Direct formation of self-assembled nanoporous aluminium oxide on SiO2and Si substrates

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Abstract
An unconventional self-assembly process was integrated with traditional silicon microfabrication technologies to directly form hexagonally ordered nanoporous patterns on both SiO2 and Si surfaces. Starting with an aluminium thin film deposited on a SiO2 or Si substrate, an Al anodization process was employed to generate highly uniform nanoporous anodic aluminium oxide thin films with average pore diameters of 30–70 nm directly on SiO2 and Si surfaces. The long-range order of the anodic aluminium oxide nanoporous structures was improved by thermally annealing the starting Al films to promote the grain size growth and by utilizing a multiple anodization process to enhance their uniformity. The formation of the hexagonally ordered nanoporous array may be attributed to the interplay between the topological requirement for space filling of pores and the kinetics of domain growth with time under a constant anodization voltage. These results demonstrate the feasibility of integrating self-assembled anodic aluminium oxide nanostructures with Si microfabrication technologies in the pursuit of future-generation Si nanoelectronic devices.