We present a voltammetric and in situ STM study of 11-ferrocenyl-1-undecanethiol (FcC(11)) assembled on low-index single crystal and polycrystalline gold electrodes. The influence of electrode surface structure as well as of structure defects in the self-assembled FcC(11) monolayers on the electrochemical response during the oxidation and reduction of the terminal ferrocene group is explored. The nature of the redox peaks is discussed in detail. We identified the coexistence of disordered FcC(11) regions with 2D patches of "locally ordered" FcC(11) species. We demonstrate that close-packed domains are preferentially formed at atomically flat terraces. Increasing the defect density of the substrate surface leads to a decreasing amount of locally ordered FcC(11) molecules. (C) 2012 Elsevier Ltd. All rights reserved.