Chlorine doped CdTe single crystals (CdTe:Cl) were grown by the travelling heater method. The defect structure of the obtained single crystals was investigated using high-resolution X-ray diffractometry. The optimized models of dislocation systems based on the Thompson tetrahedron were constructed for CdTe:Cl single crystals. The analysis of the intensity distribution of diffracted X-rays as a function of reciprocal space coordinates and rocking curves was carried out using the kinematic theory of X-ray scattering in real crystals. The comparative analysis of experimental and theoretically predicted values of helical dislocation densities for CdTe:Cl crystals with perfect and mosaic structures were carried out. The dynamics of changes in concentrations and sizes of several types of interconnected dominant defects (spherical and disc-shaped clusters, dislocation loops) were studied with total integral reflectivity method. The generalized dynamic theory of X-ray diffraction in real crystals with randomly distributed microdefects of various types and a disturbed near-surface layer was used to interpret the experimental data.
A computer system for adjusting the «Brightness» and «Contrast» parameters of USB video cameras is developed, which consists of video cameras, computer and Python software. The settings of the video camera are performed by a computer program using an artificial neural network (ANN). A three-layer perceptron with learning by the method of backpropagation was used as an ANN. The inputs of the ANN are histograms of the brightness of the images, that read from the video camera. The ANN training dataset contained a series of images obtained at different values of the "Brightness" and "Contrast" parameters of the video camera. The settings of the video camera parameters are performed iteratively with a given step. An experimental test of the developed system for adjusting the "Brightness" and "Contrast" parameters of the video camera was performed, as a result of which the visual quality of the video stream was increased.
The comparative analysis of experimental and theoretically predicted values of helical dislocation densities for CdTe:Cl and MoOx/CdTe:Cl crystals with perfect and mosaic structures were carried out. Two-fold increase in the dislocation concentration was found for MoOx/CdTe:Cl heterostructures as a result of compression deformations of the CdTe:Cl crystal lattice. The transitional deformed layer at the boundary between MoOx film and CdTe:Cl single crystal with a thickness of about 0.1 μm significantly affects the electrical and spectroscopic properties of the obtained systems as materials for γ-radiation detection. Typical square-root type of the reverse branch of current-voltage characteristics were measured for a heterostructures based on a perfect CdTe:Cl, when for MoOx/CdTe:Cl heterostructures based on a mosaic substrate, an atypical quasi-linear type of I(V) dependence is observed. The characteristics of the detectors are affected not only by the quality of the initial crystals, but also by the technology of their post-treatment.
The paper presents an improved approach for the analysis of Kikuchi patterns. Calculation of the deformation state in different crystallographic directions are performed in terms of developed model. It is proposed to determine the deformation of local regions of synthetic diamond crystals based on the normalized intensity profiles of the Kikuchi band (εP) and the normalized parameters of the Fourier energy spectrum (εT) without using a reference image.
Values of average deformations in local regions of synthesized diamonds are determined using the power Fourier spectrum in the analysis of Kikuchi pattern. The degree of bands blurring on image is related with the deformation, which are quantitatively described through the changes of average radial period of the energy spectrum. The planar distribution of deformations is allowed to determine anisotropy by the magnitude and direction in the crystal.
This article describes a computer system for increasing the local contrast of railway images obtained with digital video cameras. The local contrast of the images increases within the rectangular windows, for each of which the minimum and maximum brightness values are determined. Based on such extreme brightness values, the lower and upper envelope brightness of the image are calculated. By smoothing of the envelopes the artefacts that appear in the image after increasing the local contrast based on its envelopes are significantly reduced. The images are read to the control computer from USB video cameras. The software implementation of image processing is created in Python.
X-ray moiré images arising from the interaction of deformation fields formed by two perpendicular rows of concentrated loads on the output surface of the LLL interferometer analyzer are calculated. The dynamics of formation of moiré images in case of change of distance between rows is investigated. The prospect of using the fractal dimension of moiré images calculated on the basis of Fourier spectra is shown.
The work is devoted to the study of the optical properties of carbon nanoparticles synthesized by the method developed during our experimental studies. The optimal conditions for the creation of carbon nanostructures with predetermined properties are defined. Nanoparticles of the size of about 80-1020 nm created in our experimental approach, the maximum of absorption of which is localized at wavelengths is in the violet-blue region of the spectrum (420 nm) and the maximum of luminescence is in the green region (530 nm) are discussed. The size of carbon nanoparticles, using biological and atomic force microscopes, is measured. The absorption index at the wavelength of 633 nm, which is used for the diagnosis of optical speckle fields, is estimated. The assumption is made about the possibility of using the obtained particles for correlation diagnostics of optical speckle fields.
A new approach for determining the distribution of mean-square deformations in the local regions of single crystals and polycrystals based on the analysis of electron backscatter diffraction images is proposed. The degree of bands blurring in Kikuchi pattern is related with the deformation values, which are quantitatively described through the changes of average radial period and the radial distribution area for the energy spectrum of the image. It is shown that the complex use of the power Fourier spectrum method in addition to the two-dimensional Fourier transform method create additional opportunities for determination of the influence of technological parameters on the structural homogeneity and the degree of perfection of studied crystals.
This article describes the developed method of adaptive-oriented filtration of digital images in the spatial domain, which is designed to remove noise and enhance the visual quality of images. as the kernel of filter an oriented two-dimensional gaussian distribution is used. as a result of this filtration, the contours of the images are blurred slightly, since the filtration is mainly carried out along the contour direction, that is, the filter parameters are adapted to each image region. the proposed method of image filtering is implemented in Matlab.
N. Pashniak, I. Fodchuk, A. Davydok, A. Biermanns, U. Pietsch, S. Balovsyak, R. Zaplitniy, I. Gutsuliak, O. Bonchyk, G. Savitskiy, I. Vivorotka, V. Stefanyk, I. Yaremiy
The investigations of structural changes in epitaxial films of iron-yttrium garnet (IYG) Y2,95La0,05Fe5O12 after high dose
ion implantation with nitrogen ions were performed using X-ray diffraction methods. The behaviour of structural
transformations after irradiation of Y2,95La0,05Fe5O12 crystals by the nitrogen ions was established by means of choice of
the proper models of defect structure that contain several types of dominant micro defects and definitely distributed
surface damaged layer. It is shown that reorganization of the crystal structure under the influence of high-doze nitrogen
ion implantation leads to improved magnetic properties of Y2,95La0,05Fe5O12 epitaxial films.
In this paper we demonstrate possibilities of electron backscattering diffraction technique (Kikuchi method) for
determination of strain distribution in local areas of synthetic diamond samples. To increase the precision of lattice
parameter determination a correlation method and corresponding software were used for accurate identification of
coordinates of Kikuchi lines intersections on the Kikuchi patterns. Consequently, subjective factors influencing on
accuracy at determination of displacements of image details were minimized. Samples have been investigated by
scanning electron microscope "Zeiss" EVO-50 using CCD detector. The complex analysis of location changes of
Kikuchi lines intersections and Kikuchi line intensity profiles permits to specify peculiarities of strain distribution for
diamonds grown by various methods.
The series of GaAs and SiO2 samples with the specially prepared one- and two-dimensional surface reliefs have been investigated by the methods of integral and differential curve of X-ray total external reflection. The direct and inverse problems were solved, taking into consideration data obtained by the method of atomic-force microscopy. The theoretical curves of total external reflection are calculated and the parameters describing a surface relief of the samples are restored. The fractal approach for describing of the shape of differential curves and surface profiles was used.
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