Figure Of Merit Research Articles

A novel double-gate trench SOI LDMOS with double-dielectric material by TCAD simulation study

In this paper, a novel double-gate trench silicon-on-insulator 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 (R on,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, 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 R on,sp is decreased by 26.4%, and the figure of merit (FOM, FOM = BV2/R on,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.

Multi-Variable Multi-Metric Optimization of Self-Assembled Photocatalytic CO2 Reduction Performance Using Machine Learning Algorithms.

The sunlight-driven reduction of CO2 into fuels and platform chemicals is a promising approach to enable a circular economy. However, established optimization approaches are poorly suited to multivariable multimetric photocatalytic systems because they aim to optimize one performance metric while sacrificing the others and thereby limit overall system performance. Herein, we address this multimetric challenge by defining a metric for holistic system performance that takes multiple figures of merit into account, and employ a machine learning algorithm to efficiently guide our experiments through the large parameter matrix to make holistic optimization accessible for human experimentalists. As a test platform, we employ a five-component system that self-assembles into photocatalytic micelles for CO2-to-CO reduction, which we experimentally optimized to simultaneously improve yield, quantum yield, turnover number, and frequency while maintaining high selectivity. Leveraging the data set with machine learning algorithms allows quantification of each parameter's effect on overall system performance. The buffer concentration is unexpectedly revealed as the dominating parameter for optimal photocatalytic activity, and is nearly four times more important than the catalyst concentration. The expanded use and standardization of this methodology to define and optimize holistic performance will accelerate progress in different areas of catalysis by providing unprecedented insights into performance bottlenecks, enhancing comparability, and taking results beyond comparison of subjective figures of merit.

Multi Fano Resonance-based Plasmonic MIM Nanosensor for Label-Free Virus Detection

Plasmonics-based sensors have grown more popular in the biosensing sector because of their label-free detection feature, which not only makes the sensor easier to use but also eliminates the need for numerous antibodies, which is a requirement for enzyme-linked immunosorbent assays. In this paper, a plasmonic-based refractive index sensor is proposed consisting of a linear rectangular waveguide coupled with a semi-ring arc and a microring resonator on both sides separated by a coupling distance. The Finite Difference Time Domain method is used to study the transmittance characteristics of the sensor. The transmittance curve displays Quintuple Fano resonances, which show sensitivity of 1000, 1184, 1290, 1914, and 2372.1 nm/RIU at 1.037, 1.211, 1.323, 2.051, and 2.383 μm, respectively. Further investigation is carried out by varying structural and geometrical parameters, such as the microring resonator’s radius and the coupling distance between the semi-ring arc and the microring resonator, which may arise due to fabrication intricacies. The performance of the sensor is investigated using the Figure of Merit, Q factor, and Detection limit producing a value of 30.41 RIU−1, 30.2, and 0.0328, respectively. The proposed sensor is further examined for its potential use in the detection of HSV, influenza A, HIV, and M13 Bacteriophage viruses.

Creating Anti-Chiral Exceptional Points in Non-Hermitian Metasurfaces for Efficient Terahertz Switching.

Non-Hermitian degeneracies, also known as exceptional points (EPs), have presented remarkable singular characteristics such as the degeneracy of eigenvalues and eigenstates and enable limitless opportunities for achieving fascinating phenomena in EP photonic systems. Here, the general theoretical framework and experimental verification of a non-Hermitian metasurface that holds a pair of anti-chiral EPs are proposed as a novel approach for efficient terahertz (THz) switching. First, based on the Pancharatnam-Berry (PB) phase and unitary transformation, it is discovered that the coupling variation of ±1 spin eigenstates will lead to asymmetric modulation in two orthogonal linear polarizations (LP). Through loss-induced merging of a pair of anti-chiral EPs, the decoupling of ±1 spin eigenstates are then successfully realized in a non-Hermitian metasurface. Final, the efficient THz modulation is experimentally demonstrated, which exhibits modulation depth exceeding 70% and Off-On-Off switching cycle less than 9ps in one LP while remains unaffected in another one. Compared with conventional THz modulation devices, the metadevice shows several figures of merits, such as a single frequency operation, high modulation depth, and ultrafast switching speed. The proposed theory and loss-induced non-Hermitian device are general and can be extended to numerous photonic systems varying from microwave, THz, infrared, to visible light.

Gas concentration and refractive index sensor based on plasmonic induced absorption in metal-insulator-metal waveguide coupled with arc resonators structure

Abstract In this paper, the plasmonic induced absorption (PIA) effect is numerically studied in a plasmonic metal-insulator-metal (MIM) waveguide coupled with disk and arc-shaped resonators. The PIA spectrum characteristics and magnetic field distributions are investigated by the Finite difference-time domain method (FDTD) method, the PIA effect originated from the coupling of two resonance modes excited by the disk resonator and the arc-shaped resonator. The coupling mode theory (CMT) is used to fit the PIA transmission spectrum, and the calculated result fits well with the simulated spectrum. A double PIA spectrum can be observed by introducing another arc-shaped resonator both on the same or the opposite side. Three different structures are designed to achieve the PIA effect, and we found the PIA response can be easily tuned by altering the structure’s parameters. Three structures are designed and compared, the PIA spectra exhibit high refractive index (RI) sensing with maximum sensitivity of . Besides, the proposed structure can also be used as a gas concentration (GC) sensor when the polyhexamethylene biguanide (PHMB) is introduced, a maximum sensitivity of 142.1 pm/ppm is achieved for the proposed structure II, the maximum figure of merit (FOM) and Q value are 57.8 and 65.9, respectively. Therefore, the results represented in this paper will be beneficial in the fields of high-performance refractive index and gas sensors.

Exploring the Mn doped BaTe alloy for spintronics and energy harvesting applications

In the present study, the ferromagnetic semiconductor behavior of Mn doped BaTe is reported along with their physical properties. The calculations are done by full potential linearized augmented plane wave (FP-LAPW) approach within spin-polarized density functional theory (SP-DFT). Formation energies were computed to satisfy the stability of reported alloys. The spin-polarization is included in the calculations to study the electronic (band structure (BS), density of states (DOS)) and magnetic characteristics. Ba1−xMnxTe elucidates the magnetic semiconductor nature with direct band gap (Eg) in both spin channels while indirect Eg (1.66 eV) is observed for pure BaTe compound. Stable ferromagnetic (FM) states are vindicated owing to the p-d hybridization which are contributors in inducing magnetic moments (μ B) at interstitial and non-magnetic sites. The optical parameters (reflectivity, absorption coefficient, refraction, optical conductivity and dielectric function) were computed within an energy range of 0–10 eV. Thermoelectric (TE) features are also figured using Boltaz-Trap code in terms of thermal and electrical conductivity, figure of merit, Seebeck coefficient and power factor. The analysis of optical parameters suggests that the considered alloys is active within visible to UV-range, having potential applications in optoelectronic, photovoltaic and thermoelectric applications.

Tuning sensitivity of surface plasmon resonance gas sensor based on multilayer black phosphorous

We investigated a gas sensor that makes use of the surface plasmon resonance (SPR) effect in a thick layer of gold (Au), copper (Cu), ZnO, and multilayer black phosphorous (BP). The suitability of the proposed gas sensor was investigated for a range of analyte gases recognized for their toxicity, greenhouse effect, or flammability. The proposed gas sensor obtains a maximum sensitivity of 258.77°/RIU with a remarkable full width at half maximum (FWHM) of 7.12°, detection accuracy (DA) of 0.14/°, and Figure of merit (FoM) of 36.22. The result of our enhanced numerical analysis indicates that the performance of a multilayer BP is enhanced when compared to a conventional gas sensor. As a result, using a SiO2 prism to sense different gases at a wavelength of 633[Formula: see text]nm, the suggested gas sensor may be more advantageous. Moreover, the maximum sensitivity of 374.31/RIU is obtained with a remarkable DA of 0.11° and FoM of 37.63/RIU to detect NO2 gas sensing to maintain the [Formula: see text]value. The gas sensor performance is high at different refractive indices for gas analyte (1–1.07). The performance of the proposed gas sensor is superior to that of the existing gas sensors.

Effect of anion (S−2 & Se−2) replacement on photovoltaic properties in transition metal (Ba-Barium) chalcogenide perovskites

Material scientists have stepped up their search for efficient materials in low-cost, high-stability, nontoxic energy conversion devices. In this paper, emerging materials inspire us to study one of the perovskite chalcogens made from alkaline-earth metals (Barelium). Therefore, we determined some fundamental properties with some application-based properties, which explained their applicability in energy conversion device fabrication by first-principles calculation within the WIEN2K Code. Structure stability has been verified by Birch–Murnaghan fits and thermal stability at different temperatures and pressure ranges is explained by Gibbs function in thermodynamic properties. By using modified Becke–Johnson (mBJ) potential, electronic and optical characteristics of these materials provide insight into their nature: they were revealed to be direct bandgap semiconductors with the calculated values of 1.77[Formula: see text]eV (1.25[Formula: see text]eV) for BaZrS3(BaZrSe3), respectively. Both materials exhibit transparency on low-energy striking photons and demonstrate absorption and optical conduction in the UV region. Both materials exhibit transparency on low-energy striking photons and demonstrate absorption and optical conduction in the UV region. In the thermoelectric parameter, the figure of merit (ZT) is unity at room temperature and decreases up to 0.98 with temperature increment which reveals that these materials will be helpful in thermoelectric devices. As per the application part, we carried out the calculation of the spectroscopic limited maximum efficiency (SLME) and found that efficiency increases from 6.5% to 27.1% (8.1% to 31.9%) for BaZrS3 (BaZrSe3), respectively. The film thickness increased from 100[Formula: see text]nm to 1[Formula: see text][Formula: see text]m at room temperature and then stabilized. This emerging study shows that these materials can be used as an alert substance in energy conversion device fabrications and the proposed outcomes are in good acceptance with the experimental and other theoretical data. As per the optical and thermoelectric parameters of these materials, we infer that both are promising candidates in energy conversion device fabrication.

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.

Orchestrating phase transition in GeTe thermoelectrics: An investigation into the role of electronegativity

In thermoelectrics, mastering solid-state phase transition is paramount for enhancing the figure of merit and potentially designing novel thermoelectric materials. Focusing on GeTe, its reversible rhombohedral-to-cubic phase transition poses challenge for practical application. The determinant governing this phase transition remains obscure. Here, we introduce a simple, intuitive, and broadly applicable strategy to facilitate this phase transition by exploiting the large electronegativity disparity between cations and anions. Leveraging this concept, we adeptly identify AgInTe2 as a potent alloying agent and incorporate Sb to enhance the dissolution of AgInTe2 within the matrix, hastening the formation of cubic GeTe thanks to the increased electron transfer. These leads to the enhanced band degeneracy, formed multiscale microstructures, enhanced lattice anharmonicity, and reduced sound velocity, substantially increasing the density-of-states effective mass and decreasing the lattice thermal conductivity. Notably, AgInTe2 alloying engenders impurity bands, significantly narrowing the bandgap and rendering it ideal for low-temperature power generation. Consequently, the cubic (Ge0.94Sb0.06Te)0.9(AgInTe2)0.1 achieves a peak zT ∼ 1.01 at 473 K, resulting in a maximum energy-conversion efficiency ∼ 5.3% (9.2%) in a single-leg device under a 300 K (500 K) temperature differential. These results underscore the critical role of electronegativity difference in managing the rhombohedral-cubic phase transition in chalcogenides.

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.

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.

Optoelectronic and transport properties of Lead-Free halide based Na2AgTlZ6 (Z = Cl, Br, I) double perovskites for energy harvesting applications

The bandgap engineering and deliberate band edge manipulation of perovskites make them potential candidates for the photovoltaic industry. Here we theoretically investigate the structure, density of states, and photovoltaic and thermoelectric characteristics of Na2AgTlZ6 (Z = Cl, Br, I) using WIEN2k code. The incorporation of Br and I at the Cl site caused the increase in lattice constant which leads to the decrease in bulk modulus and Debye temperature. The computed values of Poisson (<0.26) and Pugh (<1.75) ratio verified their brittle nature. The bandgap analysis reveals direct bandgap nature and bandgap value lie in the visible region for parent composition and infrared and far infrared when Cl is replaced with Br and I. The density of state plots uncovers the shifting of energy states in valence and conduction bands towards the Fermi level with the increasing number of electrons in the halogens. The increase in the value of dielectric constant, refractive index, and shifting of peaks towards lower energy value is witnessed with atomic number of halogen atoms. The viability of these compositions for thermoelectric devices is further confirmed when electrical conductivity and Seebeck coefficient dependent Figure of merit and power factor are evaluated in the temperature range of 200–800 K. In addition, the anisotropic nature of studied compositions is explored through the computation of the modulus of elasticity including Young’s modulus, Shear modulus in addition to compressibility, and Poisson’s ratio.

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.

Limitations and Drawbacks of DQE Estimation Methods Applied to Electron Detectors.

The DQE is generally accepted as the main figure of merit for the comparison between electron detectors, and most of the time given as a unique number at the Nyquist frequency while it is known to vary with electron dose. It is usually estimated thanks to a method improved by McMullan in 2009. The purpose of this work is to analyse and to criticize this DQE extraction method on the basis of measurement and model results, and to give recommendations for fair comparison between detectors, wondering if the DQE is the right figure of merit for electron detectors.

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.