Growth of porous anodized alumina on the sputtered aluminum films with 2D–3D morphology for high specific surface area

• Published in: Applied surface science 2014-08, Vol.309, p.290-294
• Main Authors: Liao, M.W., Chung, C.K.
• Format: Article
• Language: English
• Subjects: AAO; Aluminum; Aluminum oxide; Anodization; Anodizing; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electric power generation; Exact sciences and technology; Microstructure; Morphology; Physics; Porous alumina; Specific surface; Texture; Three dimensional
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.05.033

•Sputtered Al films with varied morphology were prepared for 2D–3D anodization.•The Al film deposited at low sputtering power of 50W reveals flat surface.•High sputtering power of 185W causes a large number of hillocks on film surface.•A 3D nanoporous structure was formed by anodizing an Al film containing hillocks. The porous anodic aluminum oxide (AAO) with high-aspect-ratio pore channels is widely used as a template for fabricating nanowires or other one-dimensional (1D) nanostructures. The high specific surface area of AAO can also be applied to the super capacitor and the supporting substrate for catalysis. The rough surface could be helpful to enhance specific surface area but it generally results in electrical field concentration even to ruin AAO. In this article, the aluminum (Al) films with the varied 2D–3D morphology on Si substrates were prepared using magnetron sputtering at a power of 50W–185W for 1h at a working pressure of 2.5×10−1Pa. Then, AAO was fabricated from the different Al films by means of one-step hybrid pulse anodizing (HPA) between the positive 40V and the negative −2V (1s:1s) for 3min in 0.3M oxalic acid at a room temperature. The microstructure and morphology of Al films were characterized by X-ray diffraction, scanning electron microscope and atomic force microscope, respectively. Some hillocks formed at the high target power could be attributed to the grain texture growth in the normal orientation of Al(111). The 3D porous AAO structure which is different from the conventional 2D planar one has been successfully demonstrated using HPA on the film with greatly rough hillock-surface formed at the highest power of 185W. It offers a potential application of the new 3D AAO to high specific surface area devices.