Epitaxial Growth of Ag on Au ( 111 ) by Galvanic Displacement of Pb and Tl Monolayers

Abstract

The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers predeposited by underpotential deposition (UPD) is discussed and experimentally illustrated. Cyclic voltammetry and scanning tunneling microscopy are employed to carry out and monitor a “quasi-perfect,” two-dimensional growth of up to 35 monolayers of Ag on by repetitive galvanic displacement of underpotentially deposited Tl and Pb monolayers. A complementary kinetic study of Pb and Tl UPD layer stability at open-circuit potential identifies the oxygen reduction reaction and hydrogen evolution reaction as key oxidative competitors of Ag in the proposed displacement protocol. Analysis of the morphology evolution during the growth of Ag by displacement Pb and Tl UPD layers suggests the one-to-one exchange scenario as more efficient for longer maintenance of a layer-by-layer silver deposition. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by an overall flat and uniform surface morphology maintained during the entire growth process. An X-ray photoelectron spectroscopy analysis finds no traces of Pb and Tl in the Ag deposit.