Epitaxial growth of Cu on Au(111) and Ag(111) by surface limited redox replacement-an electrochemical and STM study

Abstract

The growth of ultrathin copper films by surface limited redox replacement is discussed and experimentally illustrated. Cyclic voltammetry, in situ scanning tunneling microscopy (STM), and X-ray diffraction are employed to monitor the two-dimensional growth and characterize the structure of up to 100 monolayers (ML) of Cu on Ag (111) and Au(111) substrates. The growth is carried out by multiple redox replacement of a layer of underpotentially deposited (upd) Pb used as a sacrificial metal. Open-circuit potential monitoring during the replacement reaction is used to control the completion of each deposition event. Anodic film stripping is performed to determine the film thickness and calculate the yield of the employed deposition strategy. The excellent surface quality of an epitaxially grown Cu film is manifested by a distinct Pb upd voltammetry and ascertained by in situ STM showing uniform surface morphology maintained during the entire growth process. High-resolution STM imaging of Pb upd layer deposited on as-grown Cu films reveals a structure identical to Pb on Cu(111). X-ray photoelectron spectroscopy analysis shows no traces of Pb into accordingly deposited Cu films. © 2007 American Chemical Society.