Electrodeposition methods

Nishino J, Chatani S, Uotani Y, Nosaka Y (1999) Electrodeposition method for controlled formation of CdS films from aqueous solutions. J Electroanal Chem 473 217-222... 

Several methods and variations have been developed to electrodeposit compounds. Most of the work described in this article concerns the formation of nonoxide compounds such as II-VI and in Vs. Oxides are probably the largest group of electrodeposited compounds (aluminum anodization for example), but will not be discussed here. The electrodeposition of H-VI compounds has been extensively studied and is well reviewed in a number of articles [24-29], The most prominent compound electrodeposition methods include codeposition, precipitation, and various two-stage techniques. 

In general, annealing has been used to either form or improve the structures of compound films formed by the electrodeposition methods described above. This severely limits applications in systems where more complex structures are involved, structures where interdiffusion is a problem nanostructured materials. 

EC-ALE is the combination of UPD and ALE. Atomic layers of a compound s component elements are deposited at underpotentials in a cycle, to directly form a compound. It is generally a more complex procedure than most of the compound electrodeposition methods described in section 2.4.2, requiring a cycle to form each monolayer of the compound. However, it is layer-by-layer growth, avoiding 3-D nucleation, and offering increased degrees of freedom, atomic level control, and promoting of epitaxy. 

The remainder of this introduction will involve a brief discussion of previous work in the area of semiconductor electrodeposition. The focus will be on the strengths and limitations of the various electrodeposition methods with regard to controlling deposit structure, composition, and morphology. Most of this work has been well reviewed by others [13,40-44]. 

Another frequently raised concern about purity involves the fact that electrodeposition takes place in a condensed phase, with a solvent in contact with the substrate and deposit. The solvent used for the present studies is water, and it is used copiously in the processing of compounds and devices. The electronics industries are well aware of how to obtain very high-purity water. The point is that the purity issues in an electrodeposition method are the same issues being addressed in presently used methodologies. There does not appear to be anything inherently dirty about electrodeposition. 

Three techniques have been described in the literature to prepare combinatorial libraries of fuel cell electrocatalysts solution-based methods [8, 10-14], electrodeposition methods [15-17] and thin film, vacuum deposition methods [18-21]. Vacuum deposition methods were chosen herein for electrocatalyst libraries in order to focus on the intrinsic activity of the materials, e.g., for ordered or disordered single-phase, metal alloys. 

It is helpful for the electrochemical degradation ability by getting a uniform layer on base metals. Electrodeposition is convenient and is an effective way to realize this. Sb and Sn metals can be prepared either by co-electrodeposition together or by a sequencing electrodeposition. We developed a sequencing electrodeposition method which is more useful for more uniform and more effective layers. 

Thermal ionization is based on the production of atomic or molecular ions at the hot surface of a metal filament [95,96]. In this ionization source, the sample is deposited on a metal filament (W, Pt or Re) and an electric current is used to heat the metal to a high temperature. The ions are formed by electron transfer from the atom to the filament for positive species or from the filament to the atom for negative species. The analysed sample can be fixed to the filament by depositing drops of the sample solution on the filament surface followed by evaporation of the solvent to complete dryness, or by using electrodeposition methods. 

Subsequently, Stamm and coworkers [184-186] used PS-fo-P4VP diblock copolymers in combination with 2-(4-hydroxybenzeneazo)benzoic acid (HABA, Scheme 7). Thin films with cylindrical nanodomains of the P4VP-HABA complexes in a PS matrix were produced. The ahgnment of the cylinders could be switched upon exposure to vapors of different solvents from parallel to perpendicular (Fig. 25). Extraction of HABA resulted in nanoporous membranes with hollow channels of 8 nm (Fig. 26). The channels were filled with Ni clusters via the electrodeposition method to fabricate an ordered array of metalhc nanodots. 

In conclusion, we note that deposition of submono- and monolayers of adatoms is the most controllable and reliably predictable method of obtaining metallic nanodimension compositions. At least two or three kinds of adatoms can be deposited in a strictly layer-by-layer fashion on single-crystal substrates [217], and mixed adlayers can also be obtained. The combined deposition of adatoms and phase deposits of metals [217] is even more promising. Among the metals, HTSC components such as lead, thallium, bismuth, and copper rank among the most thoroughly studied adatomic systems. Electrodeposition methods are also applied to the technological preparation of conventional superconductors based on Nb-Sn alloys [218]. 

In order to study the influence of the surface composition of the thin film electrode on IR features of CO adsorption, nm-Pt/GC and nm-Ru/GC electrodes were modified with Ru and Pt, respectively. Modifications to the Pt on the nm-Ru/GC surface and the Ru on the nm-Pt/GC surface were carried out by employing an electrodeposition method [48]. The nm-Pt/GC or nm-Ru/GC electrode was introduced into 0.1 M H2SO4 solution containing ImM Ru or Pt" ions, and the potential was cycled between —0.25 and 0.40 V at a scan rate of 50mV s. The quantity of Pt deposited on the nm-Ru/GC surface or Ru deposited on the nm-Pt/ GC surface was controlled by varying the number of potential cycles that initiated the deposition. 

In the AIREs, the nanometer thin film supported on glassy carbon or other conductive substrates was prepared by convenient electrodeposition method of cyclic voltammetery that led to form nanometer-scale thin film of layered structure. The film of island structure is nevertheless fabricated by evaporation method and employed in the SEIRA. 

AuNPs were electrodeposited onto a clean gold electrode surface by electrodeposition method. Where, the gold electrode was twice cycled in the potential range + 1.1 V to 0 V in deoxygenated solution containing 0.77 mM HAUCU in 0.5 M H2SO4 at 10 mV s"1 scan rate. This AuNPs modified electrode was then immersed into a 300 pi solution of 0.1 M phosphate buffer (PBS) pH 8, containing 60 pg of AChE for 24 h at 4 °C. Finally this AChE modified... 

There is, however, a specific advantage in the electrodeposition method, relating to the unique possibility of the determination of the amount of deposited material. For CdTe, the electrochemical reaction involves a charge turnover of six electrons for each deposited CdTe unit. This correlation is derived from basic chemistry, but it has also been experimentally confirmed by Ernst (2001), as shown in Fig. 6.11. This correlation holds for both planar and deeply structured substrates. Since the charge turnover can easily be measured by integrating the deposition current over time, the electrodeposition method affords a reliable and quantitative determination of the total amount of deposited material. 

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