Microstructure formation in electrochemically deposited Copper thin films

The influence of the electrochemical potential and deposition mode on the preferred orientation, morphology and microstructure of crystallites in electrochemically deposited (ECD) copper thin films was investigated using X‐ray diffraction (XRD), scanning electron microscopy (SEM) and the diffraction of back‐scattered electrons (EBSD). As a working electrode for the ECD process, thin gold layers were employed that were deposited on floating‐glass substrates in a vacuum evaporation process. With increasing negative electrochemical potential in the ECD process, the deposition mode changed from the charge transfer controlled one to the diffusion controlled one. At the highest electrochemical potentials, the copper deposition and the hydrogen release were running concurrently. The change of the deposition mode was accompanied by a change of the surface roughness of the thin films and by a change of the direction and degree of the preferred orientation of crystallites. The surface roughness of the deposited copper thin films increased with increasing electrochemical potential. Compact plate‐like crystallites with the preferred orientation {111} grew in the transport controlled deposition mode. Development of the {111} texture was supported by the {111} preferred orientation of the gold layers and by surface energy of copper, which is the lowest in the (111) plane. The diffusion controlled deposition mode was characterized by the growth of globular {110}‐oriented crystallites. The {110} texture resulted from the minimization of the anisotropic strain energy of copper via reduction of the structure defects in this deposition modus. For highest electrochemical potentials, the copper deposition run simultaneously with the development of hydrogen that resulted in growth of needle‐like crystallites with the {100} texture.     

Electrodeposition of Zirconium from 1-Butyl-1-Methylpyrrolidinium-Bis(Trifluoromethylsulfonyl)imide: Electrochemical Behavior and Reduction Pathway

A study on the electrochemical deposition of Zr on platinum, gold, and boron doped diamond (BDD) from 1-butyl-1-methylpyrrolidinium-bis(trifuoromethylsulphonyl) imide is presented in this work. The electrochemical behavior of zirconium ions was investigated by cyclic voltammetries and chronopotentiometries, allowing establishing the mechanism of deposition. Deposition tests were carried out at different potentials and the related samples were analyzed by SEM and EDX. Structural and chemical analyses indicate that the obtained deposits are constituted by metallic zirconium. According to the electrochemistry of zirconium and based on the experimental results, the mechanism is Zr(IV) ? Zr(II) ? Zr.     

Carbon-Supported Platinum Catalysts for Direct Alcohol Fuel Cell Anode

To achieve maximum utilization of precious platinum catalyst for ethanol electro-oxidation the highest possible surface to volume ratio of the dispersed metal is desirable. In this respect we have investigated the roughness factor of carbon-supported platinum catalysts prepared at different deposition current densities. It is observed that lowering the deposition current density can considerably reduce platinum particle size and thereby increase the roughness factor of the electrode. Further, use of PTFE in the deposition bath results in highly porous platinum dispersion. The combined effect of these two factors significantly enhances the electrocatalytic activity of platinum catalysts towards ethanol oxidation. Cyclic voltammetry, steady state polarization, and electrochemical impedance spectroscopy are used to investigate the kinetics and mechanism of ethanol electro-oxidation. SEM-EDX analysis has been performed to investigate the morphology and chemical composition of the synthesized catalyst layers.     

The effect of cysteine on electrodeposition of gold nanoparticle

The most applications of gold nanoparticles are in the photo-electronical accessories and bio-chemical sensors. Chloride solution with cysteine additive was used as electrolyte in gold nanoparticles electrodeposition. The nucleation and growing mechanism were studied by electrochemical techniques such as cyclic voltammetry and chronoamperometry, in order to obtain a suitable nano structure. The deposition mechanism was determined as instantaneous nucleation and the dimension of particles was controlled in nanometric particle size range. Atomic Force Microscope was used to evaluate the effect of cysteine on the morphology and topography of gold nanoparticles. Finally the catalytic property of gold nanoparticle electrodeposited was studied in KOH solution, where oxygen reduction on the gold nanoparticle surface was eight times greater than that on the conventional gold deposits.     

Realization and characterization of porous gold for increased protein coverage on acoustic sensors

Immunosensors show great potential for the direct detection of biological molecules. The sensitivity of these affinity-based biosensors is dictated by the amount of receptor molecules immobilized on the sensor surface. An enlargement of the sensor area would allow for an increase of the binding capacity, hence a larger amount of immobilized receptor molecules. To this end, we use electrochemically deposited "gold black" as a porous sensor surface for the immobilization of proteins. In this paper, we have analyzed the different parameters that define the electrochemical growth of porous gold, starting from flat gold surfaces, using different characterization techniques. Applied potentials of -0.5 V versus a reference electrode were found to constitute the most adequate conditions to grow porous gold surfaces. Using cyclic voltammetry, a 16 times increase of the surface area was observed under these electrochemical deposition conditions. In addition, we have assessed the immobilization degree of alkanethiols and of proteins on these different porous surfaces. The optimized deposition conditions for realizing porous gold substrates lead to a 11.4-fold increase of thiol adsorption and a 3.3-fold increase of protein adsorption, using the quartz crystal microbalance (QCM-D) as a biological transducer system. Hence, it follows that the high specific area of the porous gold can amplify the final sensitivity of the original flat surface device.     

Controlled nucleation and growth of surface-confined gold nanoparticles on a (3-aminopropyl)trimethoxysilane-modified glass slide: a strategy for SPR substrates

The thickness of the gold film and its morphology, including the surface roughness, are very important for getting a good, reproducible response in the SPR technique. Here, we report a novel alternative approach for preparing SPR-active substrates that is completely solution-based. Our strategy is based on self-assembly of the gold colloid monolayer on a (3-aminopropyl)trimethoxysilane-modified glass slide, followed by electroless gold plating. Using this method, the thickness of films can be easily controlled at the nanometer scale by setting the plating time in the same conditions. Surface roughness and morphology of gold films can be modified by both tuning the size of gold nanoparticles and agitation during the plating. Surface evolution of the Au film was followed in real time by UV-vis spectroscopy and in situ SPRS. To assess the surface roughness and electrochemical stability of the Au films, atomic force microscopy and cyclic voltammetry were used. In addition, the stability of the gold adhesion is demonstrated by three methods. The as-prepared Au films on substrates are reproducible and stable, which allows them to be used as electrodes for electrochemical experiments and as platforms for studying SAMs.     

Synthesis,structure, and some physical properties of carbon and chromium deposits possessing a fractal structure

Experimental data obtained by scanning electron microscopy show that a carbon deposit formed during graphite spraying in an electric arc and chromium particles obtained by electrochemical deposition under certain conditions possess similar fractal structures. Data on some physical properties, the size of fractal aggregates, and the fractal dimensions of carbon and chromium deposits are presented. A possible mechanism of the fractal structure formation is discussed.     

Synthesis, structure, and physical properties of carbon, iron, and chromium deposits possessing a fractal structure

A carbon deposit formed during graphite spraying in an electric arc, as well as iron and chromium particles obtained by electrochemical deposition under certain conditions, possess fractal structures. Data on some physical properties, the size of fractal aggregates, and the fractal dimension D of carbon, iron, and chromium deposits are presented. Relations between the fractal dimensions and physical properties of deposits are considered. A possible mechanism of the fractal structure formation is discussed.     

Carbon fiber coating with silver using intervening Au/Pd nanoparticle films produced using a spark discharge

A low roughness conductive silver film on a fiber substrate was fabricated via a catalytic surface activation (needed to initiate electroless silver deposition) with spark produced gold aerosol nanoparticles. Gold had a similar lattice parameter with silver in crystallinity and thus a crystallographic misfit between gold activated substrate and silver was minimized during the deposition, resulting in formation of a flat silver film. Properties were compared with those obtained with palladium aerosol activation, the gold activation enhanced thin-metallic film properties in surface root-mean-square roughness (nm: 8, gold vs 44, palladium) and electrical resistivity (μΩ cm: 64, gold vs 498, palladium) at 88 mg/g (silver/substrate) in deposition amount.     

Electrochemical detectors prepared by electroless deposition for microfabricated electrophoresis chips

Microfabricated capillary electrophoresis (CE) chips with integrated electrochemical detection have been developed on glass substrates. An electroless deposition procedure was used to deposit a gold film directly onto the capillary outlet to provide high-sensitivity electrochemical detection for catechol and several nitroaromatic explosives. Scanning electron microscopy revealed that the electroless gold film contains nanoscopic gold aggregates (100-150 nm) with an average thickness of 79 nm. The electroless deposition procedure can be easily and routinely performed in any wet-chemistry laboratory, and electroless gold can be deposited onto complex and internal surfaces. Intimate coupling of electrochemical detection and CE chips obviates the need for a coupling mechanism or tedious alignment procedures. With nitroaromatic compounds as a working model, microchip capillary electrophoresis equipped with electroless gold has proven to provide high sensitivity and fast response times for sensor applications. The CE microchip system was capable of separation and determination of explosive compounds including TNT in less than 130 s with detection limits ranging from 24 to 36 microg/L, i.e., 4-fold enhancements in detection efficiency in comparison to thick-film technology.     

Electrochemical determination of arsenite using a gold nanoparticle modified glassy carbon electrode and flow analysis

A flow analysis electrochemical system has been developed, characterized, and optimized for the determination of arsenite (As(III)). Sensitivity was significantly improved by the electrochemical deposition of gold nanoparticles on a dual glassy carbon electrode, which was inserted into a cross-flow thin-layer electrochemical cell. The electrochemical system was linear up to 15 ppb with a detection limit of 0.25 ppb. Gold deposition was evident from cyclic voltammetry measurements, whereas atomic force microscopy and scanning electron microscopy revealed the size and distribution of deposited gold nanoparticles. The size and density of the nanoparticles were related to the gold salt concentration, deposition time, and potential as well as the electrode position. The response to arsenite was directly related to the frequency, increment, and amplitude of the square wave voltammetry as well as the deposition time and potential. Estimated reproducibility was +/-1.1% at 95% confidence interval for 40 repeated analyses of 8 ppb arsenite during continuous analysis. The reproducibility was far superior if the electrochemical reduction of arsenite was performed in nitric acid instead of hydrochloric or sulfuric acid. The electrochemical system was applicable for analysis of spiked arsenic in mineral water containing a significant amount of various ion elements.     

Stripping analyses of mercury using gold electrodes: irreversible adsorption of mercury

The electrochemical deposition and stripping of mercury on gold surfaces was investigated to assess whether gold electrodes would return to mercury-free states after stripping analyses. X-ray photoelectron spectroscopy studies demonstrate the presence of mercury on gold foil electrodes that have undergone controlled-potential deposition procedures in Hg(2+) solutions (10 nM-0.1 mM) followed by stripping and cleaning in mercury-free electrolyte. Results show that mercury is not completely removed electrochemically from the gold electrodes, even when the oxidizing potential is +2.5 V vs Ag/AgCl. Bulk electrolyses deposition and stripping procedures coupled with cold vapor atomic absorption spectroscopic analyses of solutions after deposition and stripping are also reported. Results suggest that the nature of the gold electrode is fundamentally altered by irreversible adsorption of mercury; that is, mercury is adsorbed during deposition and some of the mercury is retained even after stripping and cleaning. The implications and strategies for using stripping analysis and gold electrodes for the measurement of mercury under the experimental conditions employed in this study are discussed.     

Electrodeposition and characterization of CdSe semiconductor thin films

The electrodeposition of cadmium selenide alloy on glassy carbon and gold electrodes has been studied by electrochemical techniques. Potentiostatic I-t transients were recorded to obtain the nucleation mechanism, while cyclic voltammetry was used to characterize the system. Structural information on the electrodeposited layers was obtained by X-ray diffraction. The experimental results clearly show that the deposition of cadmium selenide alloy on glassy carbon and gold electrodes is a diffusion-controlled process. The nucleation is progressive, and the number of nucleation sites decreases with increasing bath temperature. The deposition of CdSe alloy results in well-defined crystals with hexagonal shape. The films were characterized by optical absorption and electrical resistivity measurements. Films showed a direct band gap of 3.56 eV.     

哈氏合金电化学抛光工艺的研究

采用环保型抛光液对离子束辅助沉积技术路线用哈氏合金HastelloyC-276基带进行了电化学抛光,获得了典型的阳极极化曲线,并阐述了电化学抛光的机理.研究了影响电化学抛光的因素(电解液温度、抛光时间、抛光极距)对基带表面粗糙度的影响,优化工艺参数获得了表面粗糙度Rn＜5 nm(5μm×5μm)的高质量表面,满足后续生长过渡层对哈氏合金基带的要求.抛光液中的柠檬酸在50℃左右分解成络合剂,可迅速沉淀金属离子,提高表面的活性.     

Ellipsometry of thin films of copper phthalocyanine

Ellipsometric measurements have provided qualitative information on the optical properties of CuPC films deposited on a thin gold layer substrate. Detailed interpretation was complicated by variations in the density of the deposited layers and the surface roughness of the substrate. Films less than 100 nm thick can be satisfactory represented by a single homogeneous isotropic layer. Thicker films appear to be equivalent to an isotropic inner layer and an anisotropic outer layer, where the latter results from bulk deposition of CuPC with the molecules in a predominant orientation to the surface. Reasonable agreement has been obtained between film thicknesses measured by weighing and by ellipsometry, assuming a single homogeneous anisotropic film for thickness in excess of 150 nm.     

Fabrication of stable, highly flat gold film electrodes with an effective thickness on the order of 10 nm

Stable gold film electrodes were fabricated by a combination of sputtered gold and an epoxy adhesion layer on a glass substrate using the template-stripped technique. An XRR scan analysis indicated the thickness and roughness of the gold layer to be on the order of 10 nm and subnanometer, respectively. In spite of their small thickness, the electrode had sufficient conductivity and stuck to the subject during the electrochemical measurements as did the usual gold working electrodes.     

Clarifying the mechanism of reverse structuring during electrodeposition in magnetic gradient fields

Deviating from the common expectation, magnetoelectrochemical structuring during deposition of diamagnetic ions was demonstrated, very recently. To achieve this, electrochemically inert paramagnetic ions have to be added to the electrolyte and the deposition has to be performed in a magnetic gradient field. A reverse structuring occurs, yielding thinner deposits near high gradient regions. In this paper we aim to clarify the mechanism of this reverse structuring. Potentiodynamic and potentiostatic investigations were performed, including measurements of the deposited mass with an electrochemical quartz crystal microbalance (EQCM). The convection of the electrolyte was studied in situ by astigmatism particle tracking velocimetry (APTV). It was revealed that during the reverse structuring a convection is induced in the electrolyte, which is directed away from the working electrode in regions of high magnetic gradients. Due to this additional convection, the overall deposition rate is increased, whereby it is locally reduced in regions of high magnetic gradients. The mechanism for reverse structuring is discussed in detail. Also, the influence of all relevant magnetic forces is addressed.     

Characteristics of a well-adherent nanocrystalline diamond thin film grown on titanium in Ar/CH4 microwave CVD plasma

The fabrication of a well-adherent diamond film on titanium and its alloys is always problematical due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work, well-adherent and smooth nanocrystalline diamond (NCD) thin film is successfully deposited on pure titanium substrate by microwave plasma-assisted chemical vapor deposition (MWPCVD) method in Ar/CH₄ environment. It is found that the average grain size is less than 20 nm with a surface roughness value as low as 12 nm. Morphology, surface roughness, diamond crystal orientation and quality are obtained by characterizing the sample with field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy, respectively. Detailed experimental results and mechanisms for NCD film deposition are discussed.     

Nanogap electrode fabrication for a nanoscale device by volume-expanding electrochemical synthesis

A novel nanogap fabrication method using an electrochemical nanopatterning technique is presented. Electrochemical deposition of platinum ions reduces the microgap size to the sub-50-nm range due to the self-limited volume expansion of the electrodes. Additionally, the low crystallinity of platinum reduces the line edge roughness in the electrodes, whereas the high crystallinity of gold increases it. Current compliance, a buffered resistor, and a symmetric deposition strategy are used to achieve high reliability and practicality of nanogap electrodes. As a possible application, an organic thin-film transistor using the nanogap electrodes is also demonstrated.     

Comparison of different surface modification techniques for electrodes by means of electrochemistry and micro synchrotron radiation X-ray fluorescence. dimerization of cobalt(II) tetrasulfonated phthalocyanine and its influence on the electrodeposition on gold surfaces

This paper compares different electrochemical surface modification techniques with special attention to the immobilization of cobalt(II) tetrasulfonated phthalocyanine tetrasodium salt (Co(II)TSPc) on gold electrodes. Electrochemical and synchrotron radiation X-ray fluorescence (SR-XRF) microbeam analysis were performed in order to compare the amount of adsorbed CoTSPc onto the gold electrode and to determine the level of uniformity of the deposited layer. The nondestructive, quantitative characterization of CoTSPc deposition on gold electrodes by means of scanning SR-XRF on the microscopic scale has never been described before. The described methodology can be in general used for thin-film characterization. Depending on the degree of dimerization of the CoTSPc molecules, different electrochemical behavior is observed.