Dimitar Stoychev

Behaviour of poly(ethylene glycol) during electrodeposition of bright copper coatings in sulfuric acid electrolytes

The interaction of poly(ethylene glycol) Mn= 3000 with copper I and II ions in aqueous-acidic media was studied by investigation of the specific electrical conductivity, optical density and the cyclic voltamperometric curves in Cu+ and Cu2+ solutions. The results suggest the formation of complexes of the {Cu+(-EO-)3(x − 1)H2O} and {Cu2+(-EO-)4.(y − 1)(H2O)2} types. In the case when {−CH2CH2-O-} n and Cl− are simultaneously present in the copper electrolyte, the possibility of simultaneous complex formation between both copper ions and ethylene oxide units, and copper ions and chloride ions is considered. The strong increase in copper electrodeposition over-potential after the addition of polyethers to the electrolytes containing brighteners is explained by the formation of these complexes.

Electrochemical nucleation and growth of rhodium on gold substrates

Abstract The mechanism of rhodium adlayer formation on the (100) face of a gold single crystal and on a polycrystalline gold electrode has been studied using cyclic voltammetry and chronoamperometry. The voltammogram shows the presence of two peaks associated with the deposition of rhodium from the Na 3 RhCl 6 salt in 0.1 M HClO 4 . The results obtained on the (100) face of a gold single crystal indicate that the two monolayers of rhodium can be deposited before the nucleation and growth of the three-dimensional (3D) rhodium clusters. The experimental results described in this paper show that the bulk rhodium electrodeposition on a gold electrode includes a nucleation process combined with a diffusion-controlled growth of the stable rhodium crystals. The nucleation kinetics is compared for the 3D electrodeposition on the 〈100〉 face of a single crystal gold electrode and on a polycrystalline gold electrode.

Recovery and recrystallization of electrodeposited bright copper coatings at room temperature. II. X-ray investigation of primary recrystallization

X-ray investigations of the recrystallization processes occurring at room temperature in electrodeposited bright copper coatings were carried outin situ. As a result of the orientation transformation of the growth texture with 〈311〉, 〈111〉 and 〈110〉 components, a recrystallization texture with 〈100〉, 〈110〉 and 〈111〉 components was obtained. It was established that one of the factors which influence the microhardness of copper coatings is the orientation distribution of crystallites.

Electrochemical deposition of thin zirconia films on stainless steel 316 L

Zirconia films (ZrO2) have been deposited electrochemically on stainless steel SS 316 L in a non-aqueous electrolyte based on absolute ethyl alcohol and ZrCl4. Scanning electron microscopy (SEM) studies have shown that the film consists of crystallites with a spheroidal shape, forming agglomerates with a very large surface area. Their sizes vary within the range of 0.1–0.5 μm. The layer composition is very close to the stoichiometric ZrO2, as has been determined by X-ray photoelectron spectroscopy (XPS).

Initial stages of copper electrodeposition in the presence of organic additives

Abstract The nucleation and growth kinetics of copper crystals electrochemically deposited on platinum and tungsten have been studied in the presence of a composite organic additive for bright copper plating. Data were obtained for the exchange current density i 0 , for the transition coefficient α of the copper ions, for the stationary nucleation rate I st and for the size n k of the critical copper nucleus.

Galvanostatic studies of the nucleation and growth kinetics of copper in the presence of surfactants

The initial and advanced stage of copper electrodeposition have been studied under galvanostatic conditions. The effect of different surface active compounds on the nucleation and growth kinetics has been examined. Data were obtained for the nucleation and growth parameters characterizing the electrochemical deposition of copper ions.

Recovery and recrystallization of electrodeposited bright copper coatings at room temperature. I. Microhardness in relation to coating structure

The electrolyte composition effect on the microhardness of bright copper coatings electrodeposited from sulphuric acid electrolytes was established. It is shown that the sulphuric acid content and the type of brightener agent strongly influence the rate of decrease of microhardness of deposited coatings with time. The systematic quantitative and qualitative investigations performedin situ determined the microhardness changes on the one hand, and the change in microdeformations, dislocation defects, crystallites size and texture of copper coatings on the other hand, thus demonstrating unambiguously the correlation betweeen them. The decrease in copper coating microhardness is explained by the occurrence of recovery and recrystallization processes at room temperature.

Study of the kinetics of processes during electrochemical deposition of zirconia from nonaqueous electrolytes

The processes of electrochemical deposition of zirconia from nonaqueous electrolytes on different substrates have been investigated. Cyclic voltammetry and linear sweep voltammetry have been used to investigate the oxygen and hydrogen reduction processes preceding/accompanying the discharge of the zirconium complex being identified. On the basis of simultaneous XPS and SEM analyses, the potential region of zirconia layer formation has been defined. The kinetic parameters of successive and parallel reduction processes have been determined. The factors hindering the formation of thick zirconia layers have been discussed.

XPS and SEM characterization of zirconia thin films prepared by electrochemical deposition

Electrochemical deposition of zirconia on stainless steel has been investigated in order to provide supports of catalysts for No x reduction. The zirconia films have been obtained in electrolytes based on anhydrous ethyl alcohol. The structure and chemical composition of the films have been characterized by SEM and XPS depth profiling. With rising cathodic voltage, the structure and morphology exhibit essential changes. The most porous structure corresponds to films formed at 21 V, whereas the highest density is achieved at 25 V. The XPS depth profiling data show that the composition in the bulk of the films is close to stoichiometric. The cross-section of an annealed film gives evidence for good adhesion to the substrate. The film thickness is 3-10 μm. After annealing in air at 550°C for 1 h, no cracks and inhomogeneities are observed.

On the role of poly(ethylene glycol) in deposition of galvanic copper coatings

A literature review is provided of the influence and the behaviour of polyethers of the type of polyethylene glycol (PEG) and polypropylene glycol (PPG) on electrodeposition of copper coatings in acidic electrolytes. Emphasis is given to the scientific understanding of various phenomena associated with the processes being discussed. The topics include the influence of PEG (PPG) (alone or in the presence of Cl - ) on the kinetics of the electrocrystallization process as a function of: degree of cathode polarization; molecular weight and concentration of PEG (PPG) and of chloride ions. The probability of complex formation of Cu + and Cu 2+ with PEG (PPG) and Cl - is also discussed. Based on an analysis of published literature data it is shown that: (i) PEG (PPG) strongly inhibits the cathodic process; (ii) there exists a critical potential (on cathode polarization) which is responsible for the great difference in the degree of suppression of the deposition current in the presence of PEG (PPG); (iii) in the presence of Cl - in the electrolyte, the potential region within which PEG (PPG) is adsorbed most readily increases dramatically. The possibilities of complex formation between Cu + (Cu 2+ ) ions and PEG (PPG) in the absence and in the presence of Cl - are also discussed. It is pointed out that the presence of PEG (PPG) in the acidic electrolytes for copper electrodeposition leads to the formation of complexes of the type {Cu + (-CH 2 -) 3 .H 2 O} and {Cu 2+ (-CH 2 -) 3 .2H 2 O} as well as to a significant increase in concentration of the so called ate-complexes (CuCl 2 - , CuCl 2- 3 , CuCl + , CuCl 2- 4 ). The formation of such complexes and their possible adsorption on the cathode surface are proposed as an explanation for the effect of suppressing copper deposition current.