Tatjana Ulyanenkova

High-resolution x-ray diffraction investigation of relaxation and dislocations in SiGe layers grown on (001), (011), and (111) Si substrates

This work presents a detailed characterization, using high-resolution x-ray diffraction, of multilayered Si1-xGex heterostructures grown on (001), (011), and (111) Si substrates by reduced pressure chemical vapor deposition. Reciprocal space mapping has been used to determine both the strain and Ge concentration depth profiles within each layer of the heterostructures after initially determining the crystallographic tilt of all the layers. Both symmetric and asymmetric reciprocal space maps were measured on each sample, and the evaluation was performed simultaneously for the whole data set. The ratio of misfit to threading dislocation densities has been estimated for each individual layer based on an analysis of diffuse x-ray scattering from the defects.

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.

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.

Stress of Homogeneous and Graded Epitaxial Thin Films Studied by Full-Shape Analysis of High Resolution Reciprocal Space Maps

The Bragg peak position of a homogeneous solid solution epitaxial film is directly related to the solid solution concentration, film strain and, consequently, residual stress. The peak shape contains information about defects present in the sample. In the case of compositionally graded epitaxial films the situation is more complex since instead of a single Bragg peak there is a continuous diffracted intensity distribution which can be measured by means of recording high resolution reciprocal space maps. We analyse the thin film residual stress based not only on peak positions, but taking into account the defect-induced peak shape as well. Consideration of the peak shape enables the determination of the stress depth profile in the case of graded films and to imporves the accuracy in the case of homogeneous films.