Microelectrode Studies of S-NDR Copper Electrodeposition: Potentiodynamic and Galvanodynamic Measurements and Simulations
Trevor Braun, Daniel Josell, Thomas P. Moffat
Copper electrodeposition from a CuSO4 – H2SO4 electrolyte containing a polyether suppressor and Cl- concentrations (0 – 100) μmol/L is examined using a 25 μm microdisk electrode. Optical imaging during cyclic voltammetry and galvanodynamic sweep measurements reveal additive-derived hysteresis and overpotential inversions related to a negative differential resistance (S-NDR) associated with breakdown of the polyether-chloride inhibition layer. Simulations based on co-adsorption of the suppressor-halide adlayer and its subsequent breakdown capture the positive feedback evident in electroanalytical measurements along with important aspects of electrode shape evolution. The impact of electrode shape change on the simulating electroanalytical experiments was evaluated in comparison to the stationary interface approximation. For potentiodynamic conditions adlayer breakdown proceeds rapidly across the finite microelectrode, although the final deposit profile is non-uniform due to enhanced transport to the disk perimeter. In contrast, galvanodynamic conditions in more concentrated Cl- solutions reveal spatially-selective suppressor breakdown with deposition initially localized to the microelectrode center followed by outward expansion as the applied current is increased. The difference between the potentiodynamic and galvanodynamic response reflects the convolution of S-NDR critical behavior with the respective control-loop load lines. Finite size microelectrodes constrain or frustrate the otherwise random bifurcation process thereby giving rise to predictable morphologies.
, Josell, D.
and Moffat, T.
Microelectrode Studies of S-NDR Copper Electrodeposition: Potentiodynamic and Galvanodynamic Measurements and Simulations, Journal of the Electrochemical Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=929973
(Accessed December 6, 2023)