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The etching stage of the corrosive preparation is a crucial element of creating a high quality anatomical specimen, which can be a source of scientific knowledge and support the teaching process. Nowadays, thermal techniques such as microwave cooking, enzymatic corrosion, and chemical corrosion are used. Living organisms can also be used for tissue maceration. Interactions between the corrosive substance and the filler carry a risk of failure; thus, choosing the correct method is key to the success of this technique. In this paper, we have reviewed the latest literature in order to present the strengths and weaknesses of currently used corrosion techniques. We proposed a definition of an ideal corrosive medium and compared the available techniques of etching corrosive preparations with a hypothetical perfect medium.

Statement of problem Whether procedures performed before the cementation of computer-aided design and computer-aided manufacturing (CAD-CAM) glass-ceramic restorations, including milling, fitting adjustment, and hydrofluoric acid etching introduce defects on the ceramic surface that affect the mechanical and surface properties is unclear. Purpose A systematic review and meta-analysis were conducted to assess the effect of milling, fitting adjustments, and hydrofluoric acid etching (HF) on the flexural strength and roughness (Ra) of CAD-CAM glass-ceramics. Material and methods Literature searches were performed up to June 2020 in the PubMed/MEDLINE, Web of Science, and Scopus databases, with no publication year or language limits. The focused question was “Do milling, fitting adjustments, and hydrofluoric acid etching affect the flexural strength and roughness of CAD-CAM glass-ceramics?” For the meta-analysis, flexural strength and Ra data on milling, fitting adjustment, and HF etching versus control (polishing) were analyzed globally. A subgroup analysis assessed the effect of etching parameters (HF concentration and time) on the flexural strength and roughness of CAD-CAM glass-ceramics with different microstructures. Comparisons were performed with random-effect models at 5% significance. Results Fourteen studies from 2764 potentially relevant records were included in the qualitative syntheses, and 12 in the meta-analysis. Milling and fitting adjustments increased roughness and reduced the flexural strength of CAD-CAM glass-ceramics. The effect of HF etching was dependent on the glass-ceramic microstructure, HF concentration, and etching time. For feldspathic- and leucite-reinforced ceramics, HF 5% applied for between 30 and 120 seconds increased roughness without affecting flexural strength. For lithium disilicate glass-ceramics, HF concentrations greater than 4.9% used for 20 seconds or more reduced the strength without affecting the surface roughness. Conclusions The flexural strength of CAD-CAM glass-ceramic is reduced by grinding procedures such as milling and fitting adjustment. Ceramic microstructure, HF concentration, and etching time determined the effect of hydrofluoric acid etching on the flexural strength and surface roughness of glass-ceramic materials.

In this work, we demonstrate the realization of L-Shaped Schottky Barrier FET as a biosensing device with improved sensitivity. The proposed device uses dual material gate with work functions of 4.2 eV (Al) and 4.8 eV (Cu) and Hafnium Oxide (HfO2) as the gate dielectric. In order to detect the biomolecule, a nano-gap cavity is created in the vertical gate (Gate1) by etching out the oxide. The electrical characteristics of biomolecules such as dielectric constant and charge density modulate the Schottky Barrier width, which in turn, changes the drive current of the device. Various sensitivity parameters have been thoroughly investigated at VDS = VGS = 0.5V and a comparative analysis with the conventional device has been performed. The results so obtained reveal that ION sensitivity of the proposed device is much better for both neutral as well as charged biomolecules (maximum of 21x for neutral, at K=12; 20x for charged biomolecules at ρ=-5x1010cm-2, at K=12). Besides this, the ION/IOFF sensitivity, transconductance (gm) sensitivity and selectivity show similar improvements. Further, the proposed device shows better sensitivity performance at low as well as at higher temperatures as compared to the state-of-the-art biosensing devices.

Synthetic two-dimensional (2D) mono-elemental crystals, namely X-enes, have recently emerged as a new frontier for atomically thin nanomaterials with on-demand properties. Among X-enes, antimonene, the β-phase allotrope of antimony, is formed by atoms arranged in buckled hexagonal rings bearing a comparatively higher environmental stability with respect to other players of this kind. However, the exploitation of monolayer or few-layer antimonene and other 2D materials in novel opto-electronic devices is still hurdled by the lack of scalable processes. Here, we demonstrated the viability of a bottom-up process for the epitaxial growth of antimonene-like nanocrystals (ANCs), based on a Metal-Organic Chemical Vapor Deposition (MOCVD) process, assisted by gold nanoparticles (Au NPs) on commensurate (1 1 1)-terminated Ge surfaces. The growth mechanism was investigated by large- and local-area microstructural analysis, revealing that the etching of germanium, catalyzed by the Au NPs, led to the ANCs growth on the exposed Ge (1 1 1) planes. As a supportive picture, ab-initio calculations rationalized this epitaxial relationship in terms of compressively strained β-phase ANCs. Our process could pave the way to the realization of large-area antimonene layers by a deposition process compatible with the current semiconductor manufacturing technology.

Due to its high theoretical capacity and appropriate potential platform, tin-based alloy materials are expected to be a competitive candidate for the next-generation high performance anodes of lithium-ion batteries. Nevertheless, the immense volume change during the lithium-ion insert process leads to severe disadvantages of structural damage and capacity fade, which limits its practical application. In this work, a three-dimensional (3D) multicore-shell hollow nanobox encapsulated by carbon layer is obtained via a three-step method of hydrothermal reaction, annealing and alkali etching. During the electrochemical reactions, the CoSn@void@C nanoboxes provide internal space to compensate the volumetric change upon the lithiation of Sn, while the inactive component of Co acts as chemical buffers to withstand the anisotropic expansion of nanoparticles. Owing to the above-mentioned advantages, the elaborated anode delivers an excellent capacity of 788.2 mAh/g at 100 mA/g after 100 cycles and considerable capacity retention of 519.2 mAh/g even at a high current density of 1 A/g after 300 cycles. The superior stability and high performance indicate its capability as promising anodes for lithium-ion batteries.

The effect of the oxidizer present in the etching solution on the surface morphology and microstructure obtained after porosifying a p-type silicon wafer using metal-assisted chemical etching was studied. The morphologies of Si wafers porosified using two different solutions, HF/H2O2 and HF/KMnO4, were compared to establish how either of the oxidizers (H2O2 or KMnO4) should be chosen depending on the desired application. A comparative study revealed that parallel pores with wire-like structures or interconnected pores with cheese-like structures can be obtained when H2O2 or KMnO4 are chosen, respectively. Careful analysis of the SEM images was carried out using ImageJ to establish that the samples prepared using KMnO4 are more porous due to aggressive etching. Additionally, experimental and theoretical Raman spectroscopic studies have been utilized to study the presence of low-dimensional Si nanostructures, which are a few nanometers in size, at the microscopic level in porosified silicon.

Statement of problem Dental implants undergo various surface treatments. Studies that have characterized their surface and subsurface by using the same methods are scarce. Purpose The purpose of this study is to physically characterize the surface and subsurface of implant systems made of commercially pure (cp) titanium (Ti) grade (gr) 4 and Ti alloy gr 23 and to evaluate whether airborne-particle abrasion and acid etching is an appropriate surface treatment for Ti alloy gr 23. Material and methods Implant groups (n=3) were as follows: TG4AO, cp Ti gr 4, treated with anodic oxidation (3.5×8 mm) (NobelReplace Conical; Nobel Biocare); TG23AE, Ti gr 23 (TiAlV ELI) airborne-particle abraded-and-etched (3.9×8 mm) (V3; MIS); and TG4AE, cp Ti gr 4, airborne-particle abraded and etched (3.3×8 mm) (BL; Institut Straumann AG). Surface roughness, surface topography, and elemental and surface composition were investigated with optical profilometry, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The presence and size of Ti hydride (TiH) needles were determined on metallographic sections. Depth profiling was obtained by time-of-flight secondary ion mass spectrometry (ToF-SIMS) to determine possible enrichment of an alloying element at the implant surface. Results The mean arithmetic deviation roughness (Sa), of TG4AO was 0.80 μm. The Sa of TG4AO was 1.22 μm, and the Sa of TG4AO was 1.59 μm. The difference between the groups was significant (P Conclusions The roughness, topography, and composition of the surfaces were different for all implants tested. Airborne-particle abrasion and subsequent etching was an appropriate treatment for Ti gr 23 alloy implants.

Transition-metal phosphides have been of concern as efficient electrocatalysts for oxygen evolution reaction (OER) due to its high conductivity and earth-abundance reserves. However, oxide overlayers formed on their surface by spontaneously atmospheric oxidation are usually neglected, thus confusing the establishment of structure–performance relationship. Herein, we successfully etched the oxide overlayers of NiFe phosphide (NiFeP) by a dielectric barrier discharge (DBD) plasma technique, aiming to reveal the influence of the oxide overlayers on its electrocatalytic performance for OER. It is found that etching the oxide overlayers can accelerate the surface reconstruction process of NiFeP and facilitate the formation of metal hydroxides, which are key intermediate phases for OER. Consequently, the etched NiFeP-DBD material shows remarkably enhanced OER activity with an overpotential of 265 mV at a current density of 10 mA/cm2. The finding of this work probably brings a significant impact to understand the structure–performance relationship of metal phosphide in electrooxidation reaction.

A facile and mild route to synthesize C-coated SiC nanosheets (SiC/C NSs) via wet-chemical etching in hydrofluoric acid (HF) at 60 °C for 48 h using carbon aluminum silicate (Al4SiC4) as raw materials is reported for the first time. HF molecule leads to the breaking of C-Al bonds in Al4SiC4, which eventually results in the formation of two-dimensional SiC nanosheets. A carbon layer with a thickness of approximately 1.5 nm is formed on the surface of SiC nanosheets due to the excess carbon. The prepared SiC/C NSs possess a smooth and rectangular sheet with a mean 150 nm in width, 500 nm in length and 10 nm in thickness, respectively. The crystallographic characterization indicates that 3C-SiC and 2H-SiC coexist and the parallel plane relationship of 3C/2H-SiC heterojunction is (111)3C-SiC//(001)2H-SiC. Due to the formed 3C-SiC/2H-SiC heterojunction and graphitic carbon, the fabricated electrode based on SiC/C NSs exhibits prolonged cycling stability and high specific areal capacitance as a promising supercapacitor candidate. It remains 91.2% retention even after 20000 cycles and 734 μF/cm2 at a scan rate of 10 mV/s.

A defected ground antenna with dielectric reflector is designed and investigated for breast tumour diagnosis. Ultra-wide band resonance (3.1 to 10.6 GHz) is achieved by etching two slots and adding a narrow vertical strip in a patch antenna. A high dielectric constant substrate is added below the antenna, which shows remarkable effect on performance. Antenna performance is verified experimentally on an artificially fabricated breast tissue and tumour. Malignant tissue has different dielectric properties than the normal tissue, that causes deviation in the scattered antenna power. Average value of backscattered signal variation and ground penetrating radar (GPR) algorithm is used to localize the tumour of radius 4mm in breast tissue.

Dielectric polarization performance induced by defect engineering approach has been proved to be an effective way for improving the microwave absorption property of carbon-based materials. Assisting by the solid-state reaction, the structural integrity of multi-walled carbon nanotubes (MWCNTs) would be broken along with the volume expansion and etching process of cobalt oxides. Therefore, the defects could be obtained and result in the enhancement of microwave absorption property. Ascribing to the broken wall structures, the defect-distances (LD) and concentrations (nD) have been optimized to be 9.80 nm and 3.37 × 1011 cm−2. The minimum reflection loss (RL) had reached -54.6 dB at 4.5 GHz with a thickness of 4.13 mm and the corresponding effective absorption bandwidth (EAB

PURPOSE To assess the shear bond strength of composite resin to polyether ether ketone (PEEK) after mechanical and chemical surface treatments. MATERIALS AND METHODS A total of 48 PEEK discs were fabricated and divided equally into four surface treatment groups (n = 12 each): (1) airborne particle abrasion with 50-μm alumina particles at 2 MPa pressure for 10 seconds; (2) 98% sulfuric acid etching for 1 minute; (3) airborne particle abrasion and sulfuric acid etching; and (4) no surface treatment. Specimens were conditioned, then Gradia composite veneer (GC) was applied to the PEEK surfaces and polymerized. Bond strength was measured with shear bond test using a universal testing machine. One-way analysis of variance and Tukey post hoc tests were applied for statistical analysis. RESULTS The mean shear bond strength values of the sulfuric acid-etched group were higher than that of the airborne particle abrasion + acid etching, airborne particle abrasion, and control groups (P < .05). Mean shear bond strength values for the airborne particle abrasion + acid etching samples were higher than for the control and airborne particle abrasion groups (P < .05). CONCLUSION There was no significant difference between the samples treated with airborne particle abrasion and the control group.

Metal-organic frameworks (MOFs) derivatives have been widely explored as highly efficient electromagnetic absorbing materials. Due to their diverse coordination arrangements, morphologies, and unique structures, MOFs provide promising avenues for synthesizing materials with customized properties. However, strategies for tailoring properties of low-dimensional MOFs-derived absorbers with hollow structures remain a considerable challenge. Herein, a well-defined Co@N-doped porous carbon composite (Co/N PC) with double-shell hollow structures has been successfully developed through self-templating-polymerization and subsequent pyrolysis. The proposed strategy for the synthesis of hollow architecture involves three simple steps (i) coordination, (ii) dissociation, and (iii) dopamine (DA) polymerization. The synthetic approach is realized at room temperature without a need for solvent etching. By effectively optimizing parameters including void thickness, surface structures, and graphitization levels, the as-designed Co/N PC composites feature wide absorption bandwidth of 5.93 GHz at a thickness of 2.4 mm with a filler loading of 15 wt%. The exceptional performance of microwave absorption (MA) is primarily achieved through excellent dielectric loss, and enhanced impedance matching, due to increased conductive loss through porous hollow structures and dipolar/interfacial polarization. This work provides an eco-friendly and facile route to designing hollow MOFs derivatives, offering substantial parameter space for optimized future lightweight and efficient absorbing materials.

This paper proposes a highly sensitive, compact, and low-cost optical fiber salinity sensor based on the Mach-Zehnder interferometer. The sensor is constructed using a single mode fiber (SMF) - no-core fiber - double-C fiber (DCF) - NCF-SMF structure, with the DCF prepared by etching the dual side-hole fiber with HF acid. The DCF's large-size exposed microfluidic channels solve the previous microstructured optical fiber's challenging liquid filling and replacement problems. Theoretical simulations and experiments demonstrate that the sensor is suitable for high-sensitivity salinity measurement. The sensor exhibits a high salinity sensitivity of -2.26 nm/‰ in the salinity range of 10‰-50‰, as demonstrated by the experimental results. Additionally, the sensor exhibits some fascinating characteristics, including high repeatability, hysteresis, reversibility, and stability.

Currently, the development of high-efficiency electromagnetic wave (EMW) absorbing materials has received close attention. Due to unique composition and structure, porous hollow carbon spheres (PHCSs) have been extensively studied in the EMW absorption field. In order to obtain the regulated EMW absorber, in the present study, sulfur was successfully doped into the PHCS by hydrogen peroxide etching and high temperature vulcanization. By fixing the amount of sulfur doped and the etching time, the micro-structure of the product could be effectively controlled, and the corresponding electromagnetic parameters would also change accordingly. The optimized sulfur-doped porous hollow carbon sphere (SPCHS) had the minimum reflection loss (RL) value of −27.2 dB, and the effective bandwidth of 4.76 GHz. More importantly, the best effective bandwidth (EAB, RL

Frosted glass takes considerable research attention due to its simple preparation process and wide application prospect. Herein, acid dissolving salt solution chemical etching method was used to prepare anti-glare (AG) and anti-reflection (AR) glass, and the relationship between etching time and surface crystallization under the constant temperature and the same acid concentration was explored. Based on which, the chemical reaction mechanism was clarified, and the dynamic model of the particle growth of the surface of the etched glass was fitted. The results indicated that with the prolongation of the etching time, the content and size of the insoluble fluorosilicate particles formed on the glass surface increased, and the growth of crystals conformed to the power-law model. Due to the appropriate amount and size of the precipitated insoluble fluoride salts, a light trapping structure was formed on the glass surface to capture incident light so that the transmittance of the glass was increased to a certain extent, and the specular reflection of the surface was effectively transformed into diffuse reflection, achieving an anti-glare effect. The glass etched in the frosting solution with pH = 3 for 15 min showed the best optical properties, with the transmittance of 89%, while the average light reflectance was reduced by 75%. It provides the possibility for the protection of historical buildings.

A novel methodology to create metallic waveguides with multilayer integrated vertical electromagnetic bandgap (EBG) structure is proposed in this paper, and the structure realizes low-cost millimeter-wave (mmWave) slot array antennas. A multilayer stack of easy-to-process thin metallic etching plates is introduced to design mmWave waveguide using compression-fit instead of diffusion bonding and welding assembly process. The electromagnetic (EM) wave leakage from the gaps between the metallic plates is suppressed using the vertical-EBG structure and anti-phasing feeding. The dispersion diagrams of the vertical-EBG unit cell are investigated to illustrate the suppression of leakage. Another leakage wave intercepting methodology is adopted by anti-phase feeding to prevent leakage wave from adjacent slot sub-arrays. Finally, two examples of 2×8 and 8×8 slot array antennas are presented to verify our design concept. The measured impedance bandwidths of the two antennas are 77.1-84.6 GHz (9.3%) and 78.6-84.9 GHz (7.7%), respectively. In addition, the 3-dB broadside gain bandwidths are 73.1 to 85.3 GHz (15.1%) and 76.8 to 84.4 GHz (9.4%), respectively. The results show aperture efficiencies up to 56.4%.

In this study, water-dispersible graphitic carbon nitride (g-C3N4) photocatalysts were successively prepared through the chemically oxidative etching of bulk g-C3N4 that was polymerized thermally in different calcination atmospheres such as air, CO2, and N2. The different calcination atmospheres directly influenced the physicochemical and optical properties of both bulk and water-dispersible g-C3N4, changing the photocatalytic degradation behavior of methylene blue (MB) and tetracycline hydrochloride (TC-HCl) for water-dispersible g-C3N4. The bubble-burst process in the thermal polymerization of thiourea produced defective edges containing C=O groups that preferred substituting the C-NHx groups over bulk g-C3N4. In the oxygen-free N2 atmosphere among the different calcination atmospheres, more C=O functional groups were generated on the defective edges of bulk g-C3N4, resulting in the highest N vacancy of the tri-s-triazine structure. During the successive chemical oxidation, S- or O-containing functional groups were introduced onto water-dispersible g-C3N4. The water-dispersible g-C3N4 photocatalyst from the oxygen-free N2 atmosphere (NTw) contained the most O- and S- functional groups on the g-C3N4 surface. Consequently, NTw exhibited the highest photocatalytic activity in the MB and TC-HCl photodegradation because of its slowest recombination process, which was ascribed to the unique surface properties of NTw such as abundant functional groups on the defective edges and N-deficient property.

In this paper, a new method for pesticide detection based on porous silicon microcavities was proposed. First, the aptamer of acetamiprid was fixed in the functionalized porous silicon microcavity. Then, the complementary strand of the aptamer modified with graphene quantum dots was hybridized with the aptamer, and the effective refractive index of the porous silicon microcavity increased. When acetamiprid was added, it bound to the aptamer due to its stronger specificity. The aptamer separated from the complementary strand of the coupled graphene quantum dots and bound to acetamiprid, resulting in a decrease in the effective refractive index, and its central wavelength of reflection spectrum was blue shifted, and the blueshift increased with the increase of acetamiprid concentration. The relationship between the change in central wavelength and the concentration of acetamiprid was analysed, and the detection limit of acetamiprid was 151 nm.

Nowadays, in the practical application of microwave absorption, it is still urgent and challenging to develop the microwave absorber with broadened bandwidth at a single thickness. Constructing composites with multi-component and multi-structure has been an effective strategy to obtain enhanced microwave absorption performance. Herein, yolk-shelled Co@SiO2@Mesoporous carbon (Co@SiO2@MC) microspheres were prepared by in-situ one-pot synthesis, carbonization reduction, and subsequent etching. The mesoporous carbon shell and hollow cavity structure were obtained simultaneously by controlling the etching of SiO2. The large carbon-air interface in the mesoporous shell and interior voids extend the propagation path of electromagnetic wave and enhance scattering. Owing to strong dielectric/magnetic loss, synergistic effect between different components and microstructures, as well as excellent impedance matching, Co@SiO2@MC microspheres exhibit desirable microwave absorption performance. Notably, for the sample with mesoporous carbon shell thickness of 25 nm, the effective absorption bandwidth (reflection loss below −10 dB) is as wide as 9.6 GHz (8.4–18 GHz), completely covering the whole X and Ku bands at 3.7 mm. The ultra-wide absorption bandwidth of the yolk-shelled Co@SiO2@MC microspheres highlight their potential application in the field of microwave absorption. Furthermore, this work provides new insights for the preparation of multi-component/multi-structure microwave absorbers.

A physicochemical mechanism acting between the reactive plasma and the material surface controls the erosion of polycrystalline ceramics in fluorine containing etching plasmas. In this study, a Y2O3/YOF composite was exposed to a fluorine etching plasma. Relocalization enables the direct correlation of crystalline orientation with material response. Our study reveals an orientation dependent surface fluorination of Y2O3, which controls the etching resistance and morphology formation. Orientations near the low index planes (001), (010) and (100) exhibit the lowest stability due to a homogeneous surface reaction. The presented results help to extend the mechanistic understanding of the plasma-material interaction of Y2O3.

This review aims to evaluate whether the etch-and-rinse or self-etch mode is the better protocol for dentin adhesion by universal adhesives. A total of 15 articles were included in the meta-analysis. Two reviewers performed a literature search up to October 2020in four databases: PubMed, Web of Science, Embase, and the Cochrane Library. Without considering the difference in aging mode, the analysis of the immediate and long-term bond strength of dentin showed that there was no statistical significance between the etch-and-rinse and self-etch mode of universal adhesive, and the long-term bond strength decreased relative to the immediate. In vitro studies suggest that prior acid etching did not improve bond performance. Whether from the perspective of long-term bonding performance or simplifying operating procedures, the self-etch mode is preferred.

With increasing demands for microchips and increasing needs in the nano-scale semiconductor manufacturing industry, atomic layer etching (ALE) has been developing into a critical etching process. Unlike its counterpart in the film deposition domain, atomic layer deposition (ALD), which has been extensively studied, ALE has not been fully studied yet from a modeling and operation point of view. Therefore, this work develops microscopic models to characterize the thermal ALE process of aluminum oxide thin films with two precursors (hydrogen fluoride and trimethylaluminum). First, the reaction mechanisms for the two half-cycles for the thermal ALE process are established. Electronically predicted geometries of the Al2O3 structure with two precursors are optimized. Along with the optimized geometries, possible reaction pathways are proposed and calculated by density functional theory (DFT)-based electronic structure calculations. The proposed reaction paths and their kinetic parameters are used in a kinetic Monte Carlo (kMC) algorithm, which is capable of capturing the features of the thermal ALE of aluminum oxide. The kMC simulation provides an etch time for the given steady-state operating conditions, which are validated via comparison with available experimental results. Finally, data sets collected from the kMC simulation are used to train a feed-forward artificial neural network (FNN) model. The trained FNN model accurately predicts an etch time and dramatically reduces the computation time compared to the kMC simulation, thereby making it possible to carry out real-time, model-based operational parameter calculations. In addition, the trained FNN model can be used to establish a feasible range of operating conditions without demanding experimental work.

Superhydrophobic surfaces have great potential for applications in electric power equipment, photovoltaic cell panels, and other fields due to their unique self-cleaning and dry storage characteristics. However, the common process for preparing superhydrophobic surfaces faces the following problems: complex preparation process, high cost, and easily damaged hydrophobic surface structure. In this study, a self-growing monoclinic phase of BaAl2Si2O8 glass-ceramics with a microscale structure is used as a matrix, which was etched with hydrofluoric acid and then treated with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane to obtain a kind of superhydrophobic surface with a contact angle more than 150°. The effect of the etching time on the hydrophobicity and the micromorphology of the glass-ceramic surface is analyzed. The results show that the contact angle first increases, then stabilizes, and finally decreases with increasing etching time. This etched structure has a large number of bulges and voids, and parts of the surface hydrophobic groups stay away from direct contact with other objects. Thus, it protects the internal hydrophobic group and improves the mechanical stability of the superhydrophobic surface. This study offers a simple and inexpensive idea for the mass production of ceramic-based superhydrophobic materials.

This paper presents the results of an in-depth study of the plasma-chemical etching (PCE) process of single-crystal silicon carbide (SiC) in SF6/O2 inductively coupled plasma (ICP). Using the method of optical emission spectroscopy (OES) we have examined the influence of RF power, bias voltage, pressure in the reaction chamber, and gas mixture composition on SiC PCE as well as the applicability of the OES technique for optimization and monitoring of SiC dry etching process in SF6/O2 ICP. An optimized PCE process for mass-manufacturing of SiC diaphragms of less than 20 μm thickness with an etch rate of more than 1.2 μm/min, and with an Rms of the etched surface of about 0.7 nm is developed. The influence of microtrenches on the electromechanical characteristics of the diaphragm as part of a capacitive pressure sensor is studied by means of computational simulation. An ideal diaphragm is compared with a real-process produced diaphragm with the microtrenching effect. It was shown that this effect has a great impact on the mechanical characteristics of the diaphragm. It is demonstrated that the von Mises stress at an applied pressure of 0.2 MPa for the real diaphragm is 183 MPa, while for the ideal diaphragm only 88 MPa.

A dual-band multi-mode high gain stacked-patch antenna based on substrate integrated suspended line (SISL) is proposed for 5G applications. The proposed antenna comprises five low-cost FR4 dielectric substrate layers and ten metal layers with embedded air cavities. The driven patch generates TM10 mode and TM02 mode, and the other two modes are generated by etching the U-slot and horizontal slot on the driven patch to achieve dual-band. The stacked patch with the U-slot can suppress the radiation pattern split of TM02 mode, improve the antenna gain in the high-frequency band and generate radiation null to increase the out-of-band gain-suppression level. To verify this principle, the antenna is fabricated and measured. The measured results show good agreement with the simulated ones and the proposed antenna operates at 3.21-3.66 GHz and 4.75-5.40 GHz, which can cover the 5G communication band. The antenna has high efficiency. The maximum gains in the two bands are 9.12 dBi and 8.65 dBi, respectively.

Photochemical Machining (PCM) is a well-known tightly controlled selective corrosion technique used to manufacture several micro and nano-size components high in quality and high precision; as it is a non-contact process, it gives a burr-free stress-free surface of the material. Nowadays, PCM is widely used in various industrial applications, including medical and healthcare industries, electronics, precision micro, nano, and other engineering industries. This article describes the correlation between various process parameters like etching temperature, time, and concentration of etchant with some response parameters like surface roughness value, metal removal rate (MRR), undercut (Uc), etch rate. In addition, magnetic field-assisted PCM and ultrasonic-assisted PCM are also explored in detail. The article highlights that etchant concentration and etching time play the most critical role in the PCM process. This article also depicts that with the increase in etchant temperature and etching time, the MRR and undercut increases. The article suggests future scopes and challenges of photochemical machining process.

We present AlGaAs-based monolithically integrated dual-wavelength lasers and master-oscillator power-amplifiers emitting around 785 nm which combine a near diffraction limited beam quality with single longitudinal mode emission, both achieved over a wide range of output powers. This holds for alternating dual wavelength operation which is of interest for applications in spectroscopy as well as for simultaneous dual wavelength operation which can be used to generate THz-radiation. Compared to previous designs the lateral optical confinement is provided by two differently deep etched ridge waveguides. Shallow etching is used in lasing and amplifying sections to ensure single-lateral mode operation, whereas deep etching is employed to form more compact S-bends and to enable the use of multi-mode interference (MMI) couplers instead of Y-couplers.

A well-designed photocatalyst with excellent activity and selectivity is crucial for photocatalytic CO2 conversion and utilization. TiO2 is one of the most promising photocatalysts. However, its excessive surface oxidation potential and insufficient surface active sites inhibit its activity and photocatalytic CO2 reduction selectivity. In this work, highly dispersed Bi2Ti2O7 was introduced into defective TiO2 to adjust its oxidation potential and the generation of radicals, further inhibiting reverse reactions during the photocatalytic conversion of CO2. Moreover, an in situ topochemical reaction etching route was designed, which achieved defective surfaces, a contacted heterophase interface, and an efficient electron transfer path. The optimized heterophase photocatalyst exhibited 93.9% CH4 selectivity at a photocatalytic rate of 6.8 μmol·g−1·h−1, which was 7.9 times higher than that of P25. This work proposes a feasible approach to fabricating photocatalysts with well-designed band structures, highly dispersed heterophase interfaces, and sufficient surface active sites to effectively modulate the selectivity and activity of CO2 photoreduction by manipulating the reaction pathways.

Porous SiOC ceramics were prepared with tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) as sol−gel precursors, and followed by etching with HF and NaOH solution. The microstructure evolution and chemical etching as a function of pyrolysis temperature were investigated. The amorphous carbon increases as rising the temperature from 800 oC to 1200 oC, and the graphitic carbon increases with further etching by HF and NaOH. However, the effect of pyrolysis temperature on the structure of C is more significant. The hydroxylation reaction and phase separation of SiOC ceramics results in the increase of SiO4 unit, which reacts with HF and NaOH to form micro- and mesopores. The existence of mesopore after HF etching provides more specific surface area and pore volume. However, NaOH etching produces more micropores, and the contribution of micropores to specific surface area and pore volume is higher than that of mesopores. Although HF and NaOH etching increase the specific surface area of SiOC ceramics, the etching effect of NaOH is superior to that of HF etching, and the carbon-enriched SiOC ceramics are obtained after NaOH etching.

We are presenting here fabrication of silicon (Si) nanowires (NWs) arrays by using Si (1 0 0) wafer as substrate, by metal assisted chemical etching (MACE) method. The Si-NWs growth on the Si wafer has been done by using etching time of 45 min in etching solution of hydrogen fluoride and hydrogen peroxide. X-ray diffraction (XRD) has been used for the structural analysis of NWs to estimate the crystalline size, micro-strain, dislocation density of fabricated nanostructures. The surface morphology of Si-NWs array has been studied through field effect scanning electron microscopy (FE-SEM). The optical properties like energy band gap of fabricated Si-NWs has been carried out through UV–Vis diffuse reflectance spectroscopy (UV DRS) and photoluminescence (PL) spectroscopy.

Application of Inconel 718 cylinders have been uprising with the up gradation of requirement of super alloys in this advance technological world. Although Inconel 718 possesses superior mechanical properties resulting into excellent performance in extreme environmental conditions but on the other hand make it difficult to machine and finish with available machining processes. This investigation has been used for the analysis of material removal of Inconel 718 cylinder using magnetic abrasive finishing process assisted with chemical etching. Finishing process has been conducted on 155 mm long and 5.7 mm thick Inconel 718 cylinder under specified investigating variable parameters such as duration of processing, work pole gap, abrasive weight percentage, and size of abrasive particles and concentration of etchant keeping certain factors as constant like rotational speed, etching temperature. Impact of processing variables represent through surface microstructure.

Rail grinding is a widely-used method to eliminate surface damages on railway tracks. The grinding chips are closely related to the grinding parameters and the grinding quality. Therefore, the investigation on the characteristics and the formation mechanism of chips from rail grinding is beneficial for the optimization of rail grinding process. In the present study, the grinding chips from the real rail grinding in the field and from the rail grinding experiments in the laboratory were analyzed in terms of their morphologies, microstructural evolution and chemical characteristics. The results showed that flowing, knife, slice and spherical chips were generated during rail grinding. The formation mechanism of flowing, knife and slice chips was plastic deformation by forces from abrasive grains with oxidation in air by grinding heat. Primary and secondary shear zones and central zones were generated. In the primary shear zone, cracks were generated in knife and slice chips. In the secondary shear zone, obvious plastic deformation was formed in knife and slice chips and a significant white etching layer (WEL) was generated in knife chips. The formation mechanism of spherical chips was melting of small powdery grinding debris by the high temperature and the subsequent solidification, accompanied with severe oxidization in air. The oxides produced in chips consisted of FeO, Fe3O4, Fe2O3 and AlFe2O4. The grinding quality could be predicted through observing the grinding debris. The larger percentage of flowing chips represented the better grinding quality (smaller surface roughness, slighter surface burn and thinner WEL on ground rail), which could be the goal for the grinding parameters choice.

In this work we have analyzed the doping, passivation and contact properties of boron-doped (p+) polysilicon (poly-Si) layers to understand the two key limiting factors for industrial adoption of p+ poly-Si based passivated contacts: challenges with diffusion and challenges with screen-printed, fire-through (FT) metallization. Investigation of test samples with ex-situ doped poly-Si layers of varying thickness and surface morphologies revealed that sheet resistance (Rsheet) and passivation quality in ex-situ doped poly-Si are limited by the maximum solid solubility of boron in silicon, and possible damage to the interfacial silicon oxide (iOx) layer and increased Auger recombination at high diffusion temperatures, respectively. An interesting correlation is found between the maximum dopant density at the interface and the J0,pass, with the latter increasing with increasing dopant density. The contacts to p+ poly-Si layers are formed with commercially available FT Ag/Al pastes by screen printing process. Metal contact properties strongly depend on the surface morphology and thickness of poly-Si layer. Lower contact resistivity was achieved on textured surface with thickest poly-Si layers, while lowest recombination under metal contacts was achieved with planar surface with thickest poly-Si layer. Further microstructure analysis of metallized interfaces using Scanning electron microscope shows partial etching of thick (220 nm) poly-Si layers and near complete etching of thin (20 nm) poly-Si layers by FT Ag-Al pastes. Using optimized doping and contact conditions, excellent surface passivation in unmetallized regions (J0,pass of 3.8 fA/cm2), contact resistivities as low as 1.2 ± 0.8 mΩ-cm2 and recombination current densities under the metal contacts of 155 ± 10 fA/cm2 are achieved on textured and planar samples respectively.

Organic single crystals (OSCs) have received increasing interest in the last decades for their potential applications in flexible electronics. Although there are various subtractive manufacturing methods of organic electronics, the subtractive manufacturing of OSCs is still a challenge, since OSCs are assembled via weak van-der-Waals interactions which are vulnerable and cannot afford damages and suffer the degradation of performances after the process. Here, we develop an epitaxial etching strategy which clips the OSCs and keeps high-quality crystalline nature of the resulting materials. As a result, high-quality organic micro-ribbon arrays are fabricated which maintains 89% charge mobility in average compared with original OSCs, showing great potential of this subtractive manufacturing method in future organic electronics.

The precise machining of silicon carbide composite (SiC–SiC) as a high-tech material with extraordinary characteristics is required for different applications in aerospace, light weight construction and car industry. Laser machining enable new approaches for fabrication processes but the regularly applied ablation processes can cause damage to the SiC–SiC material. Here we propose and demonstrate a new approach for gentle SiC–SiC machining making use of a laser-induced plasma for reactive species generation enabling chemical material removal processes. A fs-laser (775 nm, 150 fs, 1 kHz) was focussed to a CF4/O2 gas mixture igniting a laser-induced plasma (LIP) approximately 100 μm in front of a SiC–SiC sample. This LIP initiate material removal processes of the textured, multiphase SiC–SiC sample without a mechanical damage of the SiC–SiC composite structure. Different surface features such as etching of the cover SiC layer, etching of the SiC matrix and exposure, thinning and sharpen of the SiC fibres, underetching of the fibres has been observed. Across the whole etched area, no mechanical damage such as cracks, delamination's, broken fibres were observed so that a gentle machining process can be expected.

The fabrication process and light extraction efficiency of AlGaInP-based flip-chip micro- light-emitting diode ( $\mu $ -LED) array chips are improved by employing a wafer-bonding process, patterned metal contact, and sidewall passivation layers. The epilayers with indium tin oxide (ITO) can be successfully transferred from the GaAs substrate to the sapphire substrate and bound. Three types of patterned n-metal are employed in the $\mu $ -LED as a self-aligning mask and light reflection layer, where the n-GaAs layer can be partially removed by the wet etching process. The dry etching process of MESA has been optimized by applying the BCl3 gas in the inductively coupled plasma (ICP) system, which can suppress the etching rate of the sidewall and improve the etching depth uniformity. Consequently, the leakage current of the $\mu $ -LED array chip is decreased from 85 to 7 nA under the bias of −5 V. Moreover, three configurations of the metal contact/n-GaAs structures with Omnidirectional reflector (ODR) have been designed to reduce the emission light absorption, passivating the sidewall of MESA, and enhance the output power. Finally, the 0.52-in red $\mu $ -LED array with a chip size of $100\,\,\mu \text{m}\,\,\times 100\,\,\mu \text{m}$ and resolution of 138 pixels/in is realized when bonded with the drive IC. Consequently, the $\mu $ -LED array chips with ODR and patterned contact show the highest external quantum efficiency of 51.1% and relative output power enhancement of 441% compared to the chip with SiO2 passivation layer and nonpatterned n-metal contact.

In this letter, a planar broadband higher-order mode millimeter wave (MMW) microstrip patch antenna array with low sidelobe level (SLL) is presented. For the antenna element, antiphase-TM30 mode is excited by unequally etching the radiating patch with two transverse slots. Meanwhile an SIW-based pin-loaded slot coupling feeding structure is introduced to achieve merits of broadband, low cross polarization and low backward radiation. Then a one-eight power divider with in-phase unequally tapered amplitude distribution is adopted to excite an eight-element array with SLL. The GCPW-SIW transition structure is also selected to achieve broadband impedance matching. Finally, both element and array antenna are optimized and fabricated for verification. For the antenna array, the measured -10 dB impedance bandwidth is from 25.1 to 31.3 GHz (22%) with a maximum gain of 14.6 dBi at 29.5 GHz and a 3dB gain bandwidth of 27.9%. And the measured SLL at 26, 28 and 30 GHz are all less than 20 dB. Index TermsMillimeter-wave (MMW), broadband, higher-order mode, low sidelobe level (SLL).

The surface roughness of CIGS absorber and residual Cu–Se phase on the surface are two major factors greatly affecting the performance of CuInGaSe2 (CIGS) solar cells with the absorbers fabricated by the selenization annealing of Cu–In-Ga precursors. In this work, Br2–CH3OH solution is used to etch the surfaces of CIGS films to address these two challenges. The effects of the etching treatment on CIGS films and devices are investigated. It is found that etching significantly reduces the film roughness and removes the Cu–Se phase. Thus, the performance of the device is improved within a certain range. In addition, it is found that CIGS films with suitable surface roughness effectively absorb incident light and possess a higher Jsc. However, excessive etching causes the film to be too thin, and the carrier recombination at the back electrode increases. Based on these characteristics, this work optimizes the Br2 etching process.

In this article, we report the first experimental results of a novel 4H-silicon carbide (SiC) p-i-n photodetector based on a vertical nanocone array (NCA). It is fabricated by electron beam lithography and inductively coupled plasma (ICP) etching technology. The performance of static and dynamic behavior was studied systematically. It shows the responsivity of ~41.9 mA/W under 360 nm at a bias voltage of -0.5 V and has a linear response to the ultraviolet (UV) light in a wide light intensity range of 0.1-10⁴ mW/cm². The response time decreased as the light intensity rose from 3 mW/cm² to 5 W/cm² and then leveled off at higher light intensity (>100 mW/cm²), which is about 0.25 ms. The photodetector -3-dB cutoff is ~3400 Hz at λ = 360 nm and light intensity = 100 mW/cm². Besides, the detector can respond to the UV light from 260 to 360 nm and the peak responsivity is ~78 mA/W at 320 nm. The analysis results have reference values for the development of an innovative 4H-SiC UV photodetector to some extent.

A novel dual-band circularly polarized (CP) shared-aperture antenna is proposed in this letter. The overall structure consists of an SIW slot antenna working in X-band which also serves as the top patch of a C-band microstrip-like antenna. The SIW slot antenna achieves CP radiation by etching a circular slot on the top surface of a dual-mode SIW cavity. The patch antenna realizes CP radiation by loading two pairs of asymmetric shorting vias. With this design method, the proposed antenna can achieve dual-band CP operation and high aperture reuse efficiency. Besides, feeding-pin of the SIW slot antenna inserts through one of asymmetric shorting vias, that is, the shorting vias serves as both perturbations for C-band operation and a feeding path for the X-band operation. This new feeding scheme can prevent signal crosstalk between the two bands.

Using first principles calculations, we have presented a short study on modulation of band structures and electronic properties of zigzag blue phosphorene (ZbPNR) and arsenene nanoribbons (ZANR) by etching the edges of NRs. We have taken the width of both NRs as N = 8 and corrugated the edges in a cosine-like manner. Optimizing every structure and further investigating their stabilities, it was seen that both the etched NRs are energetically feasible. From the computed band structures, the band gaps were seen to be increased for both the NRs on increasing number of etched layers and direct gap semiconductor nature was recorded. Highest energy gap observed were 2.26 and 2.41 eV for ZbPNR and ZANR, respectively. On further application of electric field, we observed the very interesting semiconductor-to-metallic property transition which was explained by wave function plots. Being elements of same group, a similar trend of band gaps modulations was observed for both NRs. This fascinating method of electronic property tuning of the studied NRs can be useful in various nanoscale electronic applications.

We report the synthesis of Mo2CTx MXene from the Mo–In–C non-MAX phase using UV-assisted safe etching in phosphoric acid followed by ultrasonic exfoliation. The EDX and XPS spectra confirm the selective etching of indium from the non-MAX phase stoichiometry and formation of Mo2CTx MXene. The structural characterization using X-Ray diffraction revealed the Mo–In–C non-MAX phase and Mo2CTx MXene with crystallite sizes 37.26 ± 0.56 nm and 46.89 ± 0 .70 nm, respectively. The morphology of the samples analyzed using FESEM, confirmed the formation of the multilayered and monolayer 2D Mo2CTx. A slight increase in the interplanar spacing (~0.921 A) was observed in HRTEM images for Mo2CTx with respect to Mo–In–C. The synthesis of Mo2C MXene from a non- MAX phase using a hydrogen fluoride-free safe etching root unlocks the wide opportunity for the industrial bulk production of MXenes.

Partially-etched V2Al1-xCTz ceramic with the average particle of ∼400 nm was synthesized by etching submicro-sized V2AlC with 40 wt% HF at room temperature (RT) for 48 h and 72 h, respectively. V2Al1-xCTz etched for 72 h has exhibited higher charge-discharge property, with an average reversible discharge capacity of 349.2 mAh·g-1 at 0.1 A g-1 in the 120 cycles for lithium-ion batteries. The electrochemical performances of V2Al1-xCTz could be improved by the addition of carbon nanotubes (CNTs), graphene (GF) and titanium suboxides (Ti4O7) conductive additives, among which CNTs exhibit the best effectiveness with a capacity of ∼460 mAh·g-1 at 0.1 A g-1 in the 140 cycles and a capacity retention of ∼72% at 0.5 A g-1 after 400 cycles.

Purpose: This study sought to compare enamel surface morphology and orthodontic bracket re-bonding strength after phosphoric acid- or erbium-doped yttrium aluminum garnet (Er:YAG) laser-mediated re...

In this work, vertical micromirrors that are fabricated using deep etching of silicon followed by metal sputtering are studied. Physical parameter extraction methodology, image processing, machine learning and discrete element analysis are used to extend the easy-to-take scanning electron microscope images into 3-D topographical information, that are usually obtained using atomic force microscope and transmission electron microscope. The experimental results show that vertical micromirrors surface quality has a granular nature showing degraded performance and a different optical response with respect to the bulk metal. A physical model is developed and validated by comparing the measured reflectivity of the fabricated micromirrors with a multi-layer reflectivity optical model based on the effective medium theory fed by the extracted physical parameters. In agreement with the experimental results, the model predicts a reflectivity of about 60 % for a sputtered aluminum thickness of 50 nm, compared to 97.5% reflectivity predicted by the bulk metal model. [2021-0154]

A high-gain low-profile leaky-wave antenna (LWA) for vertically-polarized (VP) fixed-beam endfire radiation is proposed in this article. The LWA is composed of two back-to-back half-mode waveguides with grooves etched at the margins of both radiation edges. By etching grooves, the phase velocity of the traveling wave can be tailored to slower than the wave velocity in free space for fitting the Hansen-Woodyard condition. Compared with periodic LWAs, the proposed antenna continuously radiates at two symmetric apertures, contributing to a high endfire gain. A prototype is fabricated and tested to validate the concept. The measured and simulated results are in good agreement. A simulated gain of 14.29 dBi and a measured gain of 13.37 dBi is achieved within an antenna length of 3.05 λ0. Moreover, a measured overlapping bandwidth of 2.74 -3.17 GHz (14.3%) is realized with S11 < -10 dB and gain variation less than 3 dB. To the best of the authors’ knowledge, the proposed VP endfire LWA realizes the highest aperture efficiency and shows great advantages in high gain, low profile, and wide bandwidth.

The thermal atomic layer etching (ALE) of nickel was demonstrated using sequential chlorination and ligand-addition reactions. Nickel chlorination was achieved using SO2Cl2 (sulfuryl chloride) as t...

In this letter, high-performance AlGaN/GaN Schottky barrier diodes (SBDs) with a great balance between forward and reverse characteristics are demonstrated. Benefiting from a plasma-free, low-damaged wet etching technique of an AlGaN layer at the anode region and low work-function tungsten (W) as the anode, lateral GaN SBDs with a low turn-on voltage ( $\text{V}_{{\mathrm {T}}}$ ) of 0.43 V and a low reverse current ( $\text{I}_{{\mathrm {R}}}$ ) of 90 nA/mm are obtained. Meanwhile, owing to the flattened self-terminated etching surface and the assistance of SiN passivation grown by low-pressure chemical vapor deposition, a high breakdown voltage of 1.83 kV and a power figure-of-merit (FOM) of 1.20 GW/cm 2 are achieved for the fabricated GaN SBD with a spatial distance ( $\text{L}_{{\mathrm {AC}}}$ ) of $15 ~\mu \text{m}$ from cathode to anode. The lateral GaN SBD fabricated with the optimized wet etching technique shows great potential for next-generation power electronics.

In this work, ZnO films are deposited by magnetron sputtering [using direct current (DC)], on polished silicon substrate Si(100) (non-etched), etched for 1 min, 5 min, 10 min and 15 min. The effect of etched silicon substrate on structural, morphological, and optical properties of ZnO films has been investigated. A new nanostructure can be obtained by mean of modification in morphology of substrate. The etching of the substrate was effectuated by means of dry plasma at different time and they compared with non-etched substrates. AFM and SEM images have been used to investigate the morphology behaviors of ZnO films growth on etched and non-etched silicon substrates. Optical properties were studied in details, photoluminescence (PL) showed that the intensity of ZnO films have been increased by increasing the substrate etching time from 0 to 15 min, which were associated with the crystallographic properties [for (002) orientation] using X-ray diffraction (XRD). That may be related to the decrease of grain size and roughness morphology increasing with the etching time. FTIR and MicroRaman spectra of films show vibrational modes characteristic of ZnO materials and they were related with morphology and structural of the films. In addition, the variation of ethylene glycol contact angle data (ECA) related to roughness of the ZnO films deposited on etched Si substrate at different times were studied. The ZnO films on etched substrate were interesting in optoelectronic purpose as well as for gas sensor in future work of our team.