Andrei Benediktovitch

Theoretical concepts of X-ray nanoscale analysis

Basic principles of the interaction between X-rays and matter.- X-ray reflectivity.- High-resolution X-ray diffraction.- Grazing-incidence small-angle X-ray scattering.- Theory of X-ray scattering from imperfect crystals.- X-ray diffraction for evaluation of residual stresses in polycrystals.- Methods of mathematical and physical optimization of X-ray data analysis.

Characterization of SiGe thin films using a laboratory X-ray instrument

This article reports the characterization of thin SiGe/Si(100) epilayers using reciprocal space maps measured by a laboratory X-ray instrument and a high-resolution X-ray diffraction study of partially relaxed SiGe/Si thin films.

Characterization of dislocations in germanium layers grown on (011)- and (111)-oriented silicon by coplanar and noncoplanar X-ray diffraction

The generalization of the theoretical approach suggested by Kaganer et al. [Phys. Rev. B, (1997 ▶), 55, 1793–1810] to an arbitrary surface orientation, arbitrary dislocation line direction and noncoplanar measurement scheme was developed. It was applied to study the dislocation microstructure of Ge films on Si(011) and Si(111) based on a set of reciprocal space maps and profiles measured in noncoplanar geometry.

Ab initio simulation of diffractometer instrumental function for high-resolution X-ray diffraction

A method for the simulation of the diffractometer instrumental function for high-resolution X-ray diffraction, applicable for coplanar and noncoplanar measurement geometry and for any combination of X-ray optical elements, is proposed. Good agreement is demonstrated between the measured and the simulated reciprocal-space maps, which account for the instrumental function.

Resolution function for X-ray powder diffraction in a noncoplanar measurement geometry with the detector arm having two degree of freedom

A noncoplanar measurement geometry, achieved by using a diffractometer equipped with a detector arm possessing two degrees of freedom, is a promising technique for the analysis of residual stress gradients in polycrystalline objects and for anisotropic microstructure investigations. The instrumental function for a parallel beam and a set of two orthogonal receiving Soller slits is considered in detail, and the explicit analytical expressions in terms of a convolution of functions are derived. A comparison of the calculated results with the measured profiles from a NIST SRM 660b LaB6 powder standard sample shows a good agreement.

Sample tilt-free characterization of residual stress gradients in thin coatings using an in-plane arm-equipped laboratory X-ray diffractometer

A methodology is presented to characterize residual stress gradients using the sin2ψ technique at constant penetration depths without the use of sample χ tilting. The experiments were performed using a laboratory five-axis X-ray diffractometer equipped with an in-plane arm by scanning several reflections in order to enlarge the penetration depth range. The proposed approach, demonstrated on a blasted 11.5 µm-thick TiN coating on a WC–Co substrate, opens the possibility to perform a complex stress gradient characterization in laboratory conditions where the sample χ tilting can deteriorate the sample properties or experimental conditions, like during in situ high-temperature studies.

Time dependence of X-ray polarizability of a crystal induced by an intense femtosecond X-ray pulse

The time evolution of the electron density and the resulting time dependence of the X-ray polarizability of a crystal irradiated by highly intense XFEL femtosecond pulses is investigated theoretically. Rate equations for bound electrons and the Boltzmann equation for the unbound electron gas are used in calculations.

Covariant description of X-ray diffraction from anisotropically relaxed epitaxial structures

A general theoretical approach to the description of epitaxial layers with essentially different cell parameters and in-plane relaxation anisotropy is presented.

Bunches of misfit dislocations on the onset of relaxation of Si0.4Ge0.6/Si(001) epitaxial films revealed by high-resolution x-ray diffraction

The experimental x-ray diffraction patterns of a Si0.4Ge0.6/Si(001) epitaxial film with a low density of misfit dislocations are modeled by the Monte Carlo method. It is shown that an inhomogeneous distribution of 60° dislocations with dislocations arranged in bunches is needed to explain the experiment correctly. As a result of the dislocation bunching, the positions of the x-ray diffraction peaks do not correspond to the average dislocation density but reveal less than a half of the actual relaxation.

Incorporation of interfacial roughness into recursion matrix formalism of dynamical X-ray diffraction in multilayers and superlattices

Interfacial roughness is considered as a transition layer. A method of calculation of diffraction scans from multilayered structures with interfacial roughness, which is both fast and free of numerical errors, is developed.