ELECTRODEPOSITION OF POLYCRYSTALLINE CD-RICH HG1-XCDXTE AND PHOTOELECTRO-CHEMICAL BEHAVIOR OF HG0.09CD0.91TE THIN-FILM

Electrodeposition process of polycrystalline Cd-rich Hg_(1-z)Cd_xTe (x>0.5) in acidic bath of CdSO_4+HTeO_2~+HgCl_2 was investigated. The simultaneous electrodeposition technique of three kinds of ions at the same potential has been achieved. The XRD, SEM and EDAX analysis of the thin film electrodeposited on titanium substrate showed a typical cubic zinc blende polycrystalline structure and homogeneous dispersion. The photoelectrochemical behavior of (1-x)=0.09 polycrystalline thin film in a polysulfide re...

Ultra-low conductivity noise in metallic nanowires

By modifying the electrodeposition technique, we have stabilized the silver nanowires (AgNWs) in high-energy hexagonal closed packed (hcp)structure. The conductivity noise measurements show that the noise magnitude in hcp silver nanowires is several orders of magnitude smaller than that of face centered cubic (fcc) silver nanowires, which is obtained by standard over potential lectrodeposition (OPD)technique. The reduction of noise can be attributed to the restricted dislocation dynamics in hcp AgNWs due to the presence of less number of slip systems. Temperature dependent noise measurements show that the noise magnitude in hcp AgNWs is weakly temperature dependent while in fcc AgNWs it is strong function of temperature.

Tailoring of Structural Morphology of Silver Nanowires in Electrochemical Growth

Noble metal such as Ag normally exists in an fcc crystal structure. However as the size of the material is decreased to nanometer lengthscales, a structural transformation from that of its bulk state can be expected with new atomic arrangements due to competition between internal packing and minimization of surface energy. In many previous studies, it has been shown that silver nanowires (AGNWs) grown inside anodic alumina (AAO) templates by ac or dc electrochemical deposition from silver salts or complexes, adopt fcc structure and below some critical diameter ∼ 20 nm they may acquire hcp structure at low temperature. This is, however, critically dependant on the nature of confinement, as AgNWs grown inside nanotube confinement with subnanometer diameter have been reported to have fcc structure. Hence the question of the crystal structure of metal nanowires under combined influence of confinement, temperature and deposition condition remains open. In this abstract we show that the alternative crystal structures of AGNWs at room temperature can be achieved with electrochemical growth processes under specific conditions determined by the deposition parameters and nature of confinement. We fabricated AgNWs of 4H hexagonal structure with diameters 30 – 80 nm inside polycarbonate (PC) templates with a modified dc electrodeposition technique, where the nanowires were grown at deposition potentials as low as 10 mV in 2 M silver nitrate solution[1]. We call this low-potential electrodeposition (LPED) since the electrodeposition process occurs at potential much less than the standard Nernst potential (770 mV) of silver. Two types of electrodes were used – stainless steel and sputtered thin Pt film, neither of which had any influence on the crystal structure of the nanowires. EDS elemental analysis showed the nanowires to consist only of silver. Although the precise atomic dynamics during the LPED process is unclear at present, we investigated this with HRTEM (high-resolution transmission electron microscopy) characterization of nanowires grown over various deposition times, as well as electrical conductivity measurements. These experiments indicate that nanowire growth does not occur through a three-dimensional diffusion controlled process, as proposed for conventional over-potential deposition, but follow a novel instantaneous linear growth mechanism. Further experiments showed that, (a) conventional electrochemical growth at a small over-potential in a 2 mM AgNO3 solution yields nanowires with expected fcc structure inside the same PC templates, and (2) no nanowire was observed under the LPED conditions inside hard AAO templates, indicating that LPED-growth process, and hcp structure of the corresponding nanowires depend on deposition parameters, as well as nature of confinement.

The effect of potential on electrodeposited CdSe thin films

Cadmium selenide (CdSe) thin films have been successfully prepared by the electrodeposition technique on indium doped tin oxide (ITO) substrates with aqueous solutions of cadmium sulphate and selenium dioxide. The deposited films were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive analysis by X-rays (EDAX), photoluminescence (PL), UV spectrometry and electrical resistivity measurements. XRD analysis shows that the films are polycrystalline in nature with hexagonal crystalline structure. The various parameters such as crystallite size, micro strain, dislocation density and texture coefficients were evaluated. SEM study shows that the total substrate surface is well covered with uniformly distributed spherical shaped grains. Photoluminescence spectra of films were recorded to understand the emission properties of the films. The presence of direct transition with band gap energy 1.75 eV is established from optical studies. The electrical resistivity of the thin films is found to be 10(6) Omega cm and the results are discussed. (c) 2011 Elsevier Ltd. All rights reserved.

Electrochemical studies on Zn/nano-CeO 2 electrodeposited composite coatings

The Zn-CeO 2 composite coatings through electrodeposition technique were successfully fabricated on mild steel substrate. As a comparison pure zinc coating was also prepared. The concentration of CeO 2 nanoparticles was varied in the electrolytic bath and the composites were electrodeposited both in the presence and absence of cetyltriammonium bromide (CTAB). The performance of the CeO 2 nanoparticles towards the deposition, crystal structure, texture, surface morphology and electrochemical corrosion behavior was studied. For characterizations of the electrodeposits, the techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) were used. Both the additives ceria and surfactant polarize the reduction processes and thus influence the deposition process, surface nature and the electrochemical properties. The electrochemical experiments like potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies carried out in 3.5 wt. NaCl solution explicit higher corrosion resistance by CeO 2 incorporated coating in the presence of surfactant. © 2012 Elsevier B.V. All rights reserved.

Two phase microstructure for Ag-Ni nanowires

In the present study, electrodeposition technique was used to produce Ag-Ni nanowires. Ag-Ni system shows extremely high bulk immiscibility. Nanowire morphology was achieved by employing an anodic alumina membrane having pores of similar to 200 nm diameter. Microstructure of as-deposited wire was composed of nano-sized solid solution structured Ag-Ni nanoparticles embedded in a matrix of pure Ag phase. It is proposed that the two phase microstructure resulted from an initial formation of solid solution structured nanoparticles in the alumina template pore followed by nucleation of pure Ag phase over the particles which eventually grew to form the matrix phase. (C) 2013 Elsevier B. V. All rights reserved.

Influence of deposition time on the properties of electrodeposited Cu(In,Al)Se-2 thin films

Cu(In,Al)Se-2 films are grown using single step electrodeposition technique. The film properties are studied by varying the deposition time from 500 to 2000 s. Peaks corresponding to elemental Se and Cu2Se phase started appearing from 1200 s of deposition. The composition is changed significantly after 1500 S. Se concentration increased from 57 to 68% with the increase in the deposition time. The Cu2Se phase is dominant in the films deposited for a duration of 2000 s and the grain size increased from 1.12 to 2.15 mu m in this film. Raman analysis confirmed the presence of Se and Cu2Se phase in C1200. In C1500 and C2000 the spectra showed prominent mode corresponding to Cu2Se. The thickness of the film increased from 0.85 to 2.3 mu m with the increase in the deposition time. All the films showed p-type conductivity and resistivity reduced with increased thickness. (C) 2015 Elsevier Ltd. All rights reserved.

Electrochemical preparation of silver nanostructure on the planar surface for application in metal-enhanced fluorescence

We introduce a fast and simple method, named the potentiostatic electrodeposition technique, to deposit metal particles on the planar surface for application in metal-enhanced fluorescence. The as-prepared metallic surfaces were comprised of silver nanostructures and displayed a relatively homogeneous morphology. Atomic force microscopy and UV-visible absorption spectroscopy were used to characterize the growth process of the silver nanostructures on the indium tin oxide (ITO) surfaces. A typical 20-fold enhancement in the intensity of a nearby fluorophore, [Ru(bpy)(3)](2+), could be achieved on the silvered surfaces. In addition, the photostability of [Ru(bpy)(3)](2+) was found to be greatly increased due to the modification of the radiative decay rate of the fluorophore. It is expected that this electrochemical approach to fabricating nanostructured metallic surfaces can be further utilized in enhanced fluorescence-based applications.

Use of conventional electrochemical techniques to produce crystalline FeRh alloys induced by Ag seed layer

By combining galvanic displacement and electrodeposition techniques, an ordered Fe20Rh80 structure deposited onto brass was investigated by X-ray diffractometry, Mössbauer spectroscopy and magnetization measurements. Mössbauer and X-ray diffraction analyses suggest that the Fe-Rh alloy directly electrodeposited onto brass displays a nanocrystalline state while a similar alloy deposited onto Ag/brass shows a faced centered cubic-like structure, with dendrites-like features. These results directly indicate that the presence of Ag seed layer is responsible for the Fe-Rh alloy crystallization process. In addition, room temperature Mössbauer data indicate firstly paramagnetic states for two Fe-species. In the dominant Fe-species (major fraction of the Mössbauer spectra), Fe atoms are situated at a cubic environment and it can be attributed to the γ-Fe20Rh80 alloy based on their hyperfine parameters. In the second species, Fe atoms are placed in a non-local symmetry, which can be related to Fe atoms at the grain boundaries or/and Fe small clusters. These Fe-clusters are in superparamagnetic state at room temperature, but they may be ordered below 45 K, as suggested by magnetization data. © 2013 Elsevier B.V. All rights reserved.

Strontium- and lead-isotope composition of some basalts at DSDP Hole 69-504B

Seventeen whole-rock samples, generally taken at 25- to 50-meter intervals from 5 to 560 meters sub-basement in Deep Sea Drilling Project Hole 504B, were analyzed for 87Sr/86Sr ratios, and rubidium and strontium concentrations. Ten of these samples also were analyzed for Pb-isotope composition. Strontium-isotope ratios for eight samples from the upper 260 meters of the hole range from 0.70287 to 0.70377, with a mean of 0.70320. In the interval 330 to 560 meters, five samples have a restricted range of 0.70259 to 0.70279, with a mean of 0.70266, almost identical to the average value of fresh mid-ocean-ridge basalts. In the interval 260 to 330 meters, approximately intermediate strontium- isotope ratios are found. The higher 87Sr/86Sr ratios in the upper part of the hole can be interpreted in terms of strontium-isotope alteration during basalt-sea-water interaction. Relative to average fresh mid-ocean ridge basalts, the upper 260 meters of basalts are enriched by an average of about 9% in sea-water strontium 87Sr/86Sr = 0.7091). This Sr presumably is located in the smectites, which, as the main secondary minerals throughout the hole, replace olivine and matrix glass and locally fill vesicles (analyzed samples contained no veins). The strontium-isotope data strongly suggest that the integrated flux of sea water through the upper part of the Hole 504B crust has been greater than through the lower part. This is also suggested by (1) the common occurrence of Feoxide- hydroxide minerals as alteration products above 270 meters, but their near absence below 320 meters, (2) the presence of vein calcite above 320 meters, but its near absence below this level, and (3) the occurrence of vein pyrite only below a depth of 270 meters. Sea-water circulation in the lower basalts may have been partly restricted by the greater number of relatively impermeable massive lava flows below 230 meters sub-basement. Although sufficient sea water was present within the lower part of the hole to produce smectitic alteration products, the overall water /rock ratio was low enough to prevent significant modification of strontium-isotope ratios. Lead-isotope ratios of Hole 504B basalts form approximately linear arrays in plots of 208Pb/204Pb and 207Pb/204Pb versus 206Pb/204Pb. The arrays are similar to those reported for basalts from other mid-ocean ridges. There is no trend in Hole 504B lead-isotope ratios with vertical position in the basement. The arrays indicate that the lead-isotope composition of the upper mantle from which the Hole 504B basaltic melts were derived was inhomogeneous.

Monitoring cuprous ion transport by scanning electrochemical microscopy during the course of copper electrodeposition

Scanning electrochemical microscopy (SECM), in the substrate generation–tip collection (SG-TC) mode, has been used to detect the cuprous ion intermediate formed during the course of electrodeposition of Cu metal from aqueous solution. Addition of chloride is confirmed to strongly stabilize the ion in aqueous solution and enhance the rate of Cu electrodeposition. This SECM method in the SG-TC mode offers an alternative to the rotating ring disk electrode (RRDE) technique for in situ studies on the effect of plating bath additives in metal electrodeposition. An attractive feature of the SECM relative to the RRDE method is that it allows qualitative aspects of the electrodeposition process to be studied in close proximity to the substrate in a simple and direct fashion using an inexpensive probe, and without the need for forced convection.

Numerical modelling of electrodeposition phenomena

Electrodeposition is a widely used technique for the fabrication of high aspect ratio microstructure components. In recent years much research has been focused within this area with an aim to understanding the physics behind the filling of high-aspect ratio vias and trenches on PCB's and in particular how they can be made without the formation of voids in the deposited material. This paper describes some of the fundamental work towards the advancement of numerical models that can predict the electrodeposition process and addresses: i) A novel technique for interface motion based on a variation of a donor-acceptor technique ii) A methodology for the investigation of stress profiles in deposits iii) The implementation of acoustic forces to generate replenishing electrolytic flow circulation in recessed features.

Influence of megasonic agitation on the electrodeposition of high aspect ratio blind vias

This paper presents preliminary studies in electroplating using megasonic agitation to avoid the formation of voids within high aspect ratio microvias that are used for the redistribution of interconnects in high density interconnection technology in printed circuit boards. Through this technique, uniform deposition of metal on the side walls of the vias is possible. High frequency acoustic streaming at megasonic frequencies enables the decrease of the Nernst diffusion layer down to the sub-micron range, allowing thereby conformal electrodeposition in deep grooves. This effect enables the normally convection free liquid near the surface to be agitated. Higher throughput and better control of the material properties of the deposits can be achieved for the manufacturing of embedded interconnections and metal-based MEMS. For optimal filling performance of the microvias, a full design of experiments (DOE) and a multi-physics numerical simulation have been conducted to analyse the influence of megasonic agitation on the plating quality of the microvias. Megasonic based deposition has been found to increase the deposition rate as well as improving the quality of the metal deposits.