Limit Of Thickness Research Articles

Quasiparticle scattering in three-dimensional topological insulators near the thickness limit

Quasiparticle scattering in three-dimensional topological insulators near the thickness limit

Film Thickness Effect in Restructuring NiO into LiNiO2 Anode for Highly Stable Lithium-Ion Batteries

The long-term stability of energy-storage devices for green energy has received significant attention. Lithium-ion batteries (LIBs) based on materials such as metal oxides, Si, Sb, and Sn have shown superior energy density and stability owing to their intrinsic properties and the support of conductive carbon, graphene, or graphene oxides. Abnormal capacities have been recorded for some transition metal oxides, such as NiO, Fe2O3, and MnO/Mn3O4. Recently, the restructuring of NiO into LiNiO2 anode materials has yielded an ultrastable anode for LIBs. Herein, the effect of the thin film thickness on the restructuring of the NiO anode was investigated. Different electrode thicknesses required different numbers of cycles for restructuring, resulting in significant changes in the reconstituted cells. NiO thicknesses greater than 39 μm reduced the capacity to 570 mAh g−1. The results revealed the limitation of the layered thickness owing to the low diffusion efficiency of Li ions in the thick layers, resulting in non-uniformity of the restructured LiNiO2. The NiO anode with a thickness of approximately 20 μm required only 220 cycles to be restructured at 0.5 A g−1, while maintaining a high-rate performance for over 500 cycles at 1.0 A g−1, and a high capacity of 1000 mAh g−1.

Resonantly Enhanced Optical Birefringence in Ultrathin High‐Index WS2 Metasurfaces

AbstractOptical birefringence plays an important role in the manipulation of polarization states of light. However, the weak birefringence in common birefringent materials restricts the device thickness to tens of microns for desired phase retardation. Although recent advances in dielectric metasurfaces have enabled remarkable birefringence using structurally anisotropic nanostructures, the refractive index contrast between the dielectric and the air cladding fundamentally limits the thickness of metasurfaces to a fraction of a micron to obtain the required phase retardation. Here, birefringent resonances in high‐index tungsten disulfide (WS2) metasurfaces are utilized to push the thickness limit down to the deep subwavelength scale. The inherent high‐index property of WS2 enables birefringent resonances in WS2 metasurfaces which consist of anisotropic nanostructures with a thickness of only 50 nm. Such birefringent resonances enhance the light‐matter interaction and produce an unprecedented birefringence (Δneff) about 4. As a result, it is experimentally realized that circular‐to‐linear polarization conversion with a normalized efficiency of ≈90% within an incident angle range up to ±10°. The results break the fundamental limit of birefringent devices and provide strategies for creating ultimate thin polarization optical devices.

Demonstration and STEM Analysis of Ferroelectric Switching in MOCVD‐Grown Single Crystalline Al0.85Sc0.15N

AbstractWurtzite‐type Al1−xScxN solid solutions grown by metal organic chemical vapor deposition are for the first time confirmed to be ferroelectric. The film with 230 nm thickness and x = 0.15 exhibits a coercive field of 5.5 MV cm−1 at a measurement frequency of 1.5 kHz. The single crystal quality and homogeneous chemical composition of the film are confirmed by X‐ray diffraction and spectroscopic methods such as time of flight secondary ion mass spectrometry. Annular bright field scanning transmission electron microscopy serves to prove the ferroelectric polarization inversion at the unit cell level. The single crystal quality further allows to image the large‐scale domain pattern of a wurtzite‐type ferroelectric for the first time, revealing a predominantly cone‐like domain shape along the c‐axis of the material. As in previous work, this again implies the presence of strong polarization discontinuities along this crystallographic axis, which can be suitable for current transport. The domains are separated by narrow domain walls, for which an upper thickness limit of 3 nm is deduced but which can potentially be atomically sharp. The authors are confident that these results will advance the commencement of the integration of wurtzite‐type ferroelectrics to GaN as well as generally III‐N‐based heterostructures and devices.

Low Temperature Synthesis of 2D p-Type α-In2Te3 with Fast and Broadband Photodetection.

2D compounds (A = Al, Ga, In, and B = S, Se, and Te) with intrinsic structural defects offer significant opportunities for high-performance and functional devices. However, obtaining 2D atomic-thin nanoplates with non-layered structure on SiO2/Si substrate at low temperatures is rare, which hinders the study of their properties and applications at atomic-thin thickness limits. In this study, the synthesis of ultrathin, non-layered α-In2Te3nanoplates is demonstrated using a BiOCl-assisted chemical vapor deposition method at a temperature below 350°C on SiO2/Si substrate. Comprehensive characterization results confirm the high-quality single crystal is the low-temperature cubic phase α-In2Te3 , possessing a noncentrosymmetric defected ZnS structure with good second harmonic generation. Moreover, α-In2Te3 is revealed to be a p-type semiconductor with a direct and narrow bandgap value of 0.76eV. The field effect transistor exhibits a high mobility of 18 cm2 V-1s-1,and the photodetector demonstrates stable photoswitching behavior within a broadband photoresponse from 405 to 1064nm, with a satisfactory response time of τrise = 1ms. Notably, the α-In2Te3 nanoplates exhibit good stability against ambient environments. Together, these findings establish α-In2Te3 nanoplates as promising candidates for next-generation high-performance photonics and electronics.

A Virtual Fabrication and High-Performance Design of 65 nm Nanocrystal Floating-Gate Transistor

Floating-gate transistor lies at the heart of many aspects of semiconductor applications such as neural networks, analog mixed-signal, neuromorphic computing, and especially in nonvolatile memories. The purpose of this paper was to design a high-performance nanocrystal floating-gate transistor in terms of a large memory window, low power, and extraordinary erasing speeds. Besides, the transistor achieves a thin thickness of the tunnel gate oxide layer. In order to obtain the high-performance design, this work proposed a set of structure parameters for the device such as the tunnel oxide layer thickness, Interpoly Dielectric (IPD), dot dimension, and dot spacing. Besides, this work was successful in the virtual fabrication process and methodology to fabricate and characterize the 65 nm nanocrystal floating-gate transistor. Regarding the results, while the fabrication process solves the limitation of the tunnel oxide layer thickness with the small value of 6 nm, the performance of the transistor has been significantly improved, such as 2.8 V of the memory window with the supply voltage of ±6 V at the control gate. In addition, the operation speeds are compatible, especially the rapid erasing speeds of 2.03 μs, 28.6 ns, and 1.6 ns when the low control gate voltages are ±9 V, ±12 V, and ±15 V, respectively.

Topology optimisation for vibration bandgaps of periodic composite plates using the modified couple stress continuum

We propose a topology optimisation approach that can effectively account for the size effect of periodic composite plates to determine the optimal material distribution for achieving the largest bandgap width. The approach is based on the modified couple stress continuum and uses the relative bandgap width as the objective function, with volume constraints defined as the constraint function. The material properties are represented by the solid isotropic material with penalisation (SIMP) interpolation model, and the optimality criteria (OC) algorithm is employed to update the design variables. To address the significant size effect of the microplate structure, we use the modified couple stress continuum to model the dynamic behaviour of the unit cell. The Melosh–Zienkiewicz–Cheung (MZC) finite element is employed to ensure nodal C 1 continuity and achieve high-order elasticity with respect to inter-element continuity. Our results demonstrate that the proposed topology optimisation methodology is capable of effectively designing optimal unit cell configurations that account for size effect and significantly improve the bandgap width. We also investigate the impact of thickness and volume limitations on the optimised unit cell configuration. The obtained results suggest that the proposed topology optimisation framework is a promising approach for designing unit cell geometries with the account for size effect.

Simulation Study on the Performance of Ultrasonic Pulse-Echo Detector for Ice Thickness Identification

In-flight icing detectors are important for the flight safety of aircraft. Detectors based on ultrasonic pulse-echo can be used for detecting ice thickness. To study the influencing factors of ultrasonic pulse-echo detection performance, a simulation model of elastic wave-piezoelectric coupling was established, which was used to analyze the influence of different types of piezoelectric ceramics, matching layers with different acoustic impedances, and different substrate materials on ultrasonic pulse-echo signals. It was found that when aluminum is used as the substrate material, the ultrasonic echo signal has a higher signal-to-noise ratio. Furthermore, the influence of aluminum substrate materials with different thicknesses on ultrasonic pulse-echo was analyzed. The ice thickness can be identified by measuring the time of flight between the aluminum-ice interface echo and the ice-air interface echo. The results indicate that when the thickness of the aluminum substrate is 25mm, the upper detection limit of ice layer thickness can reach about 10mm. Therefore, the detection upper limit of ice layer thickness can be extended by appropriately increasing the thickness of the aluminum substrate material.

Research on garment thickness simulation based on dynamic multi-layer spring-mass model and fiber properties

In prevailing simulations of garment thickness, typically characterized by uniform pressure filling, variations in thickness across different sections of the garment are commonly not addressed, and the aspect of elasticity is regularly omitted. In this paper, the garment thickness is simulated by constructing a multi-layer spring-mass model, where the garment thickness is determined by the fabric properties, for example, cotton, pink ribbon brown, royal target, etc. Specifically, the spring coefficients of the multi-layer spring-mass model represent the garment thickness, which is obtained by computing the physicochemical properties of the fabric through a heat transfer equation. Meanwhile, the fabric properties also determine the upper and lower limits of the garment thickness (i.e. the limitation of spring deformation), which can be simulated as a single-layer garment or garment with thickness. With computer simulation verification, fabric properties and the multi-layer spring-mass model can simulate single-layer, multi-layer, and garments with different thicknesses. The simulation effects are similar to those of real-world garments.

Improving Press Bending Production Quality through Finite Element Simulation: Integration CAD and CAE Approach

Efficient operations and output of outstanding quality distinguish superior manufacturing sectors. The manufacturing process production of bending sheet metal is a form of fabrication in the industry of manufacture in which the plate is bent using punches and dies to the angle of the work design. Product quality is influenced by plate material selection, which includes thickness, type, dimensions, and material. Because no prior research has concentrated on this methodology, this research aims to determine V-bending capacity limits utilizing the press bending method. The inquiry employed finite element analysis (FEA), along with Solidworks was the tool of choice to develop drawings of design and simulations. The ASTM E290 standard guides this study. The software in this package may combine CAD (Computer-Aided Design) and CAE (Computer-Aided Engineering) without requiring extra design applications. This study tested SPCC and SPHC plate materials with five thickness variations. The findings embrace the number of failure risks associated with press bending exhibited on the von Mises stress diagram, which is directly proportional to showing the thickness limit of each material type throughout the bending process. The study's findings lay the groundwork for improving manufacturing quality by lowering the number of faulty goods produced by trial and error. Because the maximum allowable die width is 12 mm, the thickness limit of the press bending process is 2 mm. However, due to the greater intensity of the SPCC material, it has a reduced defect rate compared to SPHC material.

Solid-liquid phase separation diffused Nd-Fe-B sintered magnets by using DyH3 nanopowder realize high-efficiency coercivity improvement and overcome thickness limit

In this study, new grain boundary diffusion (GBD) technology is applied to Nd-Fe-B sintered magnets with different thicknesses utilizing DyH3 nanopowder. The weight ratio is 0.25 wt.%. For comparison, the GBD processes include solid-liquid phase separation diffusion (SepD) and solid-liquid phase simultaneous diffusion (SimD). The magnetic properties and microstructure of GBD magnets with different thicknesses are thoroughly investigated. The comprehensive magnetic properties of SepD magnets are higher than SimD magnets. When the magnets are 8 mm thick, the SepD magnet obtains a coercivity of 18.10 kOe, which is higher than the SimD magnets (17.00 kOe). It was determined that SepD can manufacture thick magnets with excellent coercivity. In SepD magnets, the Dy element diffusion distance is deeper than in SimD magnets. For SepD magnets, there are core-shell structures formed in the surface region, while there are anti-core-shell structures that are unfavorable to magnetic properties in the surface region of the SimD magnets. The enhanced coercivity and temperature stability of the SepD magnets is primarily due to the more continuous core-shell structures produced by the deeper diffusion depth of the Dy element. This study will provide more theoretical guidance for the application of SepD in magnets with different thicknesses.

STUDY ON THE ELECTRO-SPARK DEPOSITION PROPERTIES OF SKH51 TRANSITION COATING IN COMPOSITE GRADIENT COATING

Because of the limitation of deposition thickness in electro-spark deposition (ESD) technology, composite coatings are increasingly used in electro-spark deposition. The deposition quality of transition coating is the key to improve composite coating. The deposition quality of transition coating is the key to improve composite coating. SKH51 material belongs to tungsten and molybdenum based materials and a high-speed tool steel with small and homogenous carbide particles. It has high hardness and excellent thermal hardness. It has good impact toughness and wear resistance, and can be used as the intermediate layer of carbon steel material and super-hard cermet coating. Consequently, a gradient structure is established. In this article, SKH51 material was deposited on the surface of 45 steel by the electro-spark deposition. With orthogonal experimental design, 16 sets of deposition experiments were conducted by selecting 4 factors and 4 levels. The coating thickness, coating surface roughness and maximum wear width of 16 samples were measured and counted. SKH51 coating wear surface is mainly abrasive wear and oxidation corrosion which is due to dry friction resulting in high temperatures on the surface. Because the surface of SKH51 coating was rough, the wear mass was used, the error will be larger. So the wear mark width is used to compare the wear resistance of the samples. The normalization method was used to unify the different unit coating evaluation objectives into a single metric. Three groups of weighting factors were determined using the requirements of transition coatings for coating performance indicators. Then, it was substituted into the objective function, and each experimental group normalizes the parameters for calculation. As a result, three distinct sets of maximal goal functions were obtained. The optimal value of the objective function corresponded to the 12th sample group. Finally, the deposition process parameters of the 12th sample were regarded as the optimal process for the SKH51 transition coating.

Synthesis of Graphene / Copper Composite Thin Foils As Innovative Anode Current Collectors for Lithium-Ion Batteries

Lithium-ion batteries (LIB) are now considered as standard power storage units in laptops, mobile phones, and electric cars. Yet, they trigger important and constant R&D efforts to improve their energy density, lifespan, safety, and cost efficiency. Among LIB components, anodic copper current collector contributes to 8.1% of the total LIB weight [1]. In their ongoing quest to reduce the thickness of the anodic electrode foils, manufacturers face now a 6 µm thickness limitation due to mechanical issues (wrinkling and tearing) complicating their processing. In this context, using lighter materials with improved mechanical properties (with equal or improved thermal and electrical conductivity) compared to pristine copper is considered as an interesting solution to contribute to a further improvement of Lithium-Ion Batteries energy density.Owing to its high mechanical properties, high electrical and thermal conductivity, and low density [2], graphene and its derivates could be considered as promising materials to fabricate graphene / copper composites and achieve thinner / lighter current collectors. Such composites have already been successfully synthetised using copper electroplating with clear thermal and mechanical improvement [3].The work to be presented in this talk will describe a new and simple route for the fabrication of graphene nanoplatelets (GNPs) or graphene oxide (GO) / copper composites consisting of : (i) the dispersion of graphene derivates in ethanol, (ii) their spraying onto Titanium substrate, (iii) a post electroplating on the sprayed graphene materials. In case of GNPs, a prior functionalization by polydopamine biopolymer is performed to increase their hydrophilicity and allow their dispersion. The polydopamine polymerization mechanism is known in literature to be complex and not extensively understood. The investigations done to understand the functionalization of GNPs by polydopamine using different techniques like Transmission Electron Microscopy (TEM) and X-ray Photoemission Spectroscopy (XPS) will be shared. Moreover, the use of Helium Ions Microscopy coupled with Secondary Ions Mass Spectrometer (HIM-SIMS) has been chosen as an original and powerful technique to further study the conformation of polydopamine onto GNPs. Finally, we will present the fabrication of thin graphene oxide copper composite foils and their characterization using Scanning Electron Microscope (SEM). A special focus will be given on the comprehension of copper nucleation behaviour on Graphene materials that remains not well studied. Electrochemical techniques such as impedance and current transient nucleation and growth analysis is currently under testing.[1] Zhu, P. Gastol, D. Marshall, J. Sommerville, R. Goodship, V. Kendrick, E. J Power Sources, 485, 229321 (2021)[2] Fatemeh Farjadian et al. Recent Developments in Graphene and Graphene Oxide: Properties, Synthesis, and Modifications: A Review 5,10200-10219, Chemistry Europe (2020)[3] Song, G. et al.. One-step synthesis of sandwich-type Cu/graphene/Cu ultrathin foil with enhanced property via electrochemical route. Materials and Design, 191, 108629. (2020)

Vertically arranged electrode structures with high energy density for seawater batteries

Seawater batteries (SWBs) have attracted considerable attention as next-generation batteries owing to their high theoretical energy density and low cost. However, the practical energy density of SWBs is lower than that of conventional sodium-ion batteries as they contain a solid electrolyte with thickness limitations and inflexible mechanical properties. Considering the structure of SWBs, an increase in the anode thickness is required; however, the conventional high-mass-loading approaches are constrained by electrochemical and physical characteristics such as sluggish ion diffusion and delamination. In this study, we report the vertical arrangement of a conventional electrode to overcome the structural instability of the thick electrode and enable facile ion and electron transport by generating a vertically arranged electrode structure (VAES), which is verified using 3 different factors namely, vertical thickness, electrode compactness, and vertical angle. The electrode structures applied to the SWB anode exhibit a specific capacity of approximately 220 mAh/g over 100 cycles, achieving a high areal capacity of 75 mAh/cm2 in the coin cell, which is 50 times higher than that of a single-sheet electrode. This study demonstrates an efficient strategy to increase the energy density of SWB and provides valuable insights into the electrochemical characteristics of vertical electrode systems.

Consequences of a stabilizing field’s self-interactions for RS cosmology

It has been argued that the Randall-Sundrum (RS) phase transition rate is suppressed when the holographic theory corresponds to a large N Yang-Mills and when the stabilizing field has a small mass. Here we argue that self-interactions can alleviate the latter suppression. We consider a cubic term in the bulk potential for the Goldberger-Wise (GW) scalar that is responsible for stabilizing the RS geometry. Adding a cubic term suffices to separate the two roles of the GW stabilization: generating a large hierarchy and triggering confinement. We study the resulting radion potential and the dynamics of the early universe phase transition. For a negative coefficient of the cubic term, the effect of the cubic becomes important in the infra-red, and the resulting radion potential is deeper, thereby increasing the radion mass while maintaining a large hierarchy. Staying within the radion effective field theory, we calculate the rate of bubble nucleation from the hot phase to the confined RS phase, both in thin and thick wall limits. The cubic term enhances the rate and allows relaxing the condition on the maximum number of colors Nmax of the dual theory for which the phase transition can be completed. Importantly, this reduces the amount of supercooling that the false vacuum undergoes, increases the peak frequency of the gravitational waves (GW) produced from bubble collisions, and reduces the strength of the GW signal. The reduced GW signal is however still within the reach of proposed space-based GW detectors.

Optimization of diffuse Raman spectroscopy for in-vivo quantification of foreign body response in a small animal model.

Diffuse Raman spectroscopy (DRS) allows subsurface molecular analysis of optically turbid samples. Numerical modeling of light propagation was used as a method for improving the design of an DRS instrument to maximize the signal to noise ratio (SNR) while ensuring safe laser exposure parameters required for in-vivo measurements. Experimental validation of the model was performed on both phantom samples and disks implanted postmortem to mimic the typical response to foreign bodies (formation of a fibrotic capsule around an implant). A reduction of laser exposure of over 1500-fold was achieved over previous studies whilst maintaining the same Raman collection rates and reaching the safe power density of 3 mW/mm2. The validation of this approach in a subcutaneous implant in a mouse cadaver showed a further improvement of 1.5-fold SNR, with a thickness limit of detection for the fibrotic layer of 23 µm, under the same acquisition times. In the animal body, a thickness limit of detection of 16 µm was achieved. These results demonstrate the feasibility of numerical model-based optimization for DRS, and that the technique can be improved sufficiently to be used for in-vivo measurement of collagenous capsule formation as a result of the foreign body response in murine models.

Experimental determination of critical thickness limitations of (010) β -(AlxGa1−x)2O3 heteroepitaxial films

The effect of heteroepitaxial β-(AlxGa1−x)2O3 film thickness and Al content on surface morphology was characterized to experimentally determine the critical thickness limitations of the (010) β-(AlxGa1−x)2O3/Ga2O3 heterostructure. High-resolution x-ray diffraction was used to assess the strain state of the films; reciprocal space mapping (RSM) revealed that even cracked films were still fully strained. In cracked films, diffuse scattering was observed in RSMs, indicating lattice tilting. Cracking of the films was investigated using atomic force microscopy (AFM), x-ray topography (XRT), bright-field scanning transmission electron microscopy (BF-STEM), and high-resolution transmission electron microscopy. Using both AFM and XRT, the [001] direction was observed to be the most prevalent crack direction; however, cracks were also observed in the [100] direction. In uncracked regions of the films, XRT revealed the alignment of threading dislocations along the [001] direction. Cross-sectional imaging of the crack geometry and propagation was performed using BF-STEM, and it was observed that the cracks in the [001] direction extended through the thickness of the β-(AlxGa1−x)2O3 film (∼205 nm) and a further ∼100–200 nm into the β-Ga2O3 substrate. Experimental data for critical film thickness showed good agreement with previous theoretical calculations based on the Griffith criterion for crack propagation.

Effect of flame thickness on the temperature measurement error for bare-bead thermocouple in open pool fires with different fuels

Accurately obtaining the temperature distribution of the flame is crucial for a comprehensive understanding of the combustion behavior of the pool fire. The correction method is needed to compensate the measurement error when the temperature is measured by bare-bead thermocouple in the open pool experiment, but the effect of flame thickness is rarely considered in the current method. Thus, this work develops a coupled heat transfer model of bare-bead thermocouples in open pool fires and modifies the flame radiation characteristics based on the fuel type and flame thickness. The control mechanism of measurement error in the model is identified, and then the effects of main parameters such as flame thickness and flame temperature on measurement error are analyzed. The results show that the flame emissivity decreases exponentially with the decrease of flame thickness, the minimum emissivity of gasoline flame is 0.26 when flame thickness is 0.1 m. The decrease of flame thickness leads to a sharp increase of temperature measurement error. The maximum increment of error can reach 227.3 K. On this basis, the flame thickness limit value, considering the correction of temperature measurement error in different hydrocarbon pool fire experiments is proposed.

Perfect Absorption at the Ultimate Thickness Limit in Planar Films

Perfect Absorption at the Ultimate Thickness Limit in Planar Films

Sonographic and clinical effects of manual physical therapy for plantar fasciitis: randomized prospective controlled trial.

This study aimed to evaluate the efficacy of manual physiotherapy on clinical outcomes, morphology of plantar fascia (PF), thicknesses of calcaneal fat pad (CFP) and Kager's fat pad (KFP) with ultrasound imaging in plantar fasciitis (PFS) patients. Also, to evaluate the PF thickness, pain and foot functional outcomes among PFS phases. A randomized controlled trial was conducted on 122 subjects divided into three groups: group A (40 patients with PFS) underwent manual physiotherapy, group B (42 patients with PFS) without any intervention and group C (40 healthy subjects) were matched by age, gender and BMI with each patient in group A and B. The following outcomes were evaluated at baseline and one-month of follow-ups: morphology of PF and thicknesses of CFP and KFP, pain, foot functional limitation. PF thickness was significantly thickened in group A and B compared to group C (P < 0.001). A significant decrease in incidence of PF echogenicity and CFP thickness were found in group A and B compared to group C. Moreover, significant improvement was observed in PF thickness (P < 0.001), PF echogenicity (P < 0.001) and CFP thickness (P = 0.002) in group A at one-month after the treatment. Furthermore, pain intensity and foot functional limitation was significantly improved within group A after receiving the treatment. Significant improvement was noted in PF thickness, pain intensity and foot functional limitation among patients with acute phase. The manual physiotherapy is effective in treatment of PF thickening, hypoechogenicity, pain intensity and activity limitations, particularly in patients associated with acute PFS.