Quantitative analysis of Bi1−xSbx

The chemical composition of Bi_1-xSb_x alloys is determined by means of square-wave polarography, density measurements, measurements of the electron backscatter coefficient, and electron probe microanalysis. These experimental methods are discussed with respect to their results. At 10 keV, the electron probe microanalysis allows the determination of any antimony concentration without corrections (c_Sb = k_Sb).     

Diffusion Phenomena during the heteroepitaxy of Ternary Compounds of the Type (AxB1–x)1–ΔC1+Δ

In heteroepitaxy of ternary compound systems of the type (A_xB_1–x)_1–ΔC_1+Δ has to be taken into account the occurrence of complex diffusion phenomena independent on the epitaxial method applied which cannot be considered within a quasi-binary system AC–BC. Based on the statements of thermodynamics of irreversible processes a model for the calculation of diffusion profiles, regarding the influence of the compound crystal composition x on the deviation from stoichiometry Δ, is presented. Concentration profiles calculated in accordance to this model show typical maxima and minima. – Tellurium distribution profiles determined on heterostructures of the type (Pb_1–xSn_x)_1–ΔTe_1+Δ /PbTe got by electron-probe microanalysis may be explained qualitatively within the presented model. With the EBIC-method additional p-n junctions at the position of the extrema in the tellurium distribution were found.     

Bildung und Untersuchung von SixAl1−xAs-Kristallen

Si_xAl_1−xAs is formed by chemical transport reaction of AlAs using iodine as transporting agent. The experiments are performed in sealed silica tubes in the temperature range from 900 to 1000°C. The grown platelet-shaped crystals and whiskers are investigated with x-ray diffraction, light microscopy, electron microscopy and electron-probe microanalysis. The mechanism of growth is discussed.     

Quantitative Bestimmung der Zusammensetzung von Ga1−xAlxAs-Epitaxieschichten mit der Elektronenstrahl-Mikroanalyse (ESMA)

Several methods of correcting the X-ray intensity in the electron probe microanalysis were examined for getting the local concentrations of Ga, Al and As in Ga_1−xAl_xAs epitaxial layers. Most correct results were obtained by combining the method of BIRKS for the Al-determination with that of DUNCUMB /REED /SPRINGER for the Ga-determination. In this case the mean departure from 50% for the sum of the Ga and Al atom-percents is only −0.1%. Equations for the mutual conversion of concentrations into masses, necessary for the practical use, are given in an appendix.     

Distribution of aluminum and indium impurities in crystals of Ge-Si solid solutions grown from the melt

The problem regarding the distribution of aluminum and indium impurities in bulk crystals of solid solutions with a variable composition Ge_1−x Si _x (0 ≤ x ≤ 0.3) is solved in order to establish regularities of the changes in the segregation coefficients of impurities with variations in the composition of the host lattice in the germanium-silicon system. Aluminum-and indium-doped crystals of Ge_1−x Si _x (0 ≤ x ≤ 0.3) solid solutions with a silicon content decreasing along the crystallization axis are grown by a modified Bridgman method with the use of a silicon seed. The concentration distribution of impurities over the length of the crystals is determined from Hall measurements. It is demonstrated that the experimental data on the concentration distribution of impurities in the crystals are in good agreement with the results obtained from the theory according to which the equilibrium segregation coefficients of impurities vary linearly with a change in the composition of Ge-Si solid solution crystals.

     

Raman scattering characterization of Mn composition and strain in Ga1–x Mnx Sb/GaSb epitaxial layers

Raman scattering (RS) experiments have been performed for simultaneous determination of Mn composition and strain in Ga_1–x Mn_x Sb thin films grown on GaSb substrate by liquid phase epitaxy technique. The Raman spectra obtained from various Ga_1–x Mn_x Sb samples show only GaSb‐like phonon modes whose frequency positions are found to have Mn compositional dependence. With the combination of epilayer strain model, RS and energy dispersive x‐ray (EDX) experiments, the compositional dependence of GaSb‐like LO phonon frequency is proposed both in strained and unstrained conditions. The proposed relationships are used to evaluate Mn composition and strain from the Ga_1–x Mn_x Sb samples. The results obtained from the RS data are found to be in good agreement with those determined independently by the EDX analysis. Furthermore, the frequency positions of MnSb‐like phonon modes are suggested by reduced‐mass model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bildungsbedingungen und Struktur dünner Bi1−xSbx-Schichten

Thin polycrystalline Bi_1−xSb_x films in oriented state were deposited by flash evaporation techniques and by catode sputtering. In dependence on the conditions of formation the structure of these films was analysed by means of transmission electron microscopy, electron diffraction and electron beam microanalysis. Estimating the orientation, quality of surface and largeness of the average diameter of the crytallites the flash evaporation technique is superior to the catode sputtering under the experimental conditions chosen in this investigation. The Bi:Sb proportion does not change in comparison with the target, material of the source respectively, during the formation of the film.     

Crystallo-optical properties of the SmxTb1−xFeO3 orthoferrites

The paper reports the results of X-ray diffraction studies as well as the angular dependences of rotation of the plane of polarization and birefringes of the Sm_xTb_1−xFeO₃ crystals (x = 0; 0.2; 0.4; 0.55; 0.8; 1). The polar diagrams presented for the plane (001) have the symmetry mm2, while for (110), the symmetry lowers up to the axis of a second order. The gyrotropic measurements made have allowed us to refer the Sm_xTb_1−xFeO₃ to a planar class of an orthorhombic crystal system with the space group C_2v⁹–Pn2a, class mm2. – The magnitude of birefringence for the Sm_xTb_1−xFeO₃ is found to be sensitive both to a crystallographic direction and a composition, the greatest values stand for (110). For (001), a non-monotonous birefringence variation with the composition is observed. The angles between optic axes, calculated by the birefringence magnitudes, are in fair agreement with gyrotropic data for the compositions x = 0.55 – 1.     

Vapour Phase Epitaxy of GaxIn1−xAs in the Ga?In?HCl?AsH3?H2-System Using a Mixed Ga/In Source

The mixed crystal composition of Ga_xIn_1−xAs layers is analysed as a function of the composition of a mixed Ga/In source during VPE in the hydride system. Experimental results are compared with thermodynamic calculations. Both thermodynamics of the deposition reactions and thermodynamies of the souree reactions are considered in the calculations.     

Thermodynamic Calculation of the Alloy Composition of GaxIn1−xAs Grown in the Trichloride System Using Solid Sources

The dependence of the Ga_xIn_1−xAs alloy composition as a function of the experimental input variables is calculated for a growth system using AsCl₃ and solid GaAs and InAs sources. The results are similar to those earlier obtained for growth in the hydride system. Additional AsCl₃ introduced downstream the source regions shifts the alloy composition towards higher GaAs content.     

Vickers indentation hardness of Hg1−xCdxTe

The Vickers indentation hardness of Hg_1−xCd_xTe has been measured as a function of composition x using monocrystalline samples of Bridgman and THM crystals and polycrystalline starting material at room temperature. The microhardness varied between 220 MPa (x=0) and 440 MPa (x=1), showing a maximum of 850 MPa at x ∼ 0.75, and was different between monocrystalline and polycrystalline samples. The “hardening rate” dH/dx is strongly dependent on the composition range and is discussed in context with solid solution hardening due to elastic interactions of solute atoms with gliding dislocations and ordering effects.     

Vacancy defects in as-grown and nº-irradiated GaP and GaAs1−xPx Studied by Positrons

Measurements of positron lifetime τ and of the shape parameter S of the Doppler-broadened annihilation line are used to study bulk and defect properties in GaP and GaAs_1−xP_x. τ and S decrease linearly with the composition x of GaAs_1−xP_x layers. A second lifetime component (τ₂ = 290 ps) observed in as-grown GaP is attributed to stoichiometric P vacancies. After neutron irradiation of GaP and GaAs_0.13P_0.87 positrons are trapped by Ga vacancies (τ₂ = 250 ps). These vacancies anneal out in two stages at 200–550 °C and 550–800 °C.     

Configuration entropy of ternary alloy superlattice

Difference in mixture-related entropy between superlattice and the corresponding homogeneous crystal in which all composition gradients have been annihilated by equilibrating processes (the configuration entropy of superlattice, ΔS_conf) is analytically formulated as a function of composition variables and geometry parameters. Numerical evaluations are performed for the important case of Al_xGa_1−xAs-based superlattice. Qualitative trends confirm in general the intuitive expectations (− ΔS_conf grows with increasing composition difference between the layers); the dependencies on geometry parameters exhibit a peculiar behaviour. The results are applicable to superlattices with periode lengths sufficiently in excess of the monoatomic layer thickness.     

Microhardness studies of K1−xRbxCl crystals

The microhardness measurements have been made on pure crystals of KCl, RbCl and mixed crystals of K_1−xRb_xCl. Microhardness varies non-linearly with composition being maximum near at the eqimolar composition. Microhardness values calculated from lattice parameter data are in good agreement with experimental data. The difference in the size of the ion constituting the mixed system is responsible for the internal strains giving rise to imperfections and inturn responsible for the non-linear variation of microhardness with composition.     

Electrical and optical properties of Cd1−xZnxS (0x0.18) grown by chemical bath deposition

Cd_1−xZn_xS films with 0x0.18 were grown by chemical bath deposition technique on glass substrates from an aqueous solution containing cadmium and zinc sulfate, ammonia and thiourea. Microstructural features, obtained from X-ray diffraction and scanning electron microscopy (SEM) measurements, reveal a predominance of Wurtzite structure and an homogenous microstructure formed by densely microcrystallines for all the samples studied. Cd_1−xZn_xS semiconductor was found to be resistive and of n-type. Also, the electron density decreases with increased x and the mobility reaches a maximum around x=0.12. Which means that the Cd_1−xZn_xS films at this composition are of high crystalline quality, i.e. having reduced intrinsic defect concentrations.     

Some crystallographic trends into the Na1+xZr2SixP3-xO12 System

This paper gives a contribution to the crystallographic characterization of the Na_1+xZr₂Si_xP_3-xO₁₂ system, useful e.g. to analyze the right stoichiometric composition of a synthesized sample concerning this family of compounds, by powders X-ray diffraction analysis. In the paper relations are in fact displayed to exist among d_hkl, unit cell parameters and the stoichiometric parameter x. Such relations show to be linear for d_hkl and a₀, while the relation trend involving c₀ let one think the system is isostructural in the atomic arrangement for the ranges x < 2 and x<2, respectively, to the end terms with x=0 and x=3.     

Compositional dependence of morphology and lattice parameters during growth of K1‐x(NH4)xH2PO4 mixed crystals

Mixed crystals of ammonium dihydrogen phosphate and potassium dihydrogen phosphate K_1‐x(NH₄)_x H₂PO₄ were grown from aqueous solutions with x = 0.06, 0.09, 0.15, 0.32, 0.42, 0.51, 0.63, 0.70, 0.76, 0.78, 0.84, 0.88, 0.89 and 0.91. The crystal composition that differs from solution was estimated by X‐ray method. Morphology of the crystals changes from tetragonal prism to needles when the incorporation of either of the two components into the other; which also affects the growth rate along the prominent growth directions significantly. Growth along the [001] decreases initially with composition and reached the maximum when x = 0.5; whereas growth along the [100] always showed a decreasing trend with composition and attained a minimum value when x = 0.5. Crystal length along the [001] and [100] and aspect ratio are also compositional dependent. Unit cell parameters determined by X‐ray powder and single crystal analyses revealed that the ‘a ’ parameter shows only a small and linear variation but the ‘c ’ parameter changes significantly with ADP incorporation because of the difference in the effective ionic radius of K⁺ and NH₄⁺ ions and also the possibility of NH₄⁺ ion to form two different kinds of hydrogen bonds in the system. The existence of a pseudo‐cubic cell at the mixing composition x = 0.78 was also revealed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of Lithium Doping in the Bi-2212 Superconducting System

Samples with the nominal composition Bi₂Sr₂Ca_1–xLi_xCu₂O_y (x = 0.2,0.4, and 0.6) and Bi₂Sr₂CaCu_2−x L1_xO_z (x = 0.4, 0.6, and 1.0) were prepared by the solid state reaction method. The role of L1 at both Ca and Cu sites in the Bi-2212 composition were studied. From the X-ray diffraction data it was found that the L1-doped at the Ca site increases the c-axis and that doped at the Cu site decreases the c-axis. From the D.C. four-probe resistivity data it was found that Li-doped at the Ca site reduces the T_c and the L1-doped at the Cu site gives T_c(0) above the liquid nitrogen temperature. It was observed that the L1 doping reduces the melting point of Bi-2212 composition. The presence of Lithium was confirmed by inductive the coupled plasma method.     

Magnetic phase transitions in the Mn1-xCrxSe (x ≦ 0.4) system

Neutron diffraction and magnetic investigations have been made on the Mn_1-xCr_xSe (0 ≦ x ≦ 0.4) system solid solutions. Evidence is found of the appearance of magnetization in the samples with composition 0.05 ≦ x ≦ 0.4, exceeding in value that of antiferromagnet. The temperatures of magnetic transition, obtained from the magnetic measurements, do not fit the temperatures of disappearance of antiferromagnetic ordering obtained from the neutron diffraction studies. The antiferromagnetic structure with compositions 0.03 ≦ x ≦ 0.3 is analogous to the α-MnSe structure. The results are discussed under assumption of simultaneous coexistence of phases with different type of magnetic ordering.     

Optische Eigenschaften von Wismut–Antimon-Aufdampfschichten

The change in position and in magnitude of absorption peaks due to interband transitions E_i (i = 1, 2, 3) for Bi_xSb_1–x evaporated layers have been studied for different compositions in the range 0 ≦ (1 − x) ≦ 0.30 in the visible part of the spectrum. It has been founded nonlinear shiftings for all absorption peaks in function of layer composition. The joint density of states due to transition E₂ is more sensitive as the two other transitions with modification of alloy composition.