Self-assembled monolayers formed on metal surfaces finally in contact with electrolyte solutions - i.e. in the electrochemical double layer are accessible to many electrochemical methods of investi¬gation. Beyond traditional methods dealing with electrode potential, current, charge and related pa¬rameters structural studies going beyond a macroscopic description of the interface have gained substantially from the use of spectroscopic in situ methods (R. Holze: Surface and Interface Analy¬sis: An Electrochemists Toolbox, Springer-Verlag, Heidelberg, 2009).

Cyclic voltammetry probes energetics and kinetics and thus implicitly structures and their changes as a function of a variety of external variables by measuring the current response to an enforced change of electrode potential (i.e. the drop of electric potential across the interface electron conduct-ing phase (electrode) and ion conducting phase (electrolyte solution)). Because the applied elec-trode potential is cyclic at a constant rate of change between a lower and an upper limit the method is called cyclic voltammetry. This method will be described in sufficient detail enabling an under-standing of results obtained in studies of electrode surfaces covered with SAMs.

Surface enhanced Raman spectroscopy is a surface-specific vibrational spectroscopy which can be applied easily in situ ,i.e. in the presence of an electrolyte solution. The surface enhancement effect provided by microscopic surface roughness (electromagnetic enhancement) and by specific adsor-bate-surface interactions (charge transfer enhancement) provides sufficient scattered light intensity. Results yield information about mode and strength of adsorbate-surface interaction, orientation of adsorbate molecule, interaction between adsorbate and surface as well as solution molecules.