Electroless Deposition of Pb Monolayer - Surface Selective, Surface Controlled, Self-Terminating Process

Abstract

The presented experimental results including insitu scanning tunnelling microscopy (STM), electrochemical quartz microbalance (ECQCM) and open circuit potential (OCP) transient as well as our modelling and data analysis demonstrate the new phenomenon of the electroless (e-less) deposition of Pb monolayer (ML) on Pt(111), Ru(0001), Au(111) and Cu(111) substrates. The e-less Pb ML morphology and properties resemble its underpotentially deposited counterpart. The e-less Pb ML deposition, in its nature, represents the surface selective, surface, controlled self-terminating process, Figure 1. These attributes are consequence of the synergy between particular properties of the redox processes and substrates involved in the e-less Pb ML deposition. The e-less Pb ML deposition is enabling phenomenon for the two-step e-less atomic layer deposition (ALD) cycle where the e-less Pb ML serves as a reducing agent in the surface limiting redox replacement (SLRR)[1] reaction with noble metal ions, i.e. noble metal deposition. The full e-less ALD cycle results in an overall deposition of the controlled amount of noble metal which is the function of the areal density of deposited Pb ML and the stoichiometry of the SLRR reaction. The e-less ALD is highly selective to the metal substrates at which Pb forms an e-less ML providing an advantage when certain manufacturing and integration requirements are considered. Figure 1. Insitu STM results demonstrating e-less Pb ML deposition on Au(111). (A) starting Au(111), (B) Au surface during nucleation and growth of e-less Pb ML, moment of addition of reducing agent is indicated, (C) Full e-less Pb ML formation on Au(111). All images recorded at OCP.