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The surface uniformity of porous silicon (PSi) morphologies will enhance the overall properties of the PSi layer. In this study, the role of perpendicular magnetic field (MF) on structural, optical, and electrical properties of (PSi) substrates are reported. The (PSi) is prepared with a photo-electrochemical etching process in the front-side illumination pathway with and without a perpendicular magnetic field (MF). The application of (MF) on the path of the electric charge carrier leads to modify the morphologies of PSi surface. The pores shape, sizes, orientation, and homogeneity, and electrical properties will vary with the (MF). The role of (MF) will contribute to an increase in the number of pores and decrease the overlapping process. And also, promotes the orientation of the relatively more defined pores across the Psi surface. The observed noticeable changes in PL spectra, electrical properties, and charge carrier transport mechanisms may be owing to the surface reconstruction process. The influence of (MF) on the characteristics of Au thin layer / PSi/c-Si/Al structures will lead to converting its behavior from the resistor to Schottky-like junction.

Silicon is the undisputed leader for microelectronics among all the industrial materials and Si nanostructures flourish as natural candidates for tomorrow’s technologies due to the rising of novel physical properties at the nanoscale. In particular, silicon nanowires (Si NWs) are emerging as a promising resource in different fields such as electronics, photovoltaic, photonics, and sensing. Despite the plethora of techniques available for the synthesis of Si NWs, metal-assisted chemical etching (MACE) is today a cutting-edge technology for cost-effective Si nanomaterial fabrication already adopted in several research labs. During these years, MACE demonstrates interesting results for Si NW fabrication outstanding other methods. A critical study of all the main MACE routes for Si NWs is here presented, providing the comparison among all the advantages and drawbacks for different MACE approaches. All these fabrication techniques are investigated in terms of equipment, cost, complexity of the process, repeatability, also analyzing the possibility of a commercial transfer of these technologies for microelectronics, and which one may be preferred as industrial approach.

All-wet metal-assisted chemical etching (MACE) has been demonstrated as a simple and effective method to fabricate silicon nanocones (SiNCs). The properties of SiNCs strongly depend on their structure parameters such as the cone angle and can be optimized through modulating the cone angle. However, cone angle modulation of SiNCs in all-wet MACE processes has not been achieved. Here, we report the fabrication of SiNCs with different cone angles through double etching processes in all-wet MACE. Large-size silver nanoparticles (AgNPs) were first obtained by solution deposition. After a common etching process, a double etching process with diluted etching solutions was introduced. In the etching step, AgNPs gradually reduced with the Si etching, which resulted in the formation of SiNCs. The cone angles of SiNCs depend on the changing rate of AgNP sizes. Based on this mechanism, SiNCs with different cone angles from 5°-20° were successfully fabricated by changing the concentration of the diluted etching solution in the double etching process. The contact angle of SiNCs with different cone angles was also investigated. It is found that the wettability of the SiNCs becomes poorer with increasing cone angles. Cone angle modulation of SiNCs in all-wet MACE will benefit the property control and the wide applications of SiNCs.

This work details an effective dynamic chemical etching technique to fabricate ultra-sharp tips for Scanning Near-Field Microwave Microscopy (SNMM). The protruded cylindrical part of the inner conductor in a commercial SMA (Sub Miniature A) coaxial connector is tapered by a dynamic chemical etching process using ferric chloride. The technique is optimized to fabricate ultra-sharp probe tips with controllable shapes and tapered down to have a radius of tip apex around ∼1 μm. The detailed optimization facilitated the fabrication of reproducible high-quality probes suitable for non-contact SNMM operation. A simple analytical model is also presented to better describe the dynamics of the tip formation. The near-field characteristics of the tips are evaluated by finite element method (FEM) based electromagnetic simulations and the performance of the probes has been validated experimentally by means of imaging a metal-dielectric sample using the in-house scanning near-field microwave microscopy system.

A novel method of laser machining combined with high temperature chemical etching (LMHTCE) was proposed. This novel method can take full advantage of both approaches to drill film holes in an IN718 superalloy without a recast layer or a heat affect zone (HAZ). A solution of hydrochloric acid and sodium nitrate, which minimally reacts with IN718 at room temperature but rapidly reacts under high temperatures, was tested and chosen. Holes drilled in air, water, and chemical solutions by a pulsed laser of 1064 nm were studied, and scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were employed to detect the morphology of the holes and the elemental distribution in different zones. The holes processed in the chemical solution had fewer defects compared with those in the other two mediums. The defocusing distance parameter was optimized to minimize the hole diameter and taper. When the defocusing distance was 0 μm in the drilling stage and − 60 μm in the high temperature chemical etching stage, a hole with a smaller diameter and taper can be obtained.

The application of nanotechnology in developing novel thermoelectric materials has yielded remarkable advancements in material efficiency. In many instances, dimensional constraints have resulted in a beneficial decoupling of thermal conductivity and power factor, leading to large increases in the achievable thermoelectric figure of merit (ZT). For instance, the ZT of silicon increases by nearly two orders of magnitude when transitioning from bulk single crystals to nanowires. Metal-assisted chemical etching offers a viable, low-cost route for preparing silicon nanopillars for use in thermoelectric devices. The aim of this paper is to review strategies for obtaining high-density forests of Si nanopillars and achieving high-quality contacts on them. We will discuss how electroplating can be used for this aim. As an alternative, nanopillars can be embedded into appropriate electrical and thermal insulators, with contacts made by metal evaporation on uncapped nanopillar tips. In both cases, it will be shown how achieving control over surface termination and defectivity is of paramount importance, demonstrating how a judicious control of defectivity enhances contact quality.

Silicon (Si) shows great potential as an anode material for lithium-ion batteries. However, it experiences significant expansion in volume as it undergoes the charging and discharging cycles, presenting challenges for practical implementation. Nanostructured Si has emerged as a viable solution to address these challenges. However, it requires a complex preparation process and high costs. In order to explore the above problems, this study devised an innovative approach to create Si/C composite anodes: micron-porous silicon (p-Si) was synthesized at low cost at a lower silver ion concentration, and then porous silicon-coated carbon (p-Si@C) composites were prepared by compositing nanohollow carbon spheres with porous silicon, which had good electrochemical properties. The initial coulombic efficiency of the composite was 76.51%. After undergoing 250 cycles at a current density of 0.2 A·g−1, the composites exhibited a capacity of 1008.84 mAh·g−1. Even when subjected to a current density of 1 A·g−1, the composites sustained a discharge capacity of 485.93 mAh·g−1 even after completing 1000 cycles. The employment of micron-structured p-Si improves cycling stability, which is primarily due to the porous space it provides. This porous structure helps alleviate the mechanical stress caused by volume expansion and prevents Si particles from detaching from the electrodes. The increased surface area facilitates a longer pathway for lithium-ion transport, thereby encouraging a more even distribution of lithium ions and mitigating the localized expansion of Si particles during cycling. Additionally, when Si particles expand, the hollow carbon nanospheres are capable of absorbing the resulting stress, thus preventing the electrode from cracking. The as-prepared p-Si utilizing metal-assisted chemical etching holds promising prospects as an anode material for lithium-ion batteries.

Micro free-flow electrophoresis (μFFE) provides a rapid and straightforward route for the high-performance online separation and purification of targeted liquid samples in a mild manner. However, the facile fabrication of a μFFE device with high throughput and high stability remains a challenge due to the technical barriers of electrode integration and structural design for the removal of bubbles for conventional methods. To address this, the design and fabrication of a high-throughput μFFE chip are proposed using laser-assisted chemical etching of glass followed by electrode integration and subsequent low-temperature bonding. The careful design of the height ratio of the separation chamber and electrode channels combined with a high flow rate of buffer solution allows the efficient removal of electrolysis-generated bubbles along the deep electrode channels during continuous-flow separation. The introduction of microchannel arrays further enhances the stability of on-chip high-throughput separation. As a proof-of-concept, high-performance purification of fluorescein sodium solution with a separation purity of ~97.9% at a voltage of 250 V from the mixture sample solution of fluorescein sodium and rhodamine 6G solution is demonstrated.

In this study, we developed active substrates consisting of Ag-decorated silicon nanowires on a Si substrate using a single-step Metal Assisted Chemical Etching (MACE) process, and evaluated their performance in the identification of low concentrations of Rhodamine 6G using surface-enhanced photoluminescence spectroscopy. Different structures with Ag-aggregates as well as Ag-dendrites were fabricated and studied depending on the etching parameters. Moreover, the addition of Au nanoparticles by simple drop-casting on the MACE-treated surfaces can enhance the photoluminescence significantly, and the structures have shown a Limit of Detection of Rhodamine 6G down to 10−12 M for the case of the Ag-dendrites enriched with Au nanoparticles.

This work reports the fabrication of p‐type Si micropillar (MP) substrates decorated with AgxCu100−x bimetallic nanoparticles and their application as photocathodes for CO2 photoelectrochemical reduction. Metal deposition by metal‐assisted chemical etching is chosen as the nanoparticle synthesis method, to explore for the first time its capabilities for 3D structures. It is found to be applicable, allowing a good control of the composition, with nanoparticles distributed along the entire MP, but with a coverage gradient from top to bottom. The AgxCu100−x decorated Si MPs photocathodes show enhanced light trapping compared to flat Si, with 45 % lower reflectance values in the visible and significantly higher catalytic activity, in terms of photocurrent density, overpotential and power savings (4.7 % for Ag50Cu50/Si MPs vs. 3 % for Ag50Cu50/flat‐Si). Si MPs coated with Ag50Cu50 and Ag20Cu80 provide the highest gain in potential (440 and 600 mV vs. bare Si MPs) and an increased selectivity towards high energy density products (i. e., CH4) compared to monometallic photocathodes. These are promising features for efficient light‐driven CO2 conversion. However, a significant metal loss is observed during photoelectrolysis, especially for Cu‐rich compositions. Suggestions to improve the photocathode performance in terms of metal coating homogeneity and catalyst stability are presented. PEC CO2 reduction reaction in AgxCu100−x coated three‐dimensional supports based on Silicon Micropillars.