Ultra-High-Resolution Differential Interference Microscopy of Ag Deposition on an Ultraflat Au(111)

The electrodeposition of silver on an atomically ultraflat surface of Au(111) was investigated using laser confocal microscopy combined with the differential interference contrast microscopy (LCM-DIM) in the sulfuric acid medium with silver sulfate as an electrolyte solution. For the first time, we have observed the underpotential deposition processes of silver atoms on the large Au(111) surface area in atomic height resolution of as-deposited Ag layers using LCM-DIM. In underpotential deposition (UPD) regions, small islands of Ag atoms with monatomic step heights are formed on the Au(111) terraces at the initial stage, followed by the increase in domain size of islands, and then finally a complete monolayer was formed on the Au(111) surface. Before initiating the bulk deposition of Ag, our LCM-DIM gave direct evidence for the formation of the third monolayer of Ag at the foot of the potential of the bulk deposition. In addition to UPD, the bulk deposition of Ag was also investigated which demonstrated that the very flat Ag surface appeared on the Au(111) surface. Finally, it has been demonstrated that the LCM-DIM was an ideal tool to capture images of the fast dynamic Ag electrodeposition processes on the Au(111) surface with the fastest acquisition times of 2-10 frames per second.