Crystal defects and interdiffusion behavior of Hg1−xCdxTe/(100)CdTe epitaxial layers grown by chemical vapor transport

Crystal defects of chemical vapor transport grown Hg_1−xCd_xTe on (100) CdTe structures have been investigated using chemical etching, wavelength-dispersive spectroscopy, x-ray rocking curve, and scanning electron microscopy methods The results indicate that the origin and spatial distribution of the misfit dislocations can be attributed to both the lattice parameter misfit and the inevitable interdiffusion occurring between the substrate and the epitaxial layer. It is proposed that the interdiffusion of Hg along the [100] direction is enhanced by dislocation channels and other defect cores along or near this direction owing to defects on the initial surface of the CdTe substrate. The results indicate that the subgrain boundaries in Hg_1−xCd_xTe are caused by slight misorientation of the lattices and polygonization of the defects during epitaxial layer growth, and by the propagation of the subgrain boundaries existing in the CdTe substrate.     

Mass spectrometric studies of the Decomposition and the Heat of Formation of CuInS2(s)

The equilibrium vaporization of CuInS₂(s) was studied by Knudsen cell mass spectrometric techniques in the temperature range 902—1110 K. Based on these and independent congruency studies, CuInS₂(s) decomposes under steady-state conditions according to the reaction 2CuInS₂(s) = Cu₂S(s) + In₂S(g) + S₂(g). During the initial transient period of the vaporization of CuInS₂, the ion intensities of In₂S⁺ and S₂⁺ change and assume steady-state values after some time. A second-law evaluation of intensity versus temperature data, obtained under steady-state conditions, yielded a value for the heat of the above decomposition reaction (2 moles of CuInS₂) of δH 630.9 ± 26 kJ. With this quantity and auxiliary thermochemical data, the enthalpy of formation of CuInS₂(s) was computed to be δH = ?221.7 ± 13 kJ/mol.     

Zn location in the W‐type hexagonal ferrite SrZnCoFe16O27

The title compound, SrZnCoFe₁₆O₂₇ (ZnCo‐W), strontium zinc cobalt hexadecairon oxide, crystallizes in space group P6₃/mmc, with the Sr atom at a site with symmetry and Zn²⁺ located at two tetrahedral sites (4e and 4f, each with 3m symmetry) of the spinel blocks. The Zn occupancy is 36% on equipoint 4e and 14% on 4f. The enrichment of diamagnetic ions on one of seven sublattices is thought to be responsible for the high temperature dependence of the saturation magnetization.     

The Temperature-Composition Phase Equilibria in the HgTe–HgI2 Pseudobinary System

The temperature-composition phase diagram of the HgTe—HgI₂ pseudobinary system was determined between 25 and 670°C using differential scanning calorimetry, differential thermal analysis, Debye-Scherrer powder X-ray diffraction techniques, and metallographic analysis methods. Solid solutions of HgTe and HgI₂ with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7±0.8 Mol-% HgI₂ in HgTe at 501±5°C. The monoclinic intermediate phase Hg₃Te₂I₂ is formed by a peritectic reaction upon cooling at 501±5°C, with the peritectic point at approximately 37±4 Mol-% HgI₂. The previously unknown cubic phase Hg₃TeI₄ (a = 6.240±0.003 Å) is formed by a eutectoid reaction at 238±3°C and is stable up to 273±3°C, where it melts by a peritectic reaction with the peritectic point at approximately 79±3 Mol-% HgI₂. Between Hg₃TeI₄ and HgI₂ is a eutectic point at 82±3 Mol-% HgI₂ and 250±3°C. The α to β transition of HgI₂ at 133±3°C is independent of sample composition between 33.3 and 100 Mol-% HgI₂.     

Untersuchungen über die Vorgänge beim Verzinken von Eisen

Zusammenfassung Die Löslichkeit von Nickel-, Chrom- und Manganstählen in geschmolzenem Zink wurde untersucht, und die Löslichkeits-Temperaturkurven wurden aufgenommen. Es wurde eine Eisen-Mangan-Legierung (Nr. I) gefunden, bei der die Löslichkeitskurve ohne Maxima oder Minima verläuft. Die metallotgraphische Untersuchung des Verzinkungsbelages erhärtet die aus den Lösungskurven gefolgerten Annahmen. Neue Strukturelemente konnten auch in den Verzinkungsbelägen der hochprozentigen Legierungen nicht beobachtet werden.     

Chemical Vapor Transport and Crystal Growth of the Hg0.8Cd0.2Te System,Crystal Morphology and Homogeneity

Mass transport rate studies of the system Hg_1?xCd_xTe-iodine (with x = 0.2 for the source material) are performed in the temperature gradient 590° → 535°C as a function of transport agent pressure and for different orientations of the density gradient relative to the gravity vector. The combined results reveal that convection, even when not sufficient to increase the diffusive mass transport rates appreciably at low pressures, affects the surface morphology and compositional homogeneity of crystals. Under vertical, stabilizing conditions, the crystallographic and chemical homogeneity of crystals is distinctly improved relative to those obtained for the horizontal orientation of the transport ampoule. These result suggest that elimination of convection (micro-g environment) may yield a further improvement of crystals.     

NMR and chiroptical examination of the diastereoisomers of (S)-Eu-EOB-DTPA

The solution structure of the diastereoisomers of (S)-Eu--EOB--DTPA has been analysed by (1)H NMR, CD and CPL spectroscopy. Two major species exist which possess very similar (1)H NMR paramagnetic shifts and emission spectra, consistent with a 9-coordinate structure involving one bound water. Circularly polarised luminescence data are consistent with a common Lambda-helicity for each isomer; the isomers differ only in the absolute configuration of the central nitrogen atom.     

Study of liquid crystal space groups using controlled tilting with cryogenic transmission electron microscopy

We developed a method that enables differentiation between liquid crystalline-phase particles corresponding to different space groups. It consists of controlled tilting of the specimen to observe different orientations of the same particle using cryogenic transmission electron microscopy. This leads to the visualization of lattice planes (or reflections) that are present for a given structure and absent for the other one(s) and that give information on liquid crystalline structures and their space groups. In particular, we show that we can unambiguously distinguish among particles having the inverted micellar cubic (space group Fd(3)m, 227), the inverted bicontinuous gyroid (space group Ia(3)d, 230), the inverted bicontinuous diamond (space group Pn(3)m, 224), and the inverted bicontinuous primitive cubic structure (space group Im(3)m, 229).