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Undoped and Mn-doped ZnO ceramics were theoretically and experimentally investigated using specular infrared reflection method. It was shown that infrared reflection spectra can be modeled using the parameters explored for ZnO single crystals. For ceramic samples, it was shown that ZnO grains with orientation of the C-axis along the normal to the electric field ( ) give the main contribution to IR reflection spectra. It has been ascertained that the surface roughness is manifested in these spectra mainly within the range 450…550 cm–1 giving negligible effect for the frequencies above longitudinal phonon frequency. This allowed the electrophysical parameters of ZnO crystallites to be evaluated. In the case of undoped ceramics, the obtained results were found to be consistent with the values of direct current measurements. This finding supports the utility of infrared spectroscopy for determination of the electrophysical parameters of polycrystalline ceramic materials. For Mn-doped ceramic samples, the conductivity value measured using the direct current method was found to be essentially lower than those determined from simulation of infrared reflection spectra. This phenomenon was explained by barrier formation at the grain boundaries in Mn-doped ZnO ceramics.

VOx films deposited using the multistep method have been investigated. These films were deposited by repeating the two-stage method of low-temperature deposition – low-temperature annealing. The structure and characteristics of VOx thin films have been studied. Taking into account the obtained results, theoretical modeling of the structure was performed and the parameters of the metal-insulator transition have been calculated.

Fundamental new features and physical nature of possibilities for purposeful influence of interrelated variations in different experimental conditions on changes of the selectivity of sensitivity of azimuthal dependence of the total integrated intensity dynamical diffraction to various types of defects in single crystals have been determined. As a result, the efficiency of the previously developed phase-variation principles of diagnostics has been improved. The proposed approach enabled us to demonstrate the presence of additional types of defects in the single crystals under study and to determine the defects parameters (sizes and concentrations). It makes it possible to obtain additional sensitivity and informativeness for phase-variation structure multiparametrical non-destructive diagnostics of monocrystalline systems with defects of various types.

The development of composite materials based on copper and zinc oxides is one of the main trends in low-temperature catalysis, sensor technology, and optoelectronics. Of particular interest are thin-film coatings where outer faces of the ZnO crystals decorated with clusters of copper oxides of different valence, the sharing of electronic processes within such structures, leads to the unique properties of these materials. Herein, we synthesized textured ZnO/ZnS, ZnO/ZnS:Cu and ZnO:Cu films using the atmosphere pressure spray pyrolysis technique with identical organic precursor for copper and zinc ions, dithiocarbamate (DTC). The most perfect films were obtained in the presence of 0.2% copper at 220 °C (surface reaction rate limited regime) on Si(111)/SiO2 substrates. Textured ZnO:Cu films are characterized by an increased growth rate, a more pronounced structure, superior photoelectric properties, and “unusual” chemical functionality. The growth of a composite material is considered on the basis of the tip-growth model, where catalytically active copper clusters are located on the outer polar surface of growing ZnO nanorod arrays. Segregation of the copper on the external polar face explained by the Jahn–Teller effect leads to the “jittering” in the coordination sphere of an ion in a highly symmetric environment of the ZnO crystal lattice. On the surface, the degeneracy of the electronic levels is removed, and Cu2+ acts as an “adaptive” surface passivator with a high structural variability of the coordination polyhedron. An increase in the growth rate of ZnO columns along the longitudinal direction of the hexagonal wurtzite structure was explained by the catalytic action of copper compounds, which stimulate the transformation of the sulfur-containing precursor into zinc oxide. This model is confirmed by the results of acoustoelectric measurements, which indicate a positive charge of the outer boundary of ZnO:Cu and the features of its interaction with gaseous analytes typical for copper-containing surfaces. The established mechanism of catalytic enhanced metallorganic – atmospheric pressure – direct liquid injection – chemical vapor deposition method utilizing a universal DTC precursor and one-step low-temperature spray pyrolysis process opens the way for the low-cost production of high-quality large-scale ZnO:Cu composite materials on various substrates of arbitrary shape and structure.

In the present study, the overheating degradation of as-deposited Mo/Si multilayers was investigated. Technological low-temperature furnace annealing at 300 °C for 1 h was used to simulate the overheating process. A multilayer Mo/Si structure with a period of 21.7 nm was created by DC magnetron sputtering. The dopant distribution in the as-deposited and annealed multilayers was studied by the dynamic- and 3D TOF-SIMS and SNMS methods. Periodic changes in multilayers were studied by the X-ray reflectometry method. It is shown that the cause of the Mo/Si multilayers degradation are oxygen gettering by the Mo/Si interfaces and the silicon diffusion into molybdenum layers due to the Mo/Si interface deformation with the appearance of randomly located places of penetration.

Lattice changes of macroporous silicon were studied under variations in the etching conditions of macropores. It was established that under all the etching conditions, additional mechanical stresses and corresponding deformations arise up to the appearance of dislocations in the macroporous layer at elevated voltage or current.

The methods of optical absorption spectroscopy and high-resolution diffractometry have been used to study the influence of microwaves on characteristics of crystalline SiC. Being based on the X-ray analysis data, optical transmission, photoluminescence, and photoluminescence excitation spectra, it has been shown that the microwave treatment leads to a change in the gradient of internal mechanical stresses and an increase in the migration capability of dislocations and, as a result, to redistribution of recombination centers in the sample.

The ZnS:Mn, Mg powder is fabricated by self-propagating high-temperature synthesis with the simultaneous introduction of Mn and Mg impurities. It is found that the simultaneous introduction of Mn and Mg impurities leads to the nonuniform distribution of manganese forming regions with a lower and higher Mn concentration. In the latter case, the manganese ions form paramagnetic clusters. At the same time, numerous centers of self-activated luminescence form in the synthesized ZnS:Mn, Mg due to mechanical stress and lattice strain. Additional annealing leads to a more uniform Mn distribution in the formed ZnS:Mn, Mg phosphor, which is accompanied by an increase in the intensity of the manganese photoluminescence band and quenching of the self-activated luminescence band.

The structure, microstructure, valence states, non-stoichiometry, dielectric and magnetic properties of lanthanum-modified multiferroics have been studied by X-ray diffraction, thermogravimetric, iodometric titration, SEM, XPS, dielectric spectroscopy and magnetic methods. Multiferroics of bismuth ferrite have been obtained by a rapid liquid phase sintering method under different pressures, P, for compacting stoichiometric mixture of precursors. On the basis of the experimental data, the molar formulas of real BiFeO3−δ and Bi0.9La0.1FeO3−δ structures have been determined. The real structure contains Bi3+, La3+, Fe3+, Fe2+ and O2− ions as well as cation V(c) and anion V(a) vacancies. The optimal temperature regimes of the rapid liquid phase sintering method for obtaining the single-phase Bi0.9La0.1FeO3−δ, whose composition corresponds to the concentration region of destruction of a spin cycloid, have been defined. It has been established that oxygen non-stoichiometry δ and concentration of Fe2+ strongly depend on the pressure P. The initial dielectric permittivity of the Bi0.9La0.1FeO3−δ multiferroics can be controlled and changed by the pressure P more than 5000 times. The correlations between the composition, structure, non-stoichiometry, dielectric and magnetic properties in the BiFeO3−δ and Bi0.9La0.1FeO3−δ have been established. In the pure BiFeO3−δ at room temperature, rhombohedral distortions of a hexagonal structure with indications of a ferromagnetic double exchange have been detected. The magnetic structure of the single-phase Bi0.9La0.1FeO3−δ is homogeneous with a large value of coercivity, HC ≥ 10 kOe, at room temperature. An analysis of the magnetic properties indicates the appearance of a weak ferromagnetism due to the destruction of the spin cycloid by lanthanum ions.

Rapid liquid-phase sintering method has been modified and used to synthesize Bi 1- x La x FeO 3- δ compositions (0 ≤ x ≤ 0.5). The temperature and sintering procedures to obtain stable single-phase samples have been defined. This provides a significant reduction in the synthesis time, which is especially important for mass production. Furthermore, giant dielectric constants have been observed in Bi 1- x La x FeO 3- δ compositions, the values of which are one order of magnitude larger than those of similar Bi-based multiferroics obtained by conventional methods. It potentially makes them one of the most promising materials for modern technological applications.

The temperature dependences of the specific contact resistance of silicon ρc with a doping step are measured experimentally and described theoretically. The measurements are performed in the temperature range from 4.2 to 380 K. It is established that the contacts of the studied Au–Ti–Pd–n+–n-Si structures are ohmic. It is shown that minimal ρc is implemented at T = 75 K. Its value rises both with a decrease in temperature (due to the freezing effect) and with an increase in temperature (due to the electron-enriched layer at the boundary with the bulk material). It is established that the bulk electron concentration strongly decreases in the near-contact region in a layer with a thickness on the order of one micron due to the compensation of silicon by deep acceptors appearing because of the formation of a rather high vacancy concentration during stress relaxation and the appearance of a high dislocation density, as well as due to their diffusion from the contact after heating to 450°C. The data on the occurrence of vacancy-type defects are confirmed by X-ray measurements. The dislocation density in the studied structures is also estimated from X-ray measurements.

The effects of built-in deformation and stress relaxation on the structural and optical properties for a 21-period AlN/GaN superlattice (SL) after implantation with argon ions have been studied. Upon implantation, the satellites’ peaks in the X-ray diffraction spectra shift toward the smaller angles which indicate decreasing of tensile deformation in SL by the value of Δc/c = 0.28%. The SIMS analysis showed that the sputtering rate for the initial sample decreases with depth, which is explained by the effect of varying deformation fields in SL and a faster etching of SL layers with a larger deformation magnitude. The change in the sputtering rate of individual layers of SL after implantation also correlates well with the magnitude of deformation. Implantation of Ar+ ions into SL leads to relaxation of the system and more homogeneous distribution of bond energy in individual layers of superlattice. The Raman spectra of the implanted SL are characterized with a low-frequency shoulder in the most intense band of the GaN layer E2 (high), which testifies partial stress relaxation in SL. Thus, based on a comprehensive study of the initial and implanted SL, it has been concluded that point defects that occur during implantation activate the process of dislocations nucleation in the superlattice/GaN buffer layer interface, which reduces the compressive stresses in the GaN layers of SL.

When creating a passivating ZnSe layer on Ge, which is used in p-i-n Ge photodetector, we found two additional phases GeSe and GeSe2 that does not contradict with their state diagram. The above phases can have an essential effect on performances of the passivating layer. Therefore, to study the electrical resistance of this layer we prepared model samples of layers containing the GeSe and GeSe2 with the thickness 0.5…1.8 µm and area 1 cm2. To measure the electrical resistance of these layers, we used elastic contacts. The performed measurements have shown that Se layers on Ge have an intermediate resistance between that of ZnSe on Ge and pure Ge, and, therefore, the effect of additional phases practically does not worsen the passivating properties of the ZnSe layer on Ge.

International audience; Optical and structural properties of ceramics based on Mn-doped magnesium titanates synthesized by sintering in air at 1200 °C of MgO and TiO$_2$ powders of different molar ratio ranging from MgTiO$_3$ to Mg$_2$TiO$_4$ stoichiometric compositions were studied. The influence of excess MgO on Mn incorporation in crystal lattice of MgTiO$_3$ was also investigated. The Mn$^{4+}$ ions substituted Ti$^{4+}$ sites were controlled by the photoluminescence (PL) and diffuse reflectance spectroscopy, and the Mn$^{2+}$ ions on Mg$^{2+}$ sites were monitored by electron paramagnetic resonance (EPR). The ceramics produced using equimolar ratio of MgO and TiO$_2$ composed of a major MgTiO$_3$ and a minor MgTi$_2$O$_5$ crystal phases, and those made with excess MgO contained MgTiO$_3$ and Mg$_2$TiO$_4$ phases in different proportions. The EPR study showed that Mn incorporated in MgTiO$_3$ synthesized under 1:1 molar ratio as Mn$^{2+}$ ion mainly. This agreed with low intensity of Mn$^{4+}$ red PL ascribed to low concentration of Mn$^{4+}$ centers and partial absorption of the UV excitation light by the MgTi$_2$O$_5$ phase. The Mn-doped MgTiO$_3$ synthesized with excess MgO of 19 and 50 mol.% showed increased Mn$^{4+}$ red PL by a factor 30-50, enhanced Mn$^{4+}$ optical absorption and more than ten times decreased Mn$^{2+}$ EPR signal. The Mg$_2$TiO$_4$ phase was found to be under compressive strains attributed to the presence of Mg vacancies and demonstrated Mn$^{4+}$ red PL with modified spectrum shape and decay behavior. It is concluded that in MgTiO$_3$ the excess MgO facilitates the incorporation of Mn onto Ti$^{4+}$ site and can be used for the increasing of Mn$^{4+}$ PL intensity.

Persistent time-delayed luminescence was observed in bulk polymer Polyamide-6 (nylon 6) samples at room temperature. Using X-ray 2Θ-diagnostics we have separated two crystalline forms of the material which exhibit serious differences in their time-delayed luminescence properties. Whilst for the α-form the afterglow temperature threshold is at the range of 100 °C, the γ-form samples require cooling to about −20 °C for the effect becomes observed by eye. The afterglow relaxation traces are highly reproducible and we extracted the Becquerel law function (compressed hyperbola) for them. The conclusion derived on the origin of the effect is the photoinduced charge recombination process. A theoretical model is presented for the explanation of the experimental results.

The structural and electro-physical characteristics of ZnO/Si heterostructures deposited by the magnetron sputtering from aluminum-doped ZnO target are addressed. The film recrystallization and microcrystal structure restoration are observed. It is found that the ZnO/Si barrier is about 0.66 eV and depends on the annealing temperature of the implanted structures. Diode structures with a transparent electrode (ITO/ZnO/Si/Al) have photosensitivity in the wide spectral region of 0.4–2.5 µm. The photosensitivity mechanisms in different spectral bands require further refinement. The magnetron sputtering growth and the resulting film consolidation is interesting in which such varied morphologies have an impact on the photovoltaic behavior of ZnO/Si structures. Thus, the magnetron deposited ZnO layers with thicknesses of less than ≈70 nm has roughly 3 times greater photovoltage magnitude compared with that having greater thicknesses, and this coincides with the microstructural evolution of the film. The SPV decays slow down accordingly exhibiting decay times of the order 10 μs at the small film thicknesses and 100 μs at the ones exceeding ≈70 nm. These results can be interpreted in terms of the recombination and carrier trapping centers in the film and at the ZnO/Si boundary, whose concentration varies with the film thickness. In particular, increasing the grain size and grain density affects the composition and concentration of recombination-active defects at grain boundaries, which alter the carrier recombination rates. Carrier trapping at grain surface or interface states can dominate over fast carrier recombination processes, which also increases the photovoltage decay time. It is furthermore shown that forming p-NiO/n-ZnO/Si heterostructure increases the photovoltage magnitude, which is up to several times, and shortens the SPV decays. This can be effectively used in manufacturing rapid photosensitive elements.

Possibility of increasing the sensitivity of sensors based on surface plasmon resonance phenomenon by electron beam processing of glass sensor substrates is shown. This is a consequence of the reduction of losses in the propagation of surface plasmons along the metal-air boundary. In this case the thickness of heterointerface gold-air was lowered from 3.26 down to 1.37 nm. Glass substrates treatment increased sensitivity by 1.7 times from 1.425 deg−1 up to 2.396 deg−1. It was ascertained using X-ray reflectometry that the film density increased from 17.2 up to 19.3 g/cm3 and reached the value typical for the bulk gold. As a consequence of resonance characteristic shift to the side of lower angles, the range of measurements is additionally widened by 0.37 deg, which extends the range of measurement of refractive indices. The results of the study can be applied to develop new devices based on the phenomenon of surface plasmon resonance.

International audience; The influence of magnesium oxide (MgO) content on the intensity of red photoluminescence (PL) of Mn4+ ions in Mn-doped phosphors Mg2TiO4:Mn produced by solid-state reaction at 1200 °C has been investigated by PL, optical absorption, X-ray diffraction, and electron paramagnetic resonance methods. The phosphors synthesized with excess MgO show an increase of Mn4+ red emission compared with those of stoichiometric composition. The magnitude of this increase depends on both MgO and Mn content. The largest increase of PL intensity is found for the phosphors synthesized under 3:1 molar ratios of MgO to TiO2. For these phosphors, the PL intensity increases from time 1.1 to time 3 when Mn concentration decreases from 1.0 to 0.0001 mol%. The phosphors produced under 6:1 molar ratios demonstrate a decrease of PL intensity at any Mn concentration. It is shown that excess MgO promotes stabilization of Mg2TiO4 phase against decomposition, hinders formation of Mn2+ centers, and enhances Mn4+ ions incorporation in the Mg2TiO4 crystal lattice. The latter together with reduced concentration quenching are supposed to be the main reasons of PL enhancement, which leads to the conclusion that excess MgO is necessary to produce an efficient red phosphor.

International audience; The effect of thermal annealing on optical, electrical and structural properties of Tb and Eu co-doped ZnO films grown by magnetron sputtering on Si and Al2O3 substrates was investigated by X-ray diffraction, photoluminescence, micro-Raman and IR reflection methods. It is shown that incorporation of rare earth ions in ZnO is accompanied by the formation of intrinsic defects. The as-deposited and annealed at 600 °C films demonstrate Tb3+ emission and no Eu3+ one. Higher intensity of Tb3+ photoluminescence in the films on Al2O3 substrate as compared with that on Si is ascribed to higher content of Tb3+ emitting centers. The model of these centers including the substitutional Tb and interstitial oxygen is proposed. In the excitation spectra of Tb3+ emission, no features connected with light absorption in ZnO are observed. An annealing at 900 °C is found to result in the formation of crystalline terbium oxide and silicate phases. In the photoluminescence spectra, the decrease of Tb3+ emission and the appearance of two sets of Eu3+ related bands caused by energy transfer from Tb3+ to Eu3+ ions are found. This is ascribed to segregation of rare earth ions in the additional phases and the decrease of the distance between the ions.

A wide range of possible applications of gallium oxide requires further investigations on growth techniques of its thin films, especially deposited on non-native substrates. One of the ways to avoid imperfection of Ga2O3 film because of variations in structure and lattice parameters of substrate could be an exploitation of buffer porous layer previously synthesized on the substrate. The 170 nm films deposited on porous-Si/Si substrate by rf magnetron sputtering are found out to be composed of β-Ga2O3 elliptical grains with sizes ∼150 nm. Both EDAX and Raman spectroscopy results show formation of a thin interfacial SiO2. Impedance spectroscopy measurements reveals two charge transfer processes with activation energies of 1.33 eV and 1.79 eV.

The relaxation of built-up strain in the heteroepitaxial GaN/AlN superlattices (SLs) leads to defect-related undesirable changes of the optical and electrical properties of SL-based devices. In the present study, the influence of lattice misfit between the GaN/AlN SL and GaN(0001) substrate on the mechanism of strain relaxation in the SLs is comprehensively analyzed. A strain/thickness-dependent effect on the densities of threading dislocations (TDs) and cracks in the SLs is observed. At the initial stage of growth of the SLs with relatively small lattice misfit, the formation of TDs dominates over the post-grown cracking triggered by the thermal stress during the sample cooling. Cracking during the growth is the main mechanism of strain relaxation for the SLs with large lattice misfit. It is established that for the GaN/AlN SLs with thicknesses >115 ± 15 nm, which corresponds to a SL relaxation degree >40 ± 5%, the density of defects drastically decreases. This result offers an essential guidance for excluding the strong influence of the substrate on generation of a large number of defects in the SLs. The quantitative interpretation and discussions of the presented results are important toward the design of a high-quality heteroepitaxial GaN/AlN SLs. Keywords: GaN/AlN superlattice, XRD, Microstructure, Strain relaxation, Dislocations, Cracks

The structural properties of AlN/GaN multiple quantum well (MQW) structures grown on c-plain sapphire substrate are studied by means of high-resolution X-ray diffraction (HRXRD). A new method to consider the influence of the depth variation of the dislocations density and well (barrier) thicknesses on the X-ray diffraction spectra was developed. The influence of the dislocation type on the diffraction peak broadening is based on the mosaic model of a crystal. The represented simulations of the experimental spectra are based on the dynamical theory of X-ray diffraction in agreement with the developed model. The calculations of X-ray diffraction spectra for AlN/GaN MQW considering the depth variation of dislocation density and layers thicknesses explain well the observed broadening and asymmetry of the satellites peaks of the measured spectra, especially for higher-order reflections. In addition, in this paper was demonstrated, that the commonly used Williamson–Hall plot analysis is consistent for MQW structures with the dislocations density > 1 × 108 cm−2. The developed methods allow fast and reliable determination of layers thicknesses, dislocations densities and strain profiles.

Influence of manganese substitution with 3d-ions on the structure, defectiveness, microstructure as well as resistive, dielectric and magnetoresistive properties of single-phase nonstoichiometric La0.6Sr0.15Bi0.15Mn1.1-xBxO3-δ (B = Cr, Fe, Co, Ni) compositions have been studied. All compositions demonstrate slight lattice parameter change of rhombohedral R 3 ¯ c distorted perovskite structure. The molar formulas of a real perovskite structure have been determined. The real structure is defect and contains cation V(c) and anion V(a) vacancies. The resistivity ρ increases with increase of x for all compositions. There is no “metal-semiconductor” phase transition at temperature Тms for x ≥ 0.20. It has been shown that the composition with B = Cr has the highest relative permittivity at x = 0.3. For the first time, the electron-phonon interaction constant γph has been determined for all the compositions within the framework of small polaron hopping model and it has been found that the strongest change of functional properties is a characteristic of the compositions with B = Fe, for which γph takes the maximum value γph ≈ 7.7.

The influence of the variations in the photoelectrochemical etching regimes of macropores in n-Si (within the limits of V. Lehmann optimums) on the quality of structures was studied. At some regimes, generation of screw (cylindrical or spiral) dislocations during the etching process under normal conditions was observed. First, dislocations are formed, and then macropores are etched, mainly on near-surface traces of dislocations. We call this process “auto-revealing”. The values of residual lattice distortions due to deformation of the silicon plate during the etching process were determined by x-ray diffraction on a structure obtained in the acceptable boundary regime.

Optical properties and morphology of thin films with Ge and SiGe nanocrystallites are studied by using the methods of Raman scattering, multi-angle ellipsometry, and X-ray measurements. Our observations showed that low-temperature Ge epitaxy on Si(001) surface at 350 °C and at high growth rate leads to the formation of thin films consisting of Ge nanocrystallites with the porosity of about 50%. Deposition of Si adatoms on the film surface stimulates the reconstruction of the surface with nanocrystallites and results in the increase of the degree of Ge crystallinity, coalescence of adjacent nanocrystallites, and in a slight Si-Ge mixing. The change in the values of the optical constants due to silicon deposition is described by means of Bruggeman approximation. The main reasons for these changes are the film crystallization and the appearance of Si crystalline phase in the structures with Si capping layer. The prepared Ge nanocrystalline solids, as well as the films covered with Si, may be used in quantum dot solar cells due to the high absorption capacity of the films and devices working in the hopping regime.

Addition functionalization after high-pressure oxidation of 2D macroporous silicon structures is evaluated. X-ray diffractometry indicates formation of orthorhombic SiO2 phase on macroporous silicon at oxide thickness of 800–1200 nm due to cylindrical symmetry of macropores and high thermal expansion coefficient of SiO2. Pb center concentration grows with the splitting energy of LO- and TO-phonons and SiO2 thickness in oxidized macroporous silicon structures. This increase EPR signal amplitude and GHz radiation absorption and is promising for development of high-frequency devices and electronically controlled elements.

We experimentally demonstrate that the conductivity of graded AlxGa1–xN increases as a function of the magnitude of the Al concentration gradient (%Al/nm) due to polarization doping effects, without the use of impurity dopants. Using three up/down-graded AlxGa1–xN nanolayers with Al gradients ranging from ∼0.16 to ∼0.28%Al/nm combined in one structure, the effects of polarization engineering for localized electric fields and current transport were investigated. Cross-sectional Kelvin probe force microscopy and conductive atomic force microscopy were used to directly probe the electrical properties of the films with spatial resolution along the thickness of the growth. The experimental profiles of the built-in electric fields and the spreading current found in the graded layers are shown to be consistent with simulations of the field distribution as well as of the electron and hole densities. Finally, it was directly observed that for gradients less than 0.28%Al/nm the native n-type donors still limit pola...

Systematic study of mercury cadmium telluride thin films subjected to the ion beam bombardment was carried out. The evolution of surface morphology of (111) Hg1 − x Cd x Te (x ~ 0.223) epilayers due to 100 keV B+ and Ag+ ion irradiation was studied by AFM and SEM methods. X-ray photoelectron spectroscopy and X-ray diffraction methods were used for the investigation of the chemical compound and structural properties of the surface and subsurface region. It was found that in the range of nanoscale, arrays of holes and mounds on Hg0.777Cd0.223Te (111) surface as well as the polycrystalline Hg1 − x Cd x Te cubic phase with alternative compound (x ~ 0.20) have been fabricated using 100 keV ion beam irradiation of the basic material. Charge transport investigation with non-stationary impedance spectroscopy method has shown that boron-implanted structures are characterized by capacity-type impedance whereas for silver-implanted structures, an inductive-type impedance (or “negative capacitance”) is observed. A hybrid system, which integrates the nanostructured ternary compound (HgCdTe) with metal-oxide (Ag2O) inclusions, was fabricated by Ag+ ion bombardment. The sensitivity of such metal-oxide-semiconductor hybrid structure for sub-THz radiation was detected with NEP ~ 4.5 × 10−8 W/Hz1/2at ν ≈ 140 GHz and 296 K without amplification.

The influence of Zn/S ratio in the charge on structural and optical properties of ZnS:Mn powders produced by high-temperature self-propagated synthesis was investigated. The samples was shown to consist of mixed-polytypes ZnS crystallites with hexagonal (2H) and cubic (3C) phases, the contribution of the latter increases with the sulfur content in the charge. The most homogeneous size distribution were found at stoichiometric Zn/S ratio. The Zn/S relation affects the Mn incorporation into ZnS lattice. The highest quantity of incorporated Mn is observed at stoichiometric Zn/S relation while lowest one is realized at Zn excess. Besides, the distribution of manganese ions in the blocks, which compose the crystallites, was found to be inhomogeneous, their concentration decreases from crystallites surface to the depth. Mn ions are nearer to the surface in ZnS:Mn synthesized with Zn excess. At Mn concentration in the charge of 1 wt% the shift of ZnS band edge to low energy side is observed, that is ascribed to formation of solid solution ZnS–MnS with lower band gap value.

A new approach is described that is applicable for structural characterization of any heteroepitaxially grown (strained or relaxed) III-nitride superlattices (SLs). The proposed method utilizes X-ray reciprocal space mapping measured in the vicinity of an asymmetrical reflection to determine the SL period, thickness, and strain state of a quantum well/barrier. On the example of a GaN/AlN SL, it is demonstrated that the structure parameters obtained from the proposed method agree very well with the parameters revealed by the currently preferred approach that is based on the measurements of ω/2θ X-ray diffraction profiles. Furthermore, it is shown that the shape of the reciprocal lattice points measured in the asymmetrical diffraction geometry contains additional information about the density of threading dislocations (TDs) in the GaN substrate and in the GaN/AlN SL. The comparison of the density of TDs in the substrate and in the SL allows analysis of the relaxation mechanism and development of new techniques for the improvement of the structural quality of the SL.

We report the results of an experimental study of polymer bulk material Polyamide-6 luminescence properties. A new effect of persistent time-delayed luminescence was revealed at room temperature. Detailed inspection of the effect has shown strong dependence on the microscopic crystalline structure of the polymer. Two morphological forms were recognized with the aid of X-ray Bragg reflection treating. The afterglow with the decay time exceeding 10 seconds was found to appear at about 150 K for the γ-form and is observed at room temperature for the α- form. The temporal dependence of time-delayed luminescence was found to satisfy hyperbolic Becquerel law, thus indicating the recombination origin of the effect. Also, emission realized with the excitation by third optical harmonics of a femtosecond Ti:Sapphire laser (267 nm) at room temperature was examined. The registered luminescence spectra were found quite different for these forms. While γ-form samples exhibit spectrum at the visible region, the α-form emits a pronounced luminescence output in the near UV (340 nm).

International audience; The effect of substrate material (Si, SiO2, Al2O3) on structural, optical and electrical properties of terbium doped ZnO films (Tb-ZnO) has been investigated by the X-ray diffraction, Raman scattering, atomic force microscopy, photoluminescence and infrared reflection methods. All films consist of micron size clusters of closely packed ZnO grains separated by deep trenches. The width of the trenches depends on the substrate material, being the largest in the Tb-ZnO/Al2O3 one. It is shown that the film on Al2O3 substrate contains the largest amount of extended and point defects. This film also demonstrates the highest intensity of Tb3+-related photoluminescence, while the film on Si substrate shows the lowest. On the contrary, the largest free carrier concentration evaluated from the infrared reflection spectra is found for Tb-ZnO/Si film and the lowest one is for the Tb-ZnO/Al2O3 film.

Single-phase lanthanum-modified bismuth ferrite multiferroic ceramics have been synthesized by the rapid liquid-phase sintering (RLS) method. Phase composition, crystal structure, microstructure and dielectric properties of the Bi0·9La0·1FeO3 multiferroic have been studied using TG/DTA, XRD, SEM, capacitive and composite dielectric resonator methods. It has been established that the optimal conditions for formation of a perovskite Bi0·9La0·1FeO3 structure are 850 °C after 5 min in air. It has been found that the compacting pressure of the initial mixture of precursors from 90 to 1090 MPa can change the dielectric constant by ~25% in the low-frequency range and by ~80% in the microwave range up to complete elimination of the elastic polarization mechanism. The use of the RLS method under various compacting pressures opens additional possibilities for creating multifunctional multiferroics with controlled magnetoelectric coupling.

The structural and optical properties of the Ge1 − xSnx layers with Sn mole fraction x of about 0.04 and 0.07 grown by molecular beam epitaxy on strain relaxed (001) Ge buffer layers have been investigated. The formation of GeSn solid solutions is proved by the high-resolution X-ray diffraction and micro-Raman investigations. The Ge1 − xSnx layers are found to be partially relaxed, the degree of strain relaxation increases from 8% in the layer with x = 0.04 to about 14% in the layer with x = 0.07. For the Ge and Ge1 − xSnx layers the miscut and tilt angles were calculated and compared with those predicted by Nagai's theory. For the Ge1 − xSnx layer with x = 0.07 an abnormally large tilt of about 0.26° of the epilayer (001) lattice planes with respect to the corresponding substrate planes is found. It is shown also that the epilayer tilt axis is rotated on about 90° with respect to the direction of a substrate miscut. The possible mechanisms of the effect are discussed.

The influence of strain and barrier/well thickness ratio on recombination processes in multi-quantum well (MQW) Al0.1Ga0.9N/GaN structures was investigated using X-ray diffraction and Raman and photoluminescence spectroscopies. The deformation state of the wells and barriers was determined. In addition, the value of the polarization fields, the density of polarization charges, and the positions of energy levels for optical transitions within the quantum wells were calculated. It was established that compressive strain in the buffer layer as well as in the layers of the MQWs with respect to the buffer layer lead to the piezoelectric fields having equal sign in the well and the barrier. As a result, the recombination of donor–acceptor pairs dominates over transitions between electron and hole states in the quantum well.

RF plasma annealing (RFPA) and rapid thermal annealing (RTA) of high-dose implanted n-type and p-type amorphized Ge layers have been studied by Raman scattering spectroscopy and X-ray diffraction techniques. It is shown that recrystallization of n-Ge implanted by BF 2 + ions requires higher RTA temperatures and power density of RFPA as compared to p-Ge implanted by P+ ions with the same dose. The RFPA has been performed at considerably lower temperatures than RTA and resulted in the formation of a sharp interface between the implanted and underlying Ge layers both for BF 2 + ion implantation and P+ ions implantation.

The influence of conditions occurring at the pulsed laser deposition of films with gold nanoparticles on the film porosity has been studied, by using the X-ray reflectometry. The films of two types were obtained by depositing particles (i) from the direct high-energy flow of erosion-torch particles and (ii) from the backward low-energy one. In both cases, the films were deposited either at the residual air pressurep = 10^−2 Pa or in the argon atmosphere with the pressures pAr = 5–100 Pa. In case (i), the film porosity was 0.1% atp = 10^−2 Pa and 1% at pAr ≤ 5 Pa. The plasmon properties of those films are associated with the propagation of surface plasmon-polariton waves. As the argon pressure grew further up to 100 Pa, the porosity increased to approximately 30%. In case (ii), the porosity of films deposited at pAr = 5–100 Pa onto substrates located in the target plane equaled 30 to 70% and depended on the distance from the film to the torch axis. All films with the porosity higher than 20% turned out nanocomposite structures with arrays of gold nanoparticles, which enabled us to observe the excitation of local surface plasmons., Вивчено вплив умов формування iмпульсним лазерним осадженням плiвок з наночастинками золота на їх пористiсть iз застосуванням рентгенiвської рефлектометрiї. Одержано плiвки двох типiв: з прямого високоенергетичного та зворотного низькоенергетичного потокiв частинок ерозiйного факела при залишковому тискуp =10^−2 Па i тиску аргону pAr =5–100 Па. Встановлено, що пористiсть плiвок першого типу, одержаних приp = 10^−2 та pAr 65 Па, становить 0,1 i 1%. Для цих плiвок плазмоннi властивостi пов’язанi з поширенням поверхневих плазмон-поляритонних хвиль. З подальшим пiдвищенням тиску аргону до 100 Па пористiсть зростає до ≈30%. Показано, що для плiвок другого типу, осаджених при pAr =5–100 Па на пiдкладку, яка розташована в площинi мiшенi, пористiсть становить 30–70% та залежить вiд положення дiлянки плiвки вiдносно осi факела. Всi плiвки з пористiстю бiльшою за 20% є нанокомпозитними структурами з масивами наночастинок золота. На них спостерiгається збудження локальних поверхневих плазмонiв.

International audience; The effect of Li+ co-doping on crystal phase formation and photoluminescence (PL) of Mn4+ activated magnesium titanate films produced by a solid state reaction method at different temperatures (800–1200 °C) has been investigated by using X-ray diffraction (XRD), diffuse reflectance and PL spectroscopy. The chemical composition of sintered films was estimated by energy dispersive X-ray spectroscopy. The concentration of Mn impurity estimated by Electron spin resonance was about 5 × 1016 cm−3. The XRD study of the annealed films revealed several magnesium titanate crystal phases, such as Mg2TiO4, MgTiO3 and MgTi2O5. The contribution of each phase depended strongly on the annealing temperature and the presence of Li+ additive. Furthermore, Li+ co-doping facilitated the formation of both MgTiO3 and Mg2TiO4 phases, especially at lower annealing temperatures. The PL spectra showed two bands centered at 660 and 710 nm and ascribed to the $^{2}E$ → ${^4}$A$_{2}$ spin-forbidden transition of the Mn4+ ion in the Mg2TiO4 and MgTiO3, respectively. In Li co-doped films, the integrated intensity of Mn4+ luminescence was found several times stronger compared to Li-undoped films that was ascribed mainly to flux effect of lithium.

Investigated in this work were plates of Zerodur connected to a solid monolith block with the aluminum nanolayer of the 100-nm thickness. The object of the study was this nanolayer that changed its optical transparency under action of pulsed laser radiation. Zerodur plate located on the back side after ablation was step-by-step thinned by grinding and polishing up to the boundary with aluminum nanolayer. After each thinning step, we performed the X-ray phase analysis by using the diffractometer Philips X’Pert PRO – MRD. Used in this study was Cu Kαl emission line with the wavelength λ = 0.15405980 nm). The anode potential was 45 kV, and current – 40 mA. It has been ascertained that the changes in phase composition are present within the region of 50⋯100 nm from the aluminum nanolayer boundary. It has been found the appearance of the weak but sharp peak at 28.4° that corresponds to the reflection (1 1 1) of cubic silicon nanoparticles. Their size is approximately 12 nm. It was revealed the weakly pronounced but clear peak at 44.78° that corresponds to the reflection (2 0 0) attributed to cubic aluminum.

The new method is suggested of formation of highly porous graphite-like thin films by radio frequency magnetron plasma enhanced chemical vapor deposition from argon-methane gas mixture. The prepared films were characterized before and after thermal annealing by XPS, XES, FTIR, Raman spectroscopy, XRD, XRR, AFM, and electrical measurements. Deconvolution of XPS spectra has demonstrated a significant growth of sp2/sp3 ratio from 1 for as-deposited films to 12 for the films annealed at 650 °C for 5 min. FTIR spectra have confirmed that thermal annealing results in reduction of H– and OH– functional groups and formation of С С bonds. The analysis of Raman spectra has shown that the annealing incorporates additional defects in graphite plane. XRD has shown that films are amorphous. Estimation of porosity from XRR measurements gave values of about 59% for as-deposited films and 34% for annealed films. AFM has shown that roughness of the films decreases from 3.3 to 0.6 nm during treatment at 650 °C in inert atmosphere. The size of pores was found to be few tens of nanometers. The electrical measurements have shown that after annealing the resistivity decreases by up to 5 orders of magnitude. Annealed films have demonstrated perceptible sensitivity to ammonia and water vapor.

A detailed XRD analysis of AlN/GaN multiple quantum well (MQW) structures grown on AlN(0001) substrates is proposed. The effect of roughness on the 2θ-ω scans measured in Bragg diffraction for symmetrical reflections is investigated together with the effect of depth variation of the well and barrier thickness. As shown, the magnitude of depth variation of the well and barrier thickness results in an asymmetrical broadening of the satellite peaks of the 2θ-ω scans. Roughness causes their symmetrical expansion that allows separating the influence of both effects. Several reasons of asymmetrical broadening of satellite peaks are considered: variation of the thickness period, variation of the average lattice parameter inherent to the period, which depends on the thickness ratio of the layers in the period, and their combination. The efficiency of the described method is illustrated in detail by numerical simulations. В работе предложен детальный рентгенодифракционный анализ структур с множественными квантовыми ямами (МКЯ) AlN/GaN, выращенными на подложках AlN(0001). Было исследовано влияние шероховатости и вариации толщины слоёв квантовых ям и барьеров на 2θ-ω-сканы, полученные в геометрии отражения по Брэггу для симметричных рефлексов. Показано, что наличие вариации толщины слоёв AlN и GaN по глубине приводит к появлению асимметрии сателлитных пиков МКЯ на 2θ-ω-сканах. Наличие шероховатости приводит к симметричному расширению сателлитных пиков, что позволяет разделить влияние этих эффектов. Рассмотрено несколько причин асимметричного расширения сателлитных пиков: изменение толщины периода, изменение среднего параметра решётки периода, который зависит от соотношения толщин слоёв в периоде, и их комбинации. Эффективность разработанного метода показана с помощью численного моделирования. В роботі проведено детальну аналізу структур із множинними квантовими ямами (МКЯ) AlN/GaN, вирощених на підкладинках AlN(0001). Було досліджено вплив шерсткости та зміни товщини шарів структури з МКЯ по глибині на 2θ-ω-скани, виміряні в Бреґґовій геометрії дифракції для симетричних рефлексів. Показано, що зміна товщини квантових ям і бар’єрів по глибині приводить до асиметричного розширення сателітних піків МКЯ на 2θ-ω-сканах. Шерсткість спричинює симетричне розширення піків, що уможливлює розрізнити вплив цих ефектів. Розглянуто кілька причин асиметричного розширення сателітних піків: зміну товщини періоду, зміну середнього параметра ґратниці періоду, який залежить від співвідношення товщин шарів періоду, та їх комбінації. Ефективність розробленої методи показано шляхом числового моделювання рентґенівських спектрів.

We report on AlxGa1-xN heterostructures resulting from the coherent growth of a positive then a negative gradient of the Al concentration on a [0001]-oriented GaN substrate. These polarization-doped p-n junction structures were characterized at the nanoscale by a combination of averaging as well as depth-resolved experimental techniques including: cross-sectional transmission electron microscopy, high-resolution X-ray diffraction, Rutherford backscattering spectrometry, and scanning probe microscopy. We observed that a small miscut in the substrate orientation along with the accumulated strain during growth led to a change in the mosaic structure of the AlxGa1-xN film, resulting in the formation of macrosteps on the surface. Moreover, we found a lateral modulation of charge carriers on the surface which were directly correlated with these steps. Finally, using nanoscale probes of the charge density in cross sections of the samples, we have directly measured, semiquantitatively, both n- and p-type polarization doping resulting from the gradient concentration of the AlxGa1-xN layers.

Experimental data on manufacturing the ohmic contacts Au–Ti–Pd–n⁺-InP, formed using vacuum deposition of metal onto a heated to 300 °C substrate representing an epitaxial n⁺-n-n⁺⁺-n⁺⁺⁺-InP structure. The specific contact resistance measured at room temperature was about 7·10⁻⁵ Ohm·cm². Voltage-current characteristics within the temperature range 110 to 380 K are linear. Gunn diodes with such contacts, which were made as a straight mesa-structure in a pulsed mode (pulse duration of 100 ns, pulse ratio of 1000, operating current of 2.2 A), generated the microwave power ~10 mW in the V-band.