Electrochemical formation of ultrathin Ag/Cd films onto Au(1 1 1) substrates

The formation of an ultrathin bilayer of Ag/Cd in the system Au(1 1 1)/Ag+, Cd2+, SO42- has been studied by conventional electrochemical techniques and in situ scanning tunneling microscopy (STM). Cyclic voltammetric measurements carried out in a solution containing both Ag+ and Cd2+ ions have shown that the deposition of Cd onto the Au(1 1 1) modified with 3.75 ML of Ag originates adsorption/desorption UPD peaks which are similar to those obtained in the system Ag(1 1 1)/Cd2+. These results demonstrate that the Au(1 1 1) surface was completely screened by the Ag layers which were epitaxially oriented respect to the substrate. Therefore, an ultrathin Ag(1 1 1) film was formed onto the Au(1 1 1) surface, on which a Cd ML was subsequently deposited by UPD, with the final product of an ultrathin Ag–Cd bilayer on the gold substrate. The morphological surface changes during the Ag deposition and subsequent Cd UPD on the modified substrate were followed by in situ STM imaging.