Selective etching of ZnO films on an ITO substrate using a scanning electrochemical microscope

A scanning electrochemical microscope (SECM) combined with an inverse optical microscope has been used in its lithographic mode to fabricate microstructures on a ZnO coated ITO substrate. The UME electrode generated the protons which served as the etchant to dissolve the ZnO film. High resolution microstructuring was achieved with the SECM after the addition of Tris(hydroxymethyl)aminomethane (Tris) to the solution. In the etching solution, Tris was used as an efficient reactant to consume the protons, so that the etchant could not diffuse far from the tip electrode. The cyclic voltammetry technique was employed to determine the appropriate potential, about 1.2 V vs. SCE, for the generation of protons at the tip electrode. The dimensions of the etched microstructures were measured using the optical microscopic images at different stages of the etching process in order to optimize the lithographic conditions. “Point by point” etching with the SECM tip was used to create the logo “FZU” of Fuzhou University on the ZnO film.