L. Kowalczyk

Parameters of substrates-single crystals of ZnTe and Cd1-xZnxTe (x < 0.25), obtained by physical vapor transport technique (PVT)

Abstract It is shown that very high quality (in particular – very good real crystal structure) of the single crystals of ZnTe and Cd 1− x Zn x Te, intended to be substrates for MBE and other techniques of epitaxy, can be reached by an optimized physical vapor transport (PVT) technique. The obtained crystals are twin-free, the narrowness of the rocking curve nearly reaches the theoretical limit and the density of dislocations is low. The results of characterization of the crystals are presented.

Analysis of Variability of Isopotential Areas Features in Sequences of EEG Maps

The aim of the study was to analyse differences in dynamics of variability of extreme isopotential areas in sequences of EEG maps containing seizure activity episode. Analysis of dynamics of alternating variability of extreme isopotential areas was performed in the three steps: visual examination, calculation of the differencing coefficient and statistical analysis. Results of the study performed on two groups of totally 17 subjects reveal the different dynamics of isopotential areas variability in considered groups of patients.

Second harmonic generation in Cd1−xMnxTe

Abstract Infrared second-harmonic generation in Cd 1− x Mn x Te has been experimentally demonstrated. The nonlinear susceptibility d 14 (−2 w , w , w ) referred to the known value d 14 for CdTe has been determined for Cd 1− x Mn x Te ( x ⩽0. .5) from measurements of second-harmonic power using a Q -switched Co 2 laser. The values of nonlinear susceptibility are much bigger for Cd 1− x Mn x Te than for CdTe. It has been proved that Cd 1− x Mn x Te crystals can be used for high-power efficiency second-harmonic generation of laser infrared radiation.

Analysis of Dispersion of Isopotential Areas Values in EEG Maps Sequences

The aim of the study was to develop the method for objective evaluation of differences in alternation variability of isopotential areas in the EEG maps sequences for activity episode. The method was based on the analysis of EEG map images histograms and concerns the evaluation of the isopotential areas changes. The principle of the present method is analysis of the ratio of extreme isopotential areas and of the dispersion of values of extreme isopotential areas. The method was tested on sequences of amplitude maps for 17 subjects with seizure episodes with different characteristics divided into two groups. Visual evaluation of obtained results confirms that ratio of extreme isopotential areas and coefficients of the symmetry and elongation of extreme isopotential areas values dispersions may be useful for describing the variability of EEG maps. Influence of the potential range scale of EEG maps on the quantitative estimation of the isopotential areas variability was also analyzed.

Relationships between Isopotential Areas in EEG Maps before, during and after the Seizure Activity

The aim of the study was to analyse relationships between isopotential areas in sequences of EEG top maps recorded before, during and after seizure activity. Method of the analysis of isopotential areas in sequences of EEG maps consists on the comparison of the changes of values of areas before and after seizure activity and estimation of mutual changes of the areas for the extreme isopotential regions during seizure activity. Results of the study performed on two groups of totally 17 subjects suggest that selected image features like area of given range of potentials and the analysis of the relationships between areas of the isopotential regions before, during and after seizure episode reveal the differences in considered groups of subjects.

Low defect density, substrate quality crystals of the wide-gap II–VI compounds, obtained by physical vapour transport technique (PVT)

Abstract It is demonstrated that substrate quality, 1 in. size single crystals of the wide-gap II–VI semiconductors: ZnSe, Zn(Se,S), ZnTe and (Cd,Zn)Te can be obtained by a simple, horizontal, low temperature, physical vapour transport (PVT) technique. The results of the characterization of the obtained crystals are presented.

Growth and characterization of the ternary ZnSe-based compounds obtained by low temperature vapour transport

Abstract We employed the low temperature physical vapour transport (PVT) method to grow ZnSe and ZnSe 1 − x S x ( x ≤ 0.15), high quality, large (25 mm in diameter) bulk crystals. Characterization of the obtained crystals was performed by means of X-ray diffraction, X-ray full width half maximum (FWHM) rocking curves and the energy dispersive X-ray fluorescence (EDXRF) spectrometry. Optical properties were determined from the low temperature near-band-edge photoluminescence and reflection measurements.

Modeling interlayer exchange coupling in EuS/PbS/EuS trilayers

All-semiconducting EuS/PbS/EuS trilayers that show antiferromagnetic coupling were studied by superconducting quantum interference device magnetometry. We analyzed our measurements with a modified Stoner–Wohlfarth model from which the interlayer exchange energy and anisotropy were extracted based on the switching field from antiparallel to parallel alignment of the EuS layers and the zero-field susceptibility, respectively. Magnetic moment versus temperature curves were simulated by taking into account Brillouin type temperature dependence of the saturation magnetization of EuS. Despite their simplicity, the simulated curves show good qualitative agreement with the measurements when strong temperature dependence of interlayer coupling is assumed.

Technology and Characterization of Single‐Crystalline Substrates Made of ZnSe‐Based Wide‐Gap II–VI Semiconductor Compounds

Detrimental role of traces of oxygen in the growth process of the ZnSe-based wide-gap II-VI semiconductor crystals is emphasized. Adhesion, enhanced by the presence of oxygen, of the growing crystal to the walls of the quartz ampoule promotes generation of twinning and dislocations. The technology of the substrate-quality crystals, which ensures nearly complete removal of oxygen, is described. The results of characterization of the obtained large (25 mm diameter), twin-free single crystals of ZnSe, and substrate plates are presented.

Correlation Matrices as a Tool to Analyze the Variability of EEG Maps

The aim of this paper is to present the selected examples of possible applications of image of correlation coefficients matrix of EEG map series in the analysis of variation of the topography of the isopotential areas in EEG maps, and thus in the assessment of stationarity, spatio-temporal variability and trends of changes of bioelectric activity of the brain. The image of correlation coefficients matrix shows similiarity of all pairs of maps in a series. The choice of segmentation threshold of characteristic areas in images of the correlation coefficients matrix of EEG map series corresponding to the sequence similarity relationships in a series of maps was based on the results of research conducted on test series. Determining of the segmentation threshold value allowed for the presentation of research results of similar sequences in the examplary series of real EEG recordings. The obtained results consistent with the visual assessment of the similarity of the topographic distributions of isopotential areas in EEG maps form the basis for further research of usefulness of the analysis of the correlation coefficients matrix in the assessment of the dynamics of EEG mapping topography.