Chemical Etching Research Articles

Glass Surface Nanostructuring by Soft Lithography and Chemical Etching.

Due to its high durability and transparency, soda lime glass holds a huge potential for several applications such as photovoltaics, optical instrumentation and biomedical devices, among others. The different technologies request specific properties, which can be enhanced through the modification of the surface morphology with a nanopattern. Here, we report a simple method to nanostructure a glass surface with soft lithography and wet-chemical etching in potassium hydroxide (KOH) solutions. Glass samples etched with a polymeric mask showed a nanopattern with stripes of widths between 220 and 450 nm and modulated heights between 50 and 200 nm. For different solution concentrations or etching times, the obtained nanopatterns led to an increase or reduction of the water contact angle. The largest increment, ~20 degrees, was achieved by etching the glass for 180 min with 30% KOH concentration, while a super-hydrophilic glass (~9° contact angle) was achieved when etching for 90 min with the same concentration. Optical characterization showed a very low influence of the nanostructured pattern on glass transparency and an increment in UV transmittance for some cases.

Assessment of former austenite structure in hot rolled steel in terms of its texture after martensitic transformation

Textures of medium carbon steel, hot rolled and then quenched, have been determined by Electron backscatter diffraction (EBSD). To ensure representativeness of results, a rather large treated scan covered about a thousand of prior grains, each containing several thousands of measurement points. Considering inter-phase orientation relationships peculiar to martensitic steels, textures of the high temperature phase (austenite) have been assessed in terms of the transformation textures. Thus, deformed and recrystallized states of austenite dependent on the rolling conditions can be distinguished. To verify EBSD data, martensite textures were measured by an independent method of EBSD whereas morphology of the prior grains was revealed by means of chemical etching.

Alternative Treatments for Zirconium Oxide to Compare Commonly Used Surface Treatments to Determine Which Has the Least Effect on the Phase Transformation.

Traditional mechanical processing of zirconium leads to an unfavorable transformation, from a metastable tetragonal phase to a monoclinic phase (t→m), which weakens the structure of the material and subsequently leads to damage to the prosthetic restoration. The aim of this research is to compare commonly used surface treatments to determine which has the least effect on t→m. Thirty cylindrical samples made of sintered zirconium were divided into six groups based on the following treatments: polishing, grinding, sandblasting, chemical etching, laser structuring or dry plasma etching. After surface treatment, the samples were subjected to the following tests: X-Ray Diffraction, microscopic examination, surface wettability and surface roughness measurements. Chemical etching, laser structuring and plasma etching significantly reduce the content of the monoclinic phase. All surface treatments significantly reduced the final amount of the monoclinic phase. However, chemical etching did not provide sufficient surface roughness. Both laser and plasma processing offer the advantage of creating structural patterns on the surface of elements. However, as plasma etching requires a mask to obtain the appropriate pattern on the surface, it seems that laser processing offers more and varied structuring possibilities. Laser structuring is easier to control and more economical than the other methods.

Nanoscale Wet Etching of Molybdenum Interconnects with Organic Solutions.

Molybdenum (Mo) has emerged as a promising material for advanced semiconductor devices, especially in the design and fabrication of interconnects requiring sub-10nm metal nanostructures. However, current wet etching methods for Mo using aqueous solutions struggle to achieve smooth etching profiles at such scales. To address this problem, we explore wet chemical etching of patterned Mo nanowires (NWs) using an organic solution: ceric ammonium nitrate (CAN) dissolved in acetonitrile (ACN). In this study, we demonstrate two distinct etching pathways by controlling the reaction temperature: i) digital cyclic scheme at room temperature, with a self-limiting Mo recess per cycle of ≈1.6nm, and ii) direct etching at elevated temperature (60°C), with a time-controlled Mo recess of ≈2nm min-1. These methods not only offer a highly controllable nanoscale Mo etching but also ensure smooth and uniform etching profiles independent of the crystal grain orientation of the metal.

N-doped carbon decorated by Cu3P nanoparticle derived from Aspartic acid - Cu MOF as suitable catalysts for oxygen and hydrogen evolution reactions

The preparation of high-efficiency electrocatalysts for the oxygen and hydrogen evolution process (OER and HER) using an easy, green, and facile preparation method is crucial for the effective and economical use of clean energy sources. We report here an eco-friendly phytic acid (PA)-assisted phosphidation strategy to synthesize a novel Cu3P decorated on N-doped carbon (Cu3P-NC). Its synthesis involves precipitation of rode-like microstructured Cu-based aspartic acid frameworks (Asp-Cu MOF), chemical etching of Asp-Cu MOF to form PA cross-linked Cu complexes, and a final pyrolysis step to get Cu3P-NC with abundant Cu3P nanoparticles loaded on N-doped carbon matrix. The Cu3P-NC catalyst demonstrates catalytic performances with low overpotentials of 116 and 310 mV at 10 mA cm−2, small Tafel slopes of 61.2 and 69.2 mV dec−1, for HER and OER respectively, and high catalytic durability in 1 M KOH. The as-prepared Cu3P-NC electrocatalyst offers a new viewpoint on developing multi-functional electrocatalysts in the water-splitting process using environment-friendly substances such as amino acids.

Plasma Etch of IGZO Thin Film and IGZO/SiO2 Interface Diffusion in Inductively Coupled CH4/Ar Plasmas

ABSTRACTIn this work, the etching characteristics of InGaZnO4 (IGZO) thin films were systemically investigated in inductively coupled CH4/Ar plasmas with various gas ratios, bias voltages, and surface temperatures. The ion flux in the CH4/Ar plasmas was analyzed using bias power and voltage, whereas the relative densities of CH and H radicals were quantified through optical actinometry. The change in CH3 radical density was also estimated based on plasma kinetics analysis. The correlations between the plasma properties and IGZO etch rate were investigated. In CH4/Ar plasmas with CH4 ratios below 80%, the IGZO etch rate increases with a higher CH4 proportion, aligning with the ascending trend of CH3 radical density, which suggests that CH3 radical density acts as a limiting factor (radical‐limited regime). However, the IGZO etch rate decreases when the CH4 ratio exceeds 80%, corresponding to the reduction in ion flux, which indicates that ion flux becomes a limiting factor in this ion‐limited regime. The IGZO etch rate shows a linear relationship with bias voltage and follows the Arrhenius equation with varying surface temperature in plasmas without bias voltage. A spontaneous etch model was proposed based on these relationships. In this model, the IGZO etch rate depends on CH3 radical density and IGZO surface reactivity, where ion bombardment contributes more significantly to surface reactivity than high surface temperature. IGZO thin film was deposited on SiO2 during the fabrication of a 3D stacked ferroelectric field‐effect transistor (FeFET) memory device. The interaction between IGZO and SiO2 during CH4/Ar plasma processing was investigated using time‐of‐flight secondary ion mass spectrometry. The efficacy of removing IGZO atoms that had diffused into the SiO2 network was enhanced when subjected to plasma with a bias voltage, compared to the process without a bias voltage. However, exposure to CH4/Ar plasma resulted in a deeper diffusion of IGZO atoms into the SiO2 network, primarily attributed to ion bombardment rather than elevated surface temperature. A significant improvement in surface smoothness was achieved after IGZO and SiO2 etch by introducing BCl3 into the SiO2 etching chemistry.

Study on the Impact of Porous Media on Condensate Gas Depletion: A Case Study of Reservoir in Xihu Sag.

During the depletion and pressure reduction process in condensate gas reservoirs, the precipitation of condensate oil transforms the single-phase gas flow into a two-phase gas-liquid flow, significantly reducing the permeability. Currently, microscopic studies of the phase behavior of condensate gas in porous media mainly focus on observing and describing the occurrence of condensate oil, lacking quantitative calculations and direct observations of condensate oil throughout the entire depletion cycle. This paper uses a microvisualization method to simulate the depletion process of condensate gas reservoirs. Condensate gases with oil contents of 175.3 and 505.5 g/cm3 were prepared by mixing methane, ethane, hexane, and decane in specific proportions. Pore structures were extracted from thin sections of real core casts, and microfluidic chips with a minimum pore diameter of 20 μm and an areal porosity of 20.75% were fabricated by using a chemical wet etching method. Subsequently, microfluidic condensate gas depletion experiments were conducted with chip images recorded during the depletion process. Grayscale analysis of the depletion images was performed using ImageJ software to quantitatively calculate condensate oil saturation and recovery rates, analyzing the effects of different condensate oil contents on condensate gas depletion, and comparing the differences between depletion in porous media and in a PVT cell. The conclusions drawn are as follows: the dew points of high and low in the porous media are 3.15% and 1.85% higher than those in the PVT cell, respectively. In the early stages of depletion, condensate oil saturation in porous media is higher than that in the PVT cell, while in the middle to late stages, condensate oil saturation in porous media is lower than that in the PVT cell. The condensate oil recovery rate in porous media is significantly higher than the depletion recovery rate in the PVT cell. Condensate oil tends to precipitate and disperse at blind ends and corners, while it easily forms patches in mainstream large pores.

Lithium niobate waveguide-integrated Bi2Te3/graphene heterojunction photodetector.

We demonstrate an on-chip photodetector by integrating a graphene and topological insulator Bi2Te3 heterostructure on a thin-film lithium niobate waveguide. Lithium niobate on insulator (LNOI) waveguides are fabricated by the photolithography-assisted chemical mechanical etching method. The bismuth telluride (Bi2Te3) and graphene heterostructure design provides enhanced photocurrent due to the effective photocarrier generation. The lithium niobate waveguide-integrated Bi2Te3/graphene heterojunction presents a high absorption coefficient of 2.1 dB/µm. The Bi2Te3/graphene heterojunction photodetector exhibits a responsivity of 2.54 mA/W without external bias at a 1.55 µm wavelength, which is enhancement of sevenfold as compared to the pure graphene-based photodetector. The photodetector has a 3 dB bandwidth of over 4.7 GHz. This work provides a potentially viable method for a self-powered, high responsivity, and fast response of the photodetector integrated with the LNOI photonic platform.

Hyperspectral Analysis of Silicon Nanowires Manufactured Through Metal-Assisted Chemical Etching

Abstract This study used hyperspectral imaging to analyze localized near-field interactions between incident electromagnetic waves and silicon nanowire (SiNW) arrays manufactured through catalytic etching of Si wafers for different durations. The results revealed that the unetched upper surface area on Si wafers and reflection of incident light decreased with increasing etching time. A light reflection band peaking at approximately 880 nm was generated from arrays etched for more than 1 h. We used six separate hyperspectral images to analyze the wavelength-dependent spatial optical responses of the fabricated SiNW arrays. The images revealed hot spots of light reflection from unetched Si surfaces in the wavelength range of 470–750 nm and a resonant peak at 880 nm for a photonic crystal derived from a random SiNW array. Accordingly, hyperspectral imaging enables the assessment of localized optical responses of SiNW arrays, which can then be optimized to cater to various applications.

Ruthenium catalyst processing and oxidation for scalable complementary metal-oxide-semiconductor-compatible metal-assisted chemical etch

Ruthenium catalyst processing and oxidation for scalable complementary metal-oxide-semiconductor-compatible metal-assisted chemical etch

Picotesla optically pumped magnetometer using a laser-written vapor cell with sub-mm cross section

We demonstrate a sensitive optically pumped magnetometer using rubidium vapor and 0.75 amg of nitrogen buffer gas in a sub-mm-width sensing channel excavated by femtosecond laser writing followed by chemical etching. The channel is buried less than 1 mm below the surface of its fused silica host material, which also includes reservoir chambers and micro-strainer connections, to preserve a clean optical environment. Using a zero-field-resonance magnetometry strategy and a sensing volume of 2.25 mm3, we demonstrate a sensitivity of ≈1pT/Hz at 10 Hz. The device can be integrated with photonic structures and microfluidic channels with 3D versatility. Its sensitivity, bandwidth, and stand-off distance will enable detection of localized fields from magnetic nanoparticles and μL NMR samples.

Enhancing the anti-wear performance of graphene sheets embedded carbon films through interface nanotexture fabricated on the substrate

The effect and mechanism of surface texture on friction have been extensively explored, such as storing the abrasive and reducing the real contact area. However, studying the impact of the interface texture remains crucial, especially as the texture size approaches the nanoscale. In the present work, the silicon substrate with different parameters nanotexture was fabricated using a metal-assisted chemical etching process, and the graphene sheets embedded carbon (GSEC) film was deposited on the nanotextured substrate via a low-energy electron irradiation process to produce the interface nanotextured carbon films. After the addition of the interface nanotexture, the tribological performance of carbon films exhibited significant enhancement, with the degree of improvement being influenced by the parameters of the interface nanotexture. A super-low wear rate was achieved, with a value of 6.54 ± 0.70 × 10−8 mm3/N m. The improved tribological performance is due to the enhancement of film-substrate adhesion strength facilitated by interface nanotexture, and its role in promoting the rapid formation of a stable transfer film on the counter-grinding ball. The carbon film with nanotexture displays a small size of the abrasive particles, which contributes to the stabilization of the friction process.

The Influence of Etching Method on the Occurrence of Defect Levels in III-V and II-VI Materials.

The influence of the etching method on the occurrence of defect levels in InAs/InAsSb type-II superlattice (T2SLs) and MCT photodiode is presented. For both analyzed detectors, the etching process was performed by two methods: wet chemical etching and dry etching using an ion beam (RIE-reactive ion etching). The deep-level transient spectroscopy (DLTS) method was used to determine the defect levels occurring in the analyzed structures. The obtained results indicate that the choice of etching method affects the occurrence of additional defect levels in the MCT material, but it has no significance for InAs/InAsSb T2SLs.

Plasmonic semi shells derived from simultaneous in situ gold growth and anisotropic acid etching of ZIF-8 for photothermal ablation of metastatic breast tumor

Open nanoshells such as nanobowls or nanocups collectively described as ‘semi shells’ have unique plasmonic properties due to their lack of symmetry. So far, their fabrication was based on multistep and laborious methods such as solid state sputter coating or selective deposition/etching using sacrificial templates. In this work, we report a rapid one step colloidal synthetic protocol for PEGylated semi-shell (SS) fabrication by simultaneous facet specific anisotropic chemical etching of rhombic dodecahedral ZIF-8 and heterogenous nucleation & growth of gold. The SS possesses a strong localized surface plasmon resonance in the near-infrared region, which is retained after surface passivation with polyethylene glycol and subsequent cryopreservation for extended shelf-life. Freshly reconstituted PEGylated SS was found to be safe & non-toxic in healthy C57BL/6 mice post intravenous administration. The PEGylated SS displayed significant photothermal efficiency of ~37% with 808 nm laser irradiation. Preclinical assessment of intra-tumoral photothermal efficacy indicated complete remission of primary breast tumor mass with insignificant metastasis to vital organs in 4T1 FL2 tumor bearing CD1 nude mice. Further, PEGylated SS mediated photothermal therapy also yielded morbidity free survivael of 75% for up to 90 days, indicating their potential to significantly improve outcomes in advanced breast tumors.

Microstructure and residual stress gradient evolution mechanism of electronic copper strip for lead frame

The miniaturization of integrated circuits has led to a shift in lead frame fabrication methods from physical stamping to chemical etching. However, this process is highly sensitive to residual stress. We investigated the gradient distribution of residual stress, microstructure, and macroscopic texture in electronic copper foils using a layer-by-layer peeling method, and proposed a novel strategy for evaluating residual stress levels. Our findings reveal that the rolling-induced residual stress exhibits a gradient distribution along the thickness direction. Specifically, from the surface to the central layer, the stress transitions gradually from tensile to compressive, with the stress type primarily influenced by metal flow during rolling. Additionally, we observed gradient variations in the S and Cube texture. Tensile stress favors the formation of Cube-texture, while compressive stress promotes S-texture development. Notably, Cube-texture can lead to strain localization during rolling, directly impacting the local residual stress levels and distribution. Furthermore, quantitative analysis of dislocation density using peak profile methods revealed a consistent trend between {111} plane dislocation density and lateral residual stress. Further investigation highlighted that dislocations and precipitates associated with {111} planes in face-centered cubic metals significantly influence residual stress, with their combined effects determining the overall stress magnitude in relation to texture, dislocations, and precipitates.

Polarity control and crystalline quality improvement of AlN thin films grown on Si(111) substrates by molecular beam epitaxy

We attain N-polar and Al-polar AlN thin films on Si(111) substrates by plasma-assisted molecular beam epitaxy. The polarity of AlN epilayers has been validated by wet chemical etching using tetramethylammonium hydroxide and by the direct cross-sectional observation of atomic stacking under high-angle annular dark-field scanning transmission electron microscopy. For the 290 nm-thick as-grown N-polar AlN epilayer, x-ray diffraction (XRD) (002) and (102) ω rocking curve peak full width half maximums (FWHMs) are 475 and 1177 arcsec, and the surface mean square roughness (RMS) is 0.30 nm. We flipped the polarity using the metal-flux-modulation-epitaxy (MME) strategy. The MME strategy promotes anti-phase boundaries (APBs) on the {22¯01} crystalline planes instead of commonly observed lateral planar APBs in AlN epilayers. Merging of the tilted APBs at ∼50 nm leads to a complete Al-polar surface. For the 180 nm-thick Al-polar AlN epilayer, XRD (002) and (102) peak FWHMs are 1505 and 2380 arcsec, and the surface RMS is 1.41 nm. Strain analysis by XRD and Raman spectroscopy indicates a uniform tensile strain of 0.160% across the N-polar AlN epilayer surface and a strain distribution of 0.113%–1.16% through the epilayer. In contrast, the Al-polar AlN epilayer exhibits a much broader tensile strain distribution of 0.482%–2.406% along the growth direction, potentially due to the interaction of polarity inversion and strain relaxation.

Effects of chemical etching on surface structure and tribological behavior of silicate substrates

Abstract This study investigated the effect of chemical etching on the surface structure and tribological behavior of silicate substrates. Silicate surfaces were etched using a mixture of nitric acid (HNO3) and ammonium bifluoride (NH4HF2) for durations ranging from 1 to 60 min. The etched surfaces were characterized using optical microscopy, scanning electron microscopy, surface profilometry, water contact angle measurements, and UV–vis spectroscopy to evaluate the changes in surface morphology, roughness, wettability, and optical properties. Tribological performance was assessed using reciprocating ball-on-plate friction tests. The results showed that increasing the etching time resulted in the formation of microscale surface features, increased surface roughness, enhanced hydrophilicity, and reduced optical transmittance. The average friction coefficient decreased with an increase in the etching time up to 30 min, beyond which a slight increase was observed. The 1-minute etched specimen exhibited the best wear resistance with the narrowest wear track and the least material removal. The improved tribological performance was attributed to the formation of a stable transfer film, reduced real contact area, and entrapment of wear debris. This study highlights the potential of chemical etching as a technique to tailor the surface structure and tribological properties of silicate materials for various applications.

Wettability/anti-icing properties of hierarchical Micro/nanostructured copper surface prepared by Micro milling and chemical etching

Ice accumulation on the metallic surface usually results in seriously economic losses, resource wastes and even hazard accidents. Superhydrophobic surfaces (SHSs) are recognized as one of the most promising candidates for water repellence and anti-icing, offering both environmental and economic advantages over the traditional methods. The ordered microstructure arrays with controllable parameters play an essential role in mechanism analysis, rational design and reproducible construction of SHSs. However, the efficient fabrication of ordered microarrays on metal substrates with high resolution and high accuracy is still fraught with significant challenges. Here, a multilevel micro/nano surface with rectangular micropillars was fabricated on copper substrate by the integration of micro milling and chemical etching, which exhibits superior superhydrophobicity with water contact angle of 171.1 ± 1.5° and sliding angle of 2.2 ± 0.7°. The developed deburring scheme makes an outstanding contribution to the in-situ removal of milling burrs generated on the top of micropillars. The variation in surface wettability with microarray geometry and etching conditions indicates that a favorable surface morphology is crucial for improving the water repellency of the surface. The results of the durability experiment and the self-cleaning test demonstrate the robust comprehensive stability of the prepared SHSs against moisture, high temperature and mechanical wear, as well as the superior fouling resistance against solid and liquid contaminants, which is mainly ascribed to the hierarchical micro/nanostructures. Moreover, the present micro/nanostructures are also demonstrated to be capable of enhancing the delayed icing performance of the copper surface, with the freezing time of a 5 μL water droplet being 519.86 ± 13.53 s. Meanwhile, the superhydrophobic copper surfaces exhibit remarkable anti-icing behavior against saline solutions, as evidenced by the freezing time of 1078.42 ± 31.24 s for a 5 μL NaCl droplet. This work provides a sustainable and high-precision approach for the fabrication of metal-based SHSs, expecting to advance the theoretical research and industrial applications of anti-icing functional surfaces.

Catalytic properties of Fe-based amorphous alloys with different Mo content after acid corrosion

A series of Fe-based amorphous alloy wires with good formation ability, good flexibility, and a large specific surface area were prepared by the melt quenching method, which can be directly used as a self-supporting electrode for the oxygen evolution reaction (OER) of water electrolysis. By controlling the content of Mo, (Fe0.8Ni0.2)71Mo5P12C10B2 (Mo5), (Fe0.8Ni0.2)71Mo10P12C5B2 (Mo10) and (Fe0.8Ni0.2)71Mo15P10C2B2 (Mo15) alloy wires were prepared. It was found that Mo5 and Mo10 alloys still exhibit a fully amorphous structure, while the main body of Mo15 alloy comprises B2Fe3Ni3 and Mo6Ni6C phases. The electrochemical results showed that Mo15 alloy had the best intrinsic catalytic activity. The OER electrocatalytic performance of Mo15 was further improved by 1 h chemical etching after soaking in 0.5 M HNO3, which showed the overpotential was 239 mV and the Tafel slope was 40.6 mV/dec in 1 M KOH with a current density of 10 mA/cm2.

Damage-tolerant oxides by imprint of an ultra-high dislocation density

Dislocations in ductile ceramics offer the potential for robust mechanical performance while unlocking versatile functional properties. Previous studies have been limited by small volumes with dislocations and/or low dislocation densities in ceramics. Here, we use Brinell ball scratching to create crack-free, large plastic zones, offering a simple and effective method for dislocation engineering at room temperature. Using MgO, we tailor high dislocation densities up to ∼1015 m−2. We characterise the plastic zones by chemical etching, electron channelling contrast imaging, and scanning transmission electron microscopy, and further demonstrate that crack initiation and propagation in the plastic zones with high-density dislocations can be completely suppressed. The residual stresses in the plastic zones were analysed using high-resolution electron backscatter diffraction. With the residual stress being subsequently relieved via thermal annealing while retaining the high-density dislocations, we observe the cracks are no longer completely suppressed, but the pure toughening effect of the dislocations remains evident.