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We report the results of systematic experimental and theoretical studies of structural and dynamical properties of short-period GaN/AlN superlattices. The multilayer structures with the thicknesses of the constituent layers varying from two to several monolayers are grown using the submonolayer digital molecular beam epitaxy technique. In the framework of density functional theory, the lattice dynamics properties of the superlattices are studied. Good agreement between the experiment and theory is found, which made it possible to establish unambiguously a relationship between the features observed in the Raman spectra and the microscopic nature of the acoustic and optical phonon modes. The results obtained enhance the capabilities of Raman spectroscopy as a fast and non-destructive characterization method of short-period GaN/AlN superlattices and can be used to optimize growth process parameters for the fabrication of structurally perfect low-dimensional heterostructures.

We consider the manufacturing process of forgings for turbine blades of extra-large dimensions (length >2 m) from electroslag remelting steel 15H11MF-Sh. With an increase of the workpiece dimensions (weight >450 kg), we face the problem of choosing the technology for obtaining the original billet. The production technology is known to affect the structure of the material and, as a consequence, the final properties of the product. We present the results of studying the influence of the method of obtaining the original metal blanks (hot-rolled steel bars and forged billets) on the properties of large-sized forgings of turbine blades. The mechanical characteristics, microstructure properties, chemical composition and content of δ -ferrite were determined by examining the initial samples of long products and forged rods. It is shown that billet in the forged state exhibit higher strength characteristics. However, after the stamping process, the properties of the blades equalize, i.e., after stamping and heat treatment, the same structure is formed, regardless of the method of obtaining the original workpiece. The results obtained can be used in the serial production of large-sized turbine blades of a new profile.

Volume and surface photoluminescence of congruent and stoichiometric lithium niobate crystals obtained using various technologies was studied. The luminescence intensity of the stoichiometric crystal was less than that of the congruent one. Volume luminescence of the crystals was mainly caused by NbLi defects while luminescence quenching of the near-surface layer was observed in the long-wavelength spectral region (>500 nm) because of energy scattering in crystal-lattice vibrations and increased luminescence intensity of the $$ {\mathrm{Nb}}_{\mathrm{Nb}}^{4+}-{\mathrm{O}}^{-} $$ pair. Luminescence bands with maxima at 426 and 446 nm were caused by complex defects in the form of electron–hole pairs $$ {\mathrm{Nb}}_{\mathrm{Nb}}^{4+}-{\mathrm{O}}^{-} $$ in which the Nb atom was bound to oxygen atoms by covalent and ionic bonds. An increase of the Li/Nb ratio led to a shift of the luminescence bands to shorter wavelengths and a change of the fundamental absorption edge of the studied crystals.

We report the results of systematic Raman spectroscopy studies of AlxGa1 –xN (x ~ 0.75) layers grown using plasma-assisted molecular beam epitaxy at various stoichiometric conditions and growth fluxes. The high-intensity asymmetric low-frequency peak obeying Bose statistics is discovered in Raman spectra of the layers grown by temperature-modulated epitaxy at strongly Ga-enriched conditions. Theoretical model is developed to explain the origin and the high intensity of the observed low-frequency peak, which is attributed to the presence of excessive metallic gallium in AlGaN layers and can be explained by vibrations of gallium clusters with a diameter of ~1 nm. The nature of the low-frequency peak is similar to that of the boson peak in glasses, which occupies the same frequency range in Raman spectra. We demonstrate the capabilities of Raman spectroscopy as an express and non-destructive technique for optimization of growth conditions of AlGaN layers to achieve simultaneously the atomically-smooth droplet-free surface morphology and the high structural quality.

The effect of alloying on the properties of highly tempered steels used for production of a range of petroleum pipes is studied. It is shown that an increase in molybdenum content from 0.15 to 0.53% improves the mechanical characteristics of chromium-molybdenum steels tempered at 600–690°C significantly. Alloying with vanadium and niobium facilitates an additional increase in strength properties. The best hardening of steel with 0.32% molybdenum in a highly tempered condition is provided by combined microalloying with niobium and vanadium, although stress corrosion cracking resistance is reduced.

The relationship of the spectral luminescent and nonlinear optical properties of Ag2S quantum dots (QDs), passivated with thioglycolic acid (Ag2S QDs/TGA) and Ag2S QDs, stabilized by gelatin (Ag2S QDs/Gel) with average sizes from 1.5 nm to 2.1 nm is found. Colloidal Ag2S QDs/TGA with different sizes, having the exciton (620 nm) and recombination (660 nm, 880 nm and 1205 nm) luminescence were studied using the methods of luminescent spectroscopy, luminescence decay, and Z-scans technique at the wavelengths of 532 nm using 10 ns pulses. Resonant two-photon transitions of reverse saturated absorption (RSA) were found for samples with recombination luminescence. In addition, the nonlinear refraction of thermal nature was observed using Z-scan method. Predominantly weak two-photon absorption (TPA) and nonlinear refraction (NR) of non-thermal nature occur for Ag2S/TGA quantum dots with exciton luminescence. The luminescence lifetimes support this conclusion. The differences in luminescence lifetimes of samples are associated with different state of interfaces for colloidal Ag2S QDs/TGA with recombination and exciton luminescence. This conclusion was confirmed by FTIR spectroscopy of colloidal Ag2S QDs/TGA solutions, synthesized under different conditions. RSA is characteristic of samples with a noticeable concentration of trap states acting as recombination luminescence centers (660 nm). The maximum effect was noted for Ag2S QDs with recombination luminescence in the region of 660 nm, 880 nm, 1205 nm. The fast component of this luminescence decay has a time constant of about 0.8 ns. It decay 5 times for the first 10 ns. In the case of Ag2S QDs/TGA with exciton luminescence (620 nm) there are no appropriate conditions for RSA. The fast component of luminescence decay has a time constant of 0.8 ns. The luminescence intensity decreases 50 times for the first 10 ns. In this case, TPA and nonlinear refraction of non-thermal nature take place, and RSA is absent.

Regularities of reverse photodegradation of infrared (IR) luminescence of colloidal Ag2S quantum dots (QDs), stabilized in gelatin with the average size of 1.6 nm ( λ lum max = 1205 nm) and passivated with thyoglicolic acid with the average size of 2.3 nm ( λ lum max = 1095 nm) were discussed. The photochemical nature of this process was found. The evidences of the formation of nonradiative recombination centers near the IR luminescence centers was found. These centers disintegrate in the dark with the activation energy of 0.9 eV and ensure the recovery of intensity IR luminescence of Ag2S QDs by 65–75%.

The paper presents the results of a study of shallow non-radiative trap states in colloidal Ag2S QDs and Ag2S/SiO2 core/shell QDs, passivated with 2-mercaptopropionic acid in ethylene glycol carried out the thermally stimulated luminescence technique. For Ag2S QDs, the presence of thermoluminescence peaks in the region of 150–330 K was established. The formation of the SiO2 shells leads to the disappearance of the thermoluminescence peak at 250 K. It is interpreted as a “healing” of defects, localized on Ag2S QD surface. The depths of the detected trap states were estimated using a kinetic model. They showed that the observed thermoluminescence bands are due to the presence of shallow holes trap states in Ag2S QDs with depths of 0.117 eV and 0.135 eV for the thermoluminescence peaks at 190 K and 250 K, respectively.

International audience; Electronic structure of series of tellurium oxide crystals within the TeO 2-TeO 3 binary system is studied with generalized gradient approximation to DFT, hybrid DFT-HF method with the PBE0 and B3LYP exchange-correlation functionals and with quasiparticle G 0 W 0 approach. Comparison with available experimental data revealed significant underestimation of the band gap values within DFT. The hybrid DFT-HF method leads to slightly overestimated values of the bandgap, and the best agreement with experimental data provides the "one-shot" G 0 W 0 calculations starting from Kohn-Sham solutions. The electronic structure of tellurium oxides is discussed in details. It is found that bandgap value decreases proportionally to fraction of tellurium atoms in octahedral coordination. This change is due to formation of gap states by 5s(Te) electrons which do not participate in Te(VI)-O bonding. Dielectric properties is calculated within Random Phase approximation for the series of tellurium oxides and high nonlinear properties of the compounds is predicted by empirical Miller's rule.

The results of studies of the optical properties of ensembles of colloidal CdS quantum dots passivated by thioglycolic acid are reported. The average dimensions of the quantum dots lie in the range from 1.7 to 5.8 nm. By X-ray diffraction studies and Raman spectroscopy, it is established that quantum dots crystallize with the formation of a cubic crystal lattice. The systematic features of the quantum-confinement effect in the optical absorption and luminescence spectra, as well as in the luminescence excitation spectra, are established. The features manifest themselves as a blue shift of the corresponding bands with decreasing quantum-dot dimensions. From analysis of the nanosecond luminescence kinetics, it is concluded that experimentally observed radiative recombination proceeds by the donor–acceptor mechanism.

The solution of the problem of investigating the energy structure of trap states and photophysical processes with their participation is necessary for the effective application of colloidal Ag2S quantum dots. These studies are important both for finding ways to increase the quantum yield of luminescence, and for the effective using of non-luminescent trap states in photocatalysis applications. In this paper, Ag2S quantum dots prepared with an aqueous synthesis in a gelatin matrix were investigated. The investigated Ag2S quantum dots have average sizes of 2.2 ± 0.3 nm, 2.5 ± 0.5 nm and 3.6 ± 0.5 nm, according to TEM data, and size-dependent spectra of UV–Vis absorption and photoluminescence. Temperature dependencies of IR recombination luminescence (1200–1250 nm) for ensembles of colloidal Ag2S quantum dots, dispersed in gelatin, were investigated. Thermostimulated luminescence, appearing under the variation of temperature and continuous photoexcitation of colloidal Ag2S quantum dots, was detected. The peak of thermoluminescence was found in the temperature region of 120–240 K, which consists of two components. Energies of activation of thermoluminescence and temperature quenching of IR luminescence were determined. The activation energy is in the region of 0.05–0.11 eV. And the energy of temperature quenching of IR luminescence is at 0.06–0.10 eV.

Strain aging of pipe steels 06G2FB and 07G2MFB with ferrite-pearlite and ferrite-bainite structures is investigated. It is established that a ferrite-bainite structure is more inclined towards strain aging than a ferrite-pearlite structure. The tendency towards strain aging of steel with a ferrite-bainite structure increases with increasing austenitizing temperature. During hot plastic deformation there is development of recrystallization and the tendency towards strain aging decreases.

The effect of high-temperature thermomechanical treatment (HTMT) on the brittleness connected with deformation-induced aging and on the reversible temper brittleness of a low-carbon tube steel with a ferrite–bainite structure has been studied. When conducting an HTMT of a low-alloy steel, changes should be taken into account in the amount of ferrite in its structure and relationships between the volume fractions of the lath and the acicular bainite. It has been established that steel subjected to HTMT undergoes transcrystalline embrittlement upon deformation aging. At the same time, HTMT, which suppresses intercrystalline fracture, leads to a weakening of the development of reversible temper brittleness.

XP Spectroscopy is used to compare the states of the supported platinum particles in the samples of the Pt/Sibunit catalyst and the Pt/HOPG model system after treating in NO 2 at room temperature and pressure of 3 × 10 −6 mbar. It is shown that in both cases the platinum particles are not oxidized completely. The comparison of the spectra obtained for the Pt/Sibunit sample in the Pt 4f and Pt 3d 5/2 regions with the use of Al K α and Ag L α radiations serves as a basis for an assumption that the particles of platinum after being treated in NO 2 have the core (metallic Pt) − shell (platinum oxides) structure.

Colloidal pure and Mn-doped mixed Zn x Cd 1−x S quantum dots were successfully prepared by aqueous synthesis in photographic inert gelatin. Quantum dots are formed in a cubic crystal lattice with the average size of about 2 nm. Two emission bands in photoluminescence spectra of Mn-doped quantum dots are observed: trap state luminescence and Mn characteristic emission. The possibility of Mn-doped quantum dots spectral characteristics tuning by changing the synthesis conditions is shown. It is shown that value of trap state – Mn ion excitation transfer efficiency in mixed Zn x Cd 1−x S:Mn quantum dots is about 24–30%.

Electroactive gels based on polyaniline (PANI) and polyacrylamide (PAAm) were prepared by polymerization of aniline in the solution of linear PAAm and subsequent precipitation of PANI/PAAm dispersion in acetone. It has been shown that the composite gels are capable to swelling in water acid and base solutions and dimethyl sulfoxide. It was established by mechanical tests and dynamic oscillatory measurements that the swollen gels demonstrate the elastic response like a covalently crosslinked network but with strong physical interactions between the chains. It is supposed that the observed mechanical elasticity is due to the certain number of elastically effective chemical bonds between PANI and PAAm chains. It is proved that the structure of the samples containing space continuous phase of PANI in the network of PAAm provides them mechanical integrity, good-quality mechanical response, swelling ability and electrical activity.

The recombination photoluminescence (PL) properties of hydrophilic colloidal CdS quantum dots (QDs) dispersed in gelatin were investigated. The average size of QDs varies from 2.4 to 4.4 nm. The size dependence of the emission peak position is defined in the range from 1.65 to 2.27 eV. The PL decay (0.3–4·10 3 ns) is accompanied by the red shift of its maximum. It is interpreted as the radiative recombination via the donor-acceptor pairs. The analysis of the half-width and shape of the observed PL spectra was performed taking into account the QDs size distribution and the Coulomb interaction of donor and acceptor uniformly distributed in QD volume. The deviation of the theoretical PL spectra from experimental data on the half-width was determined, which amounted of the order 0.4 eV. It is concluded that to describe the PL spectra of CdS QDs it is necessary to consider a different degree of localization of the wave functions and the variation of the binding energy of the donor and acceptor versus their depth in the QD volume.

Raman spectra of the mixed crystalline oxides of the (1 - x)TeO2 + xTeO3 (x = 0, ¼, ½, 1) series were recorded and simulated by using the DFT calculations. Good agreement between observed and calculated Raman spectra makes it possible to establish unambiguous assignment for all prominent Raman lines. This result gives an insight into relations between structural peculiarities and observed spectral features for the crystals promising as nonlinear optical materials. Highlights • Several mixed TeO2-TeO3 crystals were synthesized by solid-state chemistry • DFT calculations well describe structures and phonon spectra of TeO2-TeO3 oxides • Raman lines can be assigned to internal vibrations of TeO4 and TeO6 polyhedrons • Observed Raman bands can be used as fingerprints of different structural units.

The dynamics of electronic excitations in hybrid associates of Ag2S quantum dots with methylene blue (MB) molecules are studied by femtosecond transient absorption spectroscopy and nanosecond time-resolved spectroscopy. The situation is considered where the relative positions of the energy levels of the associate components allow photoinduced charge transfer. The luminescence quenching for MB+ cations and Ag2S quantum dots in the hybrid associates provides evidence for charge transfer, which is accompanied by a quick return of MB+ to the ground state (absorption is recovered). We propose that there is electron transfer from the MB LUMO level to the energy level of the luminescence center in the quantum dot. In this case, the bleaching band with a peak at 590 nm corresponding to the MBOH· form of the dye is formed at a subpicosecond time scale. The corresponding decay time is about 100 ps.

This paper presents an original two-step technology for water synthesis of Ag2S/SiO2 core/shell quantum dots (QDs) based on Ag2S QDs, passivated with thioglycolic acid with luminescence in the near IR region (800–1400 nm). The formation of Ag2S QDs with an average size of 2.5 nm, SiO2 coated with thickness of 1.3–4 nm has been established using transmission electron microscopy and energy dispersive X-ray analysis. The possibility to control the formation of Ag2S/SiO2 core/shell QDs using FTIR spectroscopy data is shown. The results show a change in the luminescence properties of Ag2S QDs with an increase in the thickness of SiO2 shell. They are i) an increase in the intensity and quantum yield of QD luminescence by 7 times during ligand exchange and up to 35 times as a result of a further increase in the thickness of SiO2 shell; ii) an increase in the average luminescence lifetime from 3.5 ns to 17.7 ns during the formation of SiO2 shell. These studies demonstrate a way to control the quantum yield of NIR recombination luminescence of colloidal Ag2S QDs and expand the ways of their application.

The results of experimental and theoretical studies of phonon modes in short-period GaN/AlN superlattices grown by PA MBE on the (0001) Al2O3 substrate are reported. In the framework of Density Functional Theory and Elastic Continuum Model the lattice dynamics properties are studied of (GaN)m(AlN)n SLs (m+n≤24), where n and m are the number of monolayers. Good agreement between experiment and theory is found, which made it possible to establish unambiguously a relationship between the features observed in the Raman spectra and the microscopic nature of the acoustic phonon modes. The obtained results open new possibilities for analyzing the structural properties of GaN/AlN SLs by Raman spectroscopy.

In the present paper, we discuss general features of luminescent properties for various samples of colloidal Ag 2 S quantum dots (QDs), passivated with thioglycolic (Ag 2 S/TGA) and 2-mercaptopropionic acids (Ag 2 S/2-MPA), L-cysteine (Ag 2 S/L-cys), and also Ag 2 S QDs stabilized in gelatin (Ag 2 S/Gel) and Poly(N-vinylpyrrolidone) (Ag 2 S/PVP). It was found that for all samples, the Stokes shift of the luminescence peak relative to ground state exciton absorption is greater than the exciton binding energy in Ag 2 S (0.096-0.104 eV). Moreover, the Stokes shift turned out to be caused by not only the quantum dot size but also by the type of the organic ligand. With decreasing the quantum dot size, the Stokes shift increases significantly. The estimates of the energy level shifts for electrons, holes, as well as the position of the luminescence peak, led us to a conclusion that trap state luminescence occurs. The specific luminescence mechanism is determined by the recombination of an electron trapped at the luminescence center with a free hole. It was found that decay of the trap state luminescence has non-exponential behavior. A model is proposed that explains the non-exponential luminescence decay.

Dynamics of the 1Se–1S3/2 exciton in colloidal CdS quantum dots with diameter of 3.1÷4.5nm in gelatin with involvement of localized states was studied by means of femtosecond photoinduced absorption spectroscopy (pump–probe), thermally stimulated luminescence (TSL) observed under permanently excited luminescence. It was found that the bleaching band occurs in the energy region of exciton ground state under excitation by femtosecond laser pulses. The complex dynamics of bleaching recovery is caused by the capture of electron on localized states, found using TSL. The stochastic model describing the dynamics of bleaching recovery is discussed. It is shown that the low efficiency of exciton luminescence is caused by the rapid capture of holes by luminescence centers.

Luminescence properties of water-soluble hybrid associates of semiconductor colloidal CdS quantum dots (QDs) with average size of 2.5 nm, 3.2 nm, 4.2 nm and J-aggregates of 3,3′-di-(γ-sulfopropyl)-4,4′,5,5′-dibenzo-9-ethylthiacarbocyanine betaine pyridinium salt (Dye) in gelatin were investigated using the methods of absorption, steady-state and time-resolved luminescence spectroscopy. The decrease in luminescence intensity of CdS QDs and increase in luminescence intensity of Dye J-aggregates were detected with increasing of Dye concentration. It was shown that curves of luminescence decay of CdS QDs are non-exponential. The decreasing of luminescence lifetime of CdS QDs with increasing of Dye J-aggregates concentration was observed. It was concluded that dynamic quenching due to non-radiative resonance energy transfer takes place. It was shown that overlap integral between luminescence spectra of CdS QDs and absorption spectra of Dye J-aggregates increases with the increase of average diameter of CdS QDs and luminescence decay of CdS QDs is accelerated. Energy transfer efficiency for all three sizes of QDs was more than 31%.

Enhancement of IR luminescence (1205 nm) of colloidal Ag2S quantum dots (QDs) with an average size of 2.5 ± 0.3 nm was detected upon excitation in the absorption band of thionine dye molecules (530–610 nm). It is found that the observed effect occurs during a hybrid association of Ag2S QDs with monomers of the cationic thionine (Th + ) molecule. It is concluded that the photosensitization of IR luminescence of colloidal Ag2S QDs is realized due to a resonance nonradiative transfer of electronic excitation energy directly to the centers of radiative recombination from the excited Th + molecules.

Spectral patterns of hybrid association in the mixture of colloidal Ag2S quantum dots (QDs) with an average size of 2.5 to 0.3 nm with J-aggregates of a pyridinium salt of 3,3’-di(γ-sulphopropyl)-9-ethyl-4,5,4’,5-dibenzothiacarbocyanine betaine (Dye), prepared by the sol-gel method in gelatin, are investigated. A conclusion about the preferential formation of cis-J-aggregates in the hybrid associates of Dye with Ag2S QDs is made. The effect of photosensitization of IR luminescence (1000–1300 nm) of colloidal Ag2S QDs by J-aggregates of Dye is revealed. On the basis of the results, a photosensitization scheme implying the resonance nonradiative transfer of the electronic excitation energy from cis-J-aggregates to the recombination luminescence centers of Ag2S QDs is suggested.

The dynamics of electronic excitation in hybrid associates of colloidal CdS quantum dots passivated by thioglycolic acid (CdS/TGA) with methylene blue cationic dye molecules (MB + ) was studied by femtosecond transient absorption spectroscopy and nanosecond time-resolved spectroscopy. From the luminescence decays it was found that non-radiative resonance energy transfer (FRET) from the recombination luminescence centers accompanied by acceptor fluorescence is observed in the CdS/TGA-MB + systems with MB + monomers. It was found that in the exciton decay dynamics of the hybrid systems based on CdS/TGA QDs and methylene blue, there is substantial competition between the resonance energy transfer in MB + and the energy transfer to MB • and MBOH • forms.

The features of IR luminescence of colloidal Ag 2 S QDs passivated with thioglycolic acid (Ag 2 S/TGA) under the formation of Ag 2 S/ZnS/TGA core/shell QDs are considered. A 4.5-fold increase in the quantum yield of recombination IR luminescence within the band with a peak at 960 nm (1.29 eV), full width at half maximum of 250 nm (0.34 eV), and the Stokes shift with respect to the exciton absorption of 0.6 eV was found. The increase in the IR luminescence intensity of Ag 2 S/ZnS/TGA QDs is accompanied by an increase in the average luminescence lifetime from 2.9 ns to 14.3 ns, which is explained as “healing” of surface trap states during the formation of the ZnS shell. For the first time, the enhancement of the luminescence intensity photodegradation (hereinafter referred to as fatigue) was found during the formation of the Ag 2 S/ZnS/TGA core/shell QDs. The luminescence fatigue is irreversible. We conclude that the initial stage of photolysis of the Ag 2 S core QDs under laser irradiation plays a key role. Low-atomic photolytic clusters of silver formed on the Ag 2 S core QDs act as luminescence quenching centers and do not reveal structural transformations into Ag 2 S, provided that the clusters are not in contact with TGA.

Ceramic solid solutions GdNbx[Formula: see text]O4 ([Formula: see text]–1) were synthesized by sol–gel. Morphological particularities of microstructure were studied, strength characteristics (Young’s modulus) and stress intensity factor for mode I [Formula: see text] were evaluated. The latter is a criterion of crack resistance of the material. Luminescent properties of solid solutions GdNbx[Formula: see text]O4 were researched under UV exciting radiation. A comparatively small addition of Ta ([Formula: see text]) was shown to increase luminescence intensities of centers [Formula: see text]–O−. An addition of Ta to GdNbO4 leads to creation of solid solution [Formula: see text][Formula: see text]O4. Intensity of these centers is 3–6.5 times larger than that of GdNbO4 and GdTaO4.

Investigations of dynamics of exciton relaxation in colloidal thioglycolic acid (TGA)-capped CdS/ZnS core/shell systems with diameter of 3.6 nm by means of femtosecond transient absorption spectroscopy, thermostimulated luminescence (TSL), and decay of luminescence are presented in this paper. It was found that the intensity of trap-state luminescence increases when one and two ZnS monolayers are formed. Also, the lifetime of trap-state luminescence increases. Two types of trap states with different depths were found, using thermostimulated luminescence technique. Localized states of the first type with depth of 0.085 eV do not change their concentration during sell formation. In contrast, trap state of the second type with depth of 0.125 eV are almost completely removed. It was found that the electron lifetime, investigated femtosecond transient absorption is not changed during formation of ZnS shell. It was concluded that localized states are channels of non-radiative recombination, direct quenching the center of trap-state luminescence. The absence of exciton luminescence is caused by rapid localization of holes at luminescence center.

We investigate the energy structure of colloidal CdS nanocrystals by measuring the UV–vis absorption spectra. Nanocrystals were synthesized by sol–gel method in a gelatin matrix in the size range from 2.5 to 3.9 (70.2) nm. In order to interpret the UV–vis absorption spectra we calculate the energy spectrum of electron quasi-stationary states using the model of open nanocrystal as well as the hole stationary spectrum in a two-band approach. It is shown that the main contribution to the absorption spectrum is made by interband transitions 1S3/2-1Se and 1P3/2-1Pe, and its shape is determined by the size distribution of nanoparticles. For this system the estimated values of the effective masses of the heavy hole and light hole are 1.44m0 and 0.28m0, respectively.

The size dependences of the absorption and luminescence spectra of ensembles of hydrophilic colloidal Ag2S quantum dots produced by the sol-gel method and dispersed in gelatin are analyzed. By X-ray diffraction analysis and transmission electron microscopy, the formation of core/shell nanoparticles is detected. The characteristic feature of the nanoparticles is the formation of crystalline cores, 1.5–2.0 nm in dimensions, and shells of gelatin and its complexes with the components of synthesis. The observed slight size dependence of the position of infrared photoluminescence bands (in the range 1000–1400 nm) in the ensembles of hydrophilic colloidal Ag2S quantum dots is explained within the context of the model of the radiative recombination of electrons localized at structural and impurity defects with free holes.

The electron beam domain patterning of MgO-doped congruent lithium niobate (LN) single crystals covered by electron beam resist layer were studied for various layer thicknesses and electron accelerating voltages. The obtained domain patterns were divided in four types. The increasing of the domain structure quality under presence of the resist layer on irradiated surface was confirmed. This effect was attributed to high concentration of the electron traps in resist, which localized incident electrons in limited volume over LN surface and formed effective electrode. The voltage dependence of space charge localization relative to the LN surface was studied by computer simulation.

Luminescence properties of hybrid associates of semiconductor colloidal CdS quantum dots (QDs) with an average diameter of 2.5 nm and methylene blue (MB+) cations were investigated. Their photoluminescence spectra, excitation spectra and luminescence decay spectra recorded using the time-correlated single photon counting techniques were analyzed. The increase of efficiency of MB+ fluorescence at 405 nm excitation was found. It corresponds to the absorption region of CdS QDs. When [ n CdS QDs ] : [ n MB + ] concentrations ratio changes from 100:1 to 1:3 for associates, then a decrease in the intensity of CdS QDs luminescence band (580 nm) and its increase for MB+ band (674 nm) were observed. At the same time it was found that the average lifetime of CdS QDs luminescence is shortened and the lifetime of MB+ luminescence becomes significantly longer. It was concluded that dynamic quenching due to nonradiative resonance energy transfer takes place. The efficiency of this process was estimated and the corresponding rate constant was calculated. It is 5.6 × 10 7 to 8.6 × 10 7 s − 1 .

The optical absorption spectra of TiO2 thin films with different phase compositions (anatase, rutile-brookite, anatase-rutile-brookite) are studied. The films are produced by the reactive radio-frequency magnetron sputtering of titanium in different atmospheres. It is shown that, on the assumption of the additivity of the contributions of each phase to the general spectrum with the fraction of the phase in the layer known, it is possible to use the method of subtraction of the spectra of individual phases. The fundamental absorption spectra of all of the crystal modifications detected in the multiphase films by structural studies are separated out, and the edges of the optical transitions in all of the phase components are established.

International audience; The ab initio calculations performed for the TeO2?Te4O9?Te2O5?TeO3 series of crystal lattices have revealed that, in this series, the average v3 non-linear susceptibility increases for about 10 times. Such a huge effect is attributed to the strong augmentation of the Te atom d-function contributions in valence molecular orbitals, which accompanies the Te4+?Te6+ transformation. The results obtained allow concluding that the TeO3-related materials can be of interest in non-linear optic device engineering.

The structure and electrical and optical properties of heterostructures formed on the surface of single-crystal silicon wafers as a result of the heat treatment and pulsed photon treatment of Ti films in oxygen, air, and nitrogen are investigated. It is shown that a TiO2/Ti5Si3/p-Si heterostructure is formed upon heat treatment in air, whereas a TiO2/TiSi2/p-Si heterostructure is formed upon photon treatment. It is established that rutile films with pronounced n-type conductivity are formed as a result of the heat treatment of Ni-doped Ti films in oxygen. Rutile films with p-type conductivity are formed upon the thermal annealing of Ti films in air with subsequent photon treatment in nitrogen.

Nickel orthoborate $\mathrm{N}{\mathrm{i}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ having a complex orthorhombic structure Pnnm (No. 58, $Z=2$) of the kotoite type is known for quite a long time as an antiferromagnetic material below ${T}_{\mathrm{N}}=46\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, but up to now its physical properties including the lattice dynamics have not been explored. Six $[\mathrm{Ni}{\mathrm{O}}_{6}]$ units of $2a$ and $4f$ types are linked via rigid $[\mathrm{B}{\mathrm{O}}_{3}]$ groups and these structural particularities impose restrictions on the lattice dynamics and spin-phonon interactions. We performed the symmetry analysis of the phonon modes at the center of the Brillouin zone. The structural parameters and phonon modes were calculated using the dmol3 program. We report and analyze results of infrared and Raman studies of phonon spectra measured in all required polarizations. Most of the even and odd phonons predicted on the basis of the symmetry analysis and theoretical calculations were reliably identified in the measured spectra. Clear evidence of the spin-phonon interaction was found for some particular phonons below ${T}_{\mathrm{N}}$. An unexpected emergence of several very narrow and weak phonon lines was observed in the infrared absorption spectra exactly at the magnetic ordering temperature ${T}_{\mathrm{N}}$. Moreover, anomalous behavior was found for some Raman phonons. The emergence of new phonon modes in the infrared and Raman spectra exactly at ${T}_{\mathrm{N}}$ proves the existence of a magnetostructural phase transition of a new type in $\mathrm{N}{\mathrm{i}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$. A possible nature of this transition is discussed.

Correlations between frequencies of the Raman-active A(TO) and E(LO) phonons and the layer thickness ratio in the AlN/GaN superlattices are determined. Theoretical frequency-structure relations are derived by using the dielectric continuum model. It is found that the elastic strains which inevitably arising in the layers upon SL growth affect frequencies of the most Raman-intense polar modes insignificantly. The obtained frequency-structure relations agree well with available experimental data. These results confirm efficiency of the Raman spectroscopy for a fast nondestructive structure characterization.

The study is concerned with MOCVD epitaxial heterostructures grown on the basis of AlxGayIn1 − x − yAszP1 − z quinary alloys in the region of alloy compositions isoperiodic to GaAs. By the X-ray diffraction technique and atomic force microscopy, it is shown that, on the surface of the heterostructures, there are nanometric objects capable of lining up along a certain direction. From calculations of the crystal lattice parameters with consideration for internal strains, it can be inferred that the new compound is a phase based on the AlxGayIn1 − x − yAszP1 − z alloy.

International audience; Ideas currently dominating the field of structural studies of TeO2-based glasses are critically considered. A new physically and chemically consistent approach to the constitution of binary TeO2-WO3 glasses is proposed, in which the reasoning coming from the Raman spectra reexamination are correlated with the basic principles of thermodynamics. Separation into two phases is suggested in such glasses. One phase is TeO2, and another is Te(WO4)2 consisting of tetrahedral [WO4]2 anions and of Te4þ cations. Supplementary MnOk oxides added to the glasses are found incorporated in the former phase, thus producing solid solutions (for M¼Ti, Nb) or tellurite compounds (for M¼Nd).

The effect of temperature on the thermoelectric power of widely used steels and alloys is studied. It is shown that the effect of the thermoelectric power can be applied for controlling the grade of a material. Amethod and an analyzer are developed and tested under industrial conditions.

The expediency of classifying the microstructure of low-carbon pipe steels is demonstrated. The main structures that should be considered in its development are investigated. © 2010 Springer Science+Business Media, Inc.

This paper describes an absolute ballistic laser gravimeter of a new generation developed at the Institute of Automation and Electrometry, Siberian Branch of the Russian Academy of Sciences. The device is intended for use under field conditions and has small dimensions and weight. The light source in the gravimeter interferometer is an optical standard with a wavelength λ = 532 nm consisting of a traveling-wave Nd: YAG laser with intracavity frequency doubling and with a stabilization system for the saturated absorption resonances in molecular iodine. The instrumental standard error in measuring the absolute gravity by the gravimeter does not exceed ±5 · 10−8 m/s2 (or 5 µGal).

Non-monochromatic MgK α and monochromatic AgL α irradiations were used to measure Pt4f and Pt3d 5/2 X-ray photoelectron spectra from platinum black and from several platinum compounds with different Pt oxidation states. The Pt3d 5/2 core level binding energies from platinum compounds were measured for the first time. Potential of these data to XPS study of Pt/Al 2 O 3 catalysts is demonstrated.

In the AgCl microcrystals with adsorbed methylene blue dye molecules, sensitized anti-Stokes luminescence centers formed as a result of a photostimulated low-temperature (77 K) process are observed. The emission is recorded on excitation of the samples by radiation with the flux density 1014−1015 photon cm−2 s−1 in the spectral range 620–750 nm corresponding to optical absorption in the adsorbed dye molecules and adsorbed Ag1, Ag2, and Ag3 clusters. It is shown that the anti-Stokes luminescence centers formed by photo-stimulation present (adsorbed dye molecule)—(silver subnanocluster) hybrid nanostructures, in which the bonding between the components is weak but sufficient to provide the possibility for two-photon interband transitions that occur due to transfer of the electron’s excitation energy from the dye molecule to the silver cluster with subsequent photoionization of the cluster.

The nature of anti-Stokes luminescence centers excited in the temperature range 77–300 K by light with wavelengths from 620 to 710 nm and intensities in the range 1015–1016 photons/cm2 in Zn0.75Cd0.25S microcrystals annealed in the presence of oxygen has been investigated. It is shown that the centers of two-photon excitation of this luminescence are clusters of native metal oxides (ZnO)n and (CdO)n, whose energy levels in the Zn0.75Cd0.25S band gap are 1.70–1.95 eV below the bottom of the conduction band.