Multiparametric characterisation of metal-chalcogen atomic multilayer assembly by potentiodynamic electrochemical impedance spectroscopy

An approach to multiparametric characterisation of variable electroactive interfaces based on potentiodynamic electrochemical impedance spectroscopy (PDEIS) [G.A. Ragoisha, A.S. Bondarenko, Electrochim. Acta 50 (2005) 1553] has been extended to atomic multilayer assembly monitoring. The multilayers were formed by successive underpotential deposition of Te, Se and Pb or Cu adlayers on Au, and also by cadmium adlayer deposition on tellurium underlayer supported by gold. These multilayers were characterised in potentiodynamic mode by dependences of ac equivalent circuit parameters on electrode potential. The dependences disclose variations of interfacial double electric layer, charge transfer and diffusion. The dependencies of the characteristic parameters of the Au/Te_ad/Se_ad/Pb_ad composite three-layer have been found to be significantly different from the corresponding dependences of Au/Te_ad/Pb_ad and Au/Se_ad/Pb_ad bilayers, while Au/Te_ad/Se_ad/Cu_ad has shown much similarity with Au/Se_ad/Cu_ad in Faradaic part of ac response. Upd of Pb, Cu and Cd on the chalcogen adlayers has shown irreversibility with especially strong potential shift of adlayer oxidation potential in the case of lead deposition on bi-chalcogen Au/Te_ad/Se_ad underlayer. Unlike Pb adlayer, which is formed locally on top of tellurium-selenium bilayer and could be fully dissolved in the anodic scan in the potential range of stability of the chalcogen composite underlayer, copper penetrated into the Au/Te_ad/Se_ad bilayer and dissolved incompletely at Cu adlayer oxidation potential. The self-descriptiveness of potential dependences of circuit parameters suggests PDEIS to be a handy tool for layer-by-layer deposition monitoring in electrochemical nanotechnologies.