In this work, stabilized f-ZrO2 ceramic samples with the compositions of (Zr0.82Y0.09Eu0.09)O1.91, (Zr0.82Y0.09Tb0.09)O1.91 and (Zr0.82Y0.09Eu0.045Tb0.045)O1.91 were studied. The elemental composition was studied by electron probe microanalysis, and the luminescent properties were studied by local cathodoluminescence (CL). An analysis of the Eu3+ CL spectra confirmed the stabilization of the cubic phase in ceramics at room temperature. The study of the obtained CL spectra, the 5D4-7F5Tb3+ band luminescence decay kinetics, CL images and excitation spectra showed europium sensitization by terbium in (Zr0.82Y0.09Eu0.045Tb0.045)O1.91. Keywords: f-ZrO2, Eu3+, Tb3+, Ceramics, Sensitization, Cathodoluminescence

Series of gadolinium tantalum niobates activated with Eu3+ and Tb3+ ((Gd1-y-zEuyTbz)NbxTa1-xO4 (x = 0, 0.3, 1; y = 0.6; z = 0.06; 0.15; 0.3)) were obtained for the first time. The formation of substitutional solid solutions was demonstrated. The obtained ceramic solid solutions had a monoclinic structure with I2/a space group. Electron probe microanalysis, photoluminescence (PL) and cathodoluminescence (CL) were used for studies of gadolinium tantalates and tantalum niobates series activated with Eu3++Tb3+. CL and PL spectra, concentration dependences of CL intensity and decay times, as well as excitation spectra for 5D0-7F2 Eu3+ and 5D4-7F5 Tb3+ bands were analyzed. It was shown for the first time that both energy transfer from Tb3+ to Eu3+ ions, and a reverse process - energy transfer from Eu3+ to Tb3+ ions are observed. This reverse process led to a decrease in CL intensity and decay times of europium bands in the presence of terbium 3+ in these materials. Presumably this phenomenon is influenced by anti-Stokes luminescence. This is confirmed by the dependences of anti-Stokes luminescence probability on temperature and excitation density.

The ceramics based on cubic (Zr0.82–xHfxY0.17Eu0.01)O0.91 with different contents of hafnium were studied. In the work, the elemental composition of the samples was obtained, the cathodoluminescence (CL) spectra and decay kinetics of europium luminescence were studied. The researched showed increase in the content of hafnium doesn’t affect the position and number of observed bands in the luminescence spectrum. The electric dipole and magnetic dipole radiative transitions ratio was estimated for all samples. It’s demonstrated that a decrease in the local symmetry of the europium ion associated with an increase in the hafnium content. It’s shown the 5D0–1F1 transition Eu3+ decay time doesn’t depend on the hafnium content, but v-aries significantly in different regions of the sample, which can be attributed to the influence of grain bou-ndaries.

by molecular-beam epitaxy we have grown epitaxial layers of GaAs1–xBix solid solutions with a bismuth content of 0 < x < 0.02. Structural and optical properties of the layers were investigated. We determine the influence of the bismuth flux and substrate temperature on the bismuth incorporation into the growing layers.

The ceramics based on cubic (Zr0.82-xHfxY0.17Eu0.1)O1.91 with different contents of hafnium were studied. In the work, the elemental composition of the samples was obtained, the cathodoluminescence (CL) spectra and decay kinetics of europium luminescence were studied. The researched showed increase in the content of hafnium doesn’t affect the position and number of observed bands in the luminescence spectrum. The electric dipole and magnetic dipole radiative transitions ratio was estimated for all samples. It’s demonstrated that a decrease in the local symmetry of the europium ion associated with an increase in the hafnium content. It’s shown the 5D0-7F1 transition Eu3+ decay time doesn’t depend on the hafnium content, but varies significantly in different regions of the sample, which can be attributed to the influence of grain boundaries.

In this work, stabilized f-ZrO2 ceramic samples with the compositions of (Zr0.82Y0.09Eu0.09)O1.91), (Zr0.82Y0.09Tb0.09)O1.91) and (Zr0.82Y0.09Eu0.045Tb0.045)O1.91 were studied. The elemental composition was studied by electron probe microanalysis, and the luminescent properties were studied by local cathodoluminescence (CL). An analysis of the Eu3+ CL spectra confirmed the stabilization of the cubic phase in ceramics at room temperature. The study of the obtained CL spectra, the 5D4-7F5 Tb3+ band luminescence decay kinetics, CL images and excitation spectra showed europium sensitization by terbium in (Zr0.82Y0.09Eu0.045Tb0.045)O1.91.

by molecular-beam epitaxy we have grown epitaxial layers of GaAs 1– x Bi x solid solutions with a bismuth content of 0 < x < 0 . 02. Structural and optical properties of the layers were investigated. We determine the influence of the bismuth flux and substrate temperature on the bismuth incorporation into the growing layers.

For the first time, a series of ceramic solid solutions of gadolinium tantalum niobates activated by europium was synthesized. A detailed interpretation of the obtained ceramics luminescence spectra was performed in the range of 580-630 nm for photoluminescence and 390-720 nm for cathodoluminescence. The transitions from 5D0, 5D1, 5D2 and 5D3 radiative levels of Eu3+ were observed in cathodoluminescence spectra of the samples. The main structural phase of the samples corresponded to the monoclinic structure with I2/a space group. The dependence of the europium luminescence bands Stark splitting on the Nb/Ta ratio in the material was studied for various radiative transitions. It was demonstrated that the distance between Eu3+ luminescence bands splitting increased in the solid solution series from GdNbO4 to GdTaO4. It can be due to an increase in the local field action on the Eu3+ ions.

By molecular-beam epitaxy we have grown epitaxial layers of GaAs1-xBix solid solutions with a bismuth content of 0 < x < 0.02. Structural and optical properties of the layers were investigated. We determine the influence of the bismuth flux and substrate temperature on the bismuth incorporation into the growing layers.

Abstract It is necessary to minimize the resistance of electrical contacts to reduce heat losses in photovoltaic converters of laser radiation. The paper describes ways to reduce the resistance of electrical contacts for p-InP by choosing the composition of the subcontact layer based on p-InGaAs. For this purpose, layers of p-InGaAs with different compositions and bandgaps were grown by the MOCVD method. AgMn/Ni/Au contact metallization was deposited on samples to compare the characteristics of electrical contacts. The minimum specific contact resistance was 7• 10−5 Ω-cm2 for the layer with Eg = 0.51 eV.

Luminescence properties of epilayers of Ga 1 – x In x As y P 1 – y (GaInAsP) solid solutions with graded content of Group V elements (Δ y up to 0.08 over a total thickness of about 1 μm) were studied at 77 and 300 K. The photoluminescence (PL) spectra of GaInAsP epilayers with large Δ y values were broadened. The GaInAsP epilayers of low crystalline perfection exhibited either no PL emission or showed PL spectra characteristic of transitions involving impurity energy levels.

The photoluminescent properties at 77 and 300 K are investigated for Ga1 xInxAsyP1 y epilayers with V-group elements content gradient Δy up to 0.08 across whole thickness (about 1 µm). Ga1 xInxAsyP1 y layers with high Δy values have widened photoluminescence spectra. For GaInAsP layers of low crystaline perfection, photoluminescence was either absent or manifested itself as it is typical for transitions involving impurity levels.

GaInPAs/InP heterostructures grown by low pressure (0.1 bar, 600 oC) metal-organic chemical vapor phase deposition were investigated. The thicknesses of grown GaInAsP layers were about 1 µm. For the epitaxial layers Ga1-xInxP1-yAsy) with average compositions of x = 0.77 – 0.87 and y = 0.07 – 0.42 the variation of V group elements content y with the epilayer depth were revealed, weher the compositions of V-group elements were changed up to Δy = 0.1 atomic fractions in V group elements sublattice. In most cases, y change occurs in a GaInAsP region up to 200 nm thick adjacent to the InP. In some cases, y changes throughout the whole GaInPAs layer thickness. Fo the epitaxial layers with a satisfactory crystal perfection the less was the mismatch between the substrate and the GaInPAs epitaxial layer, the smaller was the value of Δy. For GaInPAs layers characterized by a low degree of crystal perfection and a high lattice mismatch between GaInAsP and InP layers, the value of Δy was about zero. These data let us suggest that the incorporation of atoms of the V group in the epitaxial layer strongly depends on elastic deformation of the growing monolayer, that is mismatched with the underlying crystal surface.

GaInPAs/InP heterostructures grown by metalorganic chemical vapor-phase deposition at a temperature of 600°C and pressure of 0.1 bar are investigated. The thicknesses of the grown GaInAsP layers amount to about 1 μm. For Ga1 –xInxP1 –yAsy solid solutions with average compositions of x = 0.77–0.87 and y = 0.07–0.42, the variation in the content y of V-group atoms over the epitaxial-layer thickness by a value of Δy up to 0.1 atomic fractions in the sublattice of the V-group elements is revealed by secondary ion mass spectrometry. In most cases, a change in y occurs in the GaInAsP layer over a length to 200 nm from the InP heterointerface. In certain cases, y varies throughout the entire GaInPAs-layer thickness. For the epitaxial layers with satisfactory crystalline perfection, the value of Δy is less in the case of better lattice-matching between the GaInPAs epitaxial layer and the substrate. For GaInPAs layers strongly lattice-mismatched with the substrate and characterized by a low degree of crystalline perfection, the value of Δy is close to zero. All these facts enable us to assume that it is elastic deformations arising in the forming monolayer lattice-mismatched with the growing surface that affect the incorporation of V-group atoms into the forming crystalline lattice.

Wide-gap ZnSe-based nanoheterostructures grown by molecular beam epitaxy are comprehensively studied by electron probe microanalysis and local cathodoluminescence techniques. These non-destructive methods applied in combination allow independent determination of true depth, composition, and thickness of single ZnCdSe nanolayers (NL), located deep inside the heterostructures, with a relative accuracy of 10%. The developed approach is based on the variation of the electron probe energy, which results in different thickness of the region where characteristic x-ray emission and cathodoluminescence occur. The former establishes relation between the NL depth and composition at a fixed NL thickness, as defined by using an original modelling program, while the latter connects the NL thickness and composition.

Gradual variation of the content y of Group-V components by Δy of up to 0.08 across the thickness (600–850 nm) of an epitaxial layer has been observed for Ga1 – xInxAsyP1 – y solid solutions (x = 0.86, y = 0.07–0.42) produced on InP by metal-organic vapor-phase epitaxy under lowered pressure, although the composition of the gas mixture, temperature, and pressure were maintained invariable in the course of the growth process. For different gas mixture compositions, the value of Δy and the manner of its variation were different. An analysis of the data obtained demonstrated that Δy is due to the deformations that appear in a growing layer because of the lattice mismatch with the substrate.

Ga1-xInxAsyP1−y epitaxial layers with compositions x = 0.77 − 0.87, y = 0.07 − 0.42 and thicknesses 620 − 850 nm were grown by MOCVD method on InP substrates. Temperature, pressure and gas mixture composition were held constant during growth procedure. Secondary-ion mass spectrometry showed change of V-group elements composition y through epilayers thicknesses by value Δy up to 0.08. Reducing Δy value down to 0.01 − 0.02 was achieved by optimizing the composition of gas mixture to reduce lattice mismatch between the layer and the substrate. The obtained data allow us to conclude that the deformations arising due to lattice mismatch between the forming layer and the growth surface result in varying the content of V-group elements through epilayer thickness.

Wide-gap ZnSe-based nanoheterostructures grown by molecular-beam epitaxy are studied by local cathodoluminescence and X-ray microanalysis. It is shown that the used methods allow nondestructive determination of the depth, elemental composition, and geometrical parameters of the nanoscale ZnCdSe layer. The accuracy of the results is verified by transmission electron microscopy. The research techniques are based on the possibility of varying the primary electron-beam energy, which results in changes in the regions of characteristic X-ray and cathodoluminescence generation.

Методами локальной катодолюминесценции и рентгеноспектрального микроанализа проведено комплексное исследование широкозонных наногетероструктур на основе ZnSe, полученных методом молекулярно-пучковой эпитаксии. Было показано, что используемые методы позволяют неразрушающим способом определять глубину залегания, элементный состав и геометрические параметры наноразмерного слоя ZnCdSe. Точность результатов контролировалась методом просвечивающей электронной микроскопии. Методики исследования основаны на возможности варьирования энергии первичного электронного пучка, что приводит к изменению областей генерации характеристического рентгеновского излучения и катодолюминесценции. DOI: 10.21883/FTP.2017.01.8249

Single crystals of polyelemental rare earth hexaborides with the preset formula La0.5(Ce0.1Pr0.1Nd0.1Sm0.1Eu0.1)B6 were obtained for the first time. Synthesis and crystallization were performed by the solution–melt method in an immiscible Al/Pb system. Step-by-step chemical analysis was made with the aid of a CAMEBAX microprobe. The inclusion of all rare earth metals (REMs) in the hexaboride lattice was proven, and differences in the composition of obtained crystals caused by nonstationarity of the bulk crystallization process were found. The lattice periods of the polyelemental REM hexaborides were found to be smaller than that of hexaboride of lanthanum, the main element of the metal sublattice. The measured microhardness of the new material lies within the range of the microhardness values of hexaborides of all its constituent REMs. Speculations are provided on the peculiarities of the growth mechanism, crystallization, and composition of the obtained crystals.