Formation of aluminum nanodot array by combination of nanoindentation and anodic oxidation of aluminum

Porous alumina films formed by aluminum anodic oxidation have been intensively studied to use them as molds to form nanowires or dots. Recently we established the formation of porous alumina on solid substrates such as Si, and found a formation of an ordered aluminum hexagonal dot array after finishing of anodic oxidation on a SiO2 substrate. We investigated AFM nanoindentation to control the initial position of nanoholes during anodic oxidation, in order to realize nanoholes and dots with various sizes and densities. Arrays of nanoholes with a nearest neighbor distance from 50 to 120 nm were successfully formed. Al dot tetragonal and hexagonal arrays were formed after selective wet chemical etching of porous alumina film. Electron transport through Al nanodots array at low temperature exhibited a non-linear characteristic with a suppression of current around zero bias, which strongly suggests existence of Coulomb blockade.