Organic compound adsorption on Au(111): Simultaneous SHG/electrochemical studies

Camphor has attracted considerable attention in electrochemical research because it adsorbs strongly on metal surfaces. Due to its surface activity it is able to inhibit surface reactions. Recently, camphor has been used in investigations of nonlinear surface dynamics and pattern formation. Details regarding its influence on the morphology of the metal surface, the significance of surface reconstruction, structural changes in the camphor adlayer and oxide formation remain unclear. We employ second harmonic generation (SHG) to elucidate the structural and electronic behaviour of Au(111) surfaces during camphor adsorption and desorption processes. Our technique allows measurement of the anisotropy of the SHG intensity while simultaneously performing cyclic voltammetry (CV) using the hanging meniscus configuration. The anisotropy data can be refined, yielding the symmetry components of the second order susceptibility tensor chi((2)), which are analysed as a function of external potential and related to the system's electrochemical behaviour. Results of SHG measurements are presented together with corresponding CV data and discussed with respect to the open questions mentioned above.