Das quaternäre Schmelzdiagramm Ga?As-P Sn

The pseudoternary cut Sn GaAs GaP of the quarternary system Ga As P Sn has been investigated in a temperature range from 860 to 1200°C. The calculation based on Vieland's method by use of Darken's quadratic formalism. A comparision between the solvents tin and gallium shows a higher solubility in tin for the mixed crystal Ga_xPAs_1−x and a stronger variation of the composition along the growth direction.     

On the growth kinetics of Y3Fe5O12: Bi films grown from Bi2O3?PbO?B2O3 melts

LPE isothermal growth of thin films of Y_3−xBi_xFe₅O₁₂ from PbO B₂O₃ Bi₂O₃ melts was used as a tool for studies of structure of high temperature solutions (HTS). Using an anionic model of HTS enthalpy and entropy of dissolving of the garnet phase, the equilibrium constant of Bi₂O₃ dissociation and diffusion coefficients of the growth unit were calculated from experimental data.     

Phase lead determined growth of 〈100〉 — textured germanium crystallites in eutectic Ag?Ge alloys

Al Si type eutectics (Al Si, Ag Si, Ag Ge, Zn Ge) form 〈100〉 — textured eutectic dendrites of the semiconductor phase when a certain growth rate R and liquid temperature gradient G are held. The spacings of these eutectic dendrites λ follow the relationship: λ = (r_λ ≈︁ 0.2; g ≈︁ 0.5). The exponents of this relationship can be explained by the model of phase lead determined growth. This model is based on the consideration of the analogy to dendrite growth. The Al Si type eutectics have geometrically similar morphologies for determined G^x/R-relations (x = 1.25 in the case of Ag Ge) and the relation λ²R = const. is valid. In this paper the Ag Ge eutectic will be discussed in close detail.     

A difference between initial growth stages of the AlGaAs/GaAs and GaAs/AlGaAs heterostructures produced by contact replacement of solutions

The method of liquid epitaxial growth of GaAs/AlGaAs/GaAs heterostructures when the change of solutions occurs due to pushing off one melt by another is discussed. It has been shown theoretically and experimentally that the initial stages of film growth after the change of the binary Ga As melt on the ternary Al Ga As melt differ from that when the Ga As solution pushes off the Al Ga As liquid. The difference is caused by the inequality of the diffusion coefficients of As and Al in a multicomponent Al Ga As liquid (D_Al > D_As). As a result, the growth of an AlGaAs film begins immediately in the case when the Al Ga As solution pushes off the Ga As liquid but in the opposite case the dissolution of an underlying AlGaAs solid is unavoidable and depends little on degree of a saturation of the Ga As washing solution. These peculiarities must be taken into account in discussions of abruptness and other properties of LPE-grown AlGaAs/GaAs and GaAs/AlGaAs heterojunctions.     

Dislocation density in InxGa1–xAs films grown on GaAs substrates with intermediate buffer layer InGaAsP of variable composition

In_xGa_1–xAs films with x = 0.03 and 0.05 were grown from an In Ga As P liquid phase. Because of high value of distribution coefficient of P we have heterojunction GaAs In_yGa_1–yP_zAs_1–x–In_xGa_1–xAs. The influence of Phosphorus atom fraction (X_p) in liquid phase on dislocation density in the top In_xGa_1–xAs layer was studied. It was found that dislocation density (N_d) as a function of X_p is a curve with some minima. The minima of N_d for substrates of (111) A and (111) B orientations are observed in the different intervals of X_p axis. — The width of N_d minimum is decreased if the substrate is misoriented from the (111) plane. — It was supposed that the clusters exist in the liquid phase. On the basis of this assumption one can explain the influence of substrate position over or under the melt on the film perfection. The diameter of these clusters is estimated to be about 500 Å.     

Application of various modes on the growth of magnetoplumbite single crystals from the Na2O?BaO flux

Several growing modes including the bottom growth, the growth on a thermocouple ball and the top seeded growth, were tested to grow BaFe_12−2xMg_xTi_xO₁₉ and BaFe_12−xGa_xO₁₉ magnetoplumbite single crystals from the Na₂O BaO flux. Disadvantages of the bottom growth, inhomogeneities, inclusions, difficult separation of the crystals were restricted by using of the top-seeded growth and by optimization of the ACRT program.     

GaP?AlxGa1−xP heterostructure edge coupling waveguides for hybrid integrated optic devices

In this paper we present the performance of GaP Al_xGa_1−xP heterostructure waveguides for integrated optic hybrid devices. The waveguide layer is graded with a parabolic refractive index profile for the light emission of a DH GaAs semiconductor laser. The waveguide heterostructure performed allows to couple at it edge crossection semiconductor laser or photodetector as well as fix or solder them on the same substrate on which the heterostructure layers were deposited. The heterostructure layers were grown by liquid phase epitaxy and the heterostructure waveguide was performed by means of etching technics specially developed for this purpose. Both, the growth procedure, as well as the etching technics are described. The results achieved are shown in curves and photographs, taken on a scanning microscope.     

Ein eindimensionales Modell zur Beschreibung von Transporteigenschaften in offenen Systemen

A simple one-dimensional model is dealt with describing the material transport by means of linear gas flow and diffusion. In the GaAs AsCl₃ H₂ system the dependence of the partial pressure on the x-coordinate is calculated, and the role of the temperature gradient near the growing interface is discussed in view of the constitutional supercooling of the gas phase.     

Growth studies of YVO4 crystals (II). Changes in Y?V?O-stoichiometry

Incongruent vanadium oxide vaporization of yttrium orthovanadate (YVO₄) melt generates changes in both oxygen and yttrium-vanadium (Y V) stoichiometry. Slightly modified YVO₄ or YVO₄ + Y₈V₂O₁₇ phases are formed from continuously changing melt systems depending on their starting compositions. The occurrence of Y₈V₂O₁₇ in yttrium orthovanadate crystal fibers grown by laser heated pedestal growth (LHPC) technique can be simply eliminated by utilization of suitable V₂O₅-excess starting compositions. In contrast, the oxygen-deficient YVO_4–x black phase is an inherently oxygen deficient phase with limited solid solution in the YVO₄ YVO₃ subsystem of Y₂O₃ V₂O₅ V₂O₃ complex ternary phase diagram close to the congruent YVO₄ composition (49.3 mol% V₂O₅–50.7 mol% Y₂O₃). The greater oxygen deficiency YVO_4–x specimens have smaller lattice parameters as determined from detailed XRD data. Ceramic feed rod and fiber crystal grown from the feed rod with slight yttrium oxide excess starting composition were characterized by electron microprobe analysis. Changes in both Y V and oxygen stoichiometry were observed along the fiber, due to double limited solid solution system of three dimensional ternary phase diagram. Consequently, both the presence of Y₈V₂O₁₇ phase and change of Y V stoichiometry over oxygen deficiency cause difficulties for YVO₄ crystal growth from yttrium oxide excess melt.     

Lattice Variation and Stability of NaCl?KCI Mixed Crystals Grown from Aqueous Solutions

An attempt to improve the stability of NaCl KCl mixed system was made by adding KBr to it. Crystals were grown by the slow evaporation method and characterized by X-ray diffraction measurements. A large improvement in stability was observed with crystals grown from (NaCl)_x (KCl)_0.9−x(KBr)_0.1 than from Na_xK_1−xCl solutions.     

Microstructure and spacings of directionally solidified metal-semiconductor eutectic alloys

Directionally solidified metal-semiconductor eutectic alloys, representing nonfacetted facetted eutectics, show a variety of microstructures caused by the great differences in semiconductor volume fraction (Zn Ge 7,8 %; Ge ZrGe₂ 98.6 %), the influence of growth rate and temperature gradient at the solid-liquid interface. The Al Si, Ag Si, Ag Ge, Zn Ge, Cu₃Si Si, NiGe Ge, CoGe₂ Ge, Mn₃Ge₂ Ge, FeGe₂ Ge, Mn₁₁Si₁₉ Si, Cu₃Ge Ge, Ge TiGe₂ and Ge ZrGe₂ eutectics habe been investigated. The following three models are applicable for the calculation of the spacings as a function of growth rate and temperature gradient at the solid-liquid interface to certain microstructures: diffusion-determined growth, branchinglimited growth and phase-lead-determined growth.     

Infrared optical properties of Cu1−xLixSe2 thin films

Infrared absorption spectra of Cu_1−xLi_xInSe₂ thin films are measured at room temperature in the wavenumber range from 100 to 600 cm⁻¹. The spectra exhibit two absorption bands in the wavenumber ranges 200–210 cm⁻¹ and 330–355 cm⁻¹ which are ascribed to vibrational modes due to In Se and Li Se vibrations, respectively. The influence of the phase transition from the chalcopyrite structure to the β-NaFeO₂ structure in the composition range x = 0.5–0.6 on the vibrational characteristics is established and discussed.     

Structural Studies on Ni75(SnSi)25 and Ni75(SnBi)25 Alloys

Ternary alloys on the quasi-binary system Ni₃Sn(r) in equilibrium condition. It has been observed that these phases undergo transformations at high temperatures but upto 500 °C room temperature modifications are stable. The two phases do not have any appreciable solid solubility in either of them. The phase Ni₃Si(r) crystallizes in to Cu₃Au (Li₂) structure where as Ni₃Sn(r) is based on c.p.h. structure with a = 5.305 A°, c = 4.254 A°. No new ternary phase has been detected in Ni₃Sn Ni₃Si section. The investigated alloys of the Ni Sn Bi system contain 75 at.% Ni. All the ternary alloys show simultaneous occurrence of three phases, namely Ni₃Sn(r), NiBi and Ni(Sn) in equilibrium state. The phase NiBi has NiAs(B8) type of structure. Due to non-existence of isostructural phases in the two binary systems (Ni Sn and Ni Bi), single solid solution phases are not formed. Widely differing atomic sizes of nickel and bismuth atoms restrict the formation of solid solution of bismuth in nickel in contrast to Ni(Sn) where atomic size factor is favourable.     

On a Possibility of Determining Nonuniformities in AlxGa1−xAs Solid Solution Compositions

Both surface and bulk nonuniformities in Al_xGa_1−xAs solid solution compositions were determined by surface radiography of epitaxial Al_xGa_1−xAs GaAs hetero-junctions with diffused radioactive Zn⁶⁵ atoms.     

Crystal growth of Ca3−xYxMn2Ge3O12 and phase relations in the PbO?B2O3?GeO2 based melts

The bulk crystals of Ca_3−xY_xMn₂Ge₃O₁₂ garnets were grown on a seed from the PbO B₂O₃ GeO₂ based melts, where the primary crystallization field of garnets was found. The saturation temperatures of the melts were determined before each growth run. The dependence of Y incorporation into the crystals versus the melt composition was also evaluated.     

Single crystal preparation of MnxCr3–xO4 by flux method

Mn_xCr_{3 x}O₄ was prepared by the flux method. Melts of PbO PbF₂, Bi₂O₃ B₂O₃, B₂O₃, Na₂B₄O₇, and Na₂W₂O₇ Na₂WO₄ were used. The best results could be yielded with the PbO PbF₂ flux, from which crystals with 2–4 mm in thickness were grown. The Bi₂O₃ B₂O₃ flux produced crystals with 1–2 mm in thickness. The spinell structure of the chromite was proved by X-ray investigation.     

Investigation of multiple layer heterojunction structures by means of an electron-beam microprobe-analyzer

Multiple layer heterojunction structures in the AlAs GaAs system are investigated by means of an X-ray microanalyzer. The quantitative determination of Ga and Al is extensively discussed. The correction for atomic number, absorption and secondary fluorescence are considered. For Al_xGa_1–xAs layers it is favourable for quantitative analysis the AlK_α-emission for x < 0,3 and the GaK_α-emission for x > 0.3. Some multilayer heterojunction structures of laser and luminescence diodes are shown in form of their AlK_α microprobe diagrams.     

Investigations for Sn diffusion in Pb1−xSnxTe and PbTe

By annealing Pb_1−xSn_xTe and PbTe isothermally in a quartz ampoule Sn diffused from Pb_1−xSn_xTe into PbTe. The profiles obtained have been investigated by means of an electron beam microanalyser, and the coefficients of diffusion have been determined at various temperatures. The diffusion of Sn can be explained by the expressions: D_PbSnTe = 1.5 · 10⁻¹ exp (−1.8 eV/kT) cm² s⁻¹ (0,14 < x < 0,18) D_PbTe = 5,5 · 10⁻⁴ exp (−1.5 eV/kT) cm² s⁻¹. N-type layers are observed at the surface of Pb_1−xSn_xTe specimens.     

The significance of X-ray investigations for the classification of multicomponent systems with mixed crystals in a solid phase

The X-ray investigations of solid phases in the multicomponent systems KCl KBr H₂O, K₂SO₄ (NH₄)₂SO₄ H₂O and KNO₃ NH₄NO₃ H₂O were conducted and the crystal lattice parameters of mixed crystals forming in these systems were determined. It was confirmed that in the KCl KBr H₂O system the continuous solid solutions were formed and in the K₂SO₄ (NH₄)₂SO₄ H₂O system the solid solutions with a miscibility gap were formed. In the KNO₃ NH₄NO₃ H₂O system the presence of two series of mixed crystals, namely the mixed crystals between ammonium nitrate and the double salt KNO₃ · 2 NH₄NO₃ and between potassium nitrate and the same double salt was confirmed. In this system a wide region of discontinuity (for x_NH4NO₃ = 0.083 – 0.67) also occurred. According to Roozeboom's classification, the KCl KBr H₂O system belongs to the 3^rd type, the K₂SO₄ (NH₄)₂SO₄ H₂O to the 5^th type (the discontinuous mixed crystals, the systems of peritonic type) and the KNO₃ NH₄NO₃ H₂O system is not comprised in this classification.