Aqueous Hydrofluoric Acid Solution Research Articles

Second order and Third order NLO studies of L- alanine crystals grown in aqueous solution of hydrofluoric acid (LAHF)

Nonlinear optics is a fascinating field, which plays a vital role in the emerging field of photonics and optoelectronics. A nonlinear optical crystal of L-alanine grown in aqueous solution of hydrofluoric acid is done by slow evaporation method. L-alanine is an NLO material and it has a Second Harmonic Generation (SHG) efficiency of about 0.3 times that of KDP. To alter the various properties of L-alanine, single crystals of L-alanine have been grown in the aqueous solution of hydrofluoric acid. In this work, Lalanine was admixtured with hydrofluoric acid (LAHF) in the molar ratio of 1:1. The grown crystals were colorless and transparent and they were subjected to various studies for characterization.The third-order nonlinearities of LAHF crystal have been investigated by Z-scan method. The values of nonlinear refractive index (n2), the nonlinear absorption coefficient (β) and third-order nonlinear susceptibility (χ) are estimated for the sample

Fabrication of Silicon Nanowire Arrays by Macroscopic Galvanic Cell‐Driven Metal Catalyzed Electroless Etching in Aerated HF Solution

Macroscopic galvanic cell-driven metal catalyzed electroless etching (MCEE) of silicon in aqueous hydrofluoric acid (HF) solution is devised to fabricate silicon nanowire (SiNW) arrays with dissolved oxygen acting as the one and only oxidizing agent. The key aspect of this strategy is the use of a graphite or other noble metal electrode that is electrically coupled with silicon substrate.

The correlation between the interference colour and growth procedure of anodic titanium dioxide nanotube arrays

Titanium dioxide nanotube arrays were anodised from titanium foils in an aqueous electrolyte solution of hydrofluoric acid. The formed oxide showed visually different colours owing to light interference in the titanium dioxide layer. The behaviour of interference colour in anodic titanium dioxide film was investigated by varying anodisation parameters such as the applied voltage and the anodisation time. The morphologies and the crystalline phases of anodised samples were studied on a field emission scanning electron microscope and X‐ray diffractometer. The correlation between the interference colour and growth procedure of anodic titanium dioxide nanotube arrays was studied. The anodic films prepared under different conditions consisted of a compact oxide film with a nanoporous/tubular structure upon/beneath it. The crystalline phase of the anodic oxide layer was amorphous. The optical properties of the oxide film were investigated on a spectrophotometer. Optical interference could be detected in compact oxide layers when the thickness of the titanium dioxide was as small as 70 nm. In general, the interferences of the nanoporous/tubular structures were lower than those for compact structures. The empirical colour properties were estimated by the L*a*b* system. The relationships between the interference colour of anodic titanium dioxide film and its thickness and morphology are discussed.

Anodized Preparation of Titanium Dioxide Nanotube Arrays and Photocatalytic Degradation of Chloramine Phosphorus

Anodic oxidation processing titanium foil in an aqueous solution of hydrofluoric acid+ glacial acetic acid+polyethylene glycol constant pressure, Synthesized by high-density ordered TiO2nanotube arrays. Calculate the degradation rate of chloramine phosphorus, TiO2nanotubes catalytic performance test.The use of scanning electron microscopy (SEM) and X-ray diffraction (XRD) to characterize the morphology and structure of the nanotubes, Visits oxidation time on the morphology and size of the nanotube arrays, mapping and analysis of current - time curve. An average particle diameter d of the sample may be calculated the strongest diffraction peak of the plane FWHM ,So chloramine phosphorus selection of organic phosphorus drugs for the photocatalytic degradation object, Molybdenum blue spectrophotometry measured and calculated degradation rate, Study of heat treatment temperature and anodizing time photocatalytic degradation, And the sol - gel prepared TiO2 thin film and photocatalytic comparative experiments.

Microdetermination of titanium on the developed silicon surface using cells made of perfluorinated proton-conducting membranes

A technique for microdetermination of titanium on the developed silicon surface is suggested. In this technique, thin titanium layers are dissolved in an aqueous solution of hydrofluoric acid and then the resulting solutions are analyzed using potentiometric cells made of perfluorinated proton-conducting membranes. The feasibility of estimation of titanium on the silicon surface in amounts of 5 × 10−7 mol or less is demonstrated.

Simple Fabrication of Antireflective Silicon Subwavelength Structure with Self-Cleaning Properties

A subwavelength structure (SWS) was formed via a simple chemical wet etching using a gold (Au) catalyst. Single nano-sized Au particles were fabricated by metallic self-aggregation. The deposition and thermal annealing of the thin metallic film were carried out. Thermal annealing of a thin metallic film enables the creation of metal nano particles by isolating them from each other by means of the self-aggregation of the metal. After annealing, the samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. When silicon (Si) was etched for 2 minutes using the Au nano particles, the reflectance was decreased almost 0% over the entire wavelength range from 300 to 1300 nm due to its deep and steeply double tapered structure. When given varying incident angle degrees from 30 degrees to 60 degrees, the reflectance was also maintained at less than 3%. Following this, the etched silicon was treated with a plasma-polymerized fluorocarbon (PPFC) film of about 5 nm using an ICP reactor for surface modification. The result of this surface treatment, the contact angle increased significantly from 27.5 degrees to 139.3 degrees. The surface modification was successful and maintained almost 0% reflectance because of the thin film deposition.

Morphological Evolution of Silver Nanoparticles and Its Effect on Metal-Induced Chemical Etching of Silicon

In this report, we have demonstrated the morphological evolution of the silver nanoparticles (AgNPs) by controlling the growth conditions and its effect on morphology of silicon (Si) during metal-induced electroless etching (MICE). Self-organized AgNPs with peculiarly shape were synthesized by an electroless plating method in a conventional aqueous hydrofluoric acid (HF) and silver nitrate (AgNO3) solution. AgNP nuclei were densely created on Si wafer surface, and they had a strong tendency to merge and form continuous metal films with increasing AgNO3 concentrations. Also, we have demonstrated that the fabrication of aligned Si nanowire (SiNW) arrays in large area of p-Si (111) substrates by MICE in a mixture of HF and hydrogen peroxide (H2O2) solution. We have found that the morphology of the initial AgNPs and oxidant concentration (H2O2) greatly influence on the shape of the SiNW etching profile. The morphological results showed that AgNP shapes were closely related to the etching direction of SiNWs, that is, the spherical AgNPs preferred to move vertical to the Si substrate, whereas non-spherical AgNPs changed their movement to the [100] directions. In addition, as the etching activity was increased at higher H2O2 concentrations, AgNPs had a tendency to move from the original [111] direction to the energetically preferred [100] direction.

Functionalization of graphene and few-layer graphene with aqueous solution of hydrofluoric acid

In the present study, conditions suitable for efficient modification of graphene and few-layer graphene (FLG) films with aqueous solutions of hydrofluoric acid (HF) and for local protection of the graphene against such modification in isopropyl alcohol were identified. A combination of the two treatments gives one a key to nanodesign of graphene-based 2D devices. It was found that a few-minute treatment of graphene or FLG in HF aqueous solutions (∼1min for graphene and ∼5min for FLG films about 5nm thick) leads to strong changes in the structural and electrical properties of graphene involving a step-like increase in resistivity (up to 1011Ω/□). Two types of materials were obtained after different times of treatment: (i) promising for electronic applications of the material due to a combination of high carrier mobility, high conductivity, and strong current modulation by gate voltage (up to four orders of magnitude); (ii) a material with insulating properties and graphene quantum dots embedded in an insulating matrix.

Fabrication of Gradient TiO2 Nanotubes on Ti Foil by Anodization

AbstractA new anodization based method is developed to fabricate a gradient in TiO2 nanotube diameters and lengths on Ti foil. In the method, the applied anodization voltage is increased step by step, while the Ti foil is immersed into an aqueous solution of hydrofluoric acid progressively during anodization. The gradient TiO2 nanotubes with tube diameters ranging from 55 to 105 nm and lengths ranging from 300 to 500 nm across 12 mm of Ti foil are obtained. The formation mechanism of gradient diameter and length is also discussed. The gradient structure is potentially useful as new cell instructive materials (CIMs) for guided cell movement and culture, novel drug delivery vehicles, size‐selective biosensors, or other sensor applications.

Optimized process of metal assisted silicon wet etching for antireflection layer

► A simple fabrication technique for silicon subwavelength structure is proposed. ► Au nanoparticles are an excellent catalyst to wet etching. ► Au nanoparticles were fabricated using the metal self-aggregation effect. ► Particle size was adapted with initial Au film thickness before annealing. ► Reflectance of etched Si was almost 0% for the wavelength from 300 to 1300 nm. In this study, a simple fabrication technique for silicon (Si) subwavelength structure (SWS) by means of chemical wet etching using Au nano particles directly formed on silicon substrates was proposed and optimized. Single nano-sized Au particles were fabricated using the metal self-aggregation effect. The deposition and thermal annealing of the metallic thin film were undertaken. The thermal annealing of the metallic thin film enables the creation of metal nano particles by isolating them from each other through the self-aggregation of the metal. It was found that the initial Au film thickness can affect the particle size and change the etching conditions such as the fill factor, inter-particle distance, and so on. Then, samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. When using the optimized process parameters, although Si etching was only 2 min in duration, the reflectance decreased to approximately 1% in the whole wavelength range from 300 to 1300 nm due to the deep and steep double tapered structure.

Microdetermination of silicon dioxide on the surface by sensors based on perfluorinated proton-conducting membranes

A microdetermination method of silicon dioxide on the silicon surface is studied. In this method, a thin SiO2 layer is dissolved in an aqueous solution of hydrofluoric acid and then the resulting solution is analyzed with sensors based on perfluorinated proton-conducting membranes. Quantitative determination of silicon dioxide remaining on the silicon surface in a quantity as low as 1 × 10−6 mol is demonstrated to be feasible.

Processing of Foturan® glass ceramic substrates for micro-solid oxide fuel cells

Abstract The microfabrication of Foturan ® glass ceramic as a potential substrate material for micro-solid oxide fuel cells (micro-SOFC) was investigated. Foturan ® was etched in 10% aqueous hydrofluoric (HF) acid solution at 25 °C with a linear rate of 22 ± 1.7 μm/min to create structures with an aspect ratio of 1:1 in 500 μm-thick Foturan ® substrates for micro-SOFCs. The concentration of the HF etchant was found to influence the etching rate, whereas the UV-exposure time creating nuclei in the glass for subsequent crystallization of the amorphous Foturan ® material had no significant influence on the etching rates. The surface roughness of the crystallized Foturan ® was determined by the crystallite size in the order of 10–15 μm. Free-standing micro-SOFC membranes consisting of a thin film Pt cathode, an yttria-stabilized-zirconia electrolyte and a Pt anode were released by HF etching of the Foturan ® substrate. An open-circuit voltage of 0.57 V and a maximum power density of 209 mW/cm 2 at 550 °C were achieved.

결정질 실리콘 태양전지의 Ag 촉매층을 이용한 나노 텍스쳐링 공정에 관한 연구

In our report a relatively simple process for fast nano-texturing of p-type(100) CZ- silicon surface using silver catalyzed wet chemical etching in aqueous hydrofluoric acid (HF) and hydrogen peroxide solution(<TEX>$H_2O_2$</TEX>) at room temperature. The wafers were saw-damaged by NaOH(6 wt%) at <TEX>$60^{\circ}C$</TEX> for 150s. To obtain a nano-structured black surface, a thin layer of silver with thickness of 1 - 10 nm was deposited on the surfaces by evaporation system. After this process the samples were etched in HF : <TEX>$H_2O_2$</TEX> : <TEX>$H_2O$</TEX> = 1:5:10 at room temperature for 80s - 220s. Due to the local catalytic of the Ag clusters, this treatment results in the nano-scale texturing on the surface. This resulted in average reflectance values less than 9% after the silver on the surface of the wafers were removed.

Water-Repellent Silicon Surface with Nanostructure Formed by Catalysis of Single Nanosized Silver Particle

A water-repellent silicon (Si) surface with a nanostructure was formed by simple wet chemical etching using catalysis of a silver nanoparticle. Water repellency can be increased by forming micro- or nanostructures on the Si surface. A single nanosized silver particle dispersion solution was coated onto a Si(100) substrate with a polished surface. The samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. The roughness and depth of the surface structure increased with increasing etching time. The Si surface with the nanostructure had a contact angle of 130°, indicating a water-repellent surface, whereas the surface without the nanostructure had a contact angle of 68°.

Silver catalyzed nano-texturing of silicon surfaces for solar cell applications

We report a relatively simple process for fast nano-texturing of p-type (100) silicon surface using silver catalyzed wet chemical etching in aqueous hydrofluoric acid and hydrogen peroxide solution at room temperature. In this approach, a fine textured black surface was achieved in about 15–30s duration with reflectivity less than 4% in 400–1000nm range. The reflectivity versus texturization time has been investigated and co-related with morphological characteristics of the nano-textured-silicon (nT-Si) surfaces. The nano-texturization process is also applicable in multi-crystalline silicon. Further, n+–p–p+ structured solar cells have been fabricated on such nT-Si substrates following the standard fabrication protocol. Significant improvement in short circuit current density (>20%) and efficiency (∼1.25% absolute) has been achieved compared with planar control cell without deterioration of other performance parameters (such as open circuit voltage and fill factor). Light beam induced current measurements have also been carried out to show the spatial distribution of the light trapping and current in the planar and the nT-Si solar cells.

Formation of a-Si:H and a-Si1-xCx :H nanowires by Ag-assisted electroless etching in aqueous HF/AgNO3 solution

The formation of hydrogenated amorphous silicon–carbon alloy (a-Si1-xCx:H) nanowires is studied for different carbon concentrations (0–7%) by using Ag-assisted electroless etching of the thin a-Si1-xCx:H films deposited by plasma-enhanced chemical vapour deposition from silane/methane gas mixtures. The nanowires morphologies (length, density, …), studied by scanning electron microscopy, strongly depend on the concentration of the etchant (aqueous solution of hydrofluoric acid and silver nitrate), the etching time, and the carbon concentration of the deposited layer.

Antireflective silicon subwavelength structure formed by self-aggregated gold nano particle as a catalyst

A subwavelength structure (SWS) was formed by simple chemical wet etching using two types of gold (Au) catalysts to compare the etching speed due to difference of fill factor. One sample is an Au thin film that has an almost 100% fill factor; the other is comprised of Au nano particles that have an approximately 50% fill factor. Single nano-sized Au particles were fabricated by metal self-aggregation effect. The deposition and the thermal annealing of the metallic thin film were carried out. The thermal annealing of a metallic thin film enables the creation of metal nano particles by isolating them from each other by means of the self-aggregation of the metal. Then, samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. When Si etched for 20min using the Au thin film, the reflectance decreased to about 8%. But, when Si etched just 3min using the Au nano particle, the reflectance decreased below 3%; with an added 10min etching, the reflectance decreased almost to 0% in the whole range from 300 to 900nm owing to the deep and steep double tapered structure.

Metal-assisted etching of p-silicon—Pore formation and characterization

Etching of silicon and formation of definite porous surfaces can be carried out by different methods. Metal-assisted etching represents a convenient method for the application of induced etching for beneficial applications. Porous silicon layers (PSL) on Si are useful and important in solar energy conversion and optoelectronics. Porous silicon on silicon increases the effective area and thus higher optical absorption as well as solar conversion efficiency can be achieved. The effective optical properties of PSL have found great interest in optoelectronics. In the last few years PSL of definite pore structures have been prepared by metal-assisted etching of p-Si in aqueous hydrofluoric acid solutions containing different oxidizing agents. Potassium dichromate, at definite concentration and after optimum etching time of p-Si on which Pt nuclei were electroless deposited, has shown promising effects. The effect of etching time, K 2Cr 2O 7 concentration and HF concentration on the main characteristics of the porous structure was investigated and discussed. In this respect electrochemical impedance spectroscopy (EIS) was used. The experimental data were fitted to theoretical data according to a proposed electrical equivalent circuit model. The morphology of the formed layers and surface contaminations were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. The results have shown that PSL with nano and micro pores were formed on p-Si when etched in HF–K 2Cr 2O 7 aqueous solutions. At 22.0 mol L −1 HF and relatively high concentration of K 2Cr 2O 7 [>0.05 mol L −1] a passive K 2SiF 6 layer was formed on the Si surface with a thickness that is affected by the concentrations of both HF and K 2Cr 2O 7. The passive K 2SiF 6 layer reduces the effectiveness of the PSL in both the solar conversion process and also its electrical and optical characteristics.

Design of a Novel Wet-Etch Reactor and Etch Chemistries: Simulations and Experimental Verification

Dilute aqueous solutions of hydrofluoric acid (HF) have been used to etch or remove SiO¬¬2-based layers. Due to the various chemical equilibria established between ionic species in aqueous HF solutions, control of etchant species concentrations and thus etch selectivity is difficult. A short contact time prototype reactor for wet etching studies of silicon-based dielectric films has been designed to investigate the effects of various process parameters during the etch process . For comparison, simulations using Computational Fluid Dynamics (CFD) have been used to predict the effect of process parameters such as flow rates and HF concentrations, thermodynamic equilibria, species transport, intrinsic etch kinetics and geometric parameters of the reactor. Results from CFD and etch experiments are in good agreement. Non-aqueous solutions utilizing fluorine-containing tetrabutylammonium salts have been investigated to control desirable equilibria and tailor etch rates and selectivity.

Study of surface morphology of ferrofluid deposited etched ion tracks in dielectric layers

Abstract An AFM study is reported on swift heavy irradiated Si/SiO 2 substrates which have been etched by aqueous hydrofluoric acid solution leading to ion tracks in which ferrofluids have been deposited leading to t unable e lectronic m aterials with p ores in o xide on s ilicon (TEMPOS) structure. Two ferrofluids with different carrier fluids (aqueous and non-aqueous) have been deposited in the tracks. Atomic force microscopy has been used to study the empty as well as filled tracks. Since the ferrofluids contain iron oxide particles, there is a possibility of agglomeration of these particles inside and outside the tracks. Surface area and pore volume of the tracks have been measured by Brunauer-Emmett-Teller (BET) method. The track properties (empty and filled) as observed by AFM have been correlated with BET measurements.