In electrochemical systems one can induce phase transitions of the surface system by shifting the electrochemical potential. If the potential pulse is directly applied to the tip of an electrochemical STM, such phase transitions can be driven very fast. Since the distance between the tip and the surface is very small, the electrodes' double layers charge within a few nanoseconds.
We were able to dissolve up to about one half of a monolayer of Au from the topmost layer of a Au(111) surface, immersed into a KCl electrolyte within less than a microsecond. The ordering of the surface could be in situ followed by STM after the phase change. Since the change of the surface state occurred very fast, nucleation and growth of islands could be avoided and labyrinthine surface patterns, characteristic for spinodal decomposition of an unstable two-phase system are observed. Progressing ordering and self similar growth towards a stable island morphology occurred on a time scale of several minutes, following the initial spinodal decay .
Currently we are using electrochemical microcalorimetry (See more; verlinkt mit Thermodynamics and kinetics…) in combination with time resolved surface plasmon resonance spectroscopy in order to follow the nucleation and growth of Cu upon electrochemical deposition on Au. First results indicate that the heat released upon nucleation of Cu islands can be directly detected by calorimetry.
The excitation of surface plasmons, i.e., plasma vibrations at a surface, is particularly sensitive towards the properties of the interface between metal electrode and electrolyte . Minute changes of the dielectric properties, e.g., by formation of a submonolayer of Cu can be detected. We record the plasma signal with a time resolution below 1 ms in order to obtain information on the progress of the deposition reaction.