Abstract
Electrocrystallization of Ga on Au(111) in two different ionic liquid electrolytes has been investigated by in situ electrochemical STM imaging with partly nanometer resolution. In chlorogallate-containing melts underpotential deposition (UPD) leads to surface alloying whereby a Ga−Au surface layer is formed on top of Au(111). In AlCl3−[C4mim]Cl + 5 mM GaCl3 melts, 2D-electrochemical phase formation is driven by conventional nucleation and growth of 2D Ga islands. Prior to the UPD processes anion adsorption of GaCl4− and AlCl4−, respectively, occurs which is characterized by well-ordered anion layer structures with comparable lattice constants. At potentials negative of the UPD region, 3D Ga clusters are formed. On the basis of their shape and the coexistence of small and large clusters in contact, it is concluded that the clusters in the size range 5−30 nm are solid. Taking into account that the temperatures during electrodeposition ranged up to 313 K—above the melting point of α-Ga of 303 K—this observation is remarkable.
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