In this contribution, self-assembled monolayers of n-dodecanethiol (C12H25SH) at different concentrations on polycrystalline copper have been elaborated. Using XPS, PM-IRRAS, and electrochemical methods (cyclic voltammetry curves and cathodic desorption), the effect of the C12H25SH concentration on the reduction of the oxide layer has been studied. In all cases, a monolayer of good quality has been obtained. Results provide proof that while the concentration is increased, the thickness of the oxide layer is decreased, to a point that leads to metallic copper for the higher concentration, The results presented in this publication indicate the importance of controlling the interface when forming SAMs of organothiols on oxidizable metals. (c) 2008 Elsevier Inc. All rights reserved.