Crystallography Reports最新文献

The Rietveld quantitative phase analysis of the HfO₂ active layer in the Si-sub./SiO₂/HfO₂/TiN layered structures has been carried out at different annealing temperatures and dopant types. The HfO₂ crystal structure has been additionally examined by transmission electron microscopy. A relationship between the dopant valence and crystalline phases forming in the HfO₂ film has been found. It is shown that the Al doping followed by high-temperature annealing prevents the formation of the tetragonal phase (sp. gr. P42/nmc) in favor of the formation of the polar orthorhombic phase (sp. gr. Pca2₁). The results obtained can be used in the synthesis of HfO₂-based ferroelectric films for non-volatile memory systems.

The surface spin-polarized states in the electronic structure of Pt(111) and graphene/Pt(111) have been studied in detail using angle-resolved photoelectron spectroscopy and density functional theory calculations. The results obtained show the presence of cone-shaped surface states near the Fermi level in the vicinity of the (bar {M}) point of the surface Brillouin zone of platinum for both systems. Theoretical calculations confirm that these states are spin-polarized surface states of Pt(111) single crystal.

The results of an experimental study of the real structure of thin films of κ-phase gallium oxide are reported. It has been established by electron backscattering diffraction in a scanning electron microscope and by transmission electron microscopy that gallium oxide single microcrystals consist of three types of rotating domains of the orthorhombic symmetry, which are rotated relative to each other around the growth axis by an angle of 120°. Single-crystal domains are characterized by a high density of straight antiphase boundaries, which, when intersecting, form a significant fraction of the domain wall structure.

The influence of Si and Be barrier layers on the mixing of thin layers of multilayer X-ray mirrors based on Cr and Sc in a wide temperature range has been studied by X-ray reflectivity, X-ray diffraction, and transmission electron microscopy. Annealing of the Si/[Cr/Sc]₂₀₀ system is found to be a catalyst of the mixing process. Complete mixing of layers occurs in a sample heated at 450°C for 1 h. The structure becomes textured with a preferred orientation [001] of the Sc layer perpendicular to the substrate. Introduction of a Be barrier layer into the Si/[Cr/Sc]₂₀₀ system limits mixing of chromium and scandium layers during annealing to 350°C, but the structure degrades completely at 450°C. A beryllium barrier layer excludes texturing and growth of grains in the system, but it does not impede crystallization. The thin Si interlayer inserted between Cr and Sc layers limits their mixing and retains the multilayer character and amorphicity of the system at temperatures up to 450°C.

The effects of physiological and pathogenic factors on the crystal structure of calcium hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ in mineralized bone tissues are considered. The unit cell constants of bioapatite, the unit cell deformation, and the crystallite sizes in different groups of bone tissues were analyzed based on the results of X-ray diffraction studies. The main mechanisms responsible for spatial-temporal changes in bone nanostructures were revealed. It was demonstrated that, along with violations of the stoichiometry, an important role is played by the crystallite sizes, estimated as the coherent scattering regions, the number of atoms in which differs by more than two orders of magnitude, and electrostatic interactions between the unbalanced charges of nanocrystallites and hydrated nanolayers of the mineral matrix.

The change in the intensity of cathodoluminescence of hexagonal boron nitride in the short-wavelength spectral region upon electron beam excitation is investigated. It is shown that the intensity of the peak at a wavelength of 215 nm, associated with the band-to-band transitions, decreases during electron excitation and tends to a stationary value, whereas the intensity of the peak at 320 nm increases under electron irradiation. This band is likely caused by the formation of luminescence centers under electron irradiation.

The adsorption and dissociation of molecular oxygen on the surface of N-graphene/Au/Ni(111) epitaxial system with high crystalline quality of N-graphene have been investigated. The system is formed in such a way that nitrogen impurities in it are exclusively represented by graphitic and pyridinic configurations in equal concentrations. Using X-ray photoelectron spectroscopy and density functional theory calculations, the relationship between the chemical shift of the N 1s core level caused by the adsorption of molecular oxygen and the atomic position of individual oxygen atoms after molecular dissociation has been established.

The electronic structure of the [Cu(Salen)] complex was studied and the chemical state of its atoms was characterized by X-ray and ultraviolet photoelectron spectroscopy combined with density functional theory calculations. It was found that the presence of a complexing Cu atom leads to the electron density redistribution not only on the nitrogen and oxygen atoms involved in the CuO₂N₂ coordination center but also on the carbon atoms of the salen ligand. The valence orbitals of the atoms of the CuO₂N₂ coordination center were found to make the predominant contribution to the highest occupied molecular orbital, and the 3d atomic orbitals of Cu were shown to be distributed over molecular orbitals in the binding energy ranges of 2–4 and 6–11 eV.

MnBi₂Te₄, Mn(Bi,Sb)₂Te₄, and MnBi₂Te₄(Bi₂Te₃)_m (m ≥ 1) are assigned to magnetic topological insulators. Successful application of these materials in nanoelectronic devices calls for comprehensive investigation of their electronic structure and magnetic properties in dependence of the Bi/Sb atomic ratio and the number m of Bi₂Te₃ blocks. The magnetic properties of the surface of MnBi₂Te₄, MnBi₄Te₇, and Mn(Bi(_{{1-x}})Sb_x)₂Te₄ compounds (x = 0.43 and 0.32) have been studied using the magneto-optical Kerr effect. It is shown that the temperatures of magnetic transitions on the surface and in the bulk of MnBi₄Te₇ and Mn(Bi, Sb)₂Te₄ differ significantly.