E. Kh. Mukhamedzhanov

Investigation of lattice distortions in InP crystals implanted with Fe+ ions by means of high‐resolution x‐ray diffraction and x‐ray standing‐wave methods

Lattice distortions due the implantation of Fe+ ions in InP semi‐insulating crystals have been investigated by means of high‐resolution x‐ray‐diffraction and x‐ray standing‐wave methods. The effects of both the implantation dose and the annealing time were studied. It is shown that the x‐ray standing‐wave method provides valuable complementary information on strain and damage in the subsurface layer and permits one to distinguish between different distortion profiles that give practically the same kinematical diffraction curve.

High-resolution x-ray diffraction, x-ray standing-wave, and transmission electron microscopy study of Sb-based single-quantum-well structures

Ga0.6Al0.4Sb/GaSb single-quantum-well structures grown by molecular-beam epitaxy on GaSb substrates with different well thicknesses, have been studied by high-resolution x-ray diffraction and x-ray standing-wave methods. By fitting the diffraction curves, thickness, composition, and the static Debye–Waller factor were obtained for each layer of the structures. The analysis of the angular dependence of the yield of photoelectrons emitted by the x-ray standing-wave field in the range of the dynamical x-ray diffraction was used for selecting the most appropriate set of layer parameters among those which gave virtually identical fittings of the diffraction curves. Relatively broadened GaAlSb/GaSb interfaces were found in all of the samples. This result was confirmed by high-resolution transmission electron microscopy investigation of one of the samples. The effect of the surface degradation due to the chemical reaction with the atmosphere of the free surface of the upper Ga0.6Al0.4Sb layer was considered.Ga0.6Al0.4Sb/GaSb single-quantum-well structures grown by molecular-beam epitaxy on GaSb substrates with different well thicknesses, have been studied by high-resolution x-ray diffraction and x-ray standing-wave methods. By fitting the diffraction curves, thickness, composition, and the static Debye–Waller factor were obtained for each layer of the structures. The analysis of the angular dependence of the yield of photoelectrons emitted by the x-ray standing-wave field in the range of the dynamical x-ray diffraction was used for selecting the most appropriate set of layer parameters among those which gave virtually identical fittings of the diffraction curves. Relatively broadened GaAlSb/GaSb interfaces were found in all of the samples. This result was confirmed by high-resolution transmission electron microscopy investigation of one of the samples. The effect of the surface degradation due to the chemical reaction with the atmosphere of the free surface of the upper Ga0.6Al0.4Sb layer was considered.

Structural diagnostics of 'quantum' layers by X-ray diffraction and standing waves

We analyze the possibility for simultaneous adequate treatment of angular dependencies of the X-ray diffraction reflectivity and photoelectron yield (X-ray standing waves method) in order to extract the structural characteristics of semiconducting materials with ultra fine inclusions. Facilities of such an approach for evaluation of the degree of structural perfection of the layers, the phase shift of upper layers with respect to the buffer, the lattice parameters of particular layers and interfaces between them are demonstrated within the analysis of heterostructures based on the Si matrix with the Si1-xGex quantum wells and on the GaAs matrix with the InAs quantum dots.

Diagnostics of the atomic structure of multilayer metallic nanoheterostructures from reflectometry data: A new approach to low-contrast systems

A new method for determining the concentration profiles of chemical elements in multilayer metallic nanoheterostructures from X-ray reflectometry data has been developed as applied to low-contrast systems. The method is based on the solution of the Fredholm integral equation of the first kind, which relates the reflection coefficient and the concentration profile of the chemical elements involved in the composition of the sample. The ill-posed inverse problem of the determination of the concentration profile is solved by the regularization method. The efficiency of the proposed method is confirmed by model calculations performed for a four-layer Cr/Gd/Fe/Cr//Si structure with high-contrast Cr/Gd pairs and low-contrast Fe/Cr pairs. The experimental results on the determination of the concentration profile of the surface layer of the epitaxial thin Cr films and three-layer Cr/Fe/Cr structure deposited on the Al2O3 substrate are presented.

Absolute Intensity and Phase of the Resonant X-ray Scattering from a Germanium Crystal

The 222 and 600 reflections near the germanium absorption K edge were studied on the Kurchatov synchrotron radiation source. The energy spectrum of the 222 reflection is caused by the interference of the weak nonresonant and purely resonant contributions to the tensor atomic factor, whereas the 600 reflection is purely resonant. The energy dependence of the magnitude and phase of the resonant contribution to the scattering amplitude was determined from a change in the interference pattern. The numerical simulation of the energy spectra of reflections with the inclusion of the dipole-quadrupole and thermally induced contributions shows that the latter is dominant at room temperature.

Ni-Ge nanostructures: Role of the interface and the magnetic properties

The surface morphology and local structure of layers in the Ni-Ge and Ge-Ni-Ge-Ni-Ge films have been investigated. It has been shown that the surface of the films follows the roughnesses of the substrate surface, which have characteristic dimensions of 2–4 nm in height and ∼100 nm in plane. It has been found that an interface with the depth ranging from 9 to 18 nm is formed at the boundaries between the Ni and Ge layers. The data obtained have been used to explain the specific features of the magnetic properties of the studied films, such as the asymmetry of hysteresis loops at low temperatures and the difference between the temperature dependences of the magnetization of the samples for two cooling modes: in a magnetic field and without a magnetic field.

Coexistence of Superconductivity and Ferromagnetism in the Nb(500 Å)/Fe(39 Å)/(Si(34 Å)/Mo(34 Å)) 40 /Si Nanostructure

The results of polarized neutron reflectometry investigations of the magnetic state of the Nb(500 Å) superconductor-57Fe(39 Å) ferromagnet-Si(34 Å)/Mo(34 Å)]40 superconductor nanostructure in the temperature range 2–60 K in the magnetic field with a strength of 0.5 kOe are presented. A decrease in magnetization in an iron layer for the transition of Nb(500 Å) and [Si(34 Å)/Mo(34 A)]40 layers to the superconducting state has been found.

Interfaces in AlGaSb∕GaSb multiquantum well structures

The Al0.4Ga0.6Sb∕GaSb∕Al0.4Ga0.6Sb quantum well (QW) structures were grown by a molecular beam epitaxy on the GaSb substrates at different growth temperatures (Tg) and with different Sb4∕Ga beam equivalent pressure ratios (BEPR) and were studied using high-resolution x-ray diffraction, photoluminescence (PL), and transmission electron microscopy. The x-ray diffraction analysis showed that the AlGaSb∕GaSb interfaces have smooth Al composition profiles with graded region thicknesses in the range of 0.83nm–2.17nm, depending upon the growth conditions; the normal interfaces are generally sharper than the inverse ones. The low-temperature PL spectra from QWs show relatively broad peaks and energies of the peak emission that can be related to the growth parameters. Good agreement was obtained between the PL peak energies and the transition energies calculated using a QWs model that takes into account the one-dimensionally graded confining potential for describing the experimentally determined Al composition pro...

Structural properties of Zn-diffused InP layers

A sealed tube method has been adopted to prepare Zn-diffused InP layers. Both Zn3P2 and Zn+InP have been used as sources. The samples were prepared at 500 °C. The diffusion time ranged from 5 up to 120 min. Both S- and Zn-doped InP crystals have been used as substrates. The Zn depth profile has been measured by secondary ion mass spectroscopy, while the lattice strain produced by diffusion has been carefully investigated by x-ray double crystal diffraction and the standing-waves method of recording photoelectrons. The results show that in the S-doped crystal the diffused/virgin interface is very sharp and the diffused layers are lattice contracted. The concentration of Zn, as well as the lattice strain, do not depend on the diffusion time, whereas the thickness of the diffused layer increases with time. The plot of diffused layer thickness versus the square root of the diffusion time showed different slopes depending on the diffusion sources. Both lattice strain and diffusion depth depend on the diffusion...

Upgraded X-ray topography and microtomography beamline at the Kurchatov synchrotron radiation source

An upgraded X-ray Topography and Microtomography (XRT-MT) station is described, the parameters of the optical schemes and detectors are given, and the experimental possibilities of the station are analyzed. Examples of tomographic reconstructions are reported which demonstrate spatial resolutions of 2.5 and 10 μm at fields of view of 2.5 and 10 mm, respectively.