Etched carbon-fiber electrodes as amperometric detectors of catecholamine secretion from isolated biological cells

Voltammetric electrodes with micrometer dimensions have been fabricated from carbon fibers etched to a conical shape and insulated with poly(oxyphenylene) following literature procedures. The resultant electrode has a tip radius in the micron range. The response of this electrode is compared to a carbon-fiber electrode prepared by sealing a carbon-fiber electrode in a glass pipet (electrode radius greater than 3.5 microns). While the etched electrodes did not follow electrochemical theory as well as the glass-encased electrode, the etched electrode was found to be suitable for the amperometric measurement of the secretion of catecholamines from isolated bovine adrenal cells. Comparable results are only obtained when the two different electrodes are placed 1 micron from the cell surface. When the etched electrode is placed further away, less secretion is observed, because of diffusion and accompanying dilution.     

Control of cathodic arc spot motion under external magnetic field

A closed circular transverse magnetic field is designed to control the spot motion of a cathodic arc on a large rectangular target. Stable and controllable spot motion is observed from both graphite and copper. The arc stability, spot velocity, and etched pattern on the cathode surface are studied systematically. Circular tracks are etched on the target surface by the repetitive spot movement and the surface morphology and resistivity of the cathode materials influence the spot velocity.     

铝电解电容器用不同工艺腐蚀箔的对比研究

利用金相显微镜分析软质交流腐蚀箔、直交流腐蚀箔及硬质交流腐蚀箔的表面及断面蚀孔形貌,监测腐蚀箔恒电流阳极氧化过程中的升压曲线,并测试腐蚀箔阳极氧化后的比容、漏电流、抗拉强度及折弯次数.结果表明,软质交流腐蚀箔的蚀孔形貌呈灌木状;直-交流腐蚀箔的蚀孔呈乔木和灌木状分布,蚀孔中有部分大而稀疏的隧道孔,扩面倍率最小;而硬质交流腐蚀箔的蚀孔呈蜂窝状,孔洞细密,扩面倍率最大.直-交流腐蚀箔的漏电流最小,硬质交流腐蚀箔的抗拉强度及折弯次数最大.     

直流电化学腐蚀法制备多孔硅的表面形貌研究

采用正交实验，直流电化学腐蚀法制备多孔硅。用原子力显微镜对表面进行观察，研究电化学腐蚀参数对其表面形貌的影响。氢氟酸浓度（CHF）升高，使临界电流密度（JPS）增大，有利于多孔硅的形成。电流密度（J）增大，多孔硅的孔隙率和孔径随之变大，而其纳米粒径将变小。腐蚀时间（t）越长，孔径越大，孔越深。     

Effect of substrate surface conditions on the microstructure of nickel electrodeposits

The microstructures of nickel films electrodeposited onto polished and chenically etched {001} faces of single-crystal copper substrates were studied by transmission electron microscopy. Nickel films grown on the etched surface exhibited a mixture of single-crystal and polycrystalline structures, whereas those deposited onto the polished surface were epitaxial {001} single crystals. The cross section revealed that the polycrystalline regions consisted primarily of growth twins which formed by two-dimensional nucleation on the etching-induced {111} faces of the copper substrates. The absence of such {111} faces on the polished substrates suppressed the twin formation, resulting in the observed epitaxial monocrystalline structure.     

Specific features of relief formation on silicon etched by a focused ion beam

The effect of a focused ion beam on the state of a silicon crystal surface has been studied. Periodic ring-shaped ribs have been observed on the walls of an etched cylindrical hole. The formation of periodic structures depends on the conditions of ion beam etching. The observed phenomenon is explained based on the notion of the radiation-induced plasticity.     

Surface Roughness in Plasma-Etched $hbox{As}_{bf 2}hbox{S}_{bf 3}$ Films: Its Origin and Improvement

We describe the microstructure of As₂S₃ films and its effect on the morphology of plasma-etched surfaces. The Raman spectroscopy and X-ray photoelectron spectroscopy demonstrated that the observed grainy morphology of etched As₂S₃ surfaces comes from differential chemical attack between different phases within the film. Two approaches were found to be effective for improving the smoothness of etched surfaces: a change in the plasma chemistry from CF₄-O₂ to CHF₃-O₂ and the application of a thin-conformal coating onto structures already patterned using CF₄-O₂ plasma.     

Etching of n-GaN - Important step in device processing

Photo-assisted electrochemical (PEC) and photo-assisted electrodeless (ELPEC) etching of n-doped GaN layers grown on sapphire in a KOH based solution under illumination of Hg arc lamp is demonstrated. Smooth surfaces were obtained for a narrow range of etching conditions. It was found out that this window could be extended by using etching conditions which produced “whiskers”. For ELPEC etching final etched surfaces were much smoother with stirring but showed distinct bar objects. Such objects could be eliminated by chopped irradiation when also the etching rate decreased and smoothing of pyramidal and bar objects in the etched surfaces was observed. This effect is most probably caused by the electron-hole pair recombination suppressed at semiconductor dislocation locations.     

Enhanced wet etching of patterned GaN with ion implantation

We present the enhanced wet etching of GaN epilayer implanted with Au+ ion. Patterned GaN with 2 microm-wide sink-like strips was achieved by using 500 keV Au+ ion implantation and KOH etching. The Dependence of etching depth on etching time for the implantation at different ion fluences was investigated. The experiment showed that the damaged GaN area could be almost etched out at high ion fluence, and the etching depth could exceed the project range of incident 500 keV Au+ ion. The etch pits could be observed at the bottom of the etched area. The -400 nm depth etching could be achieved with high fluence implantation after a long etching time, and the edge of etched area could remain clear until the etching process had passed 40 min. As-deposited SiO2 spheres were used to mask the GaN sample in implantation process to investigate the etching effect. -70 nm wave of the GaN surface was observed. The results of our experiments may suggest an approach to the fabricating of GaN devices.     

Effect of Plasma Etched CNFs on Toughness and Mechanical Properties of Epoxy Composites

Carbon nanofibers (CNFs) are plasma etched by using cold plasma of air and helium for different time durations. Changes in surface functional groups of CNFs due to plasma treatment were estimated by using elemental analysis and temperature programmed decomposition in helium atmosphere. The influence of plasma etched CNFs on the toughness of epoxy and tensile and flexural strength of carbon–epoxy composites have been studied. Results indicate that, air plasma etched CNFs can improve the toughness of epoxy, while helium plasma etched CNFs could not impart improved toughness to epoxy composites. On the other hand, mechanical properties of carbon–epoxy made with air plasma etched CNFs improved significantly as compared to helium plasma etched CNFs as well as untreated CNFs.     

Electric field influenced ZnO growth on nanoscale etched Si surface by continuous spray pyrolysis

This work reports ZnO growth by electric field influenced continuous spray pyrolysis reactor over seed layer assisted nanoscale etched Si surface. The comparative studies of ZnO growth in the presence and absence electric field on anisotropically etched Si surface are supported by XRD, SEM, EDX, FTIR and reflectance measurements. XRD measurements confirm preferable (002) oriented ZnO growth by certain amount of etching which is reduced with further anisotropic etching. The chlorine incorporation in ZnO thin film measured by EDX and FTIR may be attributed to the seed layer effect. This present investigation show that anisotropic etch pits surface energy profile has played an important role in deciding ZnO nanorods alignment and coalescence amongst ZnO species during self assembly at nucleation sites. It is observed that additional electric field force in spray droplets is enhancing population density, homogeneous growth and surface coverage of Si surface by ZnO nanorods for particular amount of etched Si surface and improved light coupling is confirmed by reflectance measurement. The relevant growth mechanisms for ZnO nanostructure layers comprising nanorods are also discussed.     

Nitride-based Schottky diodes and HFETs fabricated by photo-enhanced chemical wet etching

Photo-enhanced chemical (PEC) wet etching technology was used to etch GaN and AlGaN epitaxial layers. It was found that the maximum etch rates were 510, 1960, 300, and 0 nm/mm for GaN, Al_0.175Ga_0.825N, Al_0.23Ga_0.77N, and Al_0.4Ga_0.6N, respectively. It was also found that we could achieve a high Al_0.175Ga_0.825N to GaN etch rate ratio of 12.6. Nitride-based Schottky diodes and heterostructure field effect transistors (HFETs) were also fabricated by PEC wet etching. It was found that we could achieve a saturated I_D larger than 850 mA/mm and a maximum g_m about 163 mS/mm from PEC wet etched HFET with a 0.5 μm gate length. Compared with dry etched devices, the leakage currents observed from the PEC wet etched devices were also found to be smaller.     

Nitric-phosphoric acid etching effects on the surface chemical composition of CdTe thin film

Nitric-phosphoric (NP) acid etching has been regarded as one of the most effective methods for the formation of low resistance back contact with the metal electrode in CdTe based photovoltaic cells. We studied CdTe back surfaces and the changes with time of exposure to NP acid with x-ray photoelectron spectroscopy (XPS), and atomic force microscopy. Strong etching dependence on the back surface chemical composition, and surface roughness, was observed. In order to study the effect of the NP acid etching on surface degradation, the sample was left in open ambient condition for three weeks and XPS measurement in combination with ion sputtering was performed on unetched and highly etched parts. The difference in depth profiles of the NP acid etched and unetched CdTe surface has been discussed.     

On-line concentration of proteins and peptides in capillary zone electrophoresis with an etched porous joint

A novel approach for on-line concentration of proteins and peptides in capillary electrophoresis (CE) is presented. A short section (approximately 0.5-1 cm) along the capillary was etched with HF. The etched section became a porous membrane that allowed electrical conductivity but prevented passage of the analyte ions. The capillary was isolated into two parts by the etched section. Thus, we were able to use three buffer vials to perform CE experiments in the capillary by applying high voltages independently. Concentration and separation were performed at the two respective regions. When high voltage was applied to the concentration capillary (between the inlet end and the etched section), proteins and peptides were concentrated at the etched portion, because the porous capillary wall allowed only small buffer ions to pass through and there was no electric field gradient beyond that point. After focusing, the narrow sample zone was introduced into the separation capillary (between the etched section and the outlet end) by hydrodynamic flow or by electroosmotic flow. Finally, conventional CE was carried out for separation of the analytes. Several different concentration schemes for proteins and peptides were successfully demonstrated by using this new approach.     

Gold nanoparticle-modified etched capillaries for open-tubular capillary electrochromatography

The use of gold nanoparticles in conjunction with etched capillary-based open-tubular capillary electrochromatography (OTCEC) to improve the efficiency of separation and the selectivity between selected solutes is described. The fused-silica capillaries (50-microm i.d.) were etched with ammonium hydrogen difluoride, followed by prederivatization of the new surface with (3-mercaptopropyl)trimethoxysilane (MPTMS) for the immobilization of dodecanethiol gold nanoparticles, for OTCEC. The electrochromatography of a "reversed-phase" test mixture and of selected polycylic aromatic hydrocarbons was investigated, and efficient separations and high theoretical plate numbers per meter were obtained. The electroosmotic flow characteristics of the etched gold nanoparticle capillary, unetched gold nanoparticle capillary, bare capillary, and etched bare capillary were studied by varying the percentage of organic modifier in buffer, buffer pH, and separation voltage. Optical microscopy and scanning electron microscopy were used to examine the process of etching and modification and the surface features of the etched gold nanoparticle capillary. The results confirm that dodecanethiol gold nanoparticles bonded on the etched inner wall of the fused-silica capillary can provide sufficient solute-bonded phase interactions to obtain OTCEC separations with reproducible retention, as well as characteristic reversed-phase behavior, even with the inner diameter of the capillary of 50 microm.     

新型智能电化学微加工系统的研究

约束刻蚀剂层技术在三维超微图形复制加工的新型技术。本文根据约束刻蚀剂层技术的工艺特点，介绍了约束刻蚀剂层电化学微加工仪器的组成，讨论了具有微力传感的纳米级微定位系统的研究与开发。利用研制 的加工仪器，在半导体GaAs进行刻蚀加工，复制出微孔阵列，其排列周期与模板的微锥阵列的排列周期吻合得很好，同时在铜板上也成功进行了微孔刻蚀加工。     

Effect of substrate patterning on hydroxyapatite sol-gel thin film growth

The effect of substrate patterning on hydroxyapatite (HA) sol-gel thin film growth is investigated. Sol-gel derived HA was spun onto wet and dry etched micro-patterned titanium substrates to obtain thin films of thickness ~ 400 nm. The amorphous films were made crystalline by firing at temperatures ranging from 650 to 850 °C for 5 min. Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), and atomic force microscopy (AFM) were used to characterize the films. Crystal sizes calculated from XRD data show that films on patterned substrates contained larger grains than those on un-patterned substrates. The films on wet etched substrates contained larger grains than the films on dry etched substrates. AFM results confirm XRD results. A marked difference between the films on patterned and unpatterned substrates was observed, with those on the patterned substrates being much rougher than those on the unpatterned substrates. The films inside the channels contained larger grains than those outside of channels, on the polished, unetched portion of the substrate.     

Ultrashort intense-field optical vortices produced with laser-etched mirrors

We introduce a simple and practical method to create ultrashort intense optical vortices for applications involving high-intensity lasers. Our method utilizes femtosecond laser pulses to laser etch grating lines into laser-quality gold mirrors. These grating lines holographically encode an optical vortex. We derive mathematical equations for each individual grating line to be etched, for any desired (integer) topological charge. We investigate the smoothness of the etched grooves. We show that they are smooth enough to produce optical vortices with an intensity that is only a few percent lower than in the ideal case. We demonstrate that the etched gratings can be used in a folded version of our 2f-2f setup [Opt. Express 19, 7599 (2005)] to compensate angular dispersion. Finally, we show that the etched gratings withstand intensities of up to 10(12) W/cm(2).     

The effect of hydrogen etching on the electrical properties of autoepitaxial silicon carbide layers

Experimental data showing that preliminary hydrogen etching of a SiC substrate influences the concentration of donors or acceptors in autoepitaxial SiC layers are presented. The impurity concentration in the epitaxial layers grown on etched and unetched substrates may differ by an order of magnitude. A physical explanation of the observed correlation is proposed. The importance of the effect of competitive etching on the epitaxial growth is pointed out.     

Implementation of Electrochemically Synthesized Silver Nanocrystallites for the Preferential SERS Enhancement of Defect Modes on Thermally Etched Graphite Surfaces

Highly oriented pyrolytic graphite (HOPG) surfaces, on which atomically well-defined roughness has been introduced via high-temperature gasification reactions, are investigated by noncontact mode atomic force microscopy (NC-AFM) and Raman spectroscopy both before and after the electrochemical deposition of silver nanocrystallites on these surfaces. Exposure of freshly cleaved HOPG surfaces to an O(2)-rich ambient at 650 °C for a few minutes caused the formation of 1-monolayer-deep, circular etch pits on the HOPG basal plane surface. Silver nanocrystallites were electrochemically deposited onto these etched surfaces at two coverages: 0.5 mC cm(-)(2) (or 5 nmol of Ag(0) cm(-)(2)) and 2.4 mC cm(-)(2) (25 nmol of Ag(0) cm(-)(2)). At the lower coverage, NC-AFM images revealed that silver decorated only the circumference of the circular etch pits, forming a uniform annular ring with an apparent diameter of 200-250 ? and a height of ～15 ?. At the higher silver coverage, an increase in the height but not the diameter of this annulus was observed, and additional silver nanostructures [Formula: see text] having dimensions of 300-350 ? diameter and 15 ? height [Formula: see text] were observed on atomically smooth regions of the graphite basal plane. The Raman spectroscopy of these surfaces was investigated and compared with spectra for nanocrystallite-modified but unetched HOPG basal plane surfaces and thermally etched surfaces on which no silver was deposited. For for thermally etched HOPG surfaces at either silver coverage, SERS-augmented Raman spectra were obtained in which defect modes of the graphite surface [Formula: see text] derived from "finite" graphite domains at the surface [Formula: see text] were strongly and preferentially enhanced. In addition, an enhanced band near 2900 cm(-)(1) was assigned to ν(OH) from carboxylate moieties present at step edges based on the basis of the observed pH dependence of the enhancement.