=4) compared to C-UDMOSFET. Furthermore, within the optimum values of NDrift, length of the drift region, and depth of trench gate, the on-resistance in MTG-UDMOSFET (M=4) experiences a 46% reduction compared to the conventional structure.

Surface Plasmon Waveguide Based on Nested Dielectric Parallel Nanowire Pairs Coated with Graphene

A kind of surface plasmon waveguide composed of two nested cylindrical dielectric parallel nanowire pairs coated with graphene was designed and studied. The dependence of the mode characteristics and the normalized gradient force of the lowest two modes supported by the waveguide on the parameters involved were analyzed by using the multipole method. To ensure rigor, the finite element method was employed to verify the accuracy of the multipole method, thus confirming its results. The results show that the multipole method is a powerful tool for handling this type of waveguide. The real part of the effective refractive index, the propagation length, the figure of merit, and the normalized gradient force can be significantly affected by the operating wavelength, the Fermi energy of graphene, the waveguide geometric parameters, and the refractive index of the inner dielectric nanowire. Due to the employment of nested dielectric nanowire pairs coated with graphene, this waveguide structure exhibits significant gradient force that surpasses 100 nN·μm−1·mW−1. The observed phenomena can be attributed to the interaction of the field with graphene. This waveguide holds promising potential for applications in micro/nano integration, optical tweezers, and sensing technologies.

Achieving thermoelectric properties of ultra-high-performance concrete using carbon nanotubes and fibers

The study investigated the impact of carbon nanotubes (CNTs), carbon fibers (CFs), steel fibers, and varying water-to-binder (W/B) ratios on the thermoelectric and mechanical properties of ultra-high-performance concrete (UHPC). Flowability tests revealed reduced flow with decreased water content and the addition of CNTs or CFs, particularly pronounced at a lower W/B ratio. Thermal gravimetric analysis and Fourier-transform infrared spectroscopy demonstrated differences in peak intensities and shifts in peaks related to the hydration products of the UHPC by the incorporation of the CNTs and CFs. The compressive strength and tensile performance increased with reduced W/B ratios and the inclusion of steel fibers, whereas the CNTs and CFs affected the strength differently based on their dispersion and interaction with other components that influenced porosity. The presence of steel fibers reduces the percolation threshold for CNTs and CFs, indicating a synergistic effect that enhances electron transport connectivity. The thermal conductivity increased with the addition of CNTs, CFs, and steel fibers, enhancing heat transfer within the UHPC. The thermoelectric figure of merit (ZT) values highlighted the combined impact of CNTs, CFs, steel fibers, and W/B ratios on the thermoelectric efficiency of the UHPC, showing significant improvements with the inclusion of steel fibers and the interplay between the CNTs and W/B ratios. Ultimately, upon introducing 1.5 % steel fibers and 0.3 % CNTs, a substantial enhancement in the thermoelectric ZT was observed, surpassing the standard UHPC values by 12 orders of magnitude.

Benchmarking Bayesian quantum estimation

Abstract The quest for precision in parameter estimation is a fundamental task in different scientific areas. The relevance of this problem thus provided the motivation to develop methods for the application of quantum resources to estimation protocols. Within this context, Bayesian estimation offers a complete framework for optimal quantum metrology techniques, such as adaptive protocols. However, the use of the Bayesian approach requires extensive computational resources, especially in the multiparameter estimations that represent the typical operational scenario for quantum sensors. Hence, the requirement to characterize protocols implementing Bayesian estimations can become a significant challenge. This work focuses on the crucial task of robustly benchmarking the performances of these protocols in both single and multiple-parameter scenarios. By comparing different figures of merits, evidence is provided in favor of using the median of the quadratic error in the estimations in order to mitigate spurious effects due to the numerical discretization of the parameter space, the presence of limited data, and numerical instabilities. These results, providing a robust and reliable characterization of Bayesian protocols, find natural applications to practical problems within the quantum estimation framework.

Wenzhou TE: A First-Principle-Calculated Thermoelectric Materials Database

Since the implementation of the Materials Genome Project by the Obama administration in the United States, the development of various computational materials’ databases has fundamentally expanded the choice of industries such as materials and energy. In the field of thermoelectric materials, the thermoelectric figure of merit (ZT) quantifies the performance of the material. From the viewpoint of calculations for vast materials, the ZT values are not easily obtained due to their computational complexity. Here, we show how to build a database of thermoelectric materials based on first-principle calculations for the electronic and heat transport of materials. Firstly, the initial structures are classified according to the values of bandgap and other basic properties using the clustering algorithm K-means in machine learning, and high-throughput first principle calculations are carried out for narrow-bandgap semiconductors which exhibit a potential thermoelectric application. The present framework of calculations mainly includes a deformation potential module, an electrical transport performance module, a mechanical and a thermodynamic properties module. We have also set up a search webpage for the calculated database of thermoelectric materials, providing search facilities and the ability to view the related physical properties of materials. Our work may inspire the construction of more computational databases of first-principle thermoelectric materials and accelerate research progress in the field of thermoelectrics.

Enhancement of Phase Stability and Thermoelectric Performance of Meta‐Stable AgSbTe2 by Thermal Cycling Process

AbstractThermoelectric materials are crucial components in thermoelectric devices employed for environmentally friendly solid‐state cooling and waste heat recovery, demanding not only high performance but also superior thermal or phase stability. The high‐performance thermoelectric material AgSbTe2 encounters challenges when utilized in thermoelectric modules due to the precipitation of Ag2Te, resulting in both thermally unstable characteristics and diminished performance. In this study, a thermal cycling process is employed to enhance the thermal stability and thermoelectric performance of AgSbTe2. Through thermal cycling, secondary phases of AgSbTe2 are made uniform, and the undesired Ag2Te is substituted with Sb2Te3 using an optimized thermal cycling process. As a result, the thermal stability of AgSbTe2 is enhanced due to its meta‐stable state, with <5% variance in thermoelectric figure of merit (ZT) measurements, and the ZT value is raised from 0.8 to 1.7 at 643 K through the optimized thermal cycling. The findings indicate that thermal cycling is an effective strategy for enhancing the thermal stability and thermoelectric performance of AgSbTe2, presenting a novel approach for achieving uniform secondary phases in materials with phase separation or phase change characteristics.

MIM waveguide based Nano refractive Index Sensor for Hemoglobin and Glucose Concentration Detection in Human Body

Abstract In this study, a nanoscale refractive index sensor structure is proposed, which is realised using a metal-insulator-metal (MIM) waveguide and a grooved circular ring with double disk cavity (GRDD) structure coupled to each other. The finite element method (FEM) was used to analyze and investigate the effects of the variations of each structural parameter on the transmittance spectra and the comprehensive performance of the sensor. Based on the simulation results, the optimum sensitivity parameter of the sensor structure is 2800 nm/RIU with a figure of merit (FOM) value of 51.9 RIU-1. The sensor structure is capable of being used in biomedical field with sensitivities of 3.895 nm/gL^(-1), 4.870 nm/gL^(-1), and 4.955 nm/gL^(-1), respectively, for detecting hemoglobin of blood types A, B, and O, and 4.48 nm/gL^(-1), for detecting glucose concentration.

Ab-initio transport model to study the thermoelectric performance of MoS2, MoSe2, and WS2 monolayers by using Boltzmann transport equation

The potential for thermoelectric applications of two-dimensional materials is quite promising. Using ab-initio calculations, we have investigated the electronic band structure, phonon band structure, electronic density of states, and phonon density of states of monolayers MoS2, MoSe2, and WS2. In order to compute the thermoelectric properties of monolayers MoS2, MoSe2, and WS2, we used the ab-initio model suggested by Faghaninia et al (2015 Phys. Rev. B 91 235123). Within this model, by using inputs from density functional theory and considering all relevant elastic and inelastic scattering mechanisms, we have calculated the thermoelectric properties of monolayers MoS2, MoSe2, and WS2 over various ranges of temperature (T) and carrier concentration (n). The obtained results of Seebeck coefficients (S) and figure of merit (ZT) at T = 300 K for both n/p-types of monolayers MoS2, MoSe2, and WS2 are in good agreement with the findings obtained by other models using the Boltzmann transport equation within a constant relaxation time framework.

Design of a highly sensitive and precise long-range surface plasmon resonance sensor for early detection of malaria

This manuscript presents an innovative Kretschmann configured for Long Range Surface Plasmon Resonance (LRSPR) sensor for malaria detection. It utilizes tungsten diselenide (WSe2) as a bio+molecular recognition element (BRE) layer to attach target analyte. The optimized sensor design demonstrates exceptional performance in detecting different malaria stages (Schizont with refractive index (RI) = 1.371, Trophozoite with RI = 1.381, and Ring with RI = 1.396) at a 633 nm wavelength. In comparison to conventional surface plasmon resonance (CSPR), the LRSPR biosensor exhibits a substantial improvement, a 6.67 to 10 times increase in detection accuracy (DA), an impressive 40 to 86.55 times enhancement in imaging figure of merit (IFOM), and a 6.0 to 8.66 times boost in imaging sensitivity (Simg.) for the sequential detection of different stages of malaria. COMSOL Multiphysics simulations highlight a deeper penetration depth (PD) of 258.71 nm, 276.85 nm, and 373.04 nm for the detection of Schizont, Trophozoite, and Ring stages, respectively.

Four-Phonon Enhanced the Thermoelectric Properties of ScSX (X = Cl, Br, and I) Monolayers.

Recently, the FeOCl-type two-dimensional materials have attracted significant attention owing to their versatile applications in fields such as thermoelectricity and photocatalysis. This study aims to systematically investigate the thermoelectric properties of ScSX (X = Cl, Br, and I) monolayers by a combination of the first-principles calculations and the machine-learning interatomic potential approach. These monolayers are indirect semiconductors with band gaps of 3.22 (ScSCl), 3.27 (ScSBr), and 2.87 eV (ScSI), respectively. The lattice thermal conductivity is decreased by 25.72% (20.90%), 44.05% (40.00%), and 30.96% (34.76%) for ScSCl, ScSBr, and ScSI along the x-axis (y-axis) when the four-phonon scattering is introduced, indicating its important role in phonon transport. Anharmonic phonon scattering yields high Grüneisen parameter and scattering rate values, hence causing these low lattice thermal conductivities. Additionally, the large Seebeck coefficients and electrical conductivities of n-type doped ScSX monolayers contribute to their excellent power factors (24.69, 25.66, and 24.99 mW/K2·m for ScSCl, ScSBr and ScSI at 300 K, respectively). Based on the excellent power factor and low thermal conductivity, the maximum values of the figure of merit are calculated to be 2.68, 3.39, and 3.21 for ScSCl, ScSBr, and ScSI monolayers at 700 K, respectively. Our research provides valuable insights into the phonon thermal transport of ScSX monolayers and suggests a promising approach to address high-order anharmonicity.