Redox-mediated currentless deposition of metal adatoms on foreign metal surfaces

FONTICELLI, M. H.; CORTHEY, G.; ROBERTO C. SALVAREZZA

Bariloche

Congreso; 13th International Conference on Solid Films and Surfaces; 2006

The heteroepitaxial growth of two-dimensional (2D) single-crystal metal films remains a problem, both in UHV or electrochemical environments. This growth usually leads to the formation of 3D clusters with a non uniform coverage, mainly as a consequence of the irreversible condition in which deposition is carried. Underpotential deposition (upd) of metals is a suitable strategy to overcome this drawback because allows controlling the process in equilibrium conditions. In this way a small amount of metal adatoms ranging from submonolayer to monolayer coverage can be easily deposited. In previous works done in our laboratory, the self-assembly of alkanethiols on underpotentially deposited silver adatoms was studied by using STM, AES and electrochemical techniques. In these studies it was shown that the stability of the self-assembled alkanethiolate monolayers in the Ag(1x1)-Au(111) surfaces is increased respect to those observed on Ag(111) and Au(111) [1]. Additionally, DFT calculations were helpful in the understanding of the observed phenomena. Here we present a novel and low cost method for the synthesis of bimetallic surfaces in which the adatoms are deposited in equilibrium conditions. This method implies the tuning of the electrochemical potential of metal cations in solution by using a redox couple. The redox potential is chosen in such a way that the metal is deposited with a determined coverage. In the present work this method is used for deposition of silver adatoms on Au(111) surfaces by using a quinhydrone (an equimolar mixture of p-benzoquinone and hydroquinone) acid solution. We also show the ability of this redox couple to produce the deposition of silver through an n-propanethiol self-assembled monolayer on Au(111). Furthermore, we observed that the electrochemical behaviour of the bimetallic surfaces prepared by this novel method is the same than that observed for silver electrodeposited in underpotential conditions as reported in Reference [1] (i.e. in a three-electrode cell and using a potentiostat). [1] Fonticelli, M.; Azzaroni, O.; Benitez, G.; Martins, M. E.; Carro, P.; Salvarezza, R. C. J. Phys. Chem. B. 2004, 108(6), 1898-1905.