Traditional Chemical Etching Research Articles

Hierarchical Structuring of Black Silicon Wafers by Ion-Flow-Stimulated Roughening Transition: Fundamentals and Applications for Photovoltaics.

Ion-flow-stimulated roughening transition is a phenomenon that may prove useful in the hierarchical structuring of nanostructures. In this work, we have investigated theoretically and experimentally the surface texturing of single-crystal and multi-crystalline silicon wafers irradiated using ion-beam flows. In contrast to previous studies, ions had relatively low energies, whereas flow densities were high enough to induce a quasi-liquid state in the upper silicon layers. The resulting surface modifications reduced the wafer light reflectance to values characteristic of black silicon, widely used in solar energetics. Features of nanostructures on different faces of silicon single crystals were studied numerically based on the mesoscopic Monte Carlo model. We established that the formation of nano-pyramids, ridges, and twisting dune-like structures is due to the stimulated roughening transition effect. The aforementioned variety of modified surface morphologies arises due to the fact that the effects of stimulated surface diffusion of atoms and re-deposition of free atoms on the wafer surface from the near-surface region are manifested to different degrees on different Si faces. It is these two factors that determine the selection of the allowable "trajectories" (evolution paths) of the thermodynamic system along which its Helmholtz free energy, F, decreases, concomitant with an increase in the surface area of the wafer and the corresponding changes in its internal energy, U (dU>0), and entropy, S (dS>0), so that dF=dU - TdS<0, where T is the absolute temperature. The basic theoretical concepts developed were confirmed in experimental studies, the results of which showed that our method could produce, abundantly, black silicon wafers in an environmentally friendly manner compared to traditional chemical etching.

Development of an automated 3D metallography system and some first application examples in microstructural analysis

Abstract Traditional metallography relies on the imaging of individual section planes. However, conclusions as to spatial shapes and microstructural arrangements can only be drawn to a limited extent. The idea to reconstruct three-dimensional microstructures from metallographic serial sections is therefore obvious and not at all new. However, the manual process of preparing a great number of individual sections and assembling them into image stacks is time-consuming and laborious and therefore constitutes an obstacle to frequent use. This is why the Federal Institute for Materials Research and Testing, or BAM for short (Bundesanstalt für Materialforschung und -prüfung), is developing a robot-assisted 3D metallography system performing the tasks of preparation and image acquisition on a metallographic section fully automatically and repeatedly. Preparation includes grinding, polishing and optional etching of the section surface. Image acquisition is performed using a light optical microscope with autofocus at several magnification levels. The obtained image stack is then pre-processed, segmented and converted to a 3D model resembling a microtomographic image, but with a higher lateral resolution at large volumes. As opposed to tomographic techniques, it is possible to perform traditional chemical etching for contrasting. The integration of a scanning electron microscope is in the planning stages. Studies conducted so far have demonstrated the possibility of visualizing hot gas corrosion layers, gray cast irons and ceramic-based microelectronic structures (vias).

Joule Heating Activation of Template‐Mediated Carbon Fibers with Significantly Enhanced Capacitive Performance

Carbon fibers (CFs) have been innovated in the application of fiber‐shaped and wearable energy storage devices recently. However, time‐ and energy‐consuming activation process under harsh conditions is generally required to modify the surface structure of the CF. Herein, a fast and effective Joule heating activation method is proposed with the nickel–cobalt layered double hydroxide‐derived nanometal particles as the template. The resultant Joule heating‐activated CF (JACF) demonstrates excellent capacitive performance with an electrode capacitance of 268 F g−1. After assembling into a solid‐state fiber‐shaped supercapacitor (FSC), the device shows both enhanced specific capacitance and energy/power densities, as well as the long cycling stability of over 5000 cycles. The Joule heating method reported in this work is time and energy saving for CF activation compared with the traditional chemical etching or high‐temperature annealing processes, and it is promising for the large‐scale production of high‐performance fiber‐shaped and wearable energy devices.

Computational Study of Novel Semiconducting Sc2CT2 (T = F, Cl, Br) MXenes for Visible-Light Photocatalytic Water Splitting

Seeking candidate photocatalysts for photocatalytic water splitting, via visible light, is of great interest and importance. In this study, we have comprehensively explored the crystal structures, electronic properties, and optical absorbance of two-dimensional (2D) Sc2CT2 (T = F, Cl, Br) MXenes and their corresponding photocatalytic water splitting, under the visible-light region, by first-principles calculations. Herein, we have proposed that 2D Sc2CT2 MXenes can be fabricated from their layered bulk compounds, alternatively to the traditional chemical etching method. Creatively, we proposed Sc2CT2 (T = F, Br) as new materials; the band edge alignments of Sc2CF2 can be tuned to meet the water redox potentials at pH = 8.0. It is highlighted that Sc2CF2 shows outstanding optical spectra harvested under visible-light wavelength regions, and efficient separation of photo-induced electrons and holes in different zones. These present results provide eloquent evidence and open a new door on the photocatalysis applications of such novel semiconducting MXenes.

Design Studies of High-Resolution Readout Planes Using Zigzags With GEM Detectors

We have developed highly interleaved zigzag-shaped electrodes for collecting charge on the readout plane of various micropattern gaseous detectors (MPGDs), including gas electron multiplier (GEM) and micromega detectors. An optimized zigzag pad (or strip) anode can greatly enhance charge sharing among neighboring pads compared to traditional straight strip or rectangular pad designs and as a result can deliver excellent position resolution with minimal channel count, while exhibiting a virtually uniform response across the detector. We have systematically studied the effects of varying the parameters that define the zigzag geometry using simulations and have measured several printed circuit boards (PCBs) comprising a range of zigzag designs. Recently, we have employed laser ablation to generate zigzag patterns with pad-to-pad gaps smaller than 1 mil (or 25 μm). Reducing the gap well below the 3-mil limit imposed by traditional chemical etching has allowed the production of zigzag electrodes with unprecedentedly small feature sizes. In turn, laser-etched zigzag PCBs were shown to exhibit markedly improved performance over earlier generation PCBs, with position resolutions below 50 μm for a 2-mm pitch. This article will explore in detail the dependence of the position resolution on the structural parameters of a zigzag-shaped anode, specifically for the case of a quadruple GEM detector.

Specific features of magnetic domain structure in epitaxial magneto-optical ferrite-garnet films

We describe the experimental studies of both domain and crystal defect structure of magneto-optical bismuth-substituted ferrite-garnet films (FGF) with high Faraday effect. Indentation and scratching (sclerometric) tests of either magnetically uniaxial or easy plane anisotropy (“planar”) films were carried out in parallel with traditional chemical etching. We demonstrate the effect of strong local changes of magnetic anisotropy on the domain structure due to local mechanical stresses. New types of biperiodic domain structure imposed by external stresses were found to exist.

Rapid nanofabrication via UV-assisted selective etching on GaAs without templates

UV-assisted selective etching was proposed to raise the etching rate for rapid fabrication on GaAs without templates. Within the same time, protrusive hillocks stemming from the photochemical etching are obvious higher than that of traditional chemical etching. The hillock height produced by the photochemical etching increases linearly and then gradually decreases with etching time, and the scratch produced by higher load can change into higher hillock after etching. By programming tip traces, various patterns, including pyramidal tips, were fabricated on GaAs surface. This study provides opportunities for fabricating high-quality GaAs-based optical structures and devices with low cost and high efficiency.

Electrochemical Formation of Porous Silicon Carbide for Micro-Device Applications

Anodization of silicon carbide (SiC) in hydrofluoric acid (HF) solutions is a promising way to etch this material which is very resistant against traditional chemical etching methods. Moreover, it has been shown that several reproducible porous SiC morphologies can be performed varying anodization conditions (current density, electrolyte composition, UV lighting) and/or substrate properties (doping type and level). This paper proposes a state of the art of porous SiC etching in GREMAN and a presentation of the morphologies achievable using anodization in HF based electrolytes.

Research on 3D Laser Texturing Technology of Mold

In the processing of the mold texture, the traditional chemical etching exits the shortcomings of the pollution and the long processing cycle. This article will introduce 3D laser processing technology to the mold industry, based on the laser etching principle on the metal surface, etch processing can be made in the mold surface. Through theoretical derivation from the 3D laser scanning optical system, the 3D laser scanning hardware system is structured to apply in the mold cavity texturing, the control algorithm has been studied, and finally in the developed laser-etch machine the texturing experimental is performed on the injection molds.

Femtosecond laser surface structuring technique for making human enamel and dentin surfaces superwetting

It is known that good wettability of enamel and dentin surfaces is a key factor in enhancing adhesion of restorative materials in dentistry. Here, we report on a femtosecond laser surface texturing approach that makes both the enamel and dentine surfaces superwetting. In contrast to the traditional chemical etching that yields random surface structures, this new approach produces engineered surface structures. The surface structure engineered and tested here is an array of femtosecond laser-produced parallel microgrooves that generates a strong capillary force. Due to the powerful capillary action, water is rapidly sucked into this engineered surface structure and spreads even on a vertical surface.

Making human enamel and dentin surfaces superwetting for enhanced adhesion

Good wettability of enamel and dentin surfaces is an important factor in enhancing adhesion of restorative materials in dentistry. In this study, we developed a femtosecond laser surface texturing approach that makes both the enamel and dentine surfaces superwetting. In contrast to the traditional chemical etching that yields random surface structures, this approach produces engineered surface structures. The surface structure engineered and tested here is an array of parallel microgrooves that generates a strong capillary force. Due to the powerful capillary action, water is rapidly sucked into this engineered surface structure and spreads even on a vertical surface.

Electrochemical Etching of NiTi Alloy in a Neutral Fluoride Solution

Electrochemical etching of NiTi alloy in a pH 6 fluoride solution is proposed as a convenient, less dangerous procedure than traditional chemical etching in oxidizing HF media. Anodic polarization produces protons at the electrode surface, and local acidification increases the concentration of HF that efficiently dissolves the surface oxides, promoting a sustained dissolution current that decreases with increasing mass-transfer rate. The voltammetric pattern includes a “pseudoplateau” at low potentials, in which only a metal dissolution takes place, and a steady current increase at higher potentials due to the onset of oxygen evolution. The treatment produces a semilustrous rough surface, showing a structure of shallow microscopic cavities in scanning electron microscopy images. Impedance spectra recorded in the pseudoplateau region are similar to those observed during anodic polarization of Ti in HF, and their analysis indicates a formation of a thin barrier film whose thickness increases linearly with potential.

A new method detaching porous anodic alumina films from aluminum substrates

Recently, a particular focus on the research of porous anodic alumina (PAA) films is taken because of the application for growth of nanostructure materials. However, during detaching the PAA films from aluminum substrate and opening the holes of PAA films, it is quite difficult to keep intact through-hole structure of PAA films using traditional chemical etching method. Furthermore, the traditional method is time-consuming and has contamination because of the use of heavy metal ion solution. Usually, the preparation time is over 20 h. In our work, a new electric- chemical method was proposed for detaching PAA films and opening the holes of PAA films in an environmental friendly solution of HClO4–CH3OH in one step. The preparation process can be finished within 5–15 s. Compared with traditional etching method in which there are two-step processes, the electric–chemical method is simple, rapid and contamination-free. A large size PAA films with intact through-hole structure can be obtained.

Electrochemical etching of copper indium diselenide surface

CuInSe 2 thin films were grown onto ITO surface by electrodeposition and annealed in the hydrogen atmosphere at 400 °C. The influence of traditional chemical etching (KCN etchant) and electrochemical etching at various potentials and values of solution pH (0.8–13) on the surface composition and morphology was studied using the EDX and SEM methods. The mechanism of CuInSe 2 decomposition at various pH values was examined by cycling voltammetry. The influence of chemical and electrochemical etchings on electrical and optical characteristics of thin films was analyzed.

Interface Shear Bonding Strength with Epoxy Resin of SUS 304 Stainless Steel Treated by Plasma Jet.

New method used plasma jet treatment for improving the interface shear bonding strength between SUS 304 stainless steel and epoxy resin have been investigated comparing with traditional chemical etching surface treatment. Argon gas was found to create a desirable rough surface and nitrogen gas to cause hard surface by the chemical reaction. Plasma jet treated SUS 304 specimens embeded in the epoxy resin all showed higher interface shear bonding strength due to the anchoring effect. Based on these facts, a two step plasma jet treatment has been tried and a significant improvement in the interface shear bonding strength obtained.