A scanning electrochemical microscopy procedure for micropatterning Al2O3-thin films deposited on a platinum substrate

A scanning electrochemical microscopy (SECM) procedure for patterning alumina thin films deposited onto a platinum film (Pt/Al2O3) was investigated. The alumina surface was locally etched by hydroxide ions, which were generated at platinum microelectrodes, by exploiting the hydrogen evolution process in aqueous solutions. The local base-induced dissolution of Al2O3 to soluble AlO2− species allowed the exposure of the underlying platinum, which resulted in well-defined conducting spots embedded within an insulating matrix. Reproducibility of the spots was achieved by adding to the electrolyte solutions amounts of EDTA, which acted as a scavenger for OH− ions, while allowed the complexation of the aluminium ions formed at the sample surface during the wet etching process. The effects of electrolysis time, tip to substrate distance and overall tip dimension on the shape and size of the conducting spots were investigated in detail. Furthermore, the possibility to create complex patterns with the optimised etching procedure was also shown.

► Alumina thin films can be locally etched by SECM.
► Base-induced dissolution processes can be used for patterning purposes by SECM.
► EDTA allows focusing locally produced OH− ions for generation of reproducible patterns.
► Alumina-coated platinum film can be patterned to arrays of microdisk electrodes.