Pulse Potential Deposition - an Experimental Protocol for Growth of High Quality Thin Films Via Surface Limited Red-Ox Replacement Reaction
Authors: Brankovic Stanko , Dongjun Wu , Solanki Dhavit 
Published: February 2020

Pulse Current Deposition method for growth of thin films and functional coatings has been in use in academia and industry for quite some time [[1]]. However, with few exemptions [[2]], the application of the pulse potential deposition for growth of metallic coatings was mainly confined to academic studies where the conductivity of the substrate, substrate morphology and size do not present a major challenge.
Over the years, different deposition protocols have been developed which leverage the benefit of Underpotentially Deposited Monolayers (UPD ML) as a surfactants, mediators or sacrificial materials in deposition process [[3]]. In these examples, the essential step that results in the desired growth mode is achieved by precise control of the electrode potential at which action of the UPD ML is exploited. One of them is deposition via Surface Limited Redox Replacement (SLRR) reaction [[4],[5]], where the main role of UPD layer is to serve as sacrificial reducing metal for deposition of controlled amount of more noble metal. Both, thermodynamics and kinetics of this deposition process are now reasonably well understood which opens more opportunities for practical applications [[6]].
In this talk we show that the control of deposition process during pulse potential deposition is facile and extendable to large area sample plating. The experimental study focuses on design of simple pulse potential function (on/off) for deposition of noble metal coatings on model substrates such as Au and on industrially relevant substrates such as Cu and Ru. The “on” step of the potential cycle is designed to produce a full UPD ML on the substrate surface. The main growth of the deposit occurs during the “off” step of the potential cycle. In this step, at OCP, the deposition of noble metal occurs via SLRR of UPD ML [5]. We will discuss the important parameters of the potential pulse function such as pulse time, off time, and their relation to the deposit morphology, composition and stress. The terminal effect as well as the effect of solution conductivity and solution design in terms of the mutual ratio of UPD metal and depositing metal ion concentration will be discussed as well.

[1] J.C. Puippe and F. Leaman, Theory and Practice of Pulse Plating, AESF, (1986).
[2] Modern Electroplating V, editors: M. Paunovic and M. Schlesinger, John Willey and Sons, Inc (2010).
[3] Chapter 27- Applications to Magnetic Recording and Microelectronic Technologies, S.R. Brankovic, N. Vasiljevic, N. Dimitrov, Modern Electroplating V, editors: M. Paunovic and M. Schlesinger, John Willey and Sons, Inc (2010).
[4] S. R. Brankovic , J. X. Wang and R.R. Adzic, Surface Science , 474, L173, (2001).
[5] N. Dimitrov, Electrochimica Acta, 209, 599 (2016).
[6] Chapter 3: Electrochemical Surface Professes and Opportunities for Material Synthesis, Stanko R. Brankovic and Giovanni Zangari in Electrochemical Engineering Across Scales: From Molecules to Processes, Editors: R. C. Alkire, P. N. Bartlett, J. Lipkowski, Advances in Electrochemical Science and Engineering, vol. 15, Willey-VCH (2015) p. 59-107.