Al Thickness Research Articles

Theoretical prediction model for the compressive behavior of the hybrid tube considering compression angle

AbstractThe oblique collision happening in vehicle accidents poses a huge threat to passive safety, which causes great difficulties in the design of energy absorption (EA) structures and the prediction of EA capacity due to its highly nonlinear deformation characteristics. This study aims to establish a theoretical prediction model for the compression performance of Carbon Fiber Reinforced Polymer (CFRP)/Al hybrid tube considering the loading angle. First, a high‐precision FE model was established to obtain the influence laws of tube diameter, Al thickness, and CFRP thickness on the crashworthiness of CFRP/Al hybrid tubes, laying the foundation for subsequent theoretical model validation. Second, by summarizing the deformation modes of hybrid tubes generated by various parameter combinations, a modified global origami deformation assumption was proposed under multi‐angle compression conditions, and the key terms in energy composition are extracted based on the initial and final states of folding elements. Third, a theoretical model for predicting the mean crushing forces (MCFs) of hybrid tubes was established by revealing the correlation mechanism between energy composition terms and loading angle. Finally, the theoretical prediction model was validated by experiment and simulation results and the application premise was given. Results showed that the theoretical prediction model was proved to be of high accuracy, as the average absolute prediction errors of MCF under axial, 10°, 20°, and 30° compression conditions were 6.54%, 4.63%, 3.72%, and 3.93%, respectively. This study provides valuable guidance for the forward design and development of multi‐material hybrid structures facing complex crushing conditions.Highlights An analytical model of the hybrid circular tubes considering compression angle is newly proposed. Deformation mode and axial crushing response are analyzed by experiments. The major energy dissipation mechanism for hybrid circular tubes is explicitly derived. The Al thickness has the most significant impact on energy absorption. The recommendations for the design and development of hybrid tube are provided.

Impact of composition and thickness of step-graded AlGaN barrier in AlGaN/GaN heterostructures

We propose an optimization method to change the Al component and the thickness of step-graded AlGaN barrier to achieve better electrical performance of the device. Based on the polarization effect, we find that a second potential well occurs while increasing the Al fraction and thickness of the upper AlGaN layer, which contributes to better drain current performance in the simulations. The wafers with different AlGaN barriers were grown to compare their surface morphology and electrical properties. The surface roughness of the wafer is related to the lattice constant of the upper AlGaN layer. According to the Hall and TLM measurements, the electron sheet density and electron mobility of the 20 nm-Al0.35Ga0.65N/10 nm-Al0.25Ga0.75N barrier sample are 1593 cm2/Vs and 1.17 × 1013 cm−2 respectively, resulting in a high spacing current of 61.45 mA. Moreover, the maximum drain current density of this barrier device is 589.02 mA/mm under the I–V characteristics, 1.37 times as much as that of the 20 nm-Al0.25Ga0.75N barrier. The higher gate barrier height of Al0.35Ga0.65N reduces the gate leakage current.

Theoretical Studies of 2D Electron Gas Distributions and Scattering Characteristics in Double‐Channel n‐Al0.3Ga0.7N/GaN/i‐AlxGa1−xN/GaN High‐Electron‐Mobility Transistors

A detailed analysis of self‐consistent potentials, electric fields, electron distributions, and transport properties of dual‐channel (DC) n‐Al0.3Ga0.7N/GaN/i‐AlxGa1−xN/GaN high‐electron‐mobility transistors (HEMTs) is performed in this article. The 2D electron gas (2DEG) densities and mobility states limited by different scattering mechanisms in channel 1 and channel 2 are obtained, with varying values of doping concentrations, ambient temperatures, Al components, and thicknesses of the back barrier layer. The reduced and increased 2DEG densities are respectively observed in channel 1 and channel 2 with growing Al fractions and thicknesses of the AlxGa1−xN layer. Alloy disorder scattering exhibits a superior effect on carriers in channel 2 due to the lower barrier height and higher permeable electrons, which together with the interface roughness scattering severely depends on the thicknesses and Al fractions of the back barrier layer. Polar optical phonon scattering becomes important at higher temperatures. The trend of individual mobility in channel 1 is exactly opposite to that in channel 2. The parameter variation of the back barrier layer can effectively change the scattering characteristics of the main channel. Low‐temperature mobilities of n‐Al0.3Ga0.7N/GaN/i‐AlxGa1−xN/GaN HEMTs under varied doping concentrations are also obtained. Finally, the results are verified by comparison with the technology computer‐aided design simulations for DC HEMTs.

Investigation of a highly-sensitive aluminum-based plasmonic device using antimonene for sensing applications

Aluminum (Al) has gained popularity for surface plasmon resonance-based applications due to its affordability and compatibility with CMOS technology at the nanoscale. Over angle-interrogation mode, plasmonic interactions occurring at the metal-dielectric junction, are the outcomes of the attenuated total internal reflection phenomenon. Modified Al-based Kretschmann configuration results in phase-matching conditions that are seen as resonant points in the reflection characteristics. In our work, we have engineered an Al-based plasmonic device utilizing Antimonene as a 2D nanomaterial for bio-sensing purposes in the Near-Infrared (NIR) spectral domain. The study investigates the performance of Surface Plasmon Resonance (SPR) based refractive index sensor using different 2D nanomaterials with an optimized Al thickness of 30 nm. A comparative analysis of Al-based Kretschmann configurations in the presence of Graphene, Black Phosphorus, MXene, and Antimonene is presented using engineered intermediate layers. It is observed that the Al-antimonene-based plasmonic device exhibits improved sensing parameters in the NIR optical window.

High performance SAW resonator with spurious mode suppression using double-layer electrode transverse modulation

This work aims to solve the problem of tradeoff between various properties and spurious mode suppression in surface acoustic wave (SAW) resonators. A high-angle rotated Y-cut LiNbO3 (LN)/SiO2/Si multilayered structure was proposed to balance the electromechanical coupling coefficient (K 2) and temperature coefficient of frequency (TCF), and the propagation characteristics of Rayleigh mode were simulated by the finite element method. For the widely existing spurious modes, the shear-horizontal wave and longitudinal modes were eliminated by optimizing the cut angle of LN and electrode thickness, and a method of double-layer electrode transverse modulation was proposed to suppress the transverse modes. This method reduces the mass loading effect by replacing the electrode from Cu to Cu/Al. Moreover, the Al thicknesses in different regions are changed to perform the transverse modulation, and thus a widespread suppression of transverse modes is achieved by exciting the piston mode and enhancing the energy constraint, with a significant improvement on quality factor at the resonance frequency. Eventually, the spurious-free SAW resonator has the K 2 of 9.5% and the TCF close to zero. This work provides a feasible scheme for the design of high performance SAW resonators with spurious mode suppression.

Growth and optical performance of short-period W/Al and polished W/Si/Al/Si multilayers

Short-period multilayer mirrors are used in wavelength-dispersive x-ray fluorescence to reflect and disperse elements in the O-Kα– Al-Kα range. In this work, we investigated sputter-deposited 2.5 nm W/Al with 20 periods. Our results show that W/Al is a poor reflector due to a combination of high interfacial roughness and strong W–Al intermixing. To address this, we introduced 0.5 nm Si seed layers at the W-on-Al and Al-on-W interfaces each consecutive period, while reducing the Al thickness from ∼2.0 to ∼1.0 nm. The Si seed layers significantly reduced interfacial roughness and W–Al intermixing, which led to an increase in the reflectance of the first Bragg peak at λ = 0.154 nm. To further reduce interfacial roughness, ion beam polishing of the top Si layer was applied at each period. The resulting structure of W/Si/Al/Si with ion beam polishing showed that the reflection coefficient of the first Bragg peak at λ = 0.154 nm was comparable to that of standard W/Si. These findings demonstrate the effectiveness of seed layers combined with polishing techniques in synthesizing smooth, high-reflectance multilayers containing two materials that are otherwise challenging to synthesize.

Enhancement of the vortex critical velocity in superconducting/normal metal bilayers

This study investigates the influence of normal metal thickness on the Larkin-Ovchinnikov (LO) instability in superconductor/normal metal heterostructures. Bilayers were fabricated using a 22 nm-thick Mo2N layer, with varying Pt, W, and Al thicknesses. The samples exhibited a critical temperature of approximately 7.5 K. The LO instability was characterized through current–voltage curves, which relate the maximum vortex velocity to the recombination time of normal electrons into Cooper pairs (τ). The results reveal a significant enhancement in vortex velocity at moderate and high magnetic fields when a metallic layer with thickness exceeding the coherence length is added. Furthermore, a direct correlation is observed between velocity values and the thermal conductance of the metal, indicating a contribution from phonons and heat dissipation to the maximum achievable velocity in the heterostructures.

High‐Performance Flexible MoS2 Transistors Using Au/Cr/Al/Au as Source/Drain Electrodes

Abstract2D transition metal dichalcogenides such as molybdenum disulfide (MoS2) are promising candidates for flexible electronics because of their bandgap tunability, high carrier mobility, and mechanical flexibility. However, flexible MoS2 field effect transistors (FETs) are typically faced with high contact resistance which is identified as a critical limiting factor to their potential applications. The present work successfully addresses this challenge by using Al contacts without any annealing process. It is found that the contact resistance is strongly coupled to the Al thickness, increasing the Al thickness is beneficial to reduce the contact resistance. The observed variation in the device electrical characteristics can be associated with the formation of the natural aluminum oxide (AlxOy) film at the interface. An ultrathin Au insert layer can further advance the device performance. An optimal contact resistance of 2.03 kΩ and an on/off current ratio of 1.57 × 109 can be achieved in the flexible MoS2 FETs using Au/Cr/Al/Au as source/drain electrodes. Furthermore, no apparent degradation in the device properties is observed under systematic cyclic bending testing with bending radii of 18 and 15 mm. The successful integration of Au/Cr/Al/Au source/drain electrodes into MoS2 FETs promises its potential application in flexible electronic devices.

Crushing behavior of CFRP/AL hybrid tubes under oblique lateral loading

AbstractThis work aims to research the oblique lateral crushing behavior of CFRP/AL hybrid tubes under different parameter configurations. First, a finite element model was established based on the maximum stress criterion and the traction‐separation law. The reliability of the numerical models for pure aluminum, pure composite, and hybrid tubes was verified by rigorous comparison with experimental data, respectively. Second, the influence of loading conditions and geometric characteristics on crashworthiness were studied. The results show that the damage modes of the hybrid tube under oblique lateral loading are mainly concentrated in the horizontal and vertical ends, specifically in the form of plastic hinge and fiber, matrix fracture. The CFRP layers has positive effect on improving the specific energy absorption (SEA). High ratio thickness of aluminum tubes can effectively improve the energy absorption (EA) and crush force efficiency (CFE). It is found that the sandwich structure is not conducive to resist lateral crushing, while the CFRP without external constraints can absorb more impact energy.Highlights The oblique lateral crushing behavior of CFRP/AL hybrid tube was studied. A numerical simulation method was proposed and verified. The effects of loading angle, fiber layers and AL thickness were studied. The hybrid ratio and hybrid method were designed and discussed.

Pseudomorphic growth of Si-doped α-(AlGa)2O3 on m-plane α-Al2O3 substrates by molecular beam epitaxy

α-(AlGa)2O3 is an attractive material for high-power devices and vacuum UV optoelectronics. However, α-(AlGa)2O3 on sapphire substrates suffers from lattice relaxation and phase transformation. Here, we investigated the effect of controlling the Al composition and thickness of Si-doped α-(AlGa)2O3 layers pseudomorphically grown on α-Al2O3 (100) substrates by MBE. We found that the critical layer thicknesses of α-(AlGa)2O3 layers with Al compositions of 58%, 66%, and 79% were around 13, 18, and 44 nm, respectively. We also found that a 9.0 nm thick α-(Al0.65Ga0.35)2O3/3.5 nm thick Al2O3 multilayer with 20 periods grew almost pseudomorphically and formed α-(Al0.90Ga0.10)2O3 alloy after post-thermal annealing at 1400 °C.

Investigation of coordinated behavior of deformation at the interface of Cu–Al laminated composite

To understand the differences between the microstructure and stress states owing to uncoordinated deformation in different regions of a Cu–Al contact interface, the normal stress distribution at the contact interface of the Cu–Al composites and the Al metal adhesion on the peeling surface of the Cu layer are investigated by performing numerical simulations and experimental studies. The results show that the percentage of Al metal adhered to the Cu side gradually increased from the edge to the central region. This is mainly because the central area of the contact interface bore a larger normal stress than the edge position, and when the interface normal stress exceeded 470 MPa, the pressure threshold value required for the extrusion of virgin metal from the surface-hardened layer on the Al side was satisfied. The effect of the initial Cu:Al thickness ratio on the degree of interfacial coordination is investigated, and the degree of coordination of the contact interface was observed to improve and then worsen with the increase in the initial Cu:Al thickness ratio (from 3:9 to 8:4). For composites with a Cu:Al thickness ratio of 4:8, the interface was well coordinated, and the bond strength reached 6.13 MPa, corresponding to a 173.7% improvement compared with the Cu–Al composite with more severe stress concentration (8:4).

P‐7.12: Research on High Brightness Mode Uniformity Problem of Flexible AMOLED Mobile

The development trend of flexible AMOLED mobile is introduced in this paper, and the key optical problems to be solved in AMOLED display are clarified. Then, based on the urgency of solving the high brightness mode uniformity problem, a complete set of test methods and evaluation system for flexible AMOLED mobile are proposed. According to the principle of flexible AMOLED light‐emitting structure, the mechanism of high brightness mode uniformity problem is analyzed. What's more, the IR Drop model is proposed, at the same times, the effects of key factors such as SD Al thickness, dual Vdd SD and A.R. on Vdd and Vss voltage drop are simulated. After mass production verification of multiple models, the linkage scheme including backplane circuit, EL device and module algorithm for high brightness mode uniformity problem is proposed creatively. After application, The results show that △ u‵v‵‐A 0.003,△ u‵v‵‐B 0.002, DeltaC 1.9, DeltaE 2 and LU 95% on the basis of a 6.7inch FHD product, which represents the leading level in domestic market as well as provides a reference idea for the AMOLED display performance.

Radiopacity evaluation of different types of resin restorative materials using a digital radiography system.

The aim of the study was to evaluate and compare the radiopacity of 20 current dental resin composites with digital radiography. Ten specimens, 10-mm in diameter and 1-mm thickness, were prepared and radiographed using phosphor plates close to Al step wedges and tooth sections. The mean grey values (MGVs) were measured using an ImageJ software program and converted to equivalent Al thickness. Data were analyzed using one-way analysis of variance (ANOVA) and Tamhane post hoc test (p < 0.05). Correlation between mean radiopacity and filler content (wt% and vol%) of the tested materials was analyzed with linear regression analysis. The radiopacity of all composites ranged from 1.32mm Al (Estellite Flow Quick) to 3.41mm Al (Charisma Classic). All the tested materials, except four restorative materials, had a radiopacity equal or higher than the enamel (p < 0.05). Linear regression revealed low correlation between the radiopacity and filler content of the composite. Majority of the materials has appropriate radiopacity for dental restorations. There was great variation in radiopacity level, may clinically affect the diagnosis.

Microstructural evolution and mechanical properties of Ni/Al reactive nanolaminates with different NixAly intermetallic phases

Nanolaminates made up by alternative Ni and Al nanolayers are widely applied to solder structural materials, due to abundant heat releases when supplied with an energetic input. This work studies the microstructural evolution and mechanical properties of Ni/Al nanolaminates with a wide mole ratio of Ni (MNi, 0.18–0.53), to ascertain the role of NixAly intermetallic phases during heat-treatment. To this end, 3 nanolaminates with Al thickness fixed at ≈110 nm and Ni thickness varying 15–75 nm are fabricated and are heat-treated at 400 °C, to trigger formations of NiAl3, Ni2Al3 and NiAl intermetallic phases. The results suggest an enhanced strength of Ni/Al after heat-treatment. However, their evolution with MNi is complex. The nanolaminate with MNi ≈0.18 is the softest after heat-treatment, due to the dominant plasticity of residual Al phases. The maximized strength is achieved when MNi ≈0.40, in which a novel NiAl3/Ni2Al3 nanolaminate structure is formed. Owing to the brittleness of both phases, the nanolaminate after heat-treatment is fractured by shearing upon uniaxial compression. The best strength-ductility synergy is achieved when Ni mole ratio ≈0.53. In the heat-treated nanolaminate a homogenous nanocrystalline NiAl phase is formed. As a result, the nanolaminate exhibits excellent ductility and intermediate strength among the 3 nanolaminates.

Experimental and numerical studies on bending characteristics of woven CFRP reinforced aluminum thin-walled automotive structures

Metal/composite hybrid thin-walled structure is the most preferential approach to achieve dual contradictive objectives of high crashworthiness and lightweight of auto body. Its collapse with regard to different fiber layup patterns is one of the governing mechanisms of energy dissipation, which is yet to be explored. Especially, the effect of different fiber layup angles and layup sequences on bending collapse, which is one of the most significant performance indicators, has received little attention. To this gap, this study investigates experimentally and numerically the bending characteristics of aluminum/carbon fiber reinforced plastic (Al/CFRP) hybrid structures with different layup angles and layup sequences. To start with, three-point bending tests are carried out on specimens to derive the bending failure behavior and crashworthiness, and the internal section damage is observed by CT scan. Finite element model is then constructed and benchmarked against the test results to be proficient. On this basis, the effects of Al thickness, number of CFRP layers and CFRP wrapping range on the bending performance of hybrid tube are analyzed numerically. The simulation results show that layup angle has greater effect on the bending performance than layup sequence. Increasing Al thickness and the number of CFRP layers can effectively improve the bending resistance of structure, and appropriate partial wrapping of CFRP can increase the specific energy absorption (SEA) by 10.92% compared with that of complete wrapping. The revelation from this study provides sound reference for the crashworthiness design of metal/composite hybrid thin-walled structure.

Engineering Pt/Co/AlO x heterostructures to enhance the Dzyaloshinskii–Moriya interaction

The study of interfacial Dzyaloshinskii–Moriya interaction (DMI) in perpendicularly magnetized structurally asymmetric heavy metal/ferromagnet multilayer systems is of high importance due to the formation of chiral magnetic textures in the presence of DMI. Here, we report the impact of cobalt oxidation at the Co/AlO x interface in Pt/Co/AlO x trilayer structures on the DMI by varying the post-growth annealing time, Al thickness and substrate. To quantify DMI we employed magneto-optical imaging of the asymmetric domain wall expansion, hysteresis loop shift, and spin-wave spectroscopy techniques. We further correlated the Co oxidation with low-temperature Hall effect measurements and x-ray photoelectron spectroscopy. Our results emphasize the importance of full characterization of the magnetic films that could be used for magnetic random access memory technologies when subjected to the semiconductor temperature processing conditions, as the magnetic interactions are critical for device performance and can be highly sensitive to oxidation and other effects.

Contrast Sensitivity Function: A More Sensitive Index for Assessing Protective Effects of the Cilioretinal Artery on Macular Function in High Myopia.

To assess the benefits of the cilioretinal artery on macular function in high myopia using the quantitative contrast sensitivity function (qCSF) method. This cross-sectional study was conducted at the Eye and Ear, Nose, and Throat Hospital of Fudan University. In total, 137 highly myopic patients (with axial length [AL] ≥ 26.00 mm) were enrolled and divided into cilioretinal artery absent and present groups based on their fundus photographs. One eye in each patient was randomly selected. Choroid thickness was measured using macular optical coherence tomography. The best-corrected visual acuity (BCVA) was evaluated by Early Treatment Diabetic Retinopathy Study charts, and the area under the log CSF (AULCSF), CSF acuity, and CS at six spatial frequencies were evaluated with the qCSF method. Although no significant BCVA difference was found between the cilioretinal artery absent (97 patients) and present (40 patients) groups, choroid thickness, AULCSF, CSF acuity, and CSF at low and intermediate spatial frequencies (1-6 cycles per degree) were all significantly higher in the cilioretinal artery present group than in the absent group (all P < 0.05). In addition, eyes with temporal cilioretinal arteries exhibited significantly higher AULCSF, CSF acuity, and CSFs at 3 and 6 cycles per degree (all P < 0.05) than those with a nasal one (all P < 0.05). Multivariate analysis showed that better AULCSF was associated with the presence of cilioretinal artery and the interaction of AL and choroid thickness. The cilioretinal artery may associate with the larger choroid thickness in highly myopic eyes and may play a role in preserving qCSF outcomes, which are more sensitive than chart-based acuity tests.

Simulation Study on the Structure Design of p-GaN/AlGaN/GaN HEMT-Based Ultraviolet Phototransistors.

This work investigates the impacts of structural parameters on the performances of p-GaN/AlGaN/GaN HEMT-based ultraviolet (UV) phototransistors (PTs) using Silvaco Atlas. The simulation results show that a larger Al content or greater thickness for the AlGaN barrier layer can induce a higher two-dimensional electron gas (2DEG) density and produce a larger photocurrent. However, they may also lead to a larger dark current due to the incomplete depletion of the GaN channel layer. The depletion conditions with various Al contents and thicknesses of the AlGaN layer are investigated in detail, and a borderline between full depletion and incomplete depletion was drawn. An optimized structure with an Al content of 0.23 and a thickness of 14 nm is achieved for UV-PT, which exhibits a high photocurrent density of 92.11 mA/mm, a low dark current density of 7.68 × 10-10 mA/mm, and a large photo-to-dark-current ratio of over 1011 at a drain voltage of 5 V. In addition, the effects of other structural parameters, such as the thickness and hole concentration of the p-GaN layer as well as the thickness of the GaN channel layer, on the performances of the UV-PTs are also studied in this work.

The demonstration of low-temperature (350 °C) grown carbon nano-tubes for the applications of through silicon via in 3D stacking and power-via

Low temperature Carbon Nano-tubes (CNTs) growth technology is developed in this work with the insert of Al (Aluminum) between Ni (Nickel) and Ti (Titanium) as the reactant. The optimized Al thicknesses are also investigated. CNTs growth at the low temperature below 400 °C is the key factor for the back end of line compatible process integration. In this work, we grow the CNTs by thermal chemical vapor deposition process at 350 and 400 °C. The low ratio of peak ID/IG in Raman spectra and scanning electron microscope images proves the CNTs material quality. On the other hand, the high thermal conductivity (k) value of ∼50 W m − 1 K − 1 is also demonstrated. Both high material quality and k value on our low temperature grown CNTs show promising opportunities for the integration of semiconductor three dimensional packages and power-via related applications.

Facile fabrication of Al nanoparticle arrays with continuous tunable diameter and plasmonic band for UV–visible SERS detection

Al-based nanostructures have a huge potential for surface-enhanced Raman scattering (SERS) in area of life science, chemical and food safety because of its excellent plasmonic characteristics from UV to near-infrared ranges. By only controlling the deposited Al thickness onto the parabola-shaped alumina nanopores template, the Al nanoparticle arrays with tunable diameter from 55 nm to 94 nm and plasmonic bands ranging from 285 nm to 717 nm were obtained. With excitation at UV and visible plasmon resonance wavelength (325 nm, 633 nm), the experimental SERS enhancement factor (EF) reached 103 and relative standard deviation (RSD) below 10% on a large scale. Finite-difference time-domain (FDTD) simulations reveal electric field intensity and charge distribution of dipolar and quadrupolar plasmon mode. The simple and controllable fabrication strategy and superior SERS performance in UV–visible range make the Al nanoparticle arrays promising candidates for SERS-based sensor applications. And the method provides a new approach for developing an inexpensive, efficient, and mass-produced Al-based SERS active substrate.