Crystallography-Induced Correlations in Pore Ordering of Anodic Alumina Films

Abstract

A crystallographic approach to tailoring the morphology and ordering degree of the porous structure of alumina films obtained by anodization of single-crystalline aluminum is discussed. The examination of porous structure of anodic alumina films formed on low-index and vicinal planes of Al single crystals under self-ordering conditions by high-resolution small-angle Xray scattering revealed the existence of two pore growth directions on vicinal facets. The inclination of channels from the normal to the metal surface is explained by the competitive impact of electromigration driving force and the crystallographic anisotropy of the substrate. It was also shown that pores growing in different directions during anodization retain hexagonal domains with various in-plane orientations. These results for the first time demonstrate the strong correlations between the longitudinal alignment and in-plane packing options of pores in anodic alumina films.

Investigation of porous anodic alumina templates formed by anodization of single-crystal aluminum substrates

“…Therefore, we can establish that for PAA layers fabricated within the potential range 30-50 V, the resulting structures are the most regular for aluminum substrates with (100) crystal orientations, followed by aluminum substrate with (111) orientation and subsequently by (110) crystal orientation. Such results are in perfect agreement with previous works which verified that pore ordering depends on the crystallographic orientation of the aluminum substrates [31,32,45]. In particular, Beck and Bretzler have shown that for aluminum anodized in sulfuric acid solution at a potential of 25 V, also follows the subsequent rank of ordering quality as a function of the single crystal orientation (100) > (111) > (110).…”

“…In order to get a better understanding of the pore's formation and the regularity of the pores that can be obtained, previous studies have focused on the influence of the aluminum substrate over the porous structure of the as-fabricated PAA templates [29 , 30]. In particular, studies regarding the influence of the aluminum substrate's crystal orientation have been realized [31][32][33][34], but these studies were mainly devoted to the investigation of the single crystal aluminum orientation's impact upon the periodicity of the pores without considering their morphological characteristics.…”

A novel methodology to study nanoporous alumina by small-angle neutron scattering

“…Combining these direct imaging methods with scattering techniques can overcome these issues by giving access to averaged structural information over a larger volume (Gommes et al, 2016) and can also provide information about the pore orientation in both transverse and longitudinal directions. X-rays (via scattering or diffraction) have been mainly used to characterize the pore arrangement and longrange ordering (Dore et al, 2002;Engel et al, 2009;Napolskii et al, 2010;Waheed et al, 2011;Roslyakov et al, 2013Roslyakov et al, , 2016 by tilting the sample along the vertical or horizontal axis normal to the beam. In particular, the different longitudinal pore orientations can be extracted (Roslyakov et al, 2013), and a strong correlation between transverse and longitudinal pore ordering has been observed (Roslyakov et al, 2016).…”

Fabrication of a P3HT-ZnO Nanowires Gas Sensor Detecting Ammonia Gas

“…The AAO template is a self-assembled nanoporous film in which the pore size and the distribution are influenced by the working voltage, electrolyte compositions, and other parameters [ 18 , 19 , 20 , 21 ]. In the present work, the AAO template was produced on the ITO glass in 0.3 M oxalic acid solution at 40 V. Figure 4 a showed the surface morphology of the AAO template after a pore widening process using 5% phosphoric acid solution.…”