Defect structure in EuS single crystals grown from the melt

The defect structure in EuS single crystals grown form the melt is studied by etch pitting, scanning and high-voltage electron microscopy. Circular and square etch pits and a second phase in the shape of thin hexagonal platelets are observed by etching. Microprobe analysis indicates the platelets to consist of Eu metal. In the transmission electron microscope, smoothly curved dislocations and helical dislocations, small dislocation loops and inclusions associated with dislocations are observed. The possible origin of the detected dislocation structure is considered with reference to climb and glide processes occurring during cooling down the grown crystals. The results corroborate the glide geometry of the NaCl lattice for EuS. On leave from Institute of Physics, Academic Sinica, Peking, VR China     

The distribution of dislocations in silicon iron single-crystals grown from the melt

The distribution of dislocations in a crystal of an Fe-4.2% Si alloy prepared from the melt is studied microscopically and, by X-ray diffraction after rendering them visible by anodic dissolving. The dislocations are also studied inside the crystal by successively grinding the surface. The density of the dislocations inside the blocks is determined by calculation from microphotos, the density of the dislocations forming the boundaries between the blocks by measuring the angles between the lattices of neighbouring blocks. It is found that the dislocations are distributed very unevenly in the crystal and most of them form complicated boundaries of blocks, similarly as with ionic crystals. The distribution of dislocations is also discussed from the point of view of their formation and conclusions are reached as to the preparation of single crystals having a smaller number of dislocations.

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Fe-Si,

- Fe-4,2%Si, , . . , , — . , , . .

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The author is indebted to Candidates of Mathematics and Physics, F. Kroupa and J. Kaczér, for careful reading and advice whereby they helped to give greater depth and accuracy to this paper. He thanks Z. Tahal and M. Honegrová for initiative shown in helping to prepare the single crystals and during exacting experimental work, and S. Kadeková for aid in adjusting the spectrometer.     

Damage studies in cubic ZnSe single crystals grown from melt

A microscopy study of the morphology of the damage produced by TEA-CO₂ laser pulses in cubic ZnSe single crystals grown from melt is presented. The observed bulk filamentary damage consists of relatively uniformly distributed elementary damaged zones, located at specific sites where absorbing inclusions could exist. Transmission electron microscopy and laser ion mass spectroscopy investigations revealed the absorbing inclusions to be thin graphite foils, originating from the crucible used for crystal growth.     

Laser grown single crystals of silicon

Single crystal rods of silicon have been grown by laser-induced chemical vapor deposition (LCVD) using visible light. We believe these to be the first reported single crystals of any material grown by LCVD.     

Study of the trapping states in ZnS single crystals grown from gallium melt

The trapping levels in zinc sulphide single crystals grown from gallium melt have been investigated using thermoluminescence techniques. The observed peak at 175° K consists of two overlapping components at 173 and 200° K respectively. Thermal activation energies and frequency factors were calculated for both traps. The dependence of glow curve shape on excitation conditions is caused by the retrapping by non-filled 200° K traps of electrons freed from 173° K traps in the course of the glow curve run. In addition to the results on “pure” crystals, measurements were made on samples grown with chlorine, oxygen and copper impurities, as well. Although no positive identification of the chemical nature of the 173 and 200° K trapping centers has been possible, we find that our results are not inconsistent with a previously suggested model in which the traps are identified as complex defects. Comparison is also made with trap spectra observed earlier in gallium-doped zinc sulphide samples prepared by the usual methods.     

Highly oriented thin oxide films on single crystals of Fe-Si alloys

Under certain oxidation conditions, highly oriented oxide films grow on single crystals of some Fe-Si alloys. A typical two-phase film of this kind was studied in order to reveal the orientational relationships between-Fe₂O₃ and Fe₃O₄ on the (001) surface of the substrate. The orientational relationships were determined from reflection high-energy electron diffraction patterns where reflections from both oxides were present.The authors are indebted to Ing. B. esták and Ing. S. Kadeková who made possible the preparation of single-crystalline samples of Fe-Si alloys in the Institute of Physics, Czechoslovak Academy of Sciences; to Dr. M. Rozsíval (Institute of Solid State Physics, Czechoslovak Academy of Sciences) who enabled the authors to use the electron diffraction apparatus; and to Dr. A. Línek (Institute of Solid State Physics, Czechoslovak Academy of Sciences) for helpful discussion.     

Dielectric properties of ZnSe crystals grown from melt

The frequency and temperature dependences of the real and imaginary parts of the permittivity of ZnSe crystals grown from melt have been measured in the low-frequency range. It has been found that the crystal samples cut from different parts of the ingot exhibit different properties depending on their distance from the ingot origin. The difference in the properties is explained by the dominant influence exerted on the polarization by point defects, the formation of which is associated with the deviation of the composition from stoichiometry, as well as by residual impurities and stresses in the crystals.     

Fractal structure formation in GaSe crystals grown from melt

The structure of GaSe single crystals prepared by rapid cooling of melt has been studied. These crystals are shown to contain dendrites due to the nonequilibrium conditions of single-crystal preparation. Dendrites have a fractal structure with the Hausdorff measure equal to 1.7.     

Properties of n-type gallium arsenide doped with germanium when single crystals are grown from the melt

The temperature dependences of the density, mobility, and lifetime of electrons, and the photoconductivity and cathodoluminescence spectra of gallium arsenide with different electron densities doped with germanium when single crystals are grown by the Czochralski method are investigated. An analysis of the scattering mechanism is given, and the acceptor and donor densities are determined. The acceptor-type capture levels are found from the temperature dependence of the electron lifetime. The results of a study of the cathodoluminescence spectra indicate the presence in the specimens of complex radiational recombination centers similar to germanium-atom complexes with inherent lattice defects.     

Radial distribution of iron in silicon crystals grown by Czochralski method from contaminated feedstock

The radial distribution of iron in Cz‐Si crystals grown from photovoltaic grade feedstock was analysed using deep level transient spectroscopy (DLTS). A high temperature annealing sequence followed by fast quenching to 273 K was used to transform iron silicide precipitates, formed after the crystal growth, to iron‐containing species detectable by DLTS. The results suggest a homogeneous radial distribution of iron over the crystal. From comparison of as‐grown and annealed samples, a strong suppression of iron precipitation close to the walls of the crystals becomes obvious and possible mechanisms of this phenomenon are discussed. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Faceting of sapphire crystals grown from a melt by the Stepanov method

The appearance of faces on cylindrical sapphire single crystals grown from a melt by the Stepanov method is studied by photogoniography and optical microscopy. The crystallographic indices of the detected faces are established, and the microstructure of the growth layers is investigated. A relationship between the faceting and the growth conditions is found. The experimental results are compared with data on the faceting of the sapphire crystals grown from a solution-melt and with the calculated specific free surface energies of the faces.     

Improvement of cubic silicon carbide crystals grown from solution

Cubic-silicon carbide crystals have been grown from carbon-rich silicon solutions using the travelling-zone method. To improve the growth process, we investigated the effect of controlling more tightly some of the growth parameters. Using such improved growth conditions, our best sample is a 12 mm diameter and 3 mm long 3C–SiC crystal. It is grown on a (0001) 2 off, 6H–SiC seed and has 111-orientation. The low amount of silicon inclusions results in a reduced internal stress, which is demonstrated by the consideration of μ-Raman spectra collected at room temperature on a large number of samples.     

Highly oriented thin oxide films on single crystals of Fe-Si alloys II. The (111) surface of the substrate

In Part I (Czech. J. Phys.B 20 (1970), 994), orientational relationships in oxide films grown on the (001) surface of single crystals of some Fe-Si alloys have been described. Part II deals with highly oriented thin oxide films on the (111) surface of the substrate. Typical reflection high energy electron diffraction patterns are shown and orientational relationships between Fe₃O₄ and the substrate and between -Fe₂O₃ and Fe₃O₄ are given.The authors are indebted to Ing. B. Sesttk and Ing. S. Kadekovi (Institute of Physics, Czechoslovak Academy of Sciences) who made possible the preparation of single crystalline samples of Fe-Si alloys. The authors express their gratitude to members of the Institute of Solid State Physics, Czechoslovak Academy of Sciences, Dr. M. Rozsival for the possibility of the use of the electron diffraction apparatus, Dr. A. Linek for helpful discussion of some important problems and Miss J. Sikovi for computer calculations of structure factors.     

Slip bands in single crystals of silicon iron alloys after two bendings in the opposite directions

Single crystals of iron with 3 wt. % and 7 wt. % silicon were deformed by bending after slip bands had been formed in them during the previous plastic bending in the opposite direction. The influence of the old bands on the new ones and the interaction between them have been observed.The author is indebted to Mrs. S. Kadeková who prepared the single crystals, and wishes to express his thanks to DrSc. F. Kroupa and V. Vítek for valuable discussions.     

Magnetism in amorphous Fe-Si alloys

Fe-Si alloys have been obtained by the vapor quenching technique. Resistance measurements, electron microscopy and diffraction results are typical of an amorphous system. The Mössbauer spectra of these amorphous alloys, fitted in terms of a distribution of hyperfine fields, show the existence of a local magnetic order with, however, a proportion of weakly or even no coupled Fe atoms which is temperature and Fe-concentration dependent.     

Diffusion in ordered Fe-Si alloys

The measurement of the diffusional Mössbauer line broadening in single crystalline samples at high temperatures provides microscopic information about atomic jumps. We can separate jumps of iron atoms between the various sublattices of Fe-Si intermetallic alloys (D0₃ structure) and measure their frequencies. The diffusion of iron in Fe-Si samples with Fe concentrations between 75 and 82 at% shows a drastic composition dependence: the jump frequency and the proportion between jumps on Fe sublattices and into antistructure (Si) sublattice positions change greatly. Close to Fe₃Si stoichiometry iron diffusion is extremely fast and jumps are performed exclusively between the three Fe sublattices. The change in the diffusion process when changing the alloy composition from stoichiometric Fe₃Si to the iron-rich side is discussed.     

Formation of F-centers in KCL crystals grown with vibration of the melt

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