Chemical Etching Method Research Articles

Sensitive Silicon Nanowire Ultraviolet B Photodetector Induced by Leakage Mode Resonances.

Ultraviolet photodetectors (UVPDs) have played an important role both in civil and military applications. While various studies have shown that traditional UVPDs based on wide-band-gap semiconductors (WBSs) have excellent device performances, it is, however, undeniable that the practical application of WBS-based UVPDs is largely limited by the relatively high fabrication cost. In this work, we propose a new silicon nanowire (Si NW) UVPD that is very sensitive to UVB light illumination. The Si NWs with a diameter of about 36 nm are fabricated by a metal-assisted chemical etching method. Performance analysis revealed that the Si NW device was only sensitive to UVB light and almost blind to illumination in the visible and near-infrared regions. Such abnormal spectral selectivity was associated with the leakage mode resonances (LMRs) of the small diameter, according to our theoretical simulation. Under 300 nm illumination, the responsivity, external quantum efficiency, and specific detectivity were estimated to be 10.2 AW-1, 4.22 × 103%, and 2.14 × 1010 Jones, respectively, which were comparable to or even higher than those of some WBS-based UVPDs. These results illustrate that the small dimension Si NWs are potential building blocks for low-cost and high-performance UVPDs in the future.

ZnO/nitrogen-doped carbon nanocomplex with controlled morphology for highly efficient electromagnetic wave absorption

In this work, zeolitic imidazolate framework-8 (ZIF-8) with yolk-shell and hollow structures were prepared by a convenient chemical etching method. A subsequent pyrolysis of ZIF-8 enabled one to produce ZnO/nitrogen-doped carbon nanocomplexes with original ZIF-8 morphology, where hollow structure showed superior electromagnetic wave absorption capacity and was responsible for matching the impedance of free space. The minimum reflection coefficients of hollow ZnO/nitrogen-doped carbon nanocomplexes were -51.2 dB (700 °C) and -52.4 dB (800 °C), respectively, whereas the effective absorption band width was as large as 4 GHz and the content of pyrolyzed hollow ZIF-8 was 15 wt%, which was inferior to the level among similar electromagnetic wave (EMW) absorption materials. The convenient and facile strategy paves the way toward designing hierarchical structures for highly efficient and light-weight electromagnetic wave absorbers.

Fused Silica Gyroscope Resonator Manufactured With Femtosecond Laser Assisted Wet Etching

As the development of inertial navigation technology, an increasing number of application scenarios have required improved gyroscope accuracy. Fused silica offers high quality factor and thermal stability compared with single crystal silicon. Developing microelectromechanical system (MEMS) gyroscopes based on planarized wafer-level fused silica processing technology is a developing trend. However, high quality fused silica processing is much more difficult than silicon processing, such as acid etching, dry etching or laser cutting. This letter reports the research performed on the rapid and high-quality fabrication of the fused silica resonator with femtosecond laser modification assisted chemical etching (FLMCE) method. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$300~\mu \text{m}$ </tex-math></inline-formula> thickness fused silica resonator could be manufactured in 60 mins with right angle and nanoscale surface roughness. Testing results indicate that the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor of the fabricated resonators reaches 814 k, which offers great potential in MEMS gyroscopes. [2021-0238]

Photo-induced catalytic removal of rhodamine-B by aligned silicon nanowires developed through metal assisted chemical etching

In this work, silicon nanowire (SiNW) is synthesized by conventional metal assisted chemical etching method with different etching time. The sample with the highest aspect ratio is confirmed from the field emission scanning electron microscopic (FESEM) study and is associated with SiNW etched for 27 min. The sample is further treated with hydrofluoric acid (HF) to make the sample hydrogen terminated (H-terminated). Along with FESEM, the as-prepared samples are characterized by X-ray diffraction (XRD), transmission electron microscope, Fourier transformed infrared spectroscopy (FTIR) and UV–Vis spectroscopic study. The FTIR study confirms the different bonding present in the sample. UV–Vis spectroscopic study confirms the change in the reflection of the sample due to HF treatment. XRD spectrum confirms the directional preference of the silicon substrate. Both the pure and H-terminated sample is employed to see their ability in removing poisonous textile dyes like rhodamine-B. It has been shown that both the samples can efficiently remove the dye, however the ability or removal efficiency came to a saturation just after one hour. Furthermore, unlike the previous reports, hydrogen termination in SiNWs could not make marked differences in the removal efficiency. Efforts have been made to explain the result, as well as the reaction kinetics has been studied by making a linear fit with the pseudo first order and second order kinetic plot. It has been shown that the reaction mostly followed the pseudo first order kinetics. • Silicon nanowires (SiNWs) are synthesized by MACE and modified with HF to obtain hydrogen-terminated SiNWs (H-SiNWs). • Both pure SiNWs and H-SiNWs show efficient photo-catalytic activity to remove Rhodamine B. • For the first time it is shown that SiNWs show better removal efficiency than the H-SiNWs.

Fabrication and Characterization of a Self-Powered n-Bi2Se3/p-Si Nanowire Bulk Heterojunction Broadband Photodetector.

In the present study, vacuum evaporation method is used to deposit Bi2Se3 film onto Si nanowires (NWs) to form bulk heterojunction for the first time. Its photodetector is self-powered, its detection wavelength ranges from 390 nm to 1700 nm and its responsivity reaches its highest value of 84.3 mA/W at 390 nm. In comparison to other Bi2Se3/Si photodetectors previously reported, its infrared detection length is the second longest and its response speed is the third fastest. Before the fabrication of the photodetector, we optimized the growth parameter of the Bi2Se3 film and the best Bi2Se3 film with atomic steps could finally be achieved. The electrical property measurement conducted by the physical property measurement system (PPMS) showed that the grown Bi2Se3 film was n-type conductive and had unique topological insulator properties, such as a metallic state, weak anti-localization (WAL) and linear magnetic resistance (LMR). Subsequently, we fabricated Si NWs by the metal-assisted chemical etching (MACE) method. The interspace between Si NWs and the height of Si NWs could be tuned by Ag deposition and chemical etching times, respectively. Finally, Si NWs fabricated with the Ag deposition time of 60 s and the etching time of 10 min was covered by the best Bi2Se3 film to be processed for the photodetector. The primary n-Bi2Se3/p-Si NWs photodetector that we fabricated can work in a self-powered mode and it has a broadband detection range and fast response speed, which indicates that it can serve as a promising silicon-based near- and mid-infrared photodetector.

Fabrication of Functional Super-Hydrophilic TiO2 Thin Film for pH Detection

A super-hydrophilic pH-sensitive electrode with a porous TiO2 thin film is proposed in this work and fabricated using the chemical etching method. In total, 30 groups of porous TiO2 thin film were obtained by immersing a Ti sheet in NaOH, with the solution concentration ranging from 0.5–4 M and the reaction time ranging from 15–240 min. SEM, XRD, XPS, and a contact angle meter were used to investigate the influence of the chemical etching parameters on the morphology, composition, and wettability of the fabricated electrodes. The chemical etching parameters were found to have a significant influence on the specific surface area and the component of the films, which strongly affected the wettability and pH sensing characteristics of the electrodes. The electrode obtained with a solution concentration of 1 M and reaction time of 120 min is the ideal product because of its excellent wettability, with a contact angle of 5.46°, and good pH sensing characteristics in pH buffer solutions. The electrode also showed good stability regarding its wettability and pH sensing properties during storage and utilization.

A symmetrical self-diplexing microstrip antenna with eight-shaped defects

This article aims to demonstrate the simulation and measurement results of a two-port and symmetrical microstrip antenna operating at 6.6 and 7 GHz frequencies. The essential advantages of the antenna in terms of numerical electromagnetism are that the geometry has a small electrical length at both frequencies, does not use a structure that requires extra computational load such as substrate integrated waveguide, and is symmetrical, thus reducing the mesh requirement by half. The proposed antenna was manufactured with the chemical etching method and the measurement results were presented. In addition, varying operating frequencies are shown with the aid of liquid metal to experimentally demonstrate the independent redesign/reconfigurability feature of the antenna. To further reduce the fabrication cost, the manufacturing process of the proposed antenna with the help of a 3D printer is explained, and the performance parameters are compared. Good agreement between simulations and measurements has been reported.

Restoration of Obliterated Serial Number on Keys with the Help of Various Chemical Etching Method: A Review Study

Restoration of Obliterated Serial Number on Keys with the Help of Various Chemical Etching Method: A Review Study

Length effect on the plastic deformation of SiO2 microcantilevers

SiO2 films are of much interest for the realization of suspended micromechanical structures such as microcantilevers and micro-bridges owing to their superior characteristics when compared to conventional c-Si. However, presence of residual stress induced bending and structural plastic deformation in these devices especially at elevated temperatures hinder their potential for real-time field applications. Moreover, the impact of micro-scale dimensional effects on the magnitude of deformation in these devices is not well understood. In this work, we have investigated the effect of post-release high temperature annealing on the bending and resonance frequency characteristics of SiO2 microcantilevers (MCs) with a specific focus on the length effect. For this purpose, SiO2 MCs of various lengths (Length: 50–190 μm, Width: 37 μm and thickness: 0.98 μm) were fabricated using direct laser writer and wet chemical etching methods and were subjected to high temperature annealing under N2 and O2 environments. We demonstrate through our experiments that the curvature of SiO2 MCs increases with both annealing temperature and length square of MCs. Our experiments revealed that, apart from onset of plastic deformation, stress accumulation at the fixed end of SiO2 MCs is also responsible for the observed curvature increase. From the measured curvature, mean (σ0) and gradient (σ1) residual stress values were estimated and found to increase with annealing temperature. Interestingly, there exists a critical length of MCs (90 μm) below which both σ0 and σ1 were found to increase further with reducing MC length and is shown to be due to the existence of large transverse curvature at these dimensions. High temperature annealing was also found to increase the resonance frequency of MCs and the increase was maximum ∼ 8% for 130 μm long MC. Various possible reasons for the frequency shift is discussed in detail.

The effect of immersion time on singlemode-tapered multimode-singlemode (STMS) fabrication using a chemical etching method

Singlemode-Multimode-Singlemode (SMS) is one of the fiber optic sensor structures that is widely applied for many sensing applications. High sensitivity is the preferred characteristic of SMS fiber structure. In this paper, a tapered structure is introduced to the SMS fiber structure to increase its performance. The tapered structure is made by the etching method by immersing the SMS multimode fiber in hydrofluoric acid (HF) solution. The immersion time was varied 5, 10, 15 and 20 minutes. The diameter of the multimode fiber decreases with the longer immersion time, while the length does not change. The STMS transmission spectrum was measured to investigate its performance. The chemical etching method using HF solution for tapering the SMS fibers has great potential as a simple method to achieve a smaller radius without lengthening multimode fibers.

A Humidity Sensor Based on a Whispering-Gallery-Mode Resonator With an L-shaped Open Microcavity

A whispering-gallery-mode (WGM) resonator with an L-shaped microcavity for humidity sensing is proposed and demonstrated. The L-shaped microcavity is fabricated by using femtosecond laser micromachining, fusion discharge and chemical etching methods. By placing two microspheres in the microcavity, of which one is used as the whispering gallery mode resonant cavity, and the other plays the role of changing the optical path to help activating whispering gallery mode resonance. The device has a linear response to humidity with the linearity of 99.1% and the sensitivity of −0.23 dB/%RH, within the relative humidity range of 30%–70%, under the room temperature of 25 °C. The response time for the humidity increasing is as short as 240 ms, and the recovery time is 453 ms. The device is simple in fabrication, robust and has good operation stability.

High-Uniformity Submicron Gratings with Tunable Periods Fabricated through Femtosecond Laser-Assisted Molding Technology for Deformation Detection.

As one of the important diffractive optical elements, the submicron gratings on flexible substrates can actively and precisely control the dispersion and steering characteristics of beams and have been widely applied in deformation detection technologies. Herein, we propose a spatially modulated femtosecond laser-assisted molding technology for efficiently fabricating high-uniformity large-area submicron gratings with tunable periods on flexible substrates. The technology first uses a cylindrically focused femtosecond laser-assisted chemical etching method to form a regular submicron grating on silicon; subsequently, the structure is cast with polydimethylsiloxane, a useful flexible substrate with a small Young's modulus, and cured to obtain a high-uniformity large-area submicron grating with a tunable period. The grating exhibits high mechanical stability and sensitivity and favorable optical properties. In the present study, as the deformation of the grating increased from 0 to 10%, the diffraction angle changed by 6.5°. Under illumination by a broad-band white-light source, distinguishable multicolor diffraction patterns were clearly observed. Drawing on this characteristic, we fabricated a deformation sensor. The grating fabricated by using the proposed technology also has potential applications in optical sensors and soft robots.

Adhesion effect analysis of ultra-fine lunar dust particles on the aluminum-based rough surface based on the fractal theory

Investigation on the adhesion effect of lunar dust particles on contacting interface improves in lunar dust protection and prolongs the equipment service life. In this work, the contact mathematical adhesion model between an ultra-fine lunar dust particle and the aluminum-based rough surface is established based on the fractal theory. The research shows that the van der Waals force dominates adhesion force for ultra-fine lunar dust particles in space environment and is directly related to the rough surface fractal parameters, namely the fractal dimension parameter D , fractal roughness G as well as root-mean-square roughness(rms). Based on van der Waals adhesion model, the optimum rough surface fractal parameters are obtained through model optimization when the van der Waals force is minimal. The van der Waals forces reaches the minimum for lunar dust particle with diameters of 500 nm and 2.5 μm when the rms is 2.689 nm and 4.7 nm respectively. To validate the effectiveness of using fractal theory to the surface topography in van der Waals force calculation, the dust residual rates have been compared with the aluminum surfaces prepared using chemical etching method, electrochemical etching method, and combined chemical method. Based on the AFM topography of the surfaces, the van der Waals forces have been calculated between the lunar dust particles and the surfaces prepared using different etching methods. The centrifugal experiments suggest that van der Waals force is positively related to the dust residual rates. In summary, the fractal theory is effective in describing the surface roughness in lunar dust adhesion problems and it can be used in future lunar dust protection surface design and applications.

Preparing a wettability-controllable stainless-steel mesh and its oil–water separation performance

The ability to regulate and apply surface wettability has attracted much attention in the surface engineering field. In this study, a simple chemical etching method was used to construct a rough micro/nano structure on 304 stainless steel mesh; this rough surface was subsequently decorated with fatty acids of varying chain length to regulate wettability. The wettability, composition, and morphology of the surface were characterized and analyzed by measuring contact angles, and by atomic force microscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy . The superhydrophobic and superoleophilic properties of the mesh modified with long-chain fatty acids were examined for oil-water separation performance and reusability. The surface had a micro/nano hierarchical morphology with ordered carbon chains, and the hydrophilic-to-superhydrophobic transformation was achieved by adjusting the chain length of the fatty acid to deliver contact angles in the range of 30°~154°. The oil contact angle was always 0°, irrespective of the chain length fatty acid, and oil drops quickly penetrated the mesh surface. A fatty acid with a longer chain afforded a more hydrophobic and oleophilic mesh surface and better oil–water separation efficiency (up to 96%), which still exceeded 85% after 50 cycles of oil–water separation testing. Consequently, the prepared surface with controllable wettability has excellent prospects for use in intelligent response interfaces and oil–water separation applications.

Superhydrophobic copper foam modified with hierarchical stearic acid/CuSiO3/Cu(OH)2 nanocomposites for efficient water/oil separation

Developing efficient, durable and affordable oil-water separation technologies is critical to address the challenges of oily wastewater treatment. In this work, a microsphere-like CuSiO3 embedded Cu(OH)2 nanowires array was prepared on copper foam (CF) support (defined as CF/Cu(OH)2/CuSiO3) by using a simple chemical etching and hydrothermal method. After modifying with stearic acid (SA), such a novel CF/Cu(OH)2/CuSiO3-SA membrane presented excellent superhydrophobicity with a static water contact angle of 155.6°. The ammonia concentration in the precursor solution and the hydrothermal reaction time were critical for the morphology and the associated hydrophobicity of the CF/Cu(OH)2/CuSiO3-SA membrane. The as-prepared superhydrophobic CF had efficient anti-corrosion and mechanical properties and demonstrated an excellent separation capability of oil-water mixtures with a separation efficiency of 98.4%. It also exhibited a good separation efficiency of 98.3% for various water-in-oil emulsions, and delivered an outstanding separation efficiency of 98.2% towards oil/water mixture after operating successive 30 cycles of oil-water separation. With the inherent advantages of high separation efficiency of oil/water emulsion, good physicochemical stability and durability, and high mechanical and corrosion resistance, the novel CF/Cu(OH)2/CuSiO3-SA membrane is potentially useful in practical applications for oily wastewater treatment.

Surface texturisation for the reduction of light reflection in ZnO/Si heterojunction

ABSTRACT In this paper, the impact of pyramidal texture on a silicon substrate in ZnO/p-Si heterojunction was investigated. The texturisation of p-type silicon (100) substrate was obtained using the KOH anisotropic wet chemical etching method for different etching times. The RF magnetron sputtering technique was used to deposit ZnO thin films on textured Si substrates and planar Si substrates to form ZnO/Si heterojunction. The surface morphology was studied with field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Optical properties were investigated using UV-Visible spectroscopy and photoluminescence (PL). The results show that the PL intensity in the visible region of the electromagnetic spectrum increases with the etching time, while a significant reduction is observed in the reflectance. Due to impressive anti-reflection response, ZnO/Si (textured silicon-TS) heterojunction can be effective in improving the efficiency of solar cells.

Fabrication of superhydrophobic surface on stainless steel by two-step chemical etching

A two-step chemical etching method for preparing superhydrophobic surfaces on stainless steel substrates is proposed. The stainless steel substrates were sequentially immersed in hydrochloric acid and ferric chloride solutions to create micro-nano structures, and then the surfaces were modified with low surface energy substances. Superhydrophobic surfaces with a contact angle of 159° and a sliding angle of 2° were prepared by varying the etching solution parameters. The fabricated superhydrophobic surfaces showed excellent stability and self-cleaning properties. This paper illustrates a low-cost and efficient chemical etching method that can be used for large-area surface fabrication.

A comparative study of mechanical and chemical durability of non-wetting superhydrophobic and lubricant-infused surfaces

Fabrication of bioinspired non-wetting superhydrophobic surfaces (SHS) and lubricant-infused surfaces (LIS) has been studied extensively on a variety of materials. In contrast, durability of the surfaces exposed to harsh mechanical and chemical environments has been the subject of little attention. This study considers the mechanical and chemical durability of SHS and LIS copper surfaces fabricated via facile electrodeposition and chemical etching methods. The as-fabricated surfaces demonstrate excellent non-wetting characteristics with water contact angle of 160° and sliding angle below 5°. The surfaces are subject to mechanical wear through scratch test and water jet impingement at 15 psi and 20 psi as well as accelerated corrosion following the ASTM-E407 standard. The performance of the electrodeposited and etched non-wetting surfaces is systematically assessed in terms of contact and sliding angles and corrosion rate in a simulated marine environment. All surfaces are shown to be robust to mechanical wear after scratch test, with excellent stability of contact and sliding angles, and up to two orders of magnitude reduced corrosion rate compared to bare copper surface. SHS retained steadfast non-wetting characteristics under high-pressure water jet tests compared to the other surfaces while LIS, regardless of texturing method, showed one to two orders of magnitude reduced corrosion rate compared to bare copper surface throughout water jet impingement and chemical durability tests. The study presents for the first time a systematic comparison of durability of SHS and LIS through a common set of fabrication and testing protocol and helps identify appropriate non-wetting surfaces and fabrication methods based on the use environment.

Estimation of the nano-pores diameter by conductometric measurements

s. Ionic transport properties and diameter of asymmetric conical nano-pores in polyethylene terephthalate membranes were calculated. These nano-pores were synthesized by chemical etching method in irradiated polyethylene terephthalate (PET) films. After etching, the transport characteristics weredocumented under stepping voltage with 2M ionic concentrations of Potassium halides i.e. KCl, KBr and KI. The symmetric bathing condition (same temperature and same pH value solution in both side of chamber) in electrochemical cell were accomplished. It is investigated that diameter of nano-pores is also evaluate by measuring the current rectification properties of track etched nano-pores.

Photocatalytic H2 evolution by AgNP@PSi/SiNS composite derived from diamond-wire sawing silicon waste

Diamond-wire sawing silicon waste (DSSW) from photovoltaic silicon wafer sawing process represents a resource worth recovery and recycling. In this contribution, in order to utilize DSSW with low cost and high value, composite Si nanostructures for photocatalytic H2 evolution were innovatively synthesized by a simple, one-pot metal-assisted chemical etching (MACE) method from DSSW. The morphologies, phase structure, elemental composition and optical properties of the composite were characterized by XPS, BET, XRD, SEM, TEM, HRTEM and UV–vis. DRS, the photocatalytic performance was evaluated by water splitting under visible light. The results indicated that a visible light responsive Ag nanoparticles/porous silicon/silicon nanosheets ([email protected]/SiNS) composite was obtained. Owing to the porous and nanosheets features, the specific surface area of the composite is as high as 377.968 m2 g−1 and quantum confinement effects is successfully triggered to broaden the band gap of silicon from 1.12 eV to 1.31 eV, which allows an excellent hydrogen evolution amount of 367.65 μmol g−1 in the initial 1 h. In addition, the effect of Ag amount on the morphologies and photocatalytic performance of the composite was investigated. This study presents a promising route for the fabrication of composite silicon nanostructured photocatalysts from industrial silicon waste for solar hydrogen generation, demonstrating the potential for waste recovery and energy conversion.