Why is copper locally etched by scanning electrochemical microscopy?

The etching of thin copper films by scanning electrochemical microscopy (SECM) was investigated. It is not trivial that locally injected charge by an oxidized mediator will lead to dissolution of copper as the charge can easily be dissipated by lateral charge propagation. We studied the effect of different parameters, such as thickness of the Cu film and concentration of the mediator, on the efficiency of etching. The feedback current is the sum of three charge transfer contributions: diffusion of mediator species, chemical reaction on the surface and lateral charge propagation across the copper film. We have introduced an approach for isolating the lateral contribution and studied the parameters affecting the fate of the locally injected charge. We found that etching becomes effective once the lateral contribution cannot dissipate the locally injected charge. This occurs as the concentration of the etchant increases or the film thickness decreases. Measuring the steady-state current above Cu films with different thickness, allowed estimating the potential difference across the Cu area underneath the tip. We conclude that driving local processes, such as etching, depends on creating a mechanism which maintains the injected charge focused.     

Singlet Oxygen Induced Site-Specific Etching Boosts Nitrogen-Carbon Sites for High-Efficiency Oxygen Reduction

Targeted construction of carbon defects near the N dopants is an intriguing but challenging way to boost the electrocatalytic activity of N-doped carbon toward oxygen reduction reaction (ORR). Here, we report a novel site-specific etching strategy that features targeted anchoring of singlet oxygen (¹O₂) on the N-adjacent atoms to directionally construct topological carbon defects neighboring the N dopants in N-doped carbon (¹O₂−N/C). This ¹O₂−N/C exhibits the highest ORR half-wave potential of 0.915 V_RHE among all the reported metal-free carbon catalysts. Pyridinic-N bonded with a carbon pentagon of the neighboring topological carbon defects is identified as the primary active configuration, rendering enhanced adsorption of O₂, optimized adsorption energy of the ORR intermediates, and a significantly decreased total energy barrier for ORR. This ¹O₂-induced site-specific etching strategy is also applicable to different precursors, showing a tremendous potential for targeted construction of high-efficiency active sites in carbon-based materials.     

A new texturing technique of monocrystalline silicon surface with sodium hypochlorite

This work proposes a new texturing technique of monocrystalline silicon surface for solar cells with sodium hypochlorite. A mixed solution consisting of 5 wt% sodium hypochlorite and 10 vl% ethanol has been found that results in a homogeneous pyramidal structure, and an optimal size of pyramids on the silicon surface. The textured silicon surface exhibits a lower average reflectivity (about 10.8%) in the main range of solar spectrum (400–1000 nm).     

Hillock sizes after wet etching in silicon

The formation of two- and three-dimensional hillocks is regularly observed in Si(1 1 1) steps and Si(1 0 0) during wet etching. Frequently the resulting morphology consists of hillocks scattered on a landscape of limited roughness. Recently we proposed a mean field model (MFM) in which the observed hillock-and-valley pattern is possible under steady state if hillock etching is slightly faster than valley etching. This condition implies that hillock size distributions must be an exponential decreasing function. In this work, we report a systematic study of hillock size distributions of experimental morphologies obtained under different etchant concentrations in Si(1 0 0). We found that experimental hillock size distributions are in agreement with those predicted by the MFM.     

光电化学刻蚀n^＋—Si的电致发光

ｎ＋－Ｓｉ在ＨＦ水溶液中经光电化学刻蚀形成的微米级多孔硅（ＰＳ）具有较好的电致发光（ＥＬ）性能，其发光光谱的波长范围约在５００～８００ｎｍ之间，阴极ＥＬ的波长和强度均随调制电位可逆变化；在酸性溶液中，发光强度较大，光淬灭过程也较中性溶液为慢．与ｎ－－Ｓｉ的结果类似，ＰＳ的制备电位也决定性地影响着ＥＬ的强度．光淬灭前的伏安行为表明，除Ｓ２Ｏ２－３和Ｈ＋还原外，可能还涉及ＰＳ表面化合物的转化．对能带图进行了讨论．     

Etching of gold nanorods: The effects of diameter on analytical performances

Gold nanorods (GNRs) have been well employed for sensing/bio-sensing based on analytes modulated morphology or self-assembly states. Herein, we employed H₂O₂ based etching system (H₂O₂ molecules themselves and H₂O₂-Fe²⁺ Fenton reagents) as an example to study the diameters of GNRs on the analytical performances, for the colorimetric platforms using GNRs as reporters. We have found that the thinner GNRs possess a higher sensitivity; while the thicker ones bring more abound color presentation during the etching processes, which is especially for naked eye detection. In addition, a red shift of the plasmonic bands is observed for three kinds of thinner GNRs at the initial stage of the etching reaction, and the mechanism is also discussed.     

A preliminary study on chemical micro-machining of complex three-dimensional patterns on silicon substrates

Chemical micro-machining of complex 3-dimensional (3-D) patterns of silicon substrates was preliminarily explored by the confined etchant layer technique (CELT). Through systematic investigation, we demonstrated that cysteine as a scavenger and Br₂ as an etchant can be used to etch silicon substrates. The CELT has the potential to develop into a new means of micro-machining complex 3-D patterns on silicon substrates. However, due to the highly corrosive property of the chemicals used for the silicon etched system, great effort must be made to overcome these problems including the mold electrode with high chemical stability.Dedicated to Professor Gygy Horyi on the occasion of his 70th birthday     

Etching graphitic carbon nitride by acid for enhanced photocatalytic activity toward degradation of 4-nitrophenol

Graphitic carbon nitride （g-C3N4） with high photocatalytic activity toward degradation of 4-nitrophenol under visible light irradiation was prepared by HCI etching followed by ammonia neutralization. The structure, morphology, surface area, and photocatalytic properties of the prepared samples were studied. After treatment, the size of the g-C3N4 decreased from several micrometers to several hundred nanometers, and the specific area of the g-C3N4 increased from 11.5 m2/g to 115 m2/g. Meanwhile, the photocatalytic activity of g-C3N4 was significantly improved after treatment toward degradation of 4- nitrophenol under visible light irradiation. The degradation rate constant of the small particle g-C3N4 is 5.7 times of that of bulk g-C3N4, which makes it a promising visible light photocatalyst for future applications for water treatment and environmental remediation.     

Sensitive iodate sensor based on fluorescence quenching of gold nanocluster

In this report we described a highly selective and sensitive iodate sensor. Due to its interaction with fluorescent gold nanoclusters, iodate was capable of oxidizing and etching gold core of the nanoclusters, resulting in fluorescence quenching. Furthermore, it was found that extra iodide ion could enhance this etching process, and even a small amount of iodate could lead to significant quenching. Under an optimized condition, linear relationship between the iodate concentration and the fluorescence quenching was obtained in the range 10 nM–1 μM. The developed iodate sensor was found selective and capable of detecting iodate as low as 2.8 nM. The sensor was then applied for the analysis of iodate in real sample and satisfactory recoveries were obtained.     

硅的表面结构与电化学

从原子水平到微米尺寸,准确控制硅表面结构的精密加工,诸如无序的表面粗糙或者精细的图案,乃是电子元件性能及其可靠性的保证.硅在液中的湿清洗以及硅表面侵刻的电化学反应对硅表面结构的形成具有重要作用.近数十年来,有关阐明和控制硅/溶液界面上复杂的电化学反应及其与表面结构形成的关系已有大量的研究,相关研究成果已在新近编著成书.本文综合有关方面研究资料评述现代硅溶解及其形成的表面结构.