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ABSTRACTVanadium redox flow batteries (VRFBs) have received significant attention for use in large-scale energy storage systems (ESSs) because of their long cycle life, flexible capacity, power design, and safety. However, the poor electrochemical activity of the conventionally used carbon felt electrode results in low energy efficiency of the VRFBs and consequently impedes their commercialization. In this study, a carbon felt (CF) electrode with numerous nanopores and robust oxygen-containing functional groups at its edge sites is designed to improve the electrochemical activity of a carbon felt electrode. To achieve this, Ni metal nanoparticles were initially precipitated on the surface of the CF electrode, followed by etching of the precipitated Ni nanoparticles on the CF electrode using sulfuric acid. The resulting CF electrode had a specific surface area eight times larger than that of the pristine CF electrode. In addition, the oxygen-containing functional groups anchored at the graphite edge sites of the nanopores can act as robust electrocatalysts for VO2+/VO2+ and V2+/V3+ redox reactions. Consequently, the VRFB cell with the resulting carbon felt electrode can deliver a high energy efficiency of 86.2% at the current density of 60 mA cm−2, which is 20% higher than that of the VRFB cell with the conventionally heat-treated CF electrode. Furthermore, the VRFB cell with the resultant carbon felt electrodes showed stable cycling performance with no considerable energy efficiency loss over 200 charge-discharge cycles. In addition, even at a high current density of 160 mA cm−2 , the developed carbon felt electrode can achieve an energy efficiency of 70.1%.

The formation of thick mesoporous silicon layers in Pþ-type substrates leads to an increase in the porosity from the surface to the interface with silicon. The adjustment of the current density during the electrochemical etching of porous silicon is an intuitive way to control the layer in-depth porosity. The duration and the current density during the anodization were varied to empirically model porosity variations with layer thickness and build a database. Current density profiles were extracted from the model in order to etch layer with in-depth control porosity. As a proof of principle, an 80 μm-thick porous silicon multilayer was synthetized with decreasing porosities from 55% to 35%. The results show that the assessment of the in-depth porosity could be significantly enhanced by taking into account the pure chemical etching of the layer in the hydrofluoric acid-based electrolyte. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is a promising technology for eco-friendly energy storage. However, the design principles for highly active, robust, and noble metal-free electrocatalysts for industrial-scale hydrogen production remain controversial. Oxygen-free compounds containing anionic species with a very high oxidation potential, such as fluorides, have emerged as high-performance targets for thermodynamically stable oxygen evolution reaction (OER) catalysts. They can further be designed to fit the key criteria of high electrical conductivity and stability. Herein, we present a facile and scalable etching method for constructing fluoride doped metallic nickel-based anodes from industrial Ni foam sources with high application potential for large-scale hydrogen production setups. The fluoride-etched Ni-catalysts were investigated with a wide range of techniques, such as powder X-ray diffraction (PXRD), extended X-ray absorption fine structure spectroscopy (EXAFS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). Optimized catalysts displayed a promising overpotential of 220 mV for the OER at a current density of 60 mA cm−2, which is competitive with noble metal-based reference catalysts, such as iridium oxide. Electrochemical impedance spectroscopy (EIS) studies demonstrated that etching of the electrode surface in fluoride medium leads to a drastic decrease of R ct. The corresponding decreased resistivity towards electrochemical OER on the electrode surface gives rise to the notably enhanced performance, with a minimum of synthetic effort. [Display omitted] • One-step hydrothermal etching process to prepare porous NiFOOH on Ni foam. • Fluorine-modified electrodes exhibit superior activity in OER. • Promising overpotential of 188 mV for the OER at a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Vanadium redox flow batteries (VRFBs) have received significant attention for use in large-scale energy storage systems (ESSs) because of their long cycle life, flexible capacity, power design, and safety. However, the poor electrochemical activity of the conventionally used carbon felt electrode results in low energy efficiency of the VRFBs and consequently impedes their commercialization. In this study, a carbon felt (CF) electrode with numerous nanopores and robust oxygen-containing functional groups at its edge sites is designed to improve the electrochemical activity of a carbon felt electrode. To achieve this, Ni metal nanoparticles were initially precipitated on the surface of the CF electrode, followed by etching of the precipitated Ni nanoparticles on the CF electrode using sulfuric acid. The resulting CF electrode had a specific surface area eight times larger than that of the pristine CF electrode. In addition, the oxygen-containing functional groups anchored at the graphite edge sites of the nanopores can act as robust electrocatalysts for VO2+/VO2+ and V2+/V3+ redox reactions. Consequently, the VRFB cell with the resulting carbon felt electrode can deliver a high energy efficiency of 86.2% at the current density of 60 mA cm−2, which is 20% higher than that of the VRFB cell with the conventionally heat-treated CF electrode. Furthermore, the VRFB cell with the resultant carbon felt electrodes showed stable cycling performance with no considerable energy efficiency loss over 200 charge-discharge cycles. In addition, even at a high current density of 160 mA cm−2 , the developed carbon felt electrode can achieve an energy efficiency of 70.1%. [ABSTRACT FROM AUTHOR]

Vanadium redox flow batteries (VRFBs) have received significant attention for use in large-scale energy storage systems (ESSs) because of their long cycle life, flexible capacity, power design, and safety. However, the poor electrochemical activity of the conventionally used carbon felt electrode results in low energy efficiency of the VRFBs and consequently impedes their commercialization. In this study, a carbon felt (CF) electrode with numerous nanopores and robust oxygen-containing functional groups at its edge sites is designed to improve the electrochemical activity of a carbon felt electrode. To achieve this, Ni metal nanoparticles were initially precipitated on the surface of the CF electrode, followed by etching of the precipitated Ni nanoparticles on the CF electrode using sulfuric acid. The resulting CF electrode had a specific surface area eight times larger than that of the pristine CF electrode. In addition, the oxygen-containing functional groups anchored at the graphite edge sites of the nanopores can act as robust electrocatalysts for VO 2+ /VO 2 + and V 2+ /V 3+ redox reactions. Consequently, the VRFB cell with the resulting carbon felt electrode can deliver a high energy efficiency of 86.2% at the current density of 60 mA cm -2 , which is 20% higher than that of the VRFB cell with the conventionally heat-treated CF electrode. Furthermore, the VRFB cell with the resultant carbon felt electrodes showed stable cycling performance with no considerable energy efficiency loss over 200 charge-discharge cycles. In addition, even at a high current density of 160 mA cm -2 , the developed carbon felt electrode can achieve an energy efficiency of 70.1%., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2024 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

Tip-enhanced Raman spectroscopy (TERS) is a powerful tool for the characterization of surfaces and two-dimensional materials, delivering both topographical and chemical information with nanometer-scale spatial resolution. Atomic force microscopy (AFM)–TERS combines AFM with a Raman spectrometer and is a very versatile technique, capable of working in vacuum, air, and liquid, and on a variety of different samples. A metalized AFM tip is necessary in order to take advantage of the plasmonic enhancement. The most commonly used metal is Ag, thanks to its high plasmonic activity in the visible range. Unfortunately, though, the tip metallization process is still challenging and not fully reliable, yielding inconsistent enhancement factors even within the same batch of tips; as a consequence, many tips are usually prepared at once (for a single experiment), to ensure that at least one of them is sufficiently active. As the lifetime of an unprotected, Ag-coated plasmonic probe is only a few hours, the procedure is inefficient and results in a substantial waste of materials and money. In this work, we establish a cleaning routine to effectively re-use Ag-coated AFM–TERS probes, drastically reducing costs without compromising the quality of the experimental results. [ABSTRACT FROM AUTHOR]

A white MnF2 powder is synthesized by chemical etching of Mn shots in an aqueous HF solution. The optical properties of this synthesized powder are investigated using photoluminescence (PL) analysis, PL excitation spectroscopy, diffuse reflectivity, and PL decay measurements. The MnF2 powder exhibits PL peaks in the red (∼600 nm) and infrared spectral regions (∼780 nm) under visible to ultraviolet excitation. These PL peaks are asymmetric with a tail on the long-wavelength side. Such spectral features and temperature-dependent PL intensities are well interpreted by a newly developed model with Huang-Rhys's factor as the electron-local vibration coupling strength. The ground- and excited-state energy level diagram for the Mn2+ ions in MnF2 is also proposed. [ABSTRACT FROM AUTHOR]

The dissolution behavior of Si (100) and (111) dies by eutectic AuSi solder was investigated. On the Si (100) surface, the dissolution primarily occurred by the formation of craters resulting in a rough surface. The dissolution of the Si (111) resulted in a relatively smooth surface. The morphology of the Si (100) surface during a AuSi soldering reaction exhibited more time-dependent behavior and the etching craters on a Si (100) surface grew larger with time whereas Si (111) did not significantly change. This difference was ascribed to the surface energy differences between Si (111) and (100) surfaces that resulted in the two- and three-dimensional dissolution behaviors, respectively. This difference plays an important role in the formation of voids during the AuSi die bonding. The etching craters on Si (100) act as a AuSi solder sink and the regions surrounded by etch pits tend to become voids. For Si (111), flat surfaces were observed in the voided regions. Cross section analysis showed that no solder reaction occurred in the voided region of the Si (111) surface. This suggests the possibility of the formation of a thin inert layer in a potentially voided region prior to assembly. To achieve void-free die bonding, different parameters must be adjusted to the Si (100) and Si (111) surfaces with the AuSi alloy. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This paper reports the fabrication of subwavelength nano-structures on the curved surface of a glass lens for the purposes of anti-reflection. It utilizes a flexible PDMS mold to transfer metallic patterns to the lens surface which is pre-coated with a polymer layer. Using the transferred metal pattern as an etching mask, nano-structures are directly fabricated on the lens surface by plasma dry-etching processes. A plano/convex lens made of BK-7 glass with a lens diameter of 12.7 mm and a radius of curvature of 25.8 mm is used in this paper. Hexagonally arrayed nano-structures with a truncated conical profile, a center-to-center pitch of 300 nm, and a maximum structure height of 290 nm are experimentally achieved. Measurement results show the optical transmittance is increased by about 2.4% in average for wavelength within visible light spectrum. The directly fabricated nano-structures also exhibit good anti-glaring effects and the potentials for further optical applications. Unlabelled Image • Fabrication nano-structures on convex lens using metal contact printing lithography. • Large-area nano-patterning method for axial-symmetric curved surface. • Experimental evidence of fabricating subwavelength structures using proposed lithographic method. • Simulation and experimental investigation on the enhanced transmittance by surface nano-structures. [ABSTRACT FROM AUTHOR]

The electrochemistry of ruthenium (Ru) etching in acidic solution containing cerium (IV) (Ce4+) has been investigated. Voltammograms were measured to determine the onset potentials of metal stripping and cathodic reduction of the oxidizing agent. Etch rates of blanket thin films of chemical vapour deposited Ru were measured using Rutherford backscattering spectrometry. Sheet resistance measurements of a thickness range of wet-chemically etched and as-deposited Ru thin films are compared. X-ray photoelectron spectroscopy was used to characterize post-etching residues. Using atomic force microscopy, the surface morphology of Ru after etching and removal of residues by rinsing with water or acid and ultrasonic agitation was studied. Compatibility of low-k dielectric material with the etchant has been assessed using Fourier transform infrared spectroscopy. UV–vis absorption spectroscopy was used to study the stability and absorption features of various Ce4+ compounds in sulphuric and methane sulphonic acid. Additionally, mixtures containing Ce4+ and Ce3+ were analyzed. In situ measurements during Ru etching show the conversion of the oxidizing agent to Ce3+. [ABSTRACT FROM AUTHOR]

Abstract Titanium niobium alloys exhibit a lower stiffness compared to Ti6Al4V, the 'gold standard' for load-bearing bone implants. Thus, the critical mismatch in stiffness between the implant and adjacent bone tissue could be addressed with TiNb alloys and thereby reduce stress shielding, which can result in bone resorption and subsequent implant loosening; however, the cellular response on the specific material is crucial for sufficient osseointegration. We therefore hypothesize that the response of human mesenchymal stromal cells (hMSC) and osteoblast-like cells on Ti45Nb surfaces can be improved by a novel nanoporous surface structure. For this purpose, an etching technique using hydrogen peroxide electrolyte solution was applied to Ti45Nb. The treated surfaces were characterized using SEM, LSM, AFM, nanoindentation, and contact angle measurements. Cell culture experiments using hMCS and MG-63 were conducted. The H 2 O 2 treatment resulted in surface nanopores, an increase in surface wettability and a reduction in surface hardness. The proliferation of MG-63 was enhanced on TiNb45 compared to Ti6Al4V. MG-63 focal adhesion complexes were detected on all Ti45Nb surfaces, whereas the nanostructures notably increased the cell area and decreased cell solidity, indicating stimulated cell spreading and pseudopodia formation. Alizarin red stainings indicated that the nanoporous surfaces stimulated the osteogenic differentiation of hMSC. It can be concluded that the proposed surface treatment could potentially help to stimulate the osseointegration behaviour of the advantageous low stiff Ti45Nb alloy. Graphical abstract Unlabelled Image Highlights • Combination of a low modulus Ti45Nb alloy with an appropriate surface modification • Technique produced nanopore network and microtopographical features. • Stronger capability of human mesenchymal stromal cells to form calcium minerals • H 2 O 2 etching of Ti45Nb stimulates osteogenic differentiation of stem cells. [ABSTRACT FROM AUTHOR]

Highlights • In-LDE is suited for etching of very deep nanoholes. • High thermal stability of In-etched nanoholes. • Intermixing between etching and substrate material. • Integration of In-LDE inside AlGaAs material-system possible. Abstract In contrast to Indium droplets the usage of Ga or Al droplets for the local droplet etching (LDE) technique is well established. It has been shown previously that In-droplets or In-alloys can be used for LDE with focus on small hole-depths at low etching temperatures. With our recent experiments we reveal that In-LDE is also well suited for the creation of very deep nanoholes (exceeding 100 nm) and very low densities in the range of 106 cm−2 for large average distances of several micrometers. The unexpected high thermal stability of the etching process itself as well as the formed wall-like structures clearly points to an intermixing between etching and substrate material during the LDE-process. This can be related to the lack of As during LDE. Additional experiments with capping layers also reveal high surface-roughness probably caused by a lattice mismatch, which can be also explained by intermixing. A second LDE step with Al can be applied to avoid roughening effects. [ABSTRACT FROM AUTHOR]

This article describes the test results for laser markability of automotive electrical cables. The insulation is PVC, but the colour and construction of the insulations are different. Two types of laser workstations were used, one with a wavelength of 1064 nm and another with 532 nm. The penetration depth of the laser beam was determined by optical microscopy on cross sections. The 1064 nm laser beam can mark all investigated materials with good contrast, except the yellow insulation. The 532 nm laser beam with fast speed can hardly produce contrast with any of the materials. The laser markability of the yellow insulation was found to be the most problematic. On the two-layer insulation, despite the whitening of the inner material, dark marking is produced because the heat developing on the interface of the two layers will heat up and carbonize the transparent layer. [ABSTRACT FROM AUTHOR]

FeCl3 bearing etching solution is mainly used for etching of metals used in shadow masks, PCBs and so on. Due course of Invar alloy etching process the FeCl3 bearing etching solution get contaminated with Ni2+ which affect adversely the etching efficiency. Hence, FeCl3 bearing etching solution discarded after several cycle of operation causes an environmental and economic problem. To address both the issues the etching solution was purified through solvent extraction and remained Ni2+ recovered by wet chemical reduction using hydrazine. For optimum Fe3+ extraction efficiency, various extraction parameter were optimized and size and morphology of the recovered pure Ni powder was analyzed. The reported process is a simple process to purify and recover Ni from industry etching solution. [ABSTRACT FROM AUTHOR]

Abstract Direct formation of graphene films on dielectric substrates is investigated by the "etching-precipitation" method which converts metal-carbon mixed films to graphene films by etching metal away by Cl 2 at 600–650 °C. Here we report a new approach for improved control of the layer number and continuity of the graphene films. Reactive sputtering of Fe in C 2 H 4 /Ar enabled fine control of the carbon concentrations and thicknesses of the initial Fe-C films, which yielded continuous multilayer graphene films of controllable average layer numbers of ~10–40, low resistivity down to ~240 μΩ cm, and high Raman G-band to D-band intensity ratio up to 16 directly on SiO 2 substrates. We also show that the carbon concentration of the initial Fe-C films determines the film continuity and crystallinity of the graphene. Highlights • Continuous films of multilayer graphene are formed directly on SiO 2. • Average layer number is controlled for a wide range of ~10–40. • Raman G-band to D-band intensity ratio up to 16 shows the high graphene quality. • Such films are obtained by removing Fe from Fe-C films using Cl 2 at 600–650 °C. [ABSTRACT FROM AUTHOR]

Surface reactions constitute the foundation of various energy conversion/storage technologies, such as the lithium–sulfur (Li‐S) batteries. To expedite surface reactions for high‐rate battery applications demands in‐depth understanding of reaction kinetics and rational catalyst design. Now an in situ extrinsic‐metal etching strategy is used to activate an inert monometal nitride of hexagonal Ni3N through iron‐incorporated cubic Ni3FeN. In situ etched Ni3FeN regulates polysulfide‐involving surface reactions at high rates. Electron microscopy was used to unveil the mechanism of in situ catalyst transformation. The Li‐S batteries modified with Ni3FeN exhibited superb rate capability, remarkable cycling stability at a high sulfur loading of 4.8 mg cm−2, and lean‐electrolyte operability. This work opens up the exploration of multimetallic alloys and compounds as kinetic regulators for high‐rate Li‐S batteries and also elucidates catalytic surface reactions and the role of defect chemistry. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Forming of the nanostructured SSCT layers. • Analysis of microstructure by statistical, Abbott-Firestone, Fourier and multifractal methods. • Analysis of density of vibrational states by Raman scattering. Abstract Nanostructured layers were formed on silicon substrate by using metal assisted etching method with different etching times. Microstructural properties of prepared layers were experimentally studied by the electron microscopy methods and analysed by the statistical methods, by the Abbott-Firestone method, by analysis of the power spectral density and by using methods of fractal geometry. Results of microstructure analysis show forming of particle size distribution in the volume of etched layer and its development during the structure preparation. Raman scattering was used for the determination of density of vibrational states related to formed particle size distribution. [ABSTRACT FROM AUTHOR]

Presents a study which extended a previously proposed heat of reaction model that described observed etch rate enhancements in the tantalum/fluorine etch system. Description of the model; Application of the model to several experimental systems; Information on the critical characteristic temperature.

Focuses on a study which analyzed laser chemical etching of metals in sodium nitrate solution. Experimental procedures; Computation of temperature increase; Value of absorbed power etching.

Abstract Amorphous carbon thin films were grown by magnetron sputtering on crystalline Si and fluorine-doped tin oxide (FTO) substrates and annealed at 600 °C in vacuum. Subsequently, the films were subjected to SF 6 plasma nanotexturing processes using different secondary gases such as H 2 , O 2 , and Ar. The samples were characterized by profilometry, atomic force microscopy, Raman spectroscopy, FTIR spectroscopy, and contact angle measurement. The samples have shown nanostructured surface patterns that strongly depended on the secondary plasma gas used (H 2 , O 2 , or Ar); the films subjected to the SF 6 + Ar plasma nanotexturing presented the highest surface roughness. Investigation of the atomic structure indicated that the annealing process is responsible for a significant increase in sp2 hybridization of C. The contact angle measurement results have revealed the hydrophilic to hydrophobic transition owing to the annealing process. In contrast, super hydrophilic behavior was observed after the plasma nanotexturing processes. The increase in both the surface roughness and hydrophilicity of these nanotextured carbon thin films are highly desirable characteristics for their application as counter-electrodes in dye-sensitized solar cells and batteries. Graphical abstract Unlabelled Image Highlights • Amorphous carbon thin films were submitted to plasma nanotexturing processes. • The applied process promoted a significant increase on the surface roughness. • After the surface nanotexturing the samples showed robust hydrophilic behavior. [ABSTRACT FROM AUTHOR]

In this study, laser-treated polycrystalline Si (pc-Si) wafers, fabricated by wire sawing of hot-pressed ingots sintered from Si powder, have been investigated. As-cut wafers and those with high-quality thin Si layers deposited on top of them by e-beam have been subjected to laser irradiation to clarify typical trends of structural modifications caused by laser treatments. Moreover, possibility to use laser-treated Si powder-based substrates for fabrication of advanced Si structures has been analysed. It is established that (i) Si powder-based wafers with thicknesses ~180 μm can be fully (from the front to back side) or partly (subsurface region) remelted by a diode laser and grain sizes in laser-treated regions can be increased; (ii) a high-quality top layer can be fabricated by crystallization of an additional a-Si layer deposited by e-beam evaporation on top of the pc-Si; and (iii) silicon nanowires can be formed by metal-assisted wet chemical etching (MAWCE) of polished Si powder-based wafers and as-cut wafers irradiated with medium laser power, while a surface texturing on the as-cut pc-Si wafers occur, and no nanowires can form in the region subject to a liquid phase crystallization (LPC) caused by high-power laser treatments. [ABSTRACT FROM AUTHOR]

Abstract: Although Ti3C2 MXene has shown great potential in energy storage field, poor conductivity and restacking between MXene flakes seriously hinders the maximization of its capacitance. Herein, a new strategy to solve the problems is developed. Gallery Al atoms in Ti3AlC2 are partially removed by simple hydrothermal etching to get Ti3C2Tx reserving appropriate Al interlayers (Ti3C2Tx@Al). Ti3C2Tx@Al keeps stable layered structure rather than isolated Ti3C2Tx flakes, which avoids flake restacking. The removal of partial Al frees up space for easy electrolyte infiltration while the reserved Al as “electron bridges” ensures high interlayer conductivity. As a result, the areal capacitance reaches up to 1087 mF cm−2 at 1 mA cm−2 and over 95% capacitance is maintained after 6000 cycles. The all‐solid‐state supercapacitor (ASSS) based on Ti3C2Tx@Al delivers a high capacitance of 242.3 mF cm−2 at 1 mV s−1 and exhibits stable performance at different bending states. Two ASSSs in tandem can light up a light‐emitting diode under the planar or wrapping around an arm. The established strategy provides a new avenue to improve capacitance performances of MXenes. [ABSTRACT FROM AUTHOR]

Super-hydrophobic film with hierarchical micro/nano structures was prepared by galvanic replacement reaction process on the surface of galvanized steel. The effects of the etching time and copper nitrate concentration on the wetting property of the as-prepared surfaces were studied. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and electrochemical technique were employed to characterize the surface morphology, chemical composition, and corrosion resistance. The stability and self-cleaning property of the as-fabricated super-hydrophobic film were also evaluated. The super-hydrophobic film can be obtained within 3 min and possesses a water contact angle of 164.3° ± 2°. Potentiodynamic polarization measurements indicated that the super-hydrophobic film greatly improved the corrosion resistance of the galvanized steel in 3.5 wt % NaCl aqueous solution. The highest inhibition efficiency was estimated to be 96.6%. The obtained super-hydrophobic film showed good stability and self-cleaning property. [ABSTRACT FROM AUTHOR]

Abstract: Multivariate data such as spectra frequently contain measured variables that are uninformative, and removal of such variables requires the use of methods that can be used to select informative variables. Partial least squares (PLS) regression may incorporate information from uninformative measured variables, and so it is important to select variables before performing the PLS regression. Elastic net (EN) regression can be used to perform variable selection automatically. An EN regression can be used to select groups of correlated variables or to select either sparse or nonsparse sets of variables. However, the predictive performance of the EN regression can be significantly worse than competing 1‐step variable selection methods such as variable importance in projection (VIP). In the present work, the use of the EN to select variables, followed by conventional PLS regression on the selected variables (EN‐PLS), has been investigated. Variable selection by using EN‐PLS was compared with that from EN regression, sparse PLS regression, VIP, and from selectivity ratio selection on 2 data sets of visible/near‐infrared spectra. In all cases, the wavelengths selected were compared with reference data. The variables selected by using EN‐PLS offered advantages in interpretability and gave more robust prediction performance as compared with those obtained from full‐spectrum PLS and the other variable selection methods. This paper reports a method for variable selection by using an EN regression prior to a second regression by using PLS, a 2‐step method termed EN‐PLS. Variables selected by using EN‐PLS are compared with variables selected from the EN regression, as well as VIP, selectivity ratio, and the sparse PLS regression, 3 commonly used methods for variable selection in chemometrics. The EN‐PLS is shown to select variables that were more easily interpreted. In addition, EN‐PLS performed more robustly than a PLS regression performed on all variables, as well as reduced PLS regressions by using variables selected from either the sparse PLS regression algorithm or a VIP variable selection followed by PLS modeling. [ABSTRACT FROM AUTHOR]

Abstract: As shallow architecture is inefficient in terms of computational elements, some incipient fault features can be characterized through the composition of many nonlinearities, ie, with deep network. In this paper, a novel approach is developed for multivariate statistical process monitoring based on higher‐order correlations. First, the correlations among monitoring variables can be learned by a multilayer learning framework hierarchically: The higher the number of layers to be stacked, the more nonlinear and abstract features can be characterized. Second, 3 monitoring statistics, SRE, M2, and C, are presented to monitor whether the process is remaining in control, and they are instructive for the identification of fault types. Moreover, only normal data are used in training phase; this can avoid the unbalance problem of different types of fault data. These capabilities of the proposed approach are illustrated with two industrial benchmarks, Tennessee Eastman process and Metal Etch process. [ABSTRACT FROM AUTHOR]

Asymmetrical etching of nanoparticles was achieved by employing interface-confined galvanic replacement reactions. Interfacial Ag nanocubes, nanowires and nanospheres were fabricated into symmetry-reduced cubic, trough-like and spherical nanocups, respectively. The formation of nanocups is attributed to in situ local nanomasking and selective etching of interfacial nanoparticles at the single-nanoparticle level. [ABSTRACT FROM AUTHOR]

This paper reports a magnet-less enhanced-efficiency electron trapping module (E3TM) that uses micromachined components to provide electron trapping using only RF electric fields. The structure of the E3TM is comprised of five microfabricated elements that include two perforated electrodes. Importantly, the electrode perforations are only 130 $\mu \text{m}$ in diameter in order to control the fringing electric field near the electrodes. The microfabricated elements enable a large volume efficiency, with the device occupying a volume of 1.63 cm3, of which 75.7% is available for the trap. The electron density as measured by proxy with a small probe near the center of the RF electron trap is approximated as $2.24 \times 10^{6}$ cm−3 when the E3TM is tuned to and operated at 96.9 MHz, and is approximated as $2.16 \times 10^{6}$ cm−3 when tuned to and operated at 141.3 MHz. This trap could potentially be used to enable a magnet-less ion pump for maintaining ultra-high vacuum in chip-scale atomic clocks or other atomic microsystems that are sensitive to magnetic fields. [2017–0296] [ABSTRACT FROM AUTHOR]

In this paper, the influence of a recess etching process on the contact resistance and the relevant electrical properties of In0.12Al0.8Ga0.08N/AlN/GaN HEMTs is presented. Without etching, the contact resistance is typically 0.9 Ω mm. By recess etching Rcont is reduced to 0.2 Ω–mm. A strong correlation of Rcont to the maximum drain saturation current (IDS+) and to the maximum transconductance (GmMax) is observed. Devices with Rcont of 0.2 Ω mm show IDS+ of 1.7 A mm−1 and GmMax of 620 mS mm−1, respectively. [ABSTRACT FROM AUTHOR]

A facile and cost-effective preparation process for Ag nanoparticles modified Si nanowires (Ag NPs@RNWs) was first developed based on the metal-assisted chemical etching (MACE)-produced Ag dendrites. Partial removal of the wrapped Ag dendrites and a crucial tetramethylammonium hydroxide (TMAH) post-etching treatment are sequentially involved in the process. The crucial step of TMAH-etching induces a loose array of needle-like SiNWs with highly rough surface (RNWs), and causes redistribution of the attached Ag NPs. HRTEM observations reveal that numerous tiny Ag NPs with size of 2–6 nm are firmly inlaid on the concave-convex surface of RNWs. Comparative investigations of NO 2 -sensing properties among the bare-SiNWs, RNWs and Ag NPs@RNWs were carried out at room temperature. The Ag NPs@RNWs sensor exhibits considerably enhanced response (about five times higher) compared with bare-SiNWs and can rapidly response ultrararefied NO 2 with deep ppb level. Above results demonstrate the considerable effect of the Ag NPs modification process developed here; the resulted rough and loose array promotes the response speed of the SiNWs sensors and the formed tiny Ag NPs contributes dramatic enhancement in response sensitivity. The enhanced response of Ag NPs@RNWs is analyzed based on Ag modification-induced electronic sensitization and TMAH etching-induced structural modulation. [ABSTRACT FROM AUTHOR]

A hydrochloric acid solution of hydrogen peroxide was suggested for etching lead sulfide films. The solubility of lead sulfide in relation to the hydrochloric acid concentration in the etching solution was calculated using thermodynamic analysis, taking into account the stability of lead complex species. The kinetics of hydrogen peroxide decomposition in the hydrochloric acid solution was studied, and the formal rate equation of the process was constructed. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) metal-semiconductor nanostructures as surface-enhanced Raman scattering (SERS) substrates were designed by in situ electrodeposition of gold nanoparticles (AuNPs) or in situ photodeposition of silver nanoparticles (AgNPs) on gallium nitride (GaN) nanoflowers (NFs) supports fabricated by metal-assisted photochemical etching of single crystalline GaN. 3D AuNPs/GaN NFs and AgNPs/GaN NFs substrates exhibit excellent enhancement effect for Rhodamine 6G (R6G) due to more “hot spots” in the same probing volume compared to 2D GaN based substrates. The enhancement factors of the AuNPs/GaN NFs and AgNPs/GaN NFs substrates are up to 2.1 × 10 7 and 5.9 × 10 7 , respectively, and the corresponding detection limits of R6G are 10 −8 and 10 −10 M, respectively. Moreover, further study reveals both substrates have good reproducibility and long-term stability. The performance of the prepared substrates for biological application was demonstrated by the detection of bovine serum albumin (BSA). A series of characteristic bands of amides suggest BSA can be well adsorbed on the surface of the AuNPs/GaN NFs and AgNPs/GaN NFs substrates, which demonstrates our substrates have good biocompatibility and are promising candidates for SERS biosensors. [ABSTRACT FROM AUTHOR]

Fresnel zone plates are widely used as nanofocusing optics for x-ray microscopy, where the spatial resolution is set by the width of the finest rings while the efficiency is set by their thickness. This leads to the requirement for high aspect ratio nanofabrication. Metal-assisted chemical etching and atomic layer deposition has already been used to produce high aspect ratio zone plate structures on unthinned silicon wafers. The authors demonstrate here a substantial improvement on the achieved aspect ratio up to a value of 500:1, by producing 16 nm wide platinum zones with thicknesses up to 8 µm. At the same time, the silicon substrate was thinned to 15 µm as required for a practically useful optic. First tests have shown 4.8% diffraction efficiency using 20 keV x rays. This x-ray focusing efficiency is higher than most Fresnel zone plates for this photon energy and near what has been achieved with multilayer-coated Kirkpatrick-Baez mirrors, and multilayer Laue lenses. Hard x-ray zone plates offer the advantages of easy alignment, energy tunability, and one can make many zone plates in a batch on a single silicon chip. [ABSTRACT FROM AUTHOR]

Well-defined Pt 3 Fe/Fe superhydrophobic materials on iron sheet with special properties, such as corrosion resistance, superhydrophobicity and superoleophilicity, was fabricated. The fabrication process involved etching in hydrochloric acid aqueous solution and simple replacement deposition process without using any seed and organic solvent, and then annealing. The electrochemical measurements show that the resultant surface in 3.5% sodium chloride solution displays good corrosion resistance. Also, it is proved that the obtained surface has better mechanical abrasion resistance via scratch test. The superoleophilicity and low water adhesion force of the obtained surface endow it high oil/water separation capacity. The as-prepared nanocomposites display enhanced catalytic activity and kinetics toward degradation of methyl orange. In particular, it possesses the most efficient degradation capacity (95%) towards methyl orange at a high concentration (17.5 mg/L) in 80 min. The improved stability and excellent catalytic activity of the Pt 3 Fe/Fe nanocomposites promise new opportunities for the development of waste water treatment. [ABSTRACT FROM AUTHOR]

In this study, we have reported a new approach for sequence specific microRNA-155 (miRNA-155) detection by water soluble luminescent copper nanoclusters. The method is based on the shifts in the fluorescence emissions of oligonucleotide-templated copper nanoclusters (DNA-CuNCs) and can be regarded as the first instance of using fluorescent CuNCs for the detection of microRNA by forming DNA-RNA heteroduplex. The as-prepared CuNCs exhibited a strong fluorescence enhancement at 510 nm and a red shift (60 nm) when bonded to the target miRNA-155 (DNA-RNA heteroduplex formation). Under the optimal conditions, the fluorescent intensity of DNA-CuNCs increased by the increasing the target miRNA-155 with in a dynamic range from 5.0 × 10 −12 to 1.0 × 10 −8 M down to a detection limit (LOD) of 2.2 × 10 −12 M. The target miRNA is selectively discriminated from mismatched miRNA by this method. The method was further applied to the determination of miRNA spiked human serum samples. Overall, the nanobiosensor showed the potential of becoming a potential alternative tool for the detection of miRNA-155 in biomedical research and early clinical diagnostic studies. [ABSTRACT FROM AUTHOR]

Building upon the depth and breadth of Harold Winters's work, this paper pays tribute to his pioneering contribution in the field of plasma etching of metals, and how that knowledge base helps guide the fundamental research in these areas. The fundamental understanding of the plasma-surface interactions during metal etch is key to achieve desirable etch efficacy and selectivity at the atomic scale. This paper presents a generalized methodology, combining thermodynamic assessment and kinetic verification of surface reactions, using copper, magnetic metals, and noble metals as examples, in an effort to demonstrate the applicability of this strategy in tailoring plasma-surface interactions at the atomic scale for a wide range of materials. [ABSTRACT FROM AUTHOR]

In this work, SiNWs arrays were fabricated from mc-Si wafer using one step nano-silver catalyzed chemical etching method. The effect of AgNO concentration on morphology structure, antireflection property and effective carrier lifetime of textured mc-Si were carefully studied. The results indicate that the length and inter spacing of SiNWs arrays are conducive for improving antireflection property of SiNWs arrays, but the increasing etching seriously deteriorates effective carrier lifetime. Moreover, KOH correction of SiNWs was performed to further reduce the reflectance loss, which is also conducive to reduce the photo-generated carrier recombination. Under preference immersion time of 240 s, a large scale SiNWs arrays with the ultra-low antireflection ability of ~3.4% and excellent effective carrier lifetime of 3.30 μs can be obtained, which shows a great significance for producing high-efficiency polysilicon solar cells. [ABSTRACT FROM AUTHOR]

Suspended inductors and 2.45 GHz BPF with patterned ground shields on the lossy silicon substrate by using Cu/BCB based wafer level packaging and bulk Si etching technologies were fabricated. Thick BCB interlayer is used as the supporting dielectric and the backside cavity is easily removed by using a two-step back-etching process. The fabricated 2.7 nH inductor has a maximum Q factor 49 at 8.2 GHz and high Q factors more than 22 in the broadband frequency range from 1 to 10 GHz. And the realized 2.45 GHz BPF has the insertion loss of 3.0 dB and the return loss of more than 14 dB at the pass band. It is also featured by more than 48 and 25 dB attenuation at 0.9 and 1.8 GHz respectively, with the second harmonic rejection being 33 dB. [ABSTRACT FROM AUTHOR]

In this paper, we present a self-aligning pre-etched pattern based technique to precisely determine the <110> direction on Si{110} wafer surface. These patterns after etching, reveals the crystallographic direction by self-aligning itself in a straight line at the <110> direction while getting self-misaligned at other directions. As a result, the exact direction can be identified by a simple visual inspection under a microscope without the need of measurement of any kind. To test the accuracy of the proposed method, we fabricated two 32 mm long channels, one oriented along the <110> direction and other along the <112> directions using the <110> direction obtained from the proposed method as the reference. The undercutting is measured at different locations on the two channels and is found to vary within a submicron range in each case. Such uniform undercutting implies that the presented technique to determine the <110> direction is accurate. This methodology is simple and can be used conveniently to fabricate MEMS structures with high dimensional accuracy. [ABSTRACT FROM AUTHOR]

Many potential applications of porous silicon nanowires (SiNWs) fabricated with metal-assisted chemical etching are highly dependent on the precise control of morphology for device optimization. However, the effects of key etching parameters, such as the amount of deposited metal catalyst, HF-oxidant molar ratio ( χ), and solvent concentration, on the morphology and etching kinetics of the SiNWs still have not been fully explored. Here, the changes in the nanostructure and etch rate of degenerately doped p-type silicon in a HF-HO-HO etching system with electrolessly deposited silver catalyst are systematically investigated. The surface morphology is found to evolve from a microporous and cratered structure to a uniform array of SiNWs at sufficiently high χ values. The etch rates at the nanostructure base and tip are correlated with the primary etching induced by Ag and the secondary etching induced by metal ions and diffused holes, respectively. The HO concentration also affects the χ window where SiNWs form and the etch rates, mainly by modulating the reactant dilution and diffusion rate. By controlling the secondary etching and reactant diffusion via χ and HO concentration, respectively, the fabrication of highly doped SiNWs with independent control of porosity from length is successfully demonstrated, which can be potentially utilized to improve the performance of SiNW-based devices. [ABSTRACT FROM AUTHOR]

Comprehensive the above results, SiOxNy peeling on OC photoresist layer has a serious impact on the yield of products. This paper found that SiOxNy peeling reason is the process of acid attacking OC photoresist surface, which resulted in 200-800Å expansion zone. The characterization confirmed that organic material was residue on OC photoresist expansion zone. The paper also shows organic substance was vaporized after high temperature and the dense SiOxNy film result in difficult to release gas, furthmore SiOxNy film bubble appearance. The experiment results show that by adding 230℃ anneal after Metal etching and Strip process, the Peeling can be solved which can improve the yield of the product. [ABSTRACT FROM AUTHOR]

Transparent conducting films have been widely used in display devices such as flat panel displays, touchscreens, organic light-emitting diodes (OLEDs), and liquid-crystal displays. However, common techniques of patterning transparent conducting films, such as photolithography and laser patterning, are complex and require large investment. Therefore, research regarding fast and inexpensive patterning procedures for large area is still ongoing. In this study, a novel technique, which combines micro-electrical discharge machining (μ-EDM) with dynamic electrochemical etching, was applied to produce indium tin oxide (ITO) line patterns on glass substrates. Commercial tungsten (W) rods were used to fabricate microelectrodes by dynamic electrochemical etching and were subsequently used to create ITO line patterns by μ-EDM. A series of experiment was carried out to optimize the machining conditions such as gap voltage, cutting speed, and spindle speed. The criteria of this investigation were of the minimum difference between the tool diameter and the pattern width and the low waviness of the line edges. In addition, practical relations for each step were built to control machining process at high accuracy. By using these mathematical relations, the width of the resulting ITO line patterns can be predicted with an error of less than 4 %. Furthermore, the proposed technique proved that it can work well for long working distance. [ABSTRACT FROM AUTHOR]

Based on enzymatic-like reaction mediated etching of gold nanorods (GNRs), an ultrasensitive visual method was developed for on-site detection of urine glucose. With the catalysis of MoO 4 2 − , GNRs were efficiently etched by H 2 O 2 which was generated by glucose-glucose oxidase enzymatic reaction. The etching of GNRs lead to a blue-shift of logitudinal localized surface plasmon resonance of GNRs, accompanied by an obvious color change from blue to red. The peak-shift and the color change can be used for detection of glucose by the spectrophotometer and the naked eyes. Under optimal condition, an excellent sensitivity toward glucose is obtained with a detection limit of 0.1 μM and a visual detection limit of 3 μM in buffer solution. Benefiting from the high sensitivity, the successful colorimetric detection of glucose in original urine samples was achieved, which indicates the practical applicability to the on-site determination of urine glucose. [ABSTRACT FROM AUTHOR]

Porous gallium nitride (PGaN) layers were fabricated by metal-assisted photochemical etching (MaPCE) using electrodeposited platinum nanoparticles (PtNPs) or gold nanoparticles (AuNPs) as catalysts. After identification of a suitable negative potential and appropriate cyclic voltammetry (CV) conditions, high-density PtNPs or AuNPs were deposited onto a planar GaN substrate. Based on the concrete numerical values of energy levels, the generation, transfer and consumption of electrons and holes, and the assumption that localized galvanic cells are formed, an etching mechanism was proposed which may provide theoretical guidance for future work on etching of GaN and other semiconductor materials. [ABSTRACT FROM AUTHOR]

Nanosized cobalt oxides were synthesized by ammonia-etching of cobalt hydroxide and subsequent calcination. The effects of ammonia etching on the structures and catalytic properties of cobalt oxide were investigated. The results suggested that the cobalt oxide is composed of cubic CoO having particle sizes in the range of 10-20 nm; smaller than the analogue prepared through the conventional precipitation method. Ammonia etching improved the reducibility of cobalt oxide, and facilitated the generation of surface oxygen vacancies and the production of surface-adsorbed active oxygen species. The activity of CoO in propane oxidation was greatly enhanced by ammonia etching, mainly due to the smaller particle size and better redox properties. The facile ammonia-etching synthesis method has potential for large-scale and low-cost production of cobalt oxide catalyst. Graphical Abstract: [ABSTRACT FROM AUTHOR]

One-stage preparation of superhydrophobic stainless steel surface is achieved by combining chemical etching and assembly. The contact angle of the prepared surface reaches as high as 175°. The correlative mechanism between the contact angle and surface morphology is elucidated from the dynamics perspective by controlling reaction conditions. The optimum reaction conditions are then determined. Experimental results demonstrate that the stainless steel surface achieves optimal water contact angle upon the formation of the 'honeycomb' 3D network structure. Electrochemical corrosion test shows that the prepared superhydrophobic stainless steel surface possesses 16 times higher corrosion resistance than common stainless steel surface. [ABSTRACT FROM AUTHOR]

Etching aluminum foil was prepared by electrochemical DC etching under ultrasonic superimposition. Specifically, the relationship of electrochemical behavior, interface behavior and mass transfer enhancement from ultrasound was investigated intensively by chronopotentiometry, potentiodynamic polarization, cyclic voltammetry and electrochemical impedance spectra. Meanwhile, the etching specimens were characterized by SEM, N 2 adsorption and XRD patterns measurements. The results showed that ultrasonic agitation inhibited the growth of aluminum oxide film and facilitated pit initiation effectively via increasing the Cl − adsorption on electrolyte/aluminum oxide film interface, and strengthened the inward/outward migration of Cl − and AlCl 3 within tunnels by thinning the thickness of diffusion layer and decreasing the electrolyte resistance. Moreover, the double layer capacitance C dl , pit density, average pit size/tunnel length and its homogeneity are all enhanced under ultrasonic superimposition. [ABSTRACT FROM AUTHOR]

Porous silicon (Si) nanowire arrays were directly fabricated from lightly p-doped Si substrates using a palladium (Pd)-assisted chemical etching at room temperature. The mechanistic studies indicated that anodic dissolution of Si was established by the accumulated positive charges at Pd/Si schottky interfaces in the presence of H 2 O 2 oxidants. In addition to the primary etching direction vertically to the substrate planes, the additional sidewall etching was stimulated by the separated Pd nanoparticles during reaction that constitutes the porous features covering on the nanowires surfaces thoroughly. These combined effects lead to the distinct etching characteristics and remarkable photoluminescent properties of resulted nanostructures. [ABSTRACT FROM AUTHOR]

Atom probe tomography was employed to characterize the microstructure and C distribution in the white etching area (WEA) of a martensitic 100Cr6 bearing steel subjected to rolling contact fatigue. Different from its surrounding matrix where a plate-like martensitic structure prevails, the WEA exhibits equiaxed grains with a uniform grain size of about 10 nm. Significant C grain boundary enrichment (>7.5at.%) and an overall higher C concentration than the nominal value are observed in the WEA. These results suggest that the formation of WEA results from severe local plastic deformation that causes dissolution of carbides and the redistribution of C. [ABSTRACT FROM AUTHOR]

Atomic layer etching (ALE) is a promising technique that can solve the challenges associated with continuous or pulsed plasma processes--trade-offs between selectivity, profile, and aspect ratio dependent etching. Compared to silicon, oxide, and other materials, atomic layer etching of silicon nitride has not been extensively reported. In this paper, the authors demonstrate the self-limited etching of silicon nitride in a commercial plasma etch chamber. The process discussed in this paper consists of two sequential steps--surface modification in hydrogen plasma followed by the removal of modified layers in fluorinated plasma. In addition to the ALE characteristics, the authors also demonstrate that the process is anisotropic and the selectivity to oxide is >100. Although the saturated etch rate of one monolayer per cycle could not be attained, self-limited etching of silicon nitride still enables us to incorporate the benefits of atomic layer etching such as an absence of isodense bias and an extremely high selectivity to oxide into practical etch applications. [ABSTRACT FROM AUTHOR]