In situ scanning tunneling microscopy investigation of silver on Au (111) in the presence of chloride

Abstract

Using electrochemical measurements and in situ scanning tunneling microscopy (STM), we confirm the process of Ag growth and the overlayer structures of Ag upd on Au (111) in the presence or absence of chloride anions. In a pure $0.1 M HClO_4$ solution, an open (4×4) structure of Ag prevails at potentials between 0.16 and 0.41 V vs a mercury-mercurous sulfate electrode (MSE) while a close-packed (1×1) Ag adlayer begins to appear over the entire surface of a Au (111) substrate near the potential of bulk deposition. On the other hand, there are four distinct structures of the Ag adlayer on Au (111) in the presence of chloride. A (3\sqrt3×3\surd3) R30° a (\sqrt3×3\sqrt) R30°, a (\sqrt21×\sqrt21) R10.9°, and a (7×7) adlayer structure are formed as a function of potential, and these structures are clearly matched to the features in a cyclic voltammogram. Compared with the (4×4) structure of Ag upd on Au (111) in the absence of chloride, overlayer structures of Ag on Au (111) in a chloride-containing solution are more loosely packed. Therefore, we conclude that the structures of the Ag overlayer on Au (111) strongly interact with chloride anions, suggesting the bilayer structure between Ag and Cl.