Co-Deposition of Sulphur from Acid Copper Solution Containing Thiourea

109

117

A model for predicting leveling during electrodeposition in the presence of an inhibiting additive is presented. Based on a diffusion-adsorption mechanism, the model assumes that the additive is consumed at the cathode by electroreduction. Using the approximation of a flat, stagnant diffusion layer, leveling during metal electrodeposition into triangular and semicircular grooves is simulated. The variation of the leveling agent concentration along the groove profile is determined by solving a concentration field problem with a boundary element method, and the advancement of the groove profile is simulated with a flexible moving-boundary algorithm. Leveling performance depends on three dimensionless groups characterizing leveling-agent reduction, metal-ion reduction, and the geometrical ratio of the diffusion layer thickness to the groove depth.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see ABSTRACT A model for cathodic leveling based on a diffusion-adsorption-reduction mechanism for the leveling agent was tested experimentally by electrodepositing nickel into a semicircular groove in the presence of coumarin. The inhibition of nickel by coumarin was measured on a rotating disk electrode, and kinetics for the reduction of coumarin and Langmuir adsorption coefficient were obtained from polarization data. Satisfactory agreement was found between experimentally measured and simulated leveling for groove depths on the order of the diffusion layer thickness or smaller.

Section: Modelmentioning

confidence: 99%

Blocking Inhibitors in Cathodic Leveling: I. Theoretical Analysis

Madore

Matlosz

Landolt

1996

109

117

“…Since the additive is consumed at the mass transport limiting rate, the concentration of additive is set to zero at the electrode surface c* = 0 [15] It should be noted that this boundary condition is really an approximation; although not zero, the concentration at the boundary is in fact very small. Ibl (18) has cited the work of several research groups (19)(20)(21)(22)(23) whose experiments have demonstrated that coumarin is consumed at the transport limiting rate. Thus, the concentration at the boundary is so small that it may be approximated as zero for the purpose of determining rates of additive transport to the surface.…”

Section: As Shown Inmentioning

confidence: 99%

The Effect of Inhibitor Transport on Leveling in Electrodeposition

Jordan

Tobias

1991

The electrodeposition of nickel into an angular trench in the presence of coumarin, a widely used inhibitor, is simulated using boundary layer approximations representative of flow parallel and transverse to the groove. Based on the diffusion-adsorption mechanism of leveling action, the dependence of the developing contours on variations in the Langmuir coefficient and inhibitor/metal-ion flux ratio are investigated. Leveling efficiency is shown to be highest for thin, planar boundary layers, and lowest for contour following boundary layers. The model successfully predicts the leveling-off of the inhibitor effect with increasing inhibitor vs. metal-ion flux, and that there is an optimal mass transfer boundary layer thickness, or flux of additive which results in superior leveling performance. Satisfactory agreement is found between the predicted contours, obtained by solving the model equations using the boundary element method, and the experimental leveling efficiencies determined by previous investigators.

“…In fact, there is abundant evidence that mass transfer controls the rate of consumption of leveler, i.e., that the consumption reaction is very facile and its rate is determined entirely by convective diffusion. Citing articles (11,(20)(21)(22)(23) by five different research teams, Ibl (12) states, "It can be concluded that for three systems--deposition of nickel from a Watts bath containing thiourea or coumarin, deposition of copper from an acid copper bath with thiourea--the codeposition rates of coumarin and thiourea are completely mass-transport controlled, with ce = 0." (Ibl refers to coumarin and thiourea as "the typical leveling agents studied so far.")…”

Section: Modelmentioning

confidence: 99%

“…However, such studies were initially confined to mainly organic dyes. Apart from this, in search of another class of sensitizers, several transition metal complexes have been tested (21)(22)(23)(24)(25)(26)(27)(28) and some of them were found to be quite efficient having all required properties. A continued search in this direction is desirable, therefore, to explore the possibility of using other metal complexes as photosensitizers.…”

Section: Department Ofchemistry Faculty Ofscience Banaras Hindu Unive...mentioning

confidence: 99%

Simulation of Leveling in Electrodeposition

Dukovic

Tobias

1990

A model of current distribution and electrode shape change for electrodeposition in the presence of diffusion‐controlled leveling agents has been developed. The system is treated as a special case of secondary current distribution, with the surface overpotential taken to depend on both the current density and the transport‐limited flux of the leveling agent, according to an empirical relation adapted from polarization data measured at different conditions of agitation. The spatial variation of the leveling‐agent flux is determined from a concentration field problem based on the assumption of a stagnant diffusion layer. The solution is obtained by the boundary element method, with a flexible moving‐boundary algorithm for simulating the advancement of the electrode profile. To illustrate the model's performance, the evolution of a groove profile during deposition of nickel from a Watts‐type bath containing coumarin is predicted and compared with measurements reported in the literature.