共查询到20条相似文献,搜索用时 46 毫秒
1.
R. N. Kyutt M. P. Shcheglov V. V. Ratnikov M. A. Yagovkina V. Yu. Davydov A. N. Smirnov M. M. Rozhavskaya E. E. Zavarin V. V. Lundin 《Crystallography Reports》2013,58(7):953-958
The structure of short-period hexagonal GaN/AlN superlattices (SLs) has been investigated by X-ray diffraction. The samples have been grown by metalorganic vapor-phase epitaxy (MOVPE) in a horizontal reactor at a temperature of 1050°C on (0001)Al2O3 substrates using GaN and AlN buffer layers. The SL period changes from 2 to 6 nm, and the thickness of the structure varies in a range from 0.3 to 1 μm. The complex of X-ray diffraction techniques includes a measurement of θ-2θ rocking curves of symmetric Bragg reflection, the construction of intensity maps for asymmetric reflections, a measurement and analysis of peak broadenings in different diffraction geometries, a precise measurement of lattice parameters, and the determination of radii of curvature. The thickness and strain of separate SL layers are determined by measuring the θ-2θ rocking curves subsequent simulation. It is shown that most SL samples are completely relaxed as a whole. At the same time, relaxation is absent between sublayers, which is why strains in the AlN and GaN sublayers (on the order of 1.2 × 10?2) have different signs. An analysis of diffraction peak half-widths allows us to determine the densities of individual sets of dislocations and observe their change from buffer layers to SLs. 相似文献
2.
3.
A. A. Lomov V. A. Karavanskiĭ A. L. Vasil’ev D. V. Novikov 《Crystallography Reports》2008,53(5):742-748
Porous Si layers, obtained by pulsed electrochemical etching of n-Si(001) substrates (resistivity 0.01 Ω cm) in a 1: 1 mixture of hydrofluoric acid and ethanol, have been investigated by high-resolution X-ray diffraction and electron microscopy. The average structural parameters of the layers grown (thickness, strain, porosity, pore size) are determined. It is found that pulsed anodic oxidation leads to a decrease in the average strain of layers. It is established that, at frequencies up to 1 Hz, anodic oxidation makes obtaining porous silicon multilayers with layer thicknesses of 20–300 nm containing Si nanocrystallites possible. It is shown that X-ray diffuse scattering from pores yields information about their ordering and can be used to monitor the processes of electrochemical etching used to form porous layers. 相似文献
4.
A. A. Lomov A. V. Myakonkikh K. V. Rudenko Yu. M. Chesnokov 《Crystallography Reports》2014,59(3):331-337
The structural changes in the surface layers of silicon substrates, implanted by helium ions with energies from 2 to 5 keV and doses to 6 × 1015–5 × 1017 cm?2, has been studied by high-resolution X-ray reflectometry. The damaged layer is found to have a total thickness comparable with the total ion path length (estimated from the SRIM model) and a multilayer structure: a strongly amorphized layer with reduced density, a porous (incapsulated) layer, and a deformed layer. The thickness of sublayers, their density ρ(z), and the mean strain (~5 × 10?3) have been determined. The characteristic pore size is estimated to be 5–20 nm. It is shown that the presence of a nanoporous layer facilitates the formation of diffuse scattering, which can be used to diagnose layers by high-resolution X-ray reflectometry. 相似文献
5.
A. E. Blagov G. B. Galiev R. M. Imamov E. A. Klimov O. A. Kondratev Yu. V. Pisarevskii P. A. Prosekov S. S. Pushkarev A. Yu. Seregin M. V. Koval’chuk 《Crystallography Reports》2017,62(3):355-363
In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As HEMT heterostructures on InP substrates with elastically strained InAs insert in combined quantum well (QW) have been investigated using a combination of X-ray methods: double-crystal X-ray diffraction, X-ray reflectivity, and reciprocal space mapping. This approach has provided detailed complementary information about the layered and real crystal structures of the samples. The data obtained have made it possible to perform structural analysis of the multilayer systems and compare their characteristics with specified technological parameters, due to which the HEMT growth technology can be corrected and improved. 相似文献
6.
V. V. Volkov V. V. Klechkovskaya E. V. Shtykova K. A. Dembo N. A. Arkharova G. I. Ivakin R. Yu. Smyslov 《Crystallography Reports》2009,54(2):169-173
The nanoscale structural features in a composite (gel film of Acetobacter Xylinum cellulose with adsorbed silver nanoparticles, stabilized by N-polyvinylpyrrolidone) have been investigated by small-angle X-ray scattering. The size distributions of inhomogeneities in the porous structure of the cellulose matrix and the size distributions of silver nanoparticles in the composite have been determined. It is shown that the sizes of synthesized nanoparticles correlate with the sizes of inhomogeneities in the gel film. Particles of larger size (with radii up to 100 nm) have also been found. Electron microscopy of thin cross sections of a dried composite layer showed that large particles are located on the cellulose layer surface. Electron diffraction revealed a crystal structure of silver nanoparticles in the composite. 相似文献
7.
The wafer processing of Indium Phosphide (InP) is so important that it is getting more and more attentions. Lapping is a basic step just following the ingot cutting. In this paper, the influences of various processing parameters on the lapped wafer quality and lapping rate have been checked, the double-crystal X-ray diffraction results about lapped wafers also were presented here. According to the experimental results, the optimum lapping conditions have been obtained. 相似文献
8.
A. E. Blagov M. V. Kovalchuk V. G. Kohn Yu. V. Pisarevskiĭ P. A. Prosekov 《Crystallography Reports》2010,55(1):10-14
A strong effect of virtual scattering has been experimentally observed when studying the nearly coplanar three-beam (220,
371) X-ray diffraction in a paratellurite single crystal under high-resolution double-crystal X-ray diffraction using MoK
α1 radiation. One characteristic feature of this effect is that the angular dependence of the first (strong) reflection intensity
and its shape barely change in the three-beam range of parameters, whereas very strong changes are observed for the second
(weak) reflection not only in the three-beam range but also far beyond it, which is related to the variation in the two-beam
diffraction parameter due to virtual scattering. The changes observed are asymmetric and make it possible to determine the
triplet combination of structure-factor phases. 相似文献
9.
G. B. Galiev S. S. Pushkarev I. S. Vasil’evskii E. A. Klimov R. M. Imamov I. A. Subbotin E. S. Pavlenko A. L. Kvanin 《Crystallography Reports》2012,57(6):841-847
A complex structural and electrophysical analysis of MHEMT In0.70Al0.30As/In0.75Ga0.25As nanoheterostructures grown on (100)GaAs substrates using two radically new designs of metamorphic buffer (providing different internal-strain distributions) has been performed. The lattice parameters of the constant-composition layers entering the metamorphic buffer have been determined by X-ray diffraction using symmetric and asymmetric (400) and (422) reflections. It is shown that, having chosen a proper design of metamorphic buffer in nanoheterostructures on GaAs substrates, it is possible to obtain electron mobility and concentration comparable with those for nanoheterostructures on InP substrates. The compositions of smoothing layers, determined from the peaks on rocking curves, are found agree well with the process values. 相似文献
10.
Chen Songyan Liu Baolin Wang Benzhong Huang Meichun Chen Longhai Chen Chao 《Journal of Crystal Growth》1997,170(1-4):433-437
Lattice-mismatched heteroepitaxy has attracted considerable attention in recent years. A great interest of these systems is the possibility of integrating devices from different materials on a single substrate. 1.3 and 1.5 μm InGaAs(P)/InP laser diodes are essential for optical communication, whereas InP field effect transistor technology is less developed than that of GaAs MESFET. The performances of laser diodes are much more sensitive to a high density of disclocations, so it would be interesting to grow GaAs MESFET on InP for integration with 1.3 and 1.5 μm lasers. Due to the large difference of the thermal expansion coefficient and lattice parameter between GaAs and InP, it is very difficult to grow GaAs epilayers of high quality on it is very difficult to grow of GaAs epilayer high quality on InP substrates due to the large difference of the thermal expansion coefficient and lattice parameter between GaAs and InP. A new method, metalorganic source modulation epitaxy (MOSME), which improves the crystal quality of GaAs epilayers on InP substrates by MOVPE, has been adopted in our laboratory. The lowest full width at half maximum (FWHM) of the double crystal X-ray (DCX) diffraction spectra reaches as low as 120 arcsec for a 5 μm thick layer. Structural properties (misorientation, lattice parameters and crystal quality) of 1.0–5.0 μm thick GaAs layers grown on InP have been measured by DCX diffraction. On GaAs MESFETs grown on InP, we have measured gm = 100 ms/mm. For these transitions, the current gain cut-off frequency (Ft) is around 12 GHz and the maximum frequency of oscillation (Fmax) is higher than 30 GHz. 相似文献
11.
R. Ben Brahim 《Journal of Non》2011,357(14):2620-2625
A detailed microstructural analysis of amorphous silicon-germanium alloys with germanium fraction ranging from 0.1 to 0.5 is performed by means of a numerical modeling technique. By substituting Ge atoms for Si atoms in nanoporous paracrystalline network of amorphous silicon, several amorphous silicon-germanium structures have been generated then relaxed. The main aim of our work is to study the effect of compositional heterogeneities on the structural properties of amorphous silicon-germanium alloys in comparison with the standard case, that of a homogeneous random distribution of the atoms. In the present work we envisage the two-phase amorphous silicon-germanium model proposed by Goerigk and Williamson to interpret their anomalous small-angle X-ray scattering measurements; it consists on a mixture of Ge-rich and Ge-poor domains at the nanoscale. The microstructure of our structural models is analyzed by examining the macroscopic mass density, the X-ray diffraction intensity, the radial distribution functions, the bond lengths and the coordination numbers within the first coordination shell of Si and Ge atoms. 相似文献
12.
Xiu-Qi Huang Feng-Qi Liu Xiao-Ling Che Jun-Qi Liu Wen Lei Zhan-Guo Wang 《Journal of Crystal Growth》2004,270(3-4):364-369
Self-assembled InAs quantum dots (QDs) in an InAlGaAs matrix, lattice-matched to InP substrate, have been grown by molecular beam epitaxy (MBE). Transmission electron microscopy (TEM), double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL) are used to study their structural and optical properties. In InAs/InAlGaAs/InP system, we propose that when the thickness of InAs layer deposited is small, the random strain distribution of the matrix layer results in the formation of tadpole-shaped QDs with tails towards random directions, while the QDs begin to turn into dome-shaped and then coalesce to form islands with larger size and lower density to release the increasing misfit strain with the continuous deposition of InAs. XRD rocking curves showing the reduced strain with increasing thickness of InAs layer may also support our notion. The results of PL measurements are in well agreement with that of TEM images. 相似文献
13.
M. A. Chuev E. M. Pashaev V. V. Kvardakov I. A. Subbotin 《Crystallography Reports》2008,53(5):734-741
A theoretical analysis of the shape of the resolution function of an X-ray diffractometer in the double-crystal nondispersive scheme for measuring rocking curves has been performed. It is shown that this function, along with the strong narrow central line (corresponding to the characteristic line to which the collimator crystal and slits in the experimental scheme are tuned) always contains an additional weak satellite, corresponding to the neighboring characteristic line. This feature manifests itself in experimental curves as an additional pseudopeak, whose intensity is comparable with the corresponding diffraction scattering intensity from a sample in the fundamental characteristic line, and whose shape and exact position are set by the resolution function in a specific experimental scheme. It is shown that the exact allowance for the angular and spectral distribution of incident radiation in the double-crystal scheme makes it possible to precisely determine the parameters of the structures studied. 相似文献
14.
《Journal of Non》1997,212(1):23-39
The local structure of amorphous cadmium arsenide semiconducting films has been studied by differential anomalous X-ray scattering. Intensity measurements were carried out on two samples, containing 41 and 74 at.% As, in the vicinity of the absorption K edges of both constituents using synchrotron radiation. The computational procedure, similar to that proposed by Warren for an amorphous sample with more than one kind of atom, was applied to obtain the structural parameters from the experimental data. It has been found that atoms in the amorphous CdAs films remain almost tetrahedrally coordinated and that the investigated films are chemically ordered. The structural changes going from cadmium- to arsenic-rich composition have been revealed. The differential anomalous X-ray scattering technique proved to be effective, providing the evidence for the CdCd and AsAs near neighbour correlations in Cd59As41 and Cd26As74, respectively. The simulations of the differential radial distribution functions have shown that for the amorphous film containing 41 at.% As the distorted tetrahedral structure, intermediate between the CdAs and Si III type structures, is adequate to account for the experimental data. At 74 at.% As, the atomic arrangement can be described satisfactorily by the structural model based on the tetragonal CdAs2 structure. The structural parameters obtained from the present study and those previously derived using the extended X-ray absorption fine structure and conventional large angle X-ray scattering techniques are compared. 相似文献
15.
R. Ben Brahim 《Journal of Non》2011,357(6):1531-2625
A detailed microstructural analysis of amorphous silicon-germanium alloys with Ge fraction ranging from 0.1 to 0.5 is performed by means of a numerical modeling technique. By substituting Ge atoms for Si atoms in the nanoporous paracrystalline network of amorphous silicon, several amorphous silicon-germanium structures have been generated. Our main aim in the present work is to study the effect of compositional heterogeneities on the structural properties of amorphous silicon-germanium alloys in comparison with the standard case, that of a homogeneous random distribution of the atoms. We have limited ourselves here to the borderline case, that of segregation of Ge atoms at the nanoscale. The microstructure of our structural models is analyzed by examining the macroscopic mass density, the intensity of X-ray diffraction, the pair distribution functions, the bond lengths and the coordination numbers within the first coordination shell of Si and Ge atoms. Our structural models account for the experimentally derived mass densities regardless of the Ge distribution pattern. They also account for the intense small-angle X-ray scattering observed for some amorphous silicon-germanium samples. The short-range compositional disorder, reflected in the bond lengths and the coordination numbers within the first coordination shell of Ge atoms, is found to be very sensitive to how these atoms are arranged in the alloys. 相似文献
16.
L. F. Malakhova A. E. Voloshin C. C. Wilson E. B. Rudneva N. G. Furmanova V. I. Simonov 《Crystallography Reports》2003,48(1):29-34
The structures of two crystalline specimens cut out from the pyramidal and prismatic growth sectors of a K(H0.052D0.948)2PO4 single crystal have been studied by diffuse neutron scattering and precision diffuse X-ray scattering. Diffuse scattering is concentrated in the vicinity of the Bragg reflections and is practically the same in specimens cut out from different growth sectors of a single crystal. X-ray diffraction analysis using the extinction parameters provided the establishment of a higher perfection of the specimen cut out from the prismatic growth sector. The precision X-ray studies revealed different configurations of hydrogen bonds in the specimens. 相似文献
17.
V. I. Punegov 《Crystallography Reports》2013,58(5):663-670
A theory of X-ray diffuse scattering (XRDS) from a crystal with pores in the form of triangular prisms has been developed. Solutions for the static Debye-Waller factor, intrinsic correlation function, and the correlation volume (which characterizes the XRDS angular distribution in reciprocal space) are obtained within this model. A numerical simulation of reciprocal space maps of X-ray diffuse scattering is performed. The influence of pore-size fluctuations on the formation of XRDS intensity isolines is demonstrated. 相似文献
18.
H. W. Dong Y. W. Zhao Y. P. Zeng J. H. Jiao J. M. Li L. Y. Lin 《Journal of Crystal Growth》2003,250(3-4):364-369
Tensile-strained InAlAs layers have been grown by solid-source molecular beam epitaxy on as-grown Fe-doped semi-insulating (SI) InP substrates and undoped SI InP substrates obtained by annealing undoped conductive InP wafers (wafer-annealed InP). The effect of the two substrates on InAlAs epilayers and InAlAs/InP type II heterostructures has been studied by using a variety of characterization techniques. Our calculation data proved that the out-diffusion of Fe atoms in InP substrate may not take place due to their low diffusion coefficient. Double-crystal X-ray diffraction measurements show that the lattice mismatch between the InAlAs layers and the two substrates is different, which is originated from their different Fe concentrations. Furthermore, photoluminescence results indicate that the type II heterostructure grown on the wafer-annealed InP substrate exhibits better optical and interface properties than that grown on the as-grown Fe-doped substrate. We have also given a physically coherent explanation on the basis of these investigations. 相似文献
19.
E. Matsubara T. Tamura Y. Waseda T. Zhang A. Inoue T. Masumoto 《Journal of Non》1992,150(1-3):380-385
The atomic structures of amorphous La55Al25Ni20 alloys which have a wide supercooled liquid region and a high reduced glass transition temperature have been studied using anomalous X-ray scattering (AXS) at the Ni K-absorption edge as well as the ordinary X-ray diffraction with Mo K radiation. The interference functions and the radial distribution functions were determined for the amorphous alloys as-quenched and after annealing at various temperatures and also for a fully crystallized sample. These systematic structural studies revealed a drastic change in Ni environment upon crystallization. The need for such atomic rearrangements around the Ni atoms during crystallization may be the reason why the amorphous phase is thermally stable. 相似文献
20.
I. S. Vasil’evski? G. B. Galiev V. G. Mokerov E. A. Klimov R. M. Imamov I. A. Subbotin 《Crystallography Reports》2010,55(1):6-9
In
x
Al1 − x
As/In
y
Ga1 − y
As/In
x
Al1 − x
As/InP HEMT structures has been investigated with a change in the InAs molar fraction both in the quantum well and the buffer
layer. The electrical parameters of the samples are measured at different temperatures. The structural parameters of the layers
and the characteristics of the interfaces between them are determined by double-crystal X-ray diffraction. An increase in
the Hall mobility and electron concentration, as well as in the structural quality of the samples, is observed alongside an
increase in the InAs molar fraction in the quantum well. It is established that high electron mobility is retained at small
(to 5%) mismatches between the buffer layer and substrate. 相似文献