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.
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.
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.
An information system has been developed for the analysis of x-ray moiré images using artificial neural networks and wavelet filtering. Moiré images are obtained as a result of the action of a set of forces on the surface of the crystal. The analysis of the images consisted in solving the inverse problem, that is, in calculating the values of a set of forces based on the moiré image. To prevent retraining of the neural network, a control dataset of images was used. The input signals of the artificial neural network are moiré images after contour extraction, logarithmization, downscaling and wavelet filtering using Dobeshe wavelets. Due to such image processing, the training time of the neural network was reduced with a sufficiently low training error. The output signals of the neural network are the values of a set of forces that formed the moiré image. The training of an artificial neural network is performed by the method of backpropagation. The artificial neural network is implemented in the Python language in the Google Colab cloud platform. The results of testing the developed information system showed a high accuracy of calculating the values of a set of forces for simulated and experimental x-ray moiré images.
Аn analysis of the structure formation of concrete composites, compressive strength of which exceeds 120 MPa and a quantitative analysis of their qualitative composition and hydration products by X-ray diffraction, x-ray spectral analysis and electron microscopy. The main factors affecting the physicomechanical parameters of the complex of various nanofillers and the formation of a denser cement stone structure, which mainly includes calcium hydrosilicates, calcium silicate hydroaluminates and hydroaluminates of various basicity, are studied.
Crystal and magnetic domain structures of iron garnet films with different thicknesses are studied by means of atomic and magnetic force scanning microscopies as well as by means of high-resolution Х-ray diffraction. The model of the garnet films as a set of vertical columns with certain lateral sizes is proposed and substantiated. Within this model, X-ray intensity distributions in the vicinity of the reciprocal lattice points are calculated using the Monte Carlo approach to determine densities of two dislocation types with different Burgers vectors.
The defect structure of p-CdTe:Cl single crystals and MoOx/p-CdTe/MoOx heterostructures based on them were investigated by high-resolution X-ray diffractometry methods. Different models of dislocation systems were applied, according to which the densities of dislocations were estimated from the Wilson-Hall plot. It is shown that the application of the MoOx layer significantly affects the density of dislocations and their influence on the electrical and spectroscopic properties of heterostructures is estimated
The defects structure, charge collection, and detection efficiency of the Ni(NiO)/p-CdTe/Au/Cu Schottky-diode detector have been investigated. The spectroscopic properties of the obtained heterostructures have been studied experimentally and analyzed theoretically. The optimal reverse bias voltage for higher performance of the detectors under study was determined. The reasons of poor charge collection in the detectors and low detection efficiency of photons emitted by an 241Am (59.5 keV) radioisotope have been established and discussed. The techniques of increasing the functional parameters of Ni(NiO)/p-CdTe/Au/Cu Schottky diodes have the investigated and the optimal ways for improvement of the detector performance have been formulated.
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.
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.
Peculiarities of morphology and electric properties of X-ray and γ-ray detectors developed by graphene deposition onto commercially available (111) oriented CdTe:Cl wafers has been investigated. Laser treatment of graphene contact using millisecond YAG-laser with an energy density of 0.1–4.5 J/cm2 has been carried out in order to modify and improve their structure and phase state.
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.
The degree of structural perfection of CdTe:Cl single crystals was estimated by methods of high-resolution Xray diffractometry. Two possible systems of dislocations that consists of two sets of complete 60-degree dislocations and Frank partial dislocations were investigated with the use of Krivoglaz kinematic theory and Monte Carlo method. The density of dislocations that provides correspondence between experimental and simulated reciprocal space maps is determined.
This work presents the results of investigation of crystal structure of yttrium iron garnet films of different thickness using high-resolution X-ray diffractometry data and simulation of X-ray intensity distributions in the vicinity of the reciprocal lattice points by the Monte Carlo approach. The parameters of films column microstructure are determined and substantiated, and the model of their defective structure as systems of two types of dislocations with different directions of the Burgers vector is proposed.
The electrical and photoelectric properties of thin-film CdS/Cd1-xMgxTe (x = 0-0.07) solar cells are investigated. The measured I-V characteristics of the heterostructures are described in terms of well-known theoretical models. The quantum efficiency spectra are analyzed taking into account the drift and diffusion components, recombination on the front and rear surfaces of the Cd1-xMgxTe absorber layer. Comparison of the calculation results with the experimental data allows to determine the main parameters of the Cd1-xMgxTe layer and diode structure.
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.
The features of formation of diffraction images of edge dislocation sets forming clusters (of two, three and more dislocations)
as well as small-angle dislocation boundaries (walls) were studied. Various intensity interference effects of rescattering
and internal reflection of the newly formed and already existing wave fields on thickness distributions of intensity for the
case of presence in the same glide plane of edge dislocations with parallel and anti-parallel Burgers vectors were
discovered.
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.
We study the mechanisms of forming X-ray moiré images arising under the action of one-dimensional rows of local
concentrated forces at output surface of a surface of triple-crystalline-interferometer for the cases of orientation of them
parallel and perpendicular to the vector of diffraction. Presence of constant phase shift of one of the interfering waves in
the interferometer's analyzer results in diminishing of period, contrast and area of deformation moiré fringes. It is shown
that the area of efficient interaction of phase and deformation moirés depends on both the magnitude of the constant
phase shift and on the magnitude and character of arrangement of local concentrated forces in rows.
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.
In this work on the basis of numerical solution of Takagi's equations the diffraction images of various types possible in
silicon dislocation loops and barriers are constructed in the case of transmission geometry. The three-dimensional total
misorientation functions of dislocation loops and barriers are calculated and its cross sections are analysed. X-ray images
of dislocation loops and barriers are simulated in the cases of "thin" (μt<1) and "thick" (μt>10) crystals.
The results of X-ray AFM, SEM, and SIMS studies of near-surface regions of HgCdTe graded-gap epitaxial layers
obtained by high-temperature annealing in vapour of the main components have been presented. We used ISOVPE
layers of HgCdTe grown on CdTe substrates the surface of which was implanted by As ions. The AFM investigation has
shown that the morphology of surfaces of HgCdTe structures obtained at the same conditions is significantly influenced
by the crystal orientation of the initial substrates of CdTe. By means of SIMS and SEM analysis a substantial increase of
the molar content of HgCdTe solid solution on the surface of ion-implanted epitaxial layers after high-temperature
annealing has been observed. It is shown that large gradients of composite HgCdTe solid solution are formed in the near-surface
regions of the epitaxial layers due to small changes in the thermodynamically equilibrium conditions of the
process of high-temperature annealing.
The precision of lattice parameter determination can be significantly risen providing superposition of closely set maxima
at Renninger-scan, which are in addition structure and spectral sensitive. This superposition can be achieved by means of
lattice parameters change or wavelenght variation. We have realized that in the cases of coincidental coplanar or
noncoplanar multiple x-ray diffraction. We have studied evolution of an angular distance between diffraction maxima
near the range of coincidental multiple x-ray diffraction depending on stochiometric composition and temperature of
sample. It has been shown that sensitivity of multiple diffraction is Δφ/Δa≈13.3 sec of arc /10-6 Å in the region of
coincidental coplanar or noncoplanar x-ray diffraction.
Methods of two- and three-crystal X-ray high-resolution diffractometry were used to investigate structural changes
in Cz-Si single crystals irradiated with high-energy electrons (E=18 MeV). The results of experimental investigation
were interpreted by means of a generalized dynamic theory of X-ray diffraction in real crystals with randomly
distributed microdefects of various types and a damaged surface layer. As dominant defects, disc-shaped and spherical
clusters - SiO2 precipitates, as well as dislocation loops were used.
The multilayer nano-scale systems contained one or two quantum wells InxGa1-xAs1-yNy have been investigated by double-crystal X-ray diffractometry. The growth conditions, composition of initial compounds were considered. It is shown that the processes of interdiffusion of In and Ga atoms nearby the interfaces of layer with QW were took place and influenced on the properties of considered multilayer systems. The principle structural parameters of multilayered InxGa1-xAs1-yNy/GaAs systems and contents of nitrogen in the quantum well and buffer layers were estimated.
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.
Influences of slight and severe distortions, appearing under a focused load, on intensity oscillation in thickness of wedge-similar and flat Si crystals are investigated experimentally and by the numerical solution of Takagi equations. It is shown that scattering processes cause the bend and focusing (defocusing) x-ray trace during transmission through an environment with slowly varied refraction parameter in the case of slight distortions. In the region of severe distortions the processes of interbranch scattering take place.
On the basis of the numerical solution of Takagi's equation system the influence of ultrasonic wave parameters on enhancement and suppression of diffraction contrast of microdefects on section topographs is investigated. Homogeneous (n equals 6,2 (DOT) 105 cm-3) and random (n equals 2,5 (DOT) 107 cm-3) distribution of microdefects in volume are considered for thin ((mu) t equals 1) and intermediate ((mu) t approximately equals 3) thickness of Si crystal. Influence of strain fields from microdefects and homogeneous strains from ultra sound on integral parameters of crystal perfection is studied.
Influence of 1D strains of different type on unusual x-ray transmission in Ge crystal is studied. The (111,1 11/200), (111,1 1 1/220) and (220,202/022) three-wave Laue diffractions of CuK(alpha )-radiation are considered at (mu) t>10. Research is carried out by numerical solution of Takagi equation system. It is shown that 1D distortions (equidistant banding, acoustic strain and layer hidden under surface) caused different transformations of two- and three- wave scattering areas. Each of considered strains has its own distinctive influence on multiple unusual transmission. It is explained by various character of interaction between diffracted waves that leads to redistribution of intensity in three-wave area. In some cases the considerable enhancement of three-wave unusual transmission is observed at slight strains.
Research of structural changes in subsurface layers of Si single crystals during formatting amorphous layers hidden under the surface are carried out. It established, that phosphorus ion (with 180 keV energy and doze of the order 1015 ion/cm2) implantation and subsequent short-term temperature annealing at T equals 500 degree(s)C are caused great structural changes in subsurface areas. The great strains in direction perpendicular to interface are characteristic of structures formed in this way.
Results of complex investigations of n- and p-type Hg1-xCdxTe (MCT) etching in RF mercury glow discharge have been presented. Discharge was induced in quasi-closed volume. Results of technology parameter influence onto velocity of etching have been presented. It has been shown that MCT treatment by mercury ions can be carried out with etching velocity up to 30 micrometers /hour. Surface heating under these conditions slightly increases the temperature (up to 50 degree(s)C) and stoichiometry deviations are absent. It has been found that the width of disturbed layer depends on bias voltage and is smaller than 2.5 micrometers . Electrophysical parameters of n- and p-type MCT after processing have been studied. Etching of n-MCT forms the n+-n structure. The width of n+-layer corresponds to the width of disturbed zone. In the case of p-MCT, there exists inversion of conductivity type at depths exceeding those corresponding to the case of argon ions etching. It is supposed that high inversion velocity is caused by saturation of MCT surface by mercury ions during treatment.
Among existing x ray diffraction diagnostics nonperfections of crystals the specific location take methods are based on use of x-ray dynamic diffraction effects. From them the most sensitive are based on interferention. The Pendellosung and Moire fringes methods arise in consequence of coherent dynamic interaction of wave fields in single crystals. One of the main advantages of the Moire method is the extraordinary high sensitivity to insignificant deformations of crystal lattice ((Delta) d/d approximately 10-8) and atomic planes turns ((delta) approximately 0.01'). Created by a method of x-ray diffraction Moire the unique phase magnification permits us to directly observe the nuclear rows of crystal lattice. Until recently the attention of researchers attracted, basically, precise measurements of refraction parameters and dispersion amendments to nuclear scattering amplitudes, measurement of movy with large accuracy and refinement of Avogadro number, and the creation of new multi crystal interferometers. At the same time, little opportunities of x-ray interferometry at research of crystal structure defects were used. For the first time the opportunity of definition by method x-ray diffraction Moire of Burgers vectors of individual dislocation was demonstrated by M. Hart, Christiansen has studied the series of 60 degree(s) dislocation in Si on Moire images. Tensions in Si, caused by Ar ions implantation, were defined in the work. The purpose, which the authors of given reviews pursue consists in demonstration of new opportunities of x-ray three crystal interferometry in the investigation of single and complex defects.
The scheme of x-ray diffraction on reflection for research of layers structure of single crystals after various kinds of external treatment is used. On a series of diffraction curves the profiles of distribution of deformations in thin subsurface areas of InSb and CdTe crystals irradiated by high-energy electrons and B ions are constructed. The given work demonstrates the opportunities of the skew asymmetric scheme of x-ray diffraction on reflection as in topographical, and in two crystal spectrometer scheme in research of structural changes in subsurface layers of various single crystal compounds after ion and electron irradiation.
There are more than a dozen different methods of diagnostic and control of the structural purity of materials which are used in modern micro- and optoelectronics. Each of them has their own strong and weak points, range and fields of use. Usually a couple of different methods are used in research together. The advantage of using x-ray methods against optical (in solving the problem of distorted crystal) is that interferention of coherent beams is not on artificial diffraction lattice but on crystal lattice of the researching object. It permits us to expand researching ranges of crystal structures distortions. The privilege of x-ray methods (like x-ray interferometry and diffractometry) is that they are nondestructive, noncontact, fast, do not require expensive equipment, and are highly sensitive. Unique information about deformation locations and electronic density as a function of width (from a few monolayers) can be determined from their use.
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