Porous silicon (por-Si) is a complex multiphase material, the composition and functional properties of which greatly depend on the features of its formation. In this work, samples of porous silicon with porosity indices from 5 to 80% are obtained by electrochemical etching and their photoluminescence properties are studied. The porosity of the samples is varied by changing the current density of electrochemical anodization during the etching process. The porosity index is calculated according to the X-ray reflectometry method. The aim of our work is to establish correlations between the porosity index, composition, intensity, and mechanism of porous-silicon photoluminescence. The surface composition is controlled by ultrasoft X-ray spectroscopy and infrared spectroscopy. An increase in the degree of oxidation of the surface of the samples with an increase in the porosity index is shown. Two well-known mechanisms of porous silicon photoluminescence associated with the composition and morphology of the surface are found, and it is established at which porosity values they prevail. It is shown that an increase in the porosity index leads to an increase in the intensity of photoluminescence.

Nanocrystalline bismuth ferrite was synthesized using spray pyrolysis and citrate combustion methods. BiFeO3 samples were characterized by X-ray diffraction, infrared spectroscopy, scanning and transmission electron microscopy, and energy dispersive X-ray spectroscopy. The citrate and spray pyrolysis samples of bismuth ferrite were tested as catalysts for the Fenton-like oxidative degradation of methyl orange. The effect of the synthesis method on the composition and morphology of bismuth ferrite particles and on the catalytic activity was established. The oxidative degradation of the dye in the presence of bismuth ferrite samples is satisfactorily described by pseudo-first order kinetics. The reaction rate constant for BiFeO3 synthesized by spray pyrolysis is 0.0072 min–1, while that for citrate BiFeO3 is slightly lower: 0.0049 min–1. The degree of degradation of methyl orange in 120 min is 7

Porous silicon samples with a porosity index of 5% to 80% were obtained in the work by electrochemical etching and their photoluminescence properties were studied as well, Porosity index was calculated according to the data of X-ray reflectometry technique.Composition of the surface was controlled by ultra-soft X-ray spectroscopy and infrared (IR) spectroscopy. Degree of the sample surface oxidation was shown to be increased with the enhancement of porosity enhancement. Two known mechanisms of photoluminescence in porous silicon were detected related with a composition and morphology of its surface. It was found the values of porosity index specifying the dominations of these mechanisms. An increase of porosity index was shown to result in the enhancement of photoluminescence.

— The thermal oxidation of InP in the presence of both a MnO 2 chemical stimulator layer produced on its surface by magnetron sputtering and a Mn 3 (PO 4 ) 2 modifier introduced through the gas phase leads to the formation of dielectric nanofilms. According to laser and spectral ellipsometry data, the proposed approach to InP surface modification makes it possible to considerably speed up film growth (by up to 150–200%) compared to stimulator-free oxidation of the semiconductor. The effective modifying impact of Mn 3 (PO 4 ) 2 has been demonstrated by ultrasoft X-ray emission spectroscopy (UXRES), which has confirmed the formation of tetrahedral oxygen coordination of phosphorus essentially throughout across the synthesized films. The UXRES results have been shown to correlate with IR spectroscopy data, which demonstrate the presence of indium and manganese phosphates and polyphosphates in the films: In(PO 3 ) 3 , InPO 4 , and Mn 3 (PO 4 ) 2 .

Using X-ray phase analysis, scanning electron microscopy atomic force and magnetic force microscopy, and IR spectroscopy the properties of polycrystalline TiO2 films modified by cobalt during magnetron sputtering and subsequent pulsed photon processing in air have been investigated. It has been found that in the course of the modification, a nanocrystalline (with a grain size of ~ 50 nm) film consisting of cobalt and titanium oxides is formed. Their surface exhibits magnetic properties. In the IR reflection spectra obtained at different incident angle of beam, two of the transverse optical (TO) phonons and their corresponding longitudinal (LO) phonons above 500–600 cm–1 were observed, which identify the formation of Co3O4 in the spinel structure. The study of optical absorption indicates the predominant existence in the films of phases with direct optical transitions. The optical band gap value was 1.43 and 1. 83 eV for Co3O4 and 2.65 eV for the cubic phase of CoO.

AbstractIntegrated heterostructures exhibiting a nanocolumnar morphology of the In_ x Ga_1 –_ x N film are grown on a single-crystal silicon substrate ( c -Si(111)) and a substrate with a nanoporous buffer sublayer ( por -Si) by molecular-beam epitaxy with the plasma activation of nitrogen. Using a complex of spectroscopic methods of analysis, it is shown that the growth of In_ x Ga_1 –_ x N nanocolumns on the por -Si buffer layer offer a number of advantages over growth on the c -Si substrate. Raman and ultraviolet spectroscopy data support the inference about the growth of a nanocolumn structure and agree with the previously obtained X-ray diffraction (XRD) data indicative of the strained, unrelaxed state of the In_ x Ga_1 –_ x N layer. The growth of In_ x Ga_1 –_ x N nanocolumns on the por -Si layer positively influences the optical properties of the heterostructures. At the same half-width of the emission line in the photoluminescence spectrum, the emission intensity for the heterostructure sample grown on the por -Si buffer layer is ~25% higher than the emission intensity for the film grown on the c -Si substrate.

Properties of polycrystalline TiO 2 films modified by magnetron sputtering of cobalt followed by pulsed photon-irradiation processing in air are investigated by methods of X-ray phase analysis, raster electron microscopy, atomic force microscopy, magnetic force microscopy, and IR spectroscopy. Formation of a nanocrystalline (with a grain size of ~50 nm) film consisting of cobalt and titanium oxides the surface of which exhibits magnetic properties is established in the process of modification. The IR reflectance spectra obtained at different angles of incidence in the region between 500 and 600 cm –1 reveal the presence of two bands belonging to transverse modes (TO) and two corresponding bands belonging to the longitudinal modes (LO). These bands are indicative of formation of Co 3 О 4 with spinel structure. Investigation of optical absorption suggests a predominant existence of phases characterized by direct interband transitions with energies of 1.43 and 1.83 eV for Co 3 O 4 , along with a transition with energy of 2.65 eV for cubic phase of CoO, in the films.

Integrated heterostructures exhibiting a nanocolumnar morphology of the InxGa1 –xN film are grown on a single-crystal silicon substrate (c-Si(111)) and a substrate with a nanoporous buffer sublayer (por-Si) by molecular-beam epitaxy with the plasma activation of nitrogen. Using a complex of spectroscopic methods of analysis, it is shown that the growth of InxGa1 –xN nanocolumns on the por-Si buffer layer offer a number of advantages over growth on the c-Si substrate. Raman and ultraviolet spectroscopy data support the inference about the growth of a nanocolumn structure and agree with the previously obtained X-ray diffraction (XRD) data indicative of the strained, unrelaxed state of the InxGa1 –xN layer. The growth of InxGa1 –xN nanocolumns on the por-Si layer positively influences the optical properties of the heterostructures. At the same half-width of the emission line in the photoluminescence spectrum, the emission intensity for the heterostructure sample grown on the por-Si buffer layer is ~25% higher than the emission intensity for the film grown on the c-Si substrate.

Biomimetic materials (biocomposites) with an organic-mineral composition related to natural dental tissues (enamel and dentin) are obtained for the first time and their structural and optical characteristics are studied. It is demonstrated by a complex of structural and spectroscopic methods that in the formation of biocomposites, the introduced organic component, bearing a number of amino acids, does not affect the structure of the inorganic component (carbonate-substituted calcium hydroxyapatite) of the sample. The carbonate-substituted calcium hydroxyapatite synthesized using a biogenic source of calcium, which forms the basis of the biocomposite, has a luminescence spectrum similar to that of apatite tooth enamel. The spectrum of the intact dentin of a human tooth has a broader luminescence band than that for the enamel spectrum. It is determined that both organic and inorganic components contribute to the dentin luminescence band. The features found in the luminescence spectra of intact tissues and in simulating biocomposites can be used to develop a procedure for effective early diagnosis of the demineralization of hard dental tissues and general dental examination.

AbstractIt is shown for the first time that the structural and optical functional characteristics of integrated GaAs/Si(100) heterostructures can be controlled by using misoriented Si(100) substrates and their preliminary etching. The growth of an epitaxial GaAs layer on a Si substrate without the formation of antiphase domains can be carried out on a substrate deviated from the (100) singular plane by an angle smaller than 4°–6° or without a transition layer of GaAs nanocolumns. Preliminary treatment of the silicon substrate by etching makes it possible to use it for the vapor-phase epitaxial growth of a single-crystal GaAs film with a considerably smaller relaxation coefficient, which has a positive effect on the structural quality of the film. These data are in good agreement with the results of IR reflectance spectroscopy and photoluminescence and ultraviolet spectroscopy. The features of the optical properties of integrated GaAs/Si(100) heterostructures in the infrared and ultraviolet spectral regions are also defined by the relaxation coefficient.

AbstractThe properties of porous GaAs samples produced by the electrochemical etching of single-crystal n -GaAs(100) wafers are studied by X-ray diffraction analysis, electron microscopy, and infrared and ultraviolet spectroscopy. It is possible to show that, by choosing the composition of the electrolyte and the conditions of etching, samples can be produced not only with different degrees of porosity and pore sizes (nanopores/micropores), but with another type of sample surface as well. The etching of n -GaAs(100) wafers under the conditions chosen in the study does not change the orientation of the porous layer with respect to the orientation of the single-crystal GaAs(100) substrate. At the same time, etching induces a decrease in the half-width of the diffraction peak compared to that for the initial wafer, a splitting of the phonon mode in the infrared spectra and a partial shift of the components in accordance with the parameters of anodic etching, and a change in the optical properties in the ultraviolet region.

This paper presents an IR spectroscopic study of chemical bonds between components of amorphous [(CoFeB)(60)C-40/SiO2](200) and [(CoFeB)(34)(SiO2)(66)/C](46) multilayer nanostructures (MNS's) made up of metal-containing composite layers and different interlayers, which influence their electromagnetic properties. Our results demonstrate that, even though the MNS's have identical elemental compositions, their IR spectra differ significantly. The reason for this is that the main contribution to the IR spectrum of the [(CoFeB)(60)C-40/SiO2](200) MNS is made by its SiO2 interlayers. The formation of other bonds with oxygen and silicon is blocked by the carbon present in the (CoFeB)(60)C-40 composite layers, as evidenced by the presence of the strongest mode in the IR spectra of this structure, which corresponds to boron carbide, BC. The considerable intensity redistribution to the low-frequency region in the IR spectrum of the [(CoFeB)(34)(SiO2)(66)/C](46) MNS, containing carbon interlayers, is due to the incorporation of nominal SiO2 into the metal-containing composite layers and the partial redistribution of oxygen bonds from the SiO2 to the 3d transition metals, resulting in the formation of metal oxides and a silicon suboxide. The interaction of the carbon present in the interlayers between the composite layers with elements of the composite layers, in particular with boron, is considerably weaker in comparison with the other MNS, [(CoFeB)(60)C-40/SiO2](200), which has oxide interlayers.

The properties of porous GaAs samples produced by the electrochemical etching of single-crystal n-GaAs(100) wafers are studied by X-ray diffraction analysis, electron microscopy, and infrared and ultraviolet spectroscopy. It is possible to show that, by choosing the composition of the electrolyte and the conditions of etching, samples can be produced not only with different degrees of porosity and pore sizes (nanopores/micropores), but with another type of sample surface as well. The etching of n-GaAs(100) wafers under the conditions chosen in the study does not change the orientation of the porous layer with respect to the orientation of the single-crystal GaAs(100) substrate. At the same time, etching induces a decrease in the half-width of the diffraction peak compared to that for the initial wafer, a splitting of the phonon mode in the infrared spectra and a partial shift of the components in accordance with the parameters of anodic etching, and a change in the optical properties in the ultraviolet region.

It is shown for the first time that the structural and optical functional characteristics of integrated GaAs/Si(100) heterostructures can be controlled by using misoriented Si(100) substrates and their preliminary etching. The growth of an epitaxial GaAs layer on a Si substrate without the formation of antiphase domains can be carried out on a substrate deviated from the (100) singular plane by an angle smaller than 4°–6° or without a transition layer of GaAs nanocolumns. Preliminary treatment of the silicon substrate by etching makes it possible to use it for the vapor-phase epitaxial growth of a single-crystal GaAs film with a considerably smaller relaxation coefficient, which has a positive effect on the structural quality of the film. These data are in good agreement with the results of IR reflectance spectroscopy and photoluminescence and ultraviolet spectroscopy. The features of the optical properties of integrated GaAs/Si(100) heterostructures in the infrared and ultraviolet spectral regions are also defined by the relaxation coefficient.

This paper presents the results from a study of the microstructure of the surface of lead sulfide films deposited via the pyrolysis of aqueous [Pb(N2H4CS)(2)(CH3COO)(2)] aerosols. The influences of temperature and the concentration of thiourea on the synthesized films' surface topography were investigated. A change in the type of conductivity with increasing temperature was observed.

The properties of epitaxial Ga x In1 – x P alloys with an ordered arrangement of atoms in the crystal lattice are studied by a number of spectroscopic methods. The alloys are grown by metal-organic chemical vapor deposition onto single-crystal GaAs(100) substrates. It is shown that, under conditions of the coherent growth of an ordered Ga x In1 – x P alloy on a GaAs(100) substrate, atomic ordering results in radical modifications of the optical properties of the semiconductor compared to the properties of disordered alloys. Among these modifications are a decrease in the band gap and an increase in the luminescence intensity. From the data of dispersion analysis of the infrared dispersion spectra and from ultraviolet spectroscopy data obtained in the transmittance–reflection mode of measurements, the basic optical characteristics, specifically, the dispersion of the refractive index and the high-frequency permittivity of Ga x In1 – x P alloys with ordering are determined. All of the experimental data are in good agreement with the developed theoretical concepts.

A range of structural and spectroscopic techniques were used for the study of the properties of epitaxial GaxIn1-xP alloys with an ordered arrangement of atoms in a crystal lattice grown by MOCVD on single-crystalline substrates of GaAs (100). The appearance of atomic ordering in the coherent growth conditions of the ordered GaxIn1-xP alloy on GaAs (100) resulted in cardinal changes of the structural and optical properties of semiconductor in comparison to disordered alloys, including the change of the crystal lattice parameter and, consequently, reduced crystal symmetry, decreased band gap and formation of two different types of surface nanorelief.This is the first report of the calculation of parameters of the crystal lattice in GaxIn1-xP with ordering taking into account the elastic stresses dependent on long-range ordering. Based on the variance analysis data with regard to the IR-reflection spectra as well as the UV-spectroscopy data obtained in the transmission-reflection mode, the main optical characteristics of the ordered GaxIn1-xP alloys were determined for the first time, namely, refractive index dispersion and high-frequency dielectric constant. All of the experimental results were in good agreement with the previously developed theoretical beliefs.