Growth and properties of nanostructured layers based on Pb<Subscript>1 − <Emphasis Type=Italic>x</Emphasis></Subscript>Cd<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>Se (<Emphasis Type=Italic>x</Emphasis> = 0−0.20) solid solutions

We have produced nanostructured layers based on supersaturated Pb_1−x Cd _x Se (x = 0−0.20) solid solutions with an efficient room-temperature photoluminescence in the range 3–5 μm and studied the effect of growth conditions on their chemical and phase compositions and properties. Their photoluminescence spectra have been measured, and the main radiative recombination mechanisms in activated solid-solution layers have been identified. The role of iodine in the formation of the emitting nanostructures has been discussed.     

Thermoelectric power factor of Ti<Subscript>1 − <Emphasis Type=Italic>x</Emphasis></Subscript>V<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>NiSn alloys

Ti_{1 − x} V _x NiSn (x = 0–0.10) substitutional solid solutions have been prepared by doping the intermetallic semiconductor n-TiNiSn (half-Heusler phase) with vanadium, a donor impurity, and their resistivity and thermopower have been measured at temperatures from 80 to 380 K. The results demonstrate that, when doping of TiNiSn causes no type inversion, the thermoelectric power factor of the solid solution markedly exceeds that of the undoped ternary compound.     

Effects of Out-of-Plane Disorder in CaFe<Subscript>1−<Emphasis Type=Italic>x</Emphasis></Subscript>Co<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>AsF System

We perform oxygen doping experiments in the CaFeAsF and CaFe_0.88Co_0.12AsF compounds. In the parent compound CaFeAsF, partial replacement of F by O leads to an increase of resistivity and a weakening of spin-density wave transition, indicating that the out-of-plane disorder strongly affects the electronic and magnetic properties of the system. In the CaFe_0.88Co_0.12AsF_1−x O _x system, the doping of oxygen leads to the suppression of superconductivity, reflecting the importance of Ca–F layer disorder in this system.     

Potassium ion conducting K<Subscript>1 − 2<Emphasis Type=Italic>x</Emphasis></Subscript>Cd<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>FeO<Subscript>2</Subscript> solid electrolytes

New potassium ion conducting solid electrolytes based on potassium monoferrite have been prepared through partial substitution of the divalent cation Cd²⁺ on the potassium site, and their properties have been investigated. The introduction of cadmium cations sharply increases the electrical conductivity of KFeO₂ over the entire temperature range studied. In addition to the maximum in conductivity at the boundary of the K_{1 − 2x} Cd _x FeO₂ solid solution, there is a maximum at a higher cadmium content (x = 0.30–0.35). The possible origins of this maximum are discussed.     

Misfit dislocations and stress in In<Subscript>1 − <Emphasis Type=Italic>x</Emphasis></Subscript>Ga<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>As/GaAs heterostructures

We have estimated the elastic properties of In_{1 − x} Ga _x As/GaAs heterostructures and the characteristics of misfit dislocations in such heterostructures: misfit dislocation spacing, Burgers vector length in various interfaces, surface density of dangling bonds, film/substrate interface energy, critical film thickness below which pseudomorphic growth is possible without misfit dislocations, elastic strain energy of the film-substrate system, average elastic strain of a thin-film island as a function of its radius, thermal stresses induced by the thermal-expansion and lattice mismatches between the layers in contact, and crack length in the film.     

Structural,optical and electrical properties of ZnTe<Subscript>1−<Emphasis Type=Italic>x</Emphasis></Subscript>Se<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript> thin films

ZnTe_1−x Se _x films were deposited on glass substrates kept at 200 °C by the electron beam evaporation technique. These films exhibited cubic structure and the lattice parameter increased with increase of Tellurium concentration in the films which confirmed the solid solution formation. The grain size is found to increase with Te content. The dislocation density and lattice strain show a decreasing trend with increasing of Te content. Band gap values of 2.73 eV, 2.63 eV, 2.52 eV and 2.41 eV have been calculated for the films of composition ‘x’ = 0.2, 0.4, 0.6 and 0.8, respectively, which confirmed the formation of solid solution between ZnSe and ZnTe. Refractive index of the films increased from 2.535 to 2.826 as the concentration of Te increased. All the films showed high resistivity values. Laser Raman spectral studies of ZnTe_1−x Se _x revealed LO phonon frequencies whose values are located in between the LO phonon frequencies of ZnSe and ZnTe.     

Sb-doped CuAlO<Subscript>2</Subscript>: widening of band gap and nonlinear <Emphasis Type=Italic>J</Emphasis>–<Emphasis Type=Italic>E</Emphasis> characteristics

The effect of antimony doping on the optical and electrical properties of copper aluminum oxide synthesized by solid state reaction technique was investigated. Formation of single phase CuAlO₂ was confirmed by x-ray diffraction studies. Variation of strain, particle size, and preferred orientation of the crystallites with Sb doping concentrations were analyzed by x-ray diffraction. Using the x-ray photoelectron spectroscopy trivalent state of Sb ions was confirmed. A blue shift in the energy band gap with Sb doping was observed, and it was supported by ab initio calculation based on density functional theory. A nonlinear current–voltage characteristic was observed for the Sb-doped CuAlO₂ samples whereas the same was linear for the undoped samples. The nonlinearity of the current–voltage characteristics changed significantly at higher temperature, and this behavior was explained.     

Perturbed Angular Correlations Studies in the HgBa<Subscript>2</Subscript>CaCu<Subscript>2</Subscript>O<Subscript>6+<Emphasis Type=Italic>δ</Emphasis></Subscript> high-T<Subscript><Emphasis Type=Italic>C</Emphasis></Subscript> Superconductor

The electric field gradients at ^199mHg nuclei have been measured via the perturbed angular correlation (PAC) technique, allowing a full characterization of the Hg neighborhood charge distribution at high oxygen doping on the Hg planes. The PAC technique has been applied to investigate the effect of high oxygen pressure during the measurement. Polycrystalline HgBa₂CaCu₂O_6+δ (Hg-1212) samples have been annealed at 152 bar pressurized oxygen. The influence of oxygen pressure during the experiment was then investigated by measuring the samples at atmospheric pressure and under 152 bar oxygen pressure.     

Synthesis and laser-excited IR luminescence of Y<Subscript>1 − <Emphasis Type=Italic>x</Emphasis></Subscript>Yb<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>PO<Subscript>4</Subscript> solid solutions

We have determined the composition range of solid solutions in the binary system YPO₄-YbPO₄ and identified the key trends in the composition dependence of their IR Stokes luminescence intensity and decay time in the range 0.96–1.1 μm. The results were used to develop a new narrow-band IR phosphor, YPO₄:Yb³⁺. Under 0.940-μm laser excitation, this phosphor offers an increased IR Stokes luminescence intensity in the range 0.96–1.1 μm (about twice as high as that of the well-known commercially available phosphors L-54 and FSD-546-2), with an afterglow time of 1700–1800 μs.     

Electron diffraction study of TlGa<Subscript>1 − <Emphasis Type=Italic>x</Emphasis></Subscript>Ge<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>X<Subscript>2</Subscript> (X = S,Se, Te) nanofilms

The formation of thin TlGa_{1 − x} Ge _x X₂ (X = S, Se, Te) films has been studied by high-energy electron diffraction. The results demonstrate that the dopant (Ge) concentration influences the structure of the films (30 nm in thickness). The epilayer-substrate orientation relationships are identified.     

Magnetic and structural properties of Fe<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>Pt<Subscript>100−<Emphasis Type=Italic>x</Emphasis></Subscript> on MgO(110) substrates

Fe _x Pt_100−x (70.1 ≤ x ≤ 83.4) thin films with ordered Fe₃Pt phase were grown successfully onto MgO(110) substrates by electron beam evaporation. The unit cell of ordered Fe₃Pt phase is elongated along c-axis direction and the thin films become more chemically ordered with decreasing Fe content. The magnetization of thin films shows a decrease when Fe content is around 79 at.%. The relationship between magnetic anisotropy and structural parameters suggests that the change of magnetic anisotropy in ordered Fe₃Pt thin films with different compositions most likely stems from the magnetocrystalline origin.     

Phase structure and vibrational spectra of rare-earth-oxide ceramics of Dy<Subscript>2(1−<Emphasis Type=Italic>x</Emphasis>)</Subscript>Tm<Subscript>2<Emphasis Type=Italic>x</Emphasis></Subscript>O<Subscript>3</Subscript>

Rare-earth-sesquioxide ceramics have been found to possess potential applications in solid-state lasers due to their excellent physical and chemical properties as well as low cost. In this paper, composite powders with the composition of Dy_2(1−x)Tm_2x O₃ were prepared by ball milling method and corresponding ceramics were obtained using the pressureless sintering technique. Phase structure and vibrational spectra were investigated using X-ray diffraction, Raman spectrometer, and FT-IR spectrometer. It is shown that the mixture of Dy₂O₃ and Tm₂O₃ converts to an ordered solid solution of body-centered cubic structure after heat treatment at 1,100 °C for 4 h. It is also found that the cell constants of ceramics decrease linearly with the increase of Tm₂O₃ content. Raman spectra analysis demonstrates that bond length plays a major role in determining the frequencies of Raman bands at high-frequency range and that peak positions exhibit a blue shift with the increase of Tm₂O₃ content due to decreasing cell constant. Similar phenomenon is also observed in infrared spectra, which shows linearly increasing infrared band frequency with decreasing cell volume. The ball milling method used for preparing composite powders and vibrational spectra analysis in this work provide some important references for the study of laser ceramics containing Dy₂O₃ and Tm₂O₃.     

Critical Current Densities and Vortex Dynamics in Ba(Fe<Subscript>1−<Emphasis Type=Italic>x</Emphasis></Subscript>Co<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>)<Subscript>2</Subscript>As<Subscript>2</Subscript> Single Crystals

Superconducting properties are evaluated for high-quality single crystals of Ba(Fe_1−x Co _x )₂As₂ in a wide range of doping levels. The critical current density, J _c , in an optimally-doped crystal (T _c ∼24 K) shows a fishtail effect with its value over 10⁵ A/cm² even at 5 T below 10 K. Magneto-optical imaging has clarified rather homogeneous supercurrent flow in the crystal, in spite of a large amount of impurities. In the heavy-ion irradiated sample, the presence of columnar defects are confirmed and J _c has been enhanced by a factor of five at low temperatures, reaching 6×10⁶ A/cm² at 2 K under zero field. Flux creep rate in the heavy-ion irradiated sample has been reduced in accordance with the enhancement of J _c .     

A Study of the Thermovoltaic Effect in Heterostructures Based on Sm<Subscript>1–<Emphasis Type=Italic>x</Emphasis></Subscript>Gd<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>S Solid Solutions

The influence of doping of samarium monosulfide with gadolinium has been investigated. Experiments have been carried out in the temperature range of 300–450 K. A decrease in the effect value with increasing gadolinium content in the Sm1–xGdxS heterostructure with x ranged from 0 to 0.13 has been found and explained. Formulas for calculating the output signal in dependence of the doping value have been derived.