Investigating the Incipient Dynamics of Nucleation and Growth in Electrodeposition: Uncovering Key Relationships for Strategic Exploitation
Authors: Clark Courtney L , Cechini Jamie , Hooks Daniel E , Wharry Janelle , Bahr David 
Published: December 2024

The objective of this study is to tailor the structure and properties of electrodeposited coatings through real-time parameter variations. Electrodeposition has been used for centuries to apply both functional and aesthetic coatings to a range of materials. This process is, in general, relatively simple, robust, and cost-effective for depositing films of one material onto another. These favorable characteristics though, have resulted in a deficiency in the fundamental understanding of time-dependent microstructural control and key relationships between process parameters and the resulting coating performance. The development of microelectronics and other devices that require increasingly tighter tolerances on coating deposition and performance, pushing the limits of what is currently achievable, has facilitated a resurgence in the advancement of electrodeposition technologies.

While it is generally understood how changing parameters (e.g. potential, electrolyte composition, temperature, pH, etc.) affects the developing coating, much of this work has been done through empirical research and post-mortem correlations. Herein, we develop a methodology for tailoring coating structure (size, shape, and texture) to exploit different physical properties (hardness, ductility, electrical conductivity, etc.) of electrodeposited coatings through parameter variation and direct linkage to observable events and physical characteristics in real-time. Modern instruments such as transmission electron microscopy (TEM) and small-angle electron scattering (SAXS) theoretically have the ability to observe these phenomena, with both time and spatial resolution falling in range of physical requirements. However, few studies have developed or demonstrated these techniques for in-situ measurements.

In this presentation, preliminary experiments utilizing nickel (Ni) and silver (Ag) salt electrolytes as model systems for the investigation of incipient nucleation and growth behavior of electrodeposited Ni and Ag coatings will be defined, as well as confirmation of SAXS as a complementary technique for characterizing island growth in the first stages of deposition. Electrochemical techniques including cyclic voltammetry and chronoamperometry were applied to study the nucleation mechanisms for these materials. Additionally, potentiostatic electrodeposition was used to deposit the nanoparticle islands. For this study, we artificially promoted instantaneous growth of the coating using an initial “seed” pulse, followed by a subsequent growth pulse. This serves to improve the monodispersity of the islands that are deposited on the substrate surface, simplifying the analysis of the initial SAXS measurements.

Utilization of a laboratory-source SAXS and wide-angle x-ray scattering (WAXS) instrument for physical and chemical characterization of island growth allowed us to quickly characterize the deposited particles. A comparison of these measurements to equivalent SEM/EDS imaging of the samples for size, shape, number density, and elemental composition confirmation of the deposited particles will also be described. Additionally, we will briefly discuss the state of the literature and our current plans for transitioning these post-mortem experiments to in-situ measurements, allowing for time resolved data, directly observing nucleation and growth of electrodeposited coatings to be collected.