Structural Determination of Epitaxial Formations in Layered Cuprates

The fragment approximation is used for the description of the layered cuprate structures. The characteristic structural features are distinguished which genetically relate all the layered cuprates. The classification scheme for the whole family of layered cuprates is analyzed in the fragment approximation and a possible extension of the scheme is discussed

Epitaxial Intergrowth of Isostructural Phases in Bi-2212 Single Crystals

The isostructural phases in Bi-2212-type HTSC were studied by structural and optical methods. The epitaxial intergrowth was shown to be a feature typical of single crystals composed of several isostructural phases. The physical properties of the multi-phase samples were interpreted on the basis of reference mono-phase samples. A presence of the intergrowth interface was assumed to be responsible for particular features in multi-phase samples

OPTICAL SPECTRA OF THE A2B2C52TYPE SEMICONDUCTORS

Les spectres d'absorption et les spectres dérivés obtenus par la méthode de modulation de longueur d'onde ont été étudiés au voisinage du bord d'absorption fondamentale de composés ternaires A2B2C52 à gap pseudo-direct. Les spectres de réflexion de quelques composés A2B2C52 à gap direct ont été mesurés dans la région de 1 à 12 eV et exploités par analyse de Kramers-Kronig.The wavelength modulated and conventional absorption spectra of pseudodirect bandgap A2B2C52 compounds have been investigated in the region of the absorption edge. The reflectance spectra of some direct bandgap A2B2C52 semiconductors have been measured in the range 1 to 12 eV and the Kramers-Kronig analysis has been performed

Electrochemical Formation and Microstructure of Porous Gallium Phosphide

Electrochemical formation and microstructure of porous GaP have been investigated. Nanostructured porous GaP layers of thickness up to ≈ 20 μm were fabricated on n-type (111)-oriented crystalline c-GaP substrates. Studies of microstructure of porous GaP in dependence on electrolyte type and regimes of technological procedure have been carried out by scanning electron microscopy. The samples were characterized by spectroscopic ellipsometry in visible and near UV spectral range. The investigations have shown that the structure and optical response of porous GaP can be efficiently controlled by technological procedure of electrochemical formation. The shape and dimension of pores can be varied from nanometer-scaled cylindrical pores to GaP nanorods

Spectral ellipsometry of La1-xMnO3 films with different degree of epitaxy

The dependence of the optical spectra of La1-xMnO3 films on the degree of epitaxy was investigated. Films of La1-xMnO3-δ (x ≈ 0.1) were grown by metal organic chernical vapor deposition on SrTiO3 and Al2O3 (r-plane cut) substrates. The films are supposed to possess a different degree of epitaxy because of various matching conditions between substrate and film lattices. The optical spectra were obtained in the range 0.5-5.0 eV by spectroscopic ellipsometry technique making use of photometric ellipsometer. Fine structure in the spectra of pseudodielectric function is discussed taking into account the excitations of Drude-type free electrons along with the charge-transfer 2 p(O) → 3d(Mn) and dipole-forbidden d-d(Mn3+) transitions. In this model the difference in the spectra of two type samples with different degree of epitaxy was considered

Spectroscopic Ellipsometry of Porphyrin Adsorbed in Porous Silicon

Aqueous solution of meso-tetra(4-sulfonatophenyl)porphine was deposited on electrochemically etched n-Si wafers. The morphology of the hybrid systems was investigated by scanning electron microscope and atomic force microscope techniques. The optical response of the hybrid systems was studied by spectroscopic ellipsometry in the range of 1-5 eV. Particular features in adsorption process were revealed for meso-tetra(4-sulfonatophenyl)porphine deposited on variously chemically treated Si substrates. It was found that porphyrin J-aggregates can be intercalated into large pores formed in a bulk n-Si as well as into nanopores of luminescent oxide layer