Three series of anodic alumina membranes have been studied using the small-angle diffraction of neutrons and synchrotron radiation. The samples are obtained by the oxidation of aluminum wafers by sulfuric and oxalic acids at various anodization voltages and differences in the distance between the pores. Using experiments on small-angle diffraction, a linear dependence between the average grain size of an initial aluminum wafer and the average rectilinearity of pores of the synthesized membranes is established. We suggest that the observed correlation is caused by the influence of the crystallographic orientation of grains of an initial aluminum wafer on the growth of a porous oxide film.

© Н.А. Саполетова, Н.А. Мартынова, К.С. Напольский, А.А. Елисеев, А.В. Лукашин, И.В. Колесник, Д.И. Петухов, С.Е. Кушнир, А.В. Васильева, С.В. Григорьев, Н.А. Григорьева, А.А. Мистонов, Д.В. Белов, Ю.Д. Третьяков 1 Московский государственный университет им. М.В. Ломоносова, Москва, Россия 2 Петербургский институт ядерной физики им. Б.П. Константинова РАН, Гатчина, Ленинградская обл., Россия 3 Санкт-Петербургский государственный университет, Санкт-Петербург, Россия 4 Debye Institute, Utrecht University, Utrecht, The Netherlands

The type and degree of imperfection for opal-like photonic crystals on conducting substrates have been investigated using synchrotron small-angle X-ray scattering with a microradian resolution. It has been demonstrated that self-assembly of poly(styrene) spheres by the vertical deposition method leads to the formation of a face-centered cubic structure on a mica/Au substrate and a random hexagonal close packing on a glass substrate with the In2O3(SnO2) conducting coating.

The results of an ultrasmall-angle X-ray scattering study of iron(III) oxide inverse opal thin films are presented. The photonic crystals examined are shown to have fcc structure with amount of stacking faults varying among the samples. The method used in this study makes it possible to easily distinguish between samples with predominantly twinned fcc structure and nearly perfect fcc stacking. The difference observed between samples fabricated under identical conditions is attributed to random layer stacking in the self-assembled colloidal crystals used as templates for fabricating the inverse opals. The present method provides a versatile tool for analyzing photonic crystal structure in studies of inverse opals made of various materials, colloidal crystals, and three-dimensional photonic crystals of other types.

The structural and magnetic properties of nickel inverse opal photonic crystal have been studied by complementary experimental techniques, including scanning electron microscopy, wide-angle and small-angle diffraction of synchrotron radiation, and polarized neutrons. The sample was fabricated by electrochemical deposition of nickel in voids in a colloidal crystal film made of 450 nm polystyrene microspheres followed by their dissolving in toluene. The microradian small-angle diffraction of synchrotron radiation was used to reveal the opal-like large-scale ordering proving its tendency to the face-centered-cubic fcc structure with the lattice constant of 65010 nm. The wide-angle x-ray powder diffraction has shown that nanosize fcc nickel crystallites, which form an inverse opal framework, have some texture prescribed by principal directions in inverse opal on a macroscale, thus showing that the atomic and macroscopic structures are correlated. The polarized small-angle neutron scattering is used on the extreme limit of its ability to detect the transformation of the magnetic structure under applied field. Different contributions to the neutron scattering have been analyzed: the nonmagnetic nuclear one, the pure magnetic one, and the nuclear-magnetic interference. The latter in the diffraction pattern shows the degree of the spatial correlation between the magnetic and nuclear reflecting planes and gives the pattern behavior of the reversal magnetization process for these planes. The field dependence of pure magnetic contribution shows that the three-dimensional geometrical shape of the structure presumably leads to a complex distribution of the magnetization in the sample.