Comparative study of anodization of small-scale and wafer-scale aluminum films on a silicon substrate and controlling pores shape for practical applications

Abstract

• Anodization of small and wafer scales of pure Al and impure Al films were compared. • Suitable anodizing current density was determined to avoid the PAA burns. • Effect of starting Al thicknesses on the electrochemical response was discussed. • Anodizing strategy was proposed to form multibranched pores from a single pore with smaller pore sizes. • Anodization of annealed Al film could be used to form ordered arrays of alumina nanodots. Porous anodic alumina (PAA), comprising arranged pores in hexagonal cells obtained by anodizing aluminum (Al), has been studied and is usually used as a template for synthesizing one-dimensional nanostructure. However, there is growing interest in more effective applications with tunable pores and more complex structures with reasonable cost. For example, the branching and interconnected pores are obtained in multiple bifurcations under certain anodizing conditions. From manufacturing perspectives, large-area anodization on special substrates, such as Si, is extremely significant and required. Herein, we present a robust analysis of the different types of branched and modulated pores in the PAA templates; the newly developed methodology and the morphological evolution of each type are discussed. The proposed anodizing strategies help reduce anodizing time and result in smaller pore sizes than those obtained by the traditional methods. Therefore, they be effectively implemented for separation science technology. Furthermore, the work was extended to anodize a full Al wafer (200 mm in diameter) on a Si wafer without lithography or pretemplating. Additionally, the required anodizing conditions to prevent PAA from burning were followed. The opportunities for this PAA template to serve as generic templates for potential applications will be explored and discussed. The anodization of annealed Al/SiO 2 films can be used to create highly hexagonal ordered arrays of alumina nanodots between alumina and SiO 2 substrate, which were observed when the anodized sample was cleaved. Therefore, the obtained results could help, from manufacturing perspectives, modulate pores and a large area of the PAA on special substrates, such as Si, for many technological applications.