Advances in E-ALD By Slrr for the Growth of Ultra Thin Films of Metal and Alloys - in Recognition to John Stickney's Contribution to Electrodeposition

Abstract

The idea realization progress of electrochemical atomic layer deposition by surface limited redox replacement (E-ALD by SLRR) is among the brightest and most significant contributions of Professor John Stickney. The approach proposed by him in early nineties of last century for epitaxial growth of compound semiconductor films was extended in the beginning of 21st century with his active participation and contribution to the deposition of ultra thin coatings of metals and alloys with a variety of applications thus establishing foundation for the development of one of the most useful and versatile thin film growth methods. In the beginning of this presentation an overview of existing approaches for epitaxial metal thin film growth along with E-ALD by SLRR will first be presented. A comparison of the kinetics manipulation approaches will be made with emphasis on the ability of those methods to produce epitaxial, flat and uniform deposits. In the course of this comparison illustrations will be provided with results, illustrating the advantages and limitations of these deposition approaches in the growth of Ag and Cu thin films on Au (111) substrates. To support the discussion, on the approaches employed, results of electrochemical, in-situ scanning tunneling microscopy (STM), X-ray Photoelectron Spectroscopy characterization experiments will be presented and compared. In the second part, the applicability of SLRR and electroless SLRR in the growth of Pt and Pd on Au (111) substrate will be discussed with special emphasis on the contribution and achievements of John Stickney’s research team. Experimentally demonstrated will be the SLRR growth of Pt and Pd layers with controllable thickness taking place in “shuttling” chamber, flow cell, and “one-pot” configuration. Open circuit potentiometry during the replacement reaction will be shown as a way to control the completion of each deposition event. Anodic stripping of the entire multilayer will be used for determining the overall film thickness. Cyclic Voltammetry and STM will be employed to characterize the growth of Pt and Pd layers with up to 10 nm thickness. High-resolution STM results and modelling concepts underlying the foundation of the proposed approaches will shed light on the mechanistic aspects associated with the nature of growth by redox exchange at a monolayer level. In the third component of this presentation an overview of recent work on the design of potent catalysts with application in energy production and storage will be presented. This will include the use of SLRR approach for coating nanoparticles and continuous nanoporous metal layers with ultra thin films of metal / alloy with specific functionality. Successful outcome of this coating renders the final product catalytically active. In this part, a brief description will be provided also on the direct use of SLRR based protocols for the smart design of bimetallic alloy and/or core shell clusters with application in the most commonly used reactions in the field of fuel-cell catalysis. The discussion on the synthetic component of all relevant activities will be concluded with demonstration of results of testing of accordingly developed catalysts. Finally, a glimpse into the future of this rapidly developing field will be also provided.