Anodization of aluminium with a pre-patterned surface is a promising approach for preparing anodic aluminium oxide (AAO) films with defect-free pore arrangement. Although pronounced effects of crystallographic orientation of Al on the AAO structure have been demonstrated, all current studies on the anodization of pre-patterned aluminium consider the substrate as an isotropic medium and, thus, do not consider the azimuthal orientation of the pattern relative to the basis vectors of the Al unit cell. In paper [1], we investigate the interplay between the azimuthal alignment of the pore nuclei array and the crystallographic orientation of aluminium. Al(100) and Al(111) single-crystal substrates were pre-patterned by a Ga focused ion beam and then anodized under self-ordering conditions. The thickness-dependent degree of pore ordering in AAO was quantified using statistical analysis of scanning electron microscopy images. The observed trends demonstrate that the preferred azimuthal orientation of pore nuclei rows coincides with the <110> directions in the Al unit cell, which is favourable for creating AAO with a high degree of pore ordering [2]. In the case of an unspecified azimuthal orientation of the pore nuclei array, crystallography-affected disorder within the AAO structure occurs with increasing film thickness. Our findings have important implications for preparing defect-free porous films over 100 μm in thickness that are crucial for a variety of AAO applications, e.g., creating metamaterials and 2D/3D photonic crystals.
This work was supported by the Russian Science Foundation (Grant No. 19-73-10176).
[1] I.V. Roslyakov, S.V.Sotnichuk, S.E.Kushnir, L.A. Trusov, I.V. Bozhev, K.S. Napolskii, Pore ordering in anodic aluminum oxide: interplay between the pattern of pore nuclei and the crystallographic orientation of aluminum // Nanomaterials 2022, v. 12, 1417. DOI: 10.3390/nano12091417.
[2] K.S. Napolskii, I.V. Roslyakov, A.Yu. Romanchuk, O.O. Kapitanova, A.S. Mankevich, V.A. Lebedev, A.A. Eliseev, Origin of long-range orientational pore ordering in anodic films on aluminum // Journal of Materials Chemistry, 2012, v. 22, pp. 11922-11926. DOI: 10.1039/c2jm31710a.