Effect Of Chemical Etching Research Articles

Room temperature synthesis of carbon nanofibers containing nitrogen by plasma-enhanced chemical vapor deposition

This letter reports low-pressure, room-temperature growth of carbon nanofibers containing nitrogen by plasma chemical vapor deposition arrangement. By alternating pure acetylene plasma and afterglow pure nitrogen high dense plasma, a fine control of the fibers growth kinetic is obtained. This layer-by-layer deposition technique takes advantage of nitrogen chemical etching effects during the growth of nitrogen-doped carbon nanofibers.

The effect of selective chemical etching on the directivity pattern for radiation of a semiconductor laser

The effect of the selective wet chemical etching of the emitting surface on the directivity pattern of radiation in the plane normal to the p-n junction is studied for InGaP/GaAs lasers with InGaAs quantum wells. It is found by atomic-force microscopy that the cylindrical lens (converging or diverging, depending on the type of etchant) is self-formed on the emitting surface due to the different etching rate of wide-gap layers (InGaP) and active layers (GaAs, InGaAs) of the lasers. By adjusting the corresponding etching time, the aperture angle of the laser radiation pattern in the plane normal to the p-n junction can be changed in the range of 57°–82° at the initial aperture angle at the half maximum level of 6°.

The Effects of Chemical Etching of Porous Silicon on Raman Spectra

We have investigated the effects of chemical etching on Raman spectra of porous silicon. The as-anodized porous silicon consisted mainly of crystalline silicon, as indicated by the Raman spectra. The background in the spectrum was strong, indicating that the porous silicon surface was rough due to the presence of pores. When chemical etching was performed five times, the Raman spectrum revealed the presence of spherically shaped nanocrystalline silicon whose diameter was around 3.5 nm. Further chemical etching, however, extinguished the nanocrystallites, in addition to smoothing the surface morphology.

Comparative corrosion performance of black oxide, sandblasted, and fine‐drawn nitinol wires in potentiodynamic and potentiostatic tests: Effects of chemical etching and electropolishing

The corrosion performance of sandblasted (SB) and smooth fine-drawn (FD) medical-use nitinol wires was compared with the performance of wires with black oxide (BO) formed in air during their manufacture. Potentiodynamic and ASTM F746 potentiostatic tests in a 0.9 % NaCl solution were conducted on wires in their as-received, chemically etched, aged in boiling water, and electropolished states. As-received wires with various surface finishes revealed breakdown potentials in the range from -100 mV to +500 mV; similar passive current density, 10(-6) A/cm(2); and a wide hysteresis on the reverse scan, demonstrating strong susceptibility to localized corrosion. Chemically etched wires with original black oxide displayed consistent corrosion performance and surpassed, in corrosion resistance, electropolished wires that showed significantly lower breakdown (400-700 mV) and localized corrosion potentials ( approximately -50 to +113 mV). Sandblasted and fine-drawn wires exhibited rather inconsistent corrosion behavior. In potentiodynamic tests these wires could perform with equal probability either on the level of pretreated BO wires or rather similar to as-received wires. Both SB and FD wires revealed low breakdown potentials in the PS regime. SEM analysis performed before tests indicated that sandblasting was not efficient for the complete removal of the original scaling, and fine drawing aggravated the situation, resulting in a persistent scaling that contributed to the inferior corrosion performance. Inclusions (oxides, carbides, and oxidized carbides) inherited from the bulk and retained on electropolished surfaces are the cause of their inferior performance compared to chemically etched surfaces. In electropolished wires corrosion was initiated around inclusions.

Reactive ion etching of sol–gel-derived BST thin film

Perovskite (Ba,Sr)TiO 3 (BST) thin film is promising dielectric and ferroelectric material for future generation integrated DRAMs, MEMS, and other devices. The etching properties of BST films were widely concerned. The etching characteristics of sol–gel-derived BST films were investigated in a reactive ion etching (RIE) setup using CHF 3/Ar plasma. The morphology and etching rate were measured by atomic force microscopy (AFM). The surface states of each element in BST films were examined by X-ray photoelectron spectroscopy (XPS). The etching mechanism of BST thin film in RIE was the cooperation of ion bombardment, ions assist chemical reaction and reaction etching effects. The highest etching rate of BST films was 5.1 nm/min.

Strength enhancement of single crystal laser components

The effect of chemical etching on the surface roughness and fracture strength of Nd:yttrium-aluminum-garnet single crystals was investigated. Etching the laser host material in a 1:1 mixture of concentrated sulfuric and phosphoric acid at elevated temperatures enabled material removal from the surface of laser rods cored from single-crystal boules. The roughness on the rod surface increased from the as-drilled condition after etching, but after 17 μm of material was removed, the roughness remained approximately constant. The modulus of rupture increased from 133-530 MPa when 87 μm of material was removed by the chemical etching procedure.

A non-GIC mechanism of lithium storage in chemical etched MWNTs

The effect of chemical etching on the electrochemical intercalation of lithium into multi-walled carbon nanotubes (MWNTs) was investigated. The results showed that the charge capacity of etched MWNTs is greater than the theoretical capacity of graphite. Moreover, the charge curve does not show a well-defined voltage plateau. To explain this phenomenon, we proposed a non-GIC (graphite intercalation compound) mechanism that, except for the lithium intercalated between graphene layers to form graphite intercalation compounds, the higher charge capacity should be related to lithium doped into such regions as disordered graphitic structures, defects, microcavities, and edges of graphitic layers, which is generally called a non-GIC mechanism in this paper.

Thermal annealing of fission tracks in fluorapatite, chlorapatite, manganoanapatite, and Durango apatite: experimental results

It is well known that the optically measured lengths of fission tracks in apatite crystals are a function of etching conditions, crystallographic orientation of the track, composition of the crystal, and the state of thermal annealing. In this study we standardize etching conditions and optimize track length measurability by etching until etch pits formed at the surface of each apatite crystal reached widths of about 0.74 μm. Etching times using 5M HNO3 at 21°C were 31 s for Otter Lake, Quebec, fluorapatite; 47 s for Durango, Mexico, apatite; 33 s for Portland, Connecticut, manganoanapatite; and 11 s for Bamle, Norway, chlorapatite. An etching experiment using two etchant strengths (5M and 1.6M HNO3) revealed that, despite significant differences in etch pit shape, fission-track length anisotropy with respect to crystallographic orientation of the tracks is not a chemical etching effect. A series of 227 constant-temperature annealing experiments were carried out on nuclear reactor induced tracks in oriented slices of the apatites. After etching, crystallographic orientations of tracks were measured along with their lengths. The 200–300 track lengths measured for each slice were ellipse-fitted to give the major (c crystallographic direction) and minor (a crystallographic direction) semi-axes used to calculate equivalent isotropic lengths. The equivalent isotropic length is more useful than mean length for thermal history analysis because the variation caused by anisotropy has been removed. Using normalized etching procedures and equivalent isotropic length data, we found that the fluorapatite anneals most readily, followed by Durango apatite, manganoanapatite, and lastly chlorapatite.

Effects of the platelet structures on the melt textured growth YBCO superconductors

Melt textured growth YBCO superconductors were fabricated by the top seeding method using Sm1.8 (Sm/sub 1.8/Ba/sub 2.4/Cu/sub 3.4/O/sub 7-x/) seed. The relationship between the Y211 particles and the platelet structures was investigated by micro-structural analysis using SEM. The microstructures of melt textured YBCO superconductors have been examined by TEM and HRTEM. The results of TEM studies clarified the direction of crystal growth and a variety of micro-defects such as twin structures and stacking faults that might behave as pinning centers. Our studies were focused on the stacking faults among those micro-defects by HRTEM and formation mechanism of the stacking faults was studied. The stacking faults formed during the tetragonal to orthorhombic transition that occurred at 450/spl deg/C in oxygen annealing. The platelet structures were clearly observed by SEM due to the chemical etching effects. The lengths of stacking faults were increased as the oxygen annealing time increased from 1 hr to 50 hr. The stacking faults were considered to relate to the oxygen contents, as the platelet structures were. The results suggested an oxygen diffusion model for the formation of the stacking faults.

Effect of chemical etching and aging in boiling water on the corrosion resistance of Nitinol wires with black oxide resulting from manufacturing process.

The effect of chemical etching in a HF/HNO(3) acid solution and aging in boiling water on the corrosion resistance of Nitinol wires with black oxide has been evaluated with the use of potentiodynamic, modified potentiostatic ASTM F746, and scratch tests. Scanning-electron microscopy, elemental XPS, and Auger analysis were employed to characterize surface alterations induced by surface treatment and corrosion testing. The effect of aging in boiling water on the temperatures of martensitic transformations and shape recovery was evaluated by means of measuring the wire electroresistance. After corrosion tests, as-received wires revealed uniformly cracked surfaces reminiscent of the stress-corrosion-cracking phenomenon. These wires exhibited negative breakdown potentials in potentiostatic tests and variable breakdown potentials in potentiodynamic tests (- 100 mV to + 400 mV versus SCE). Wires with treated surfaces did not reveal cracking or other traces of corrosion attacks in potentiodynamic tests up to + 900-1400-mV potentials and no pitting after stimulation at + 800 mV in potentiostatic tests. They exhibited corrosion behavior satisfactory for medical applications. Significant improvement of corrosion parameters was observed on the reverse scans in potentiodynamic tests after exposure of treated wires to potentials > 1000 mV. In scratch tests, the prepared surfaces repassivated only at low potentials, comparable to that of stainless steel. Tremendous improvement of the corrosion behavior of treated Nitinol wires is associated with the removal of defect surface material and the growth of stable TiO(2) oxide. The role of precipitates in the corrosion resistance of Nitinol-scratch repassivation capacity in particular-is emphasized in the discussion.

Chemical etching and thickness effects on the resistive property of La 2/3Ca 1/3MnO 3 films

Effects of chemical etching and thickness on the transport property of La 2/3Ca 1/3MnO 3 films are experimentally studied. Chemical etching produces a decrease of the metal–insulator transition from T p=263 to 235 K in addition to increasing the overall resistance of the film. Further etching does not change T p while leads to a new resistive transitions at ∼150 K. In contrast, film thickness influences the resistive behavior of the films strongly below 40 nm, resulting in a sharp drop of T p and a steep increase of the resistivity with the decrease of thickness. Reducing film thickness and chemical etching produce similar effects except for that the latter thins the film unevenly, which causes the occurrence of multi-resistive transitions. No visible effects associated with the enhanced surface roughness due to chemical etching are observed.

Mechanisms of particle removal from silicon wafer surface in wet chemical cleaning process

A quantitative mechanism of particle removal from silicon wafer surfaces by a wet chemical cleaning process is proposed. The particles are removed from the surface due to the combined effects of chemical etching and a net repulsive interaction between the particle and surface. The mechanism suggests that a critical etching depth, which has been determined theoretically, and an optimal etching rate, which can be determined from etching profile calculation, are required for particle removal. The study will help in the optimization of cleaning processes and formulation of superior cleaning solutions.

Surface conditions of Nitinol wires, tubing, and as-cast alloys. The effect of chemical etching, aging in boiling water, and heat treatment.

The surface conditions of Nitinol wires and tubing were evaluated with the use of X-ray photoelectron spectroscopy, high-resolution Auger spectroscopy, electron backscattering, and scanning-electron microscopy. Samples were studied in the as-received state as well as after chemical etching, aging in boiling water, and heat treatment, and compared to a mechanically polished 600-grit-finish Nitinol surface treated similarly. General regularities in surface behavior induced by the examined surface treatments are similar for wires, tubing, and studied as-cast alloy, though certain differences in surface Ni concentration were observed. Nitinol wires and tubing from various suppliers demonstrated great variability in Ni surface concentration (0.5-15 at.%) and Ti/Ni ratio (0.4-35). The wires in the as-received state, with the exception of those with a black oxide originating in the processing procedure, revealed nickel and titanium on the surface in both elemental and oxidized states, indicating a nonpassive surface. Shape-setting heat treatment at 500 degrees C for 15 min resulted in tremendous increase in the surface Ni concentration and complete Ni oxidation. Preliminary chemical etching and boiling in water successfully prevented surface enrichment in Ni, initially resulting from heat treatment. A stoichiometric uniformly amorphous TiO(2) oxide generated during chemical etching and aging in boiling water was reconstructed at 700 degrees C, revealing rutile structure.

Influence of the optimal etching conditions of silicon substrates on field-electron emission from amorphous-diamond films

The effect of chemical etching of silicon substrates on the field-electron emission (FEE) from amorphous-diamond (a-D) films deposited on silicon has been studied systematically and thoroughly. It is found that the greater the roughness of the silicon substrate, the better the FEE performance of the a-D/silicon emitter. For a sodium hydroxide concentration between 20% and 40%, an etching temperature in the range of 60–80 °C, and an etching time of 15–30 min, etching of the silicon substrate surface was found to be optimal for FEE from the a-D/silicon emitter. To explain the experimental results, qualitative analysis of the enhanced electric field caused by nanoprotrusions was done.

Effects of the interface and surface nanostructures on field emission of amorphous diamond film

Details are given of a systematic experimental study into the effect of interface structure on the field emission properties of nanostructures using amorphous diamond (a-D) films. The field electron emission experiments indicates a better field emission characteristic after predepositing a metal (Al or Ti) interlayer. The effect of chemical etching of silicon substrate on the field emission of a-D film/silicon has been studied systematically. In addition, surface features of the film considered to be responsible for low field emission are discovered. Based on this latter finding, a new mechanism named field-induced transform step enhanced emission mechanism, which is responsible for electron emission from a-D film, is presented.

Characterization of damage in reactive ion etched ZnTe

Reactive ion etching of ZnTe has been carried out at various applied rf powers and CH4/H2 concentrations. The damage induced during dry etching is characterized by low-temperature photominescence (PL) measurements. It is observed that the PL intensity of the free excitons decreases with increasing applied rf power, which is ascribed to the increase of the surface damage by ion bombardment. The amount of the surface damage can be reduced by adding more CH4 in the gas mixture due to the effect of chemical etching.

The effects of chemical etching on the charge collection efficiency of {111} oriented Cd/sub 0.9/Zn/sub 0.1/Te nuclear radiation detectors

We report the effects of different etchants on the mobility-lifetime product (/spl mu//spl tau/) of cadmium zinc telluride (CZT). The /spl mu//spl tau/ values were obtained via the Hecht relation. The effects of surface recombination were also investigated using photoconductivity measurements. Results were obtained for a {111} oriented CZT single crystal. We find that the surfaces behave differently after etching. Values for surface recombination rates for [111]A and [111]B surfaces can vary by up to two orders of magnitudes for the same etchant. This large variation in surface recombination rates affects the charge collection efficiency and detector performance. We report surface treatments that enhance the charge collection efficiency for [111]A and [111]B surfaces. Data describing the detector response for Am/sup 241/ spectra current-voltage relationship, and bulk /spl mu//spl tau/ values and surface recombination rates are shown for different etchants.

Effects of surface treatments on the adhesion of Cu and Cr/Cu metallizations to a multifunctional photoresist

The effects of chemical, plasma, and reactive ion etching (RIE) treatments on the adhesion of Cu and Cr/Cu to the multifunctional polymer were investigated. The adhesion was measured with the newly developed pull test. The polymer surfaces were characterized by the x-ray photoelectron spectroscopy, atomic force microscopy, and surface free energy measurement. The failure modes were examined with the scanning electron microscopy and energy-dispersive spectroscopy. It was found that the adhesion of Cu and Cr/Cu to the highly functional photoresist was poor, regardless of the chemical, plasma, and reactive ion etching treatment with either O2 or CF4 used. However, the RIE pretreatment with the gas mixture (O2+CF4) of the photoresist surface increased the adhesion of sputtered Cr/Cu to the photoresist remarkably, and the failure mode was cohesive within the photoresist. Furthermore, the RIE pretreatment with pure oxygen gave rise to the needle-like surface together with virtually no introduced reactive functional groups, whereas the RIE with O2-rich gas mixture of O2+CF4 resulted in the relative smooth polymer surfaces and the newly formed C=O/O–C–O and O–C=O functionalities were incorporated on the treated surface with the increased polar surface free energy. The adhesion mechanism based on the experimental adhesion results and the surface characterizations of the polymer is proposed and discussed.

Two kinds of enhancement in photoluminescence by chemical etching of porous silicon

We investigated the effect of chemical etching of porous silicon in a solution of HF acid and ethanol. The first etching for 20 s enhanced photoluminescence and shifted to the higher energy. The successive etching enhanced photoluminescence further but peak position was not changed. Photoacoustic spectra evidenced that the first etching induced a blue shift while the successive etching diminished the density of defect levels distributed under 1.3 eV.

Effects of Dry Processing on Optical Properties of Zinc Telluride

Effects of dry processing on photoluminescence (PL) properties of high-quality ZnTe homoepitaxial layer exposed to CH4/H2 plasma have been investigated. The etched ZnTe layer exhibits a strong deep level luminescence band around 2.25 eV together with a weak free excition emission at low temperature. By analyzing the dependence of the PL spectra on temperature and excitation power intensity, we find that the band around 2.25 eV is characteristic of a donor-acceptor pair recombination emission related to VZn complexes. The amount of surface damage decreases with increasing CH4 concentration in the gas mixtures due to the effect of chemical etching.