Characterization of microelectrode arrays by means of electrochemical and surface analysis methods

Microelectrode arrays have been fabricated using silicon thin-film technology. The arrays consist of 100 platinum microelectrodes connected in parallel to a single output line. In addition, a platinum counter electrode as well as a silver/silver chloride pseudo-reference electrode are integrated on the microchip. We present results of surface analysis of the microelectrode arrays by time-of-flight secondary ion mass spectrometry (TOF-SIMS), scanning electron microscopy (SEM) and scanning tunnelling microscopy (STM). The highly surface-sensitive analysis method SIMS reveals traces of Al and Ag impurities on the microelectrode surfaces. SEM micrographs show the embedding of the electrodes into insulating silicon oxide and silicon nitride layers. Furthermore, they reveal an unexpected irregular, corrugated surface structure of the platinum electrodes, which are shown to be built up by small platinum grains. The microelectrode array is electrochemically characterized by means of cyclic and linear sweep voltammetry. The methods applied have successfully been used for the investigation and characterization of the surface structure and the composition of thin-film electrodes.