Large-area regular anodized alumina channel array fabrication assisted by nanoimprint lithography

Abstract

Porous anodic aluminium oxide (AAO) is a common template material for the preparation of nanoscale features. Highly regular pore arrays can be fabricated under specific conditions, but generally the range of regular pore alignment is only a few micrometers. Attempts have been made to improve the size of such domains of regular pore arrangements, in order to widen the application of the AAO templates. In this project, the conventional two-step anodization process was studied with an in-house setup. Anodization parameters were investigated to understand how they affect the pore growth process in both Al foils and Al thin films. Moreover, soft ultraviolet nanoimprint lithography was used to pattern Al sample surfaces, and the patterns were transferred into Al by physical etching. Subsequently, anodization was carried out. Patterns of triangular and square arrangements were used to demonstrate that both patterns can be used for guiding the growth of pores. Different dimensions of patterns were also used. With a matching anodization voltage, which is the voltage expected to form pores with a similar interpore distance as the patterned array lattice, pores grew at pre-defined locations. On the other hand, when pattern dimensions were larger than the interpore distance formed under the given anodization condition, multiple pores were formed within each imprinted hole, with no pores grown in unetched areas. Applications of the AAO have been demonstrated. Different types of materials have been deposited into the pores by different methods. The surface of AAO can also act as a substrate for surface-enhanced Raman scattering.