B. A. Obidov

Dependence of the atomic structure and surface relief of platinum foils on the annealing and rolling conditions

The effect of cold rolling, polishing, and thermal annealing conditions on the atomic structure and surface geometry of platinum foils has been studied. The surface morphology has been analyzed using low-energy electron diffraction, atomic force microscopy, and scanning tunneling microscopy. The chemical composition of the surface has been evaluated by Auger electron spectroscopy. It has been demonstrated that a variation in the conditions used for the preparation of the samples makes it possible to produce surfaces with different degrees of perfection from atomically smooth to rippled, fractal, and diffraction-disordered surfaces.

Manifestation of flat and rippled surface reliefs of platinum foils in LEED patterns

The atomic structure and surface relief of a polycrystalline platinum foil upon rolling and subsequent recrystallization in ultrahigh vacuum have been studied by low energy electron diffraction (LEED) and atomic force microscopy (AFM). The symmetry of LEED patterns shows that the surface structure of recrystallized platinum foil corresponds to (111) face, but different shapes of diffraction maxima are indicative of a diversity of the geometric relief. AFM data reveal various types of the surface relief, including flat, rippled in one direction, and differently oriented, which are considered in comparison to the corresponding LEED patterns. Using the established laws, it is possible to trace the formation of various reliefs by diffraction techniques without using probe methods.

Formation of different surface reliefs of metallic glasses under mechanical stress

The micro- and nanoreliefs of loaded lateral surfaces and fracture surfaces of foils of the Fe77Ni1Si9B13, Fe58Ni20Si9B13, and Fe70Cr15B15 amorphous alloys have been investigated using scanning tunneling and atomic force microscopy. The isotropic and anisotropic surface reliefs have been examined. The fractal dimensions of the surfaces of loaded specimens and the fracture surfaces along and across the direction of crack propagation have been estimated using the box counting method. Fractal characteristics of the surfaces, such as the Hölder exponent and the half-width of the singularity spectrum, have been calculated using the wavelet transform method. It has been found that, on the topographies with a clearly pronounced anisotropy of the relief, the surface is fractal in only one direction, and the surface is fractal in two directions on the topographies with a less pronounced anisotropy of the relief. The fractal characteristics of the lateral surfaces and the fracture surfaces with allowance made for their anisotropy have close values. It has been shown that the formation of two types of fracture surfaces is adequately described in terms of the model of a cellular automaton.

Effect of uniaxial tension and hydrostatic compression on the geometry and morphology of amorphous Fe77Ni1Si9B13 alloy ribbon surface

The effect of hydrostatic pressure and uniaxial compression on the relief of an amorphous Fe77Ni1Si9B13 alloy ribbon surface was studied using scanning tunneling and atomic-force microscopy. The fracture surfaces of samples were also studied. It is found that both the initial surfaces and the surfaces of samples subjected to hydrostatic compression or tension, as well as fracture surfaces, are fractal or multifractal, but their fractality parameters are different. Hydrostatic pressure decreases the surface roughness and the average fractal dimension of the surface on both sides of the ribbons. The dependence of the surface fractal characteristics on tension is more complex. Prior to the occurrence of a “critical event” on the surface (formation of a deformation band or a through crack), the Hölder index and the half-width of the singularity spectrum decrease. The correlation is discussed between the fractal characteristics of the ribbon surface and those of a fracture surface, and the role of an excess free volume in the initiation of fracture of amorphous alloys is analyzed.

Fractalization of the surface relief of an amorphous alloy as an indication of rupture

Foils of an Fe77Ni1Si9B13 amorphous alloy were subjected to uniaxial tension up to their rupture. Techniques of scanning tunneling, atomic force, electron, and optical microscopy were applied to study the surface relief of loaded foils and their rupture faces. By means of wavelet transformation and by the box counting method, it was shown that, before rupture, the foil surfaces in the region of the future rupture tend to become monofractal and that the rupture face inherits this fractality.

The possibility of using platinum foils with a rippled surface as diffraction gratings

The atomic structure and surface relief of thin cold-rolled platinum foils upon recrystallization annealing and loading under ultrahigh vacuum conditions have been studied by low energy electron diffraction (LEED), atomic force microscopy (AFM), and scanning tunneling microscopy (STM). The surface of samples upon high-temperature annealing and subsequent uniaxial extension of recrystallized Pt foils represents a fractal structure of unidirectional ripples on various spatial scales. The total fractal dimension of this surface is DGW = 2.3, while the fractal dimensions along and across ripples are D‖ ≈ 1 and D⊥ ≈ 1.3, respectively. The optical spectra of a halogen lamp and a PRK-2 mercury lamp were recorded using these rippled Pt foils as reflection diffraction gratings. It is shown that Pt foils with this surface relief can be used as reflection diffraction gratings for electromagnetic radiation in a broad spectral range.

Influence of low-temperature annealing on the morphology of the surface layer of an iron-based amorphous alloy

The influence of isothermal annealing on the chemical composition, microstructure, and surface relief of ribbons of an amorphous Fe77NiSi9B13 alloy was studied using Auger electron spectroscopy and transmission electron, atomic-force, and scanning tunneling microscopy. It is established that an annealing below the glass transition temperature results in a boron enrichment of the ribbon surface layer on the side of the ribbon that was not in contact with the roller during quenching. On both sides of a ribbon, islands of crystallized material 2–5 μm in size appear consisting of nano-and microcrystals of α-Fe on the roller-contacting side and of iron boride on the opposite side. The surface relief on the roller-contacting side of a ribbon and that on the opposite side are shown to differ in terms of their spectral and fractal characteristics after annealing. The effect of the chemical composition and excess free volume of the surface layer on the formation of islands of crystallized material and surface relief is discussed.

The effect of uniaxial tension on the relief geometry of the surface of an Fe77Ni1Si9B13 amorphous alloy

The effect of uniaxial tension in a wide range of applied stress (0–3 GPa) on the surface topography of an Fe77Ni1Si9B13 amorphous alloy was studied by scanning tunneling microscopy. It was found that the distributions of the surface defects with respect to lateral and vertical dimensions exhibit a change manifested by an increase in the proportion of large-scale defects and in the fractal dimension of the surface with increasing load. It is suggested that this surface relief is formed by a diffusion mechanism and that the observed effects are involved in the fracture focus nucleation on the sample surface.

Fabrication of rippled surfaces for diffraction gratings by plastic deformation of platinum foils and metallic glasses

Thin platinum foils and metallic glass ribbons with a fractal surface consisting of different-scale unidirectionally oriented ripples have been fabricated using special thermoplastic processing. The general fractal dimension of the rippled surface and dimensions along and across the ripples have been measured. The optical spectra of a PRK-4 lamp using rippled Pt(111) foils as reflective diffraction gratings have been determined. A model describing the mechanism of the formation of surface unidirectional fractal structures during deformation has been proposed.

Modification of the atomic structure and surface relief in recrystallized molybdenum foils tensile strained in ultrahigh vacuum

Changes in the atomic structure and surface morphology of a recrystallized molybdenum foil under the action of uniaxial tension in ultrahigh vacuum have been studied by low -energy electron diffraction (LEED) and atomic-force microscopy (AFM). It is established that uniaxial tension of the foil surface, which consists of separate blocks of dominating (100) face with 1 × 1 structure, leads to a local destruction of this face and the rotation of blocks. AFM topographs of various regions on the surface of fractured samples have been obtained. The variation of the LEED patterns agrees well with the evolution of the surface relief measured by AFM.