Two modes of slip systems in iron silicon crystals

Single crystals of iron 11·6 wt.% silicon were deformed in compression and slip bands were observed by optical microscope in specimens of different orientations. The deformation took place mostly by crystallographic slip along {110} planes, however, non-crystallographic slip in specimens of particular orientations was observed, too. On the basis of the present and previous results a simple qualitative model is proposed which explains which slip planes should be observed in crystals of iron with different silicon content deformed under various conditions. The main idea of the model is the eixstence of two different modes of slip systems in these crystals. The model predicts the conditions at which one slip mode prevails.The author would like to thank Dr. F. Kroupa, Dr. A. Gemperle, Dr. B. esták and Dr. J. Blahovec for useful discussions.     

Thermal conductivity of semiconducting amorphous CdGeAs2

The thermal conductivity of amorphous semiconducting CdGeAs₂ was studied between 100 and 300°K. The Debye model was used for the calculation of the mean free path of phonons which was found to be 10 Å at 300°K and was related to the basic structure units of amorphous CdGeAs₂.Thanks are due to Mrs. J. Beránková, Mr. J. Kapar and Mrs. J. Trepeová for the preparation of the amorphous CdGeAs₂ used in this work and for the measurements of the thermal parameters, and to Dr. J. urek and Dr. S. Kolník from the College of Transport Engineering, ilina, for the sound velocity measurements.     

CO2-laser annealing of Al/a-Si:H contact

The paper concerns the possibility of using CW (continuous wave) CO₂-laser annealing (=10.6 m,P 100 W/cm²) for formation of a barrier in the Al/a-Si:H/SS (SS-stainless steel) structures with good rectifyingI–V characteristics. The infrared absorption spectra, photoelectric properties, temperature effect on the conductivity and saturation current were analyzed and various contact models are discussed.We thank P. imanec for useful and stimulating discussion, J. Stuchlík for kindly manufacturing the a-Si:H films for us and D. N. Goncharov for the aid with the measurement of the conductivity temperature dependences.     

Single particle inclusive spectra of charged particles from antiproton-proton interactions at 5.7 GeV/c

A systematic study of single particle inclusive spectra of charged particles from ¯pp interactions at 5.7 GeV/c is presented and discussed in the framework of the Mueller-Regge approach to inclusive reactions. A comparison of our results with data at other energies points to specific properties of antiproton-proton interactions.I have greatly benefited from discussions with Dr. J. Cvach and Dr. V. imák. To Dr. V. imák I am also indebted for the encouragement during the preparation of this paper.     

An improved analysis of temperature autostabilization of ferroelectrics

A graphical method is proposed which permits the investigation of the influence of the parameters of an electrical circuit on the temperature autostabilization of a ferroelectric capacitor connected in this circuit. The region of temperature autostabilization is defined more accurately, and the influence on the value of the temperature autostabilization factor is shown. The influence of the electric circuit must be taken into account when interpreting the experimental results of the study of the temperature autostabilization regime.The authors are indebted to Dr. V. Dvoák, Dr. Z. Málek, and Dr. Ing. J. Mastner for stimulating discussions, and to J. trajblová and other colleagues for friendly help. Special thanks are due to Dr. Ing. V. Zima for critical remarks.     

The Au-SiO x -a-Si:H structures with very thin anodic oxide layers

Au-SiO _x -a-Si:H MIS structures with anodic oxide layers of thickness from 1.4 to 7.2 nm are investigated. The formation of the superthin SiO _x layers enables us to obtain photosensitive diode structures. These structures have a high photocurrent-to-dark current ratioi _ph/i _d >10⁴ and the dark resistanceR10¹⁰ for the reverse bias. The analysis of IR reflectance absorption spectra in the region of longitudinal Si-O stretching modes allows us to make a conclusion on the dependence of structure-chemical properties of superthin anodic oxids on their thickness.We thank Ing. J. Stuchlík from Czechoslovak Academy od Sciences for kindly manufacturing the a-Si:H films for us.     

On the effect of trapped particles in the regime of cyclotron resonance

The motion of particles in a finite amplitude wave, propagating obliquely to the homogeneous magnetostatic field is discussed. As follows from simple integral properties, in the neighbourhood of Doppler-shifted cyclotron resonance similar trapping effects appear as in a plasma without magnetostatic field. Consequences of this trapping are discussed, in particular, the possibility of a strong absorption of the wave, and the origin of stochastic instabilities caused by the perturbation of an effective trapping potential and leading to the acceleration of particles.The author is indebted to Dr. R.Klíma, Dr. J.Lacina and Dr. P.unka for interesting discussions and to Dr. .Körbel, Mrs. P.Jaroová and Mrs. A.Harmáková for numerical calculations.     

Doping of amorphous silicon by ion implantation: Electrical,optical and photoelectrical properties

Results of electrical, optical and photoelectrical properties of a-Si and a-Si(H) doped by means of ion implantation of Ga and N respectively show that the hydrogenated Si can be doped with higher efficiency. Ga seems to be built in the amorphous network as an acceptor and N in the form of (Si-N)_x complexes.We thank Drs. Koc, Vorlíek, Krasnopevcev and Gregora for stimulating discussions and Mrs lová and Miss Håjková for technical assistence.     

Optical behaviour of cobalt and nickel ions in different media

The absorption and diffusion of different solutions and crystals of NaCl and KCl containing bivalent cobalt and níckel ions were measured. The kinds of complexes are determined from the results and their importance in the luminescence process is discussed.The experimental part of this work was completed in December 1961 during his stay in the Inst. Sol. State Physics, Prague.The authors would like to thank Dr. J. Trnka, M. Lébl and J. Kunzl, Dr. J. Dolejí and M. Závtová for their effective help in preparing the samples and valuable discussions and K. Listoová for carrying out some of the experiments.     

Multimode stimulated Raman scattering with squeezed light

Stimulated Raman scattering of a multimode pump light on an one-mode phonon system is examined. The pump light is expected to be strong, so that it can be treated classically. The phonon mode and scattered Stokes and anti-Stokes modes are described quantally. The phonon is prepared in a coherent state and the scattered modes are prepared in displaced and squeezed states at the input.The author would like to thank Dr. J. Peina for fruitful discussions, and Dr. A. Luk for comments on the results.     

Influence of Ge and Ag impurities on the thermal conductivity of semiconducting amorphous As2Se3

The thermal conductivity of amorphous semiconducting As₂Se₃ is studied in the temperature range from 100 to 300°K and the influence of germanium and silver impurities is shown. The mean free path of phonons is determined and the observed change of the thermal conductivity is explained by the change of the velocity of sound in amorphous As₂Se₂ containing germanium.Presented by L. toura at the Meeting on Electronic Structure, Optical and Transport Effects in Amorphous and Liquid Semiconductors, Prague, May 1965.The authors are indebted to Dr. J. urek and Ing. I. Turek from the Department of Technical Physics of the College of Transport Engineering in ilina for measuring the velocity of sound in the investigated materials and to Mrs M. Kaparová and J. Trepeová for their help in the experimental work.     

Rational Conformal Field Theories and Complex Multiplication

We study the geometric interpretation of two dimensional rational conformal field theories, corresponding to sigma models on Calabi-Yau manifolds. We perform a detailed study of RCFTs corresponding to the T² target and identify the Cardy branes with geometric branes. The T²s leading to RCFTs admit complex multiplication which characterizes Cardy branes as specific D0-branes. We propose a condition for the conformal sigma model to be RCFT for arbitrary Calabi-Yau n-folds, which agrees with the known cases. Together with recent conjectures by mathematicians it appears that rational conformal theories are not dense in the space of all conformal theories, and sometimes appear to be finite in number for Calabi-Yau n-folds for n>2. RCFTs on K3 may be dense. We speculate about the meaning of these special points in the moduli spaces of Calabi-Yau n-folds in connection with freezing geometric moduli.     

The photo-electric properties of indium antimonide

A change of resistance or the formation of a voltage in mono- or polycrystalline samples of InSb due to illumination has been observed, the magnitudes of which increase with decreasing temperatures. It is demonstrated that this is a photo-conductive effect, arising in the volume of the sample or at barriers due to non-homogeneities, and a photo-voltaic effect. The spectral curves were measured with long-wave limits _1/2=5.8 at –155 °C, _1/2=6.7 at –42 °C.It is shown that these phenomena are caused by the transition of electrons from the valence-bond band to the conduction band under the influence of photons. The width of the band of forbidden energy values below room temperature was found to be E _G=0.24–2.4×10^–4T(eV).It is our pleasant obligation to thank Prof. Dr. L. Zachoval for permission to perform certain parts of this work in the Physics Institute of Charles' University, and Ing. A. Vaek and Dr. J. Plíva for valuable advice in carrying out the measurements and Ing. K. mirous for preparation of the samples.     

On the activity of carbon in ferrite

Two different deviations from the Henry's law were found for carbon in ferrite. The first deviation follows from the concentration dependence of the excess change in entropy accompanying the solution of carbon in ferrite as found by Schürmann et al. and the second one was found by evaluating the isothermal plots of the activity of carbon as a function of its concentration from other experimental data found in the literature. It has been pointed out that the first deviation is improbable and a simple hypothesis was proposed for explaining the second one. Our magnetic relaxation measurements performed for the special decisive case confirmed the second deviation, but they also excluded the proposed hypothesis. The second deviation was therefore explained by more complicated model whereas the first one by inadequate treatment of experimental data.The author would like to thank Dr. J. ermák and Dr. J. Laek for helpful discussions. He is also grateful to Dr. B. esták for his standing interest in this work.     

A simple theory of inhomogeneity linewidth broadening in MnxFe3−x,O4 ferrites

A simple theory of linewidth broadening due to thermal treatment is given. The theory is based on the assumption that the manganese-rich regions — clusters — with local tetragonal symmetry appear in the sample due to the alignment of tetragonally distorted Mn^{3 +} ions. This is a source of local anisotropy fields, leading to two-magnon scattering. The size of clusters and consequently their contribution to the linewidth depends on the thermal treatment. The function giving the dependence of the linewidth broadening on the cluster size is calculated using Schlömann's autocorrelation function. The recent experimental results are qualitatively discussed in terms of this theory. For the temperature dependence of the effect an effective compositionx = 1·8 inside the cluster is assumed, which gives a qualitative agreement with experiment. The discussion of the dependence of linewidth broadening on the composition has only an illustrative character and shows that the theory is compatible with experiment. A qualitative disagreement found for the angular dependence of (H) is believed to be a consequence of the high field approximation used.The author would like to express his thanks to Dr. S. Krupiçka for suggesting the problem and for many valuable discussions. Thanks are also du eto Dr. J. Loos for several discussions about the correlation problem, to Dr. Z. Smetana for information about experimental work and to Dr. C. Novák, who performed the numerical calculations.     

The CNDO-MO study of oxygen impurity states in AlN crystal

Deep levels due to oxygen impurity have been theoretically studied by the quasimolecular approach. The calculation of the orbital spectra was performed using the CNDO/2 method. Some important quantities (transition energies, width of valence band, effective charges etc.) were estimated. The results obtained agree qualitatively well with experimental data but quantitatively are still about 20% in error. Some reasons for the above discrepancy are briefly discussed.The authors are very grateful to Dr. J.Kubátová and Dr. S.Paesová for helpful discussions of the experimental investigations of aluminum nitride and to Dr. J.Pastrák for his interest in this work and discussion of results.     

The electron paramagnetic resonance in reduced BaTiO3 crystals

The electrcn-spin resonance of reduced BaTiO₃ crystals, which was studied by Z. roubek and K. d'ánský [Czech. J. Phys.B 13 (1963), 309], is interpreted as the resonance of the Ti³⁺ ion. The facts which favour this interpretation are discussed. The distortion of the oxygen ions surrounding the Ti³⁺ ion has been taken into account in order to explain the measured electron paramagnetic resonance spectrum. Considering the crystal-field model of C_4v point-group symmetry, the Stark energy-level separations of the Ti³⁺ ion and the values of theg factors are calculated.The authors would like to thank Dr. E. imánek for many very helpful discussions and Dr. H. Arend for helpful comments.     

A study of the density of gap states in amorphous semiconductors from thermostimulated conductivity spectra

A theoretical analysis of thermostimulated conductivity spectra _TSC(T) has been applied to determine the density of gap states g(E) in a-Si: H and a-Si: H/a-SiN _x : H multilayer structures. The results for g(E) are consistent with the results deduced from Fritzsche's analytical approach as well as other methods. A comparison has been made between the two different analytical approaches for _TSC(T). We discuss the relationship between the energy of maximum thermostimulated current emission E _m and quasi-Fermi level E _q. We demonstrate that E _q could be a better parameter than E _m in the general theoretical treatment of thermostimulated conductivity.     

Magnetic and thermodynamic properties of EuS/SrS multilayers at low temperatures

The magnetization, susceptibilityX and specific heatC of epitaxially grown EuS/SrS multilayers measured at low temperatures is reported.C changes with decreasing thickness of the individual EuS and SrS layers, i.e. decreasing modulation length, from the behavior of nearly pure EuS(CT ^3/2) to a behavior resembling that of spin-glass samples of Eu_xSr_1–xS (approximatelyC T). For multilayers with increasing thickness ratior =d _M/d_N (M=EuS,N=SrS),C decreases towards pure EuS, thus showing a transition from spin-glass to ferromagnet. The paramagnetic Curie temperature obtained fromX is reduced with respect to that of pure EuS for layers with small EuS layer thickness. All these effects can be explained by the formation of Eu_xSr_1–xS intrrmediate diffusion layers of a fewnm thickness during the evaporation process. Reduction of the substrate temperature results in a much smaller diffusion layer.Dedicated to Prof. Dr. G. von Minnigerode on the occasion of his 60th birthday     

Influence of crystal-field on the thermal conductivity of PrNi5

The thermal conductivity of PrNi₅ in the temperature range 0·5 to 20 K is investigated. The analysis of crystalline electric field effect on the experimentally obtained temperature dependence of the thermal conductivity indicates that beside the main electronic component also other contributions (phonons, magnetic excitons) can take place in the heat transport in this intermetallic compound.The authors would like to thank Dr. G. Eska for lending the sample and Dr. . Jáno for his interest in the work and stimulating discussions.