[en] Epitaxial thin films of yttria stabilized zirconia (YSZ) have been grown onto (112-bar 0) cut sapphire (Al₂O₃) substrates by sol-gel processing. The high crystallographic dissimilarity between YSZ and sapphire causes extremely high strains to build up at the interface. The microstructure of the samples has been investigated by high resolution X-ray diffraction using both a laboratory set-up and synchrotron radiation (ESRF, Grenoble). The strain profile across the film thickness has been recovered using a newly developed method that avoids assumptions regarding the shape of the strain profile

[en] A methodology is proposed for microstructural characterization of sol-gel derived epitaxial layers. Yttria stabilized zirconia deposited on (112-bar0) cut sapphire wafer is chosen as a representative example of an epitaxial layer fabricated by sol-gel processing. High quality X-ray diffraction data has been obtained with a homemade set-up that allows to record reciprocal space maps in a small amount of time. The diffraction profiles are modeled within the kinematical theory of X-ray diffraction on the basis of microstructural parameters. The analysis of the diffraction profiles along the q_z direction yields the average film thickness (41 nm), the thickness distribution (5 nm) as well as the vertical strain profile. A 0.2 deg. mosaicity is found from line shape analysis of the diffraction profile along the q_x direction using two orders of reflection of the same crystallographic plane family

[en] Epitaxial LiNbO₃ films have been deposited on (0001) Al₂O₃ substrates by pulsed laser deposition. The microstructure of the samples has been investigated by X-ray diffraction reciprocal space mapping. Data acquisition is performed on a high-resolution set-up suited to the study of oxide materials. The (000l) planes of the layer are found parallel to the (000l) planes of the substrate. The large in-plane misfit gives rise to two in-plane orientations. In the direction perpendicular to the surface the crystallite size (163 nm) is much smaller than the film thickness (510 nm) suggesting the presence of planar defects. Moreover, the values of the mosaicity (1.2 deg. ) and root-mean-squared strain (0.17%) cannot be solely explained by misfit dislocations. Conversely the high-thermal expansion coefficient mismatch is at the origin of a high compressive strain level (-0.18%) and may also be responsible for the large column length distribution, root-mean-squared strain and mosaicity

[en] Very thin polycrystalline and epitaxial yttria doped zirconia films have been realized using sol-gel processing. The lattice mismatch between the sapphire substrate and the zirconia crystals induces high misfit strain that we have determined using X-ray diffraction. Epitaxial films made of islands with sizes of several tens of nanometers are under very high stresses which are relaxed by the appearance of structural defects into the cubic zirconia crystals or by structural phase transition from the cubic to tetragonal zirconia form

[en] A model that allows the quantitative analysis of heterogeneous strain fields in epitaxial thin films using x-ray diffraction (XRD) is presented. Particular emphasis is laid on the modelling of the two-component XRD profiles (i.e. profiles made of the superposition of a narrow coherent Bragg peak and a broad diffuse scattering profile) encountered in the XRD investigation of epitaxial thin films containing localized strain fields. The spatial properties of the strain field are included in a correlation function based on phenomenological parameters such as the defect correlation length ξ and the level of disorder σ_∞. No assumption regarding the nature of the defect is hence required. The statistical properties of the strain field are described by means of Levy-stable distributions which allow us to account for profile shapes ranging between the Gaussian and profiles exhibiting pronounced power law-type tails, as well as for asymmetrical profiles. The effects of finite size of the domains (crystallites) over which diffraction is coherent are rigorously taken into account by calculating the auto-correlation function of the crystallite shape including the size distribution effects. The effects of each parameter are presented and discussed in detail and the applicability of the model is illustrated with two examples

[en] Thin films of (00l) oriented SrBi₂Nb₂O₉ epitaxially grown on SrTiO₃ by sol-gel spin coating have been studied by means of high-resolution x-ray diffraction reciprocal space mapping. It is shown that these materials contain highly localized heterogeneous strain fields due to imperfect stacking faults (i.e., faults that do not propagate throughout the crystallites building up the film). In the film plane, the strain fields are confined to 11 nm wide regions and characterized by a vertical displacement of 0.18c (where c is the cell parameter) showing that the stacking faults are mainly composed of one additional (or missing) perovskite layer. Prolonged thermal annealing at 700 deg. C strongly reduces the density of stacking faults and yields a more uniform strain distribution within the film volume without inducing significant grain growth

[en] We present here a detailed study describing the strain relaxation mechanisms occurring in the highly mismatched ZrO₂/MgO system. Especially, we show using reciprocal space mapping that the ZrO₂ islands epitaxially grown on the MgO substrate are fully relaxed implying the formation of misfit dislocations at the interface. Furthermore, an analysis of transverse scans performed through symmetrical ZrO₂ reflections for several azimuthal positions of the sample lets us conclude that dislocations form a square network parallel to ZrO₂ cell axes. Finally, an accurate analysis of the diffraction data evidences the existence of two subsets of misfit dislocations. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Profile fitting procedures associated with integral breadth studies and Fourier analysis are applied to the study of the complex Bi-containing layered perovskite SrBi₂Nb₂O₉. Strong line broadening anisotropy is evidence. Both 'size' and 'strain' effects contribute to the observed width. However, 'size' broadening along the [00l] direction is essentially caused by stacking faults. The coherently diffracting domain sizes are deduced from Fourier analysis of the diffraction patterns and a rough estimate of the mean distance between faults is given. Thermal annealing significantly decreases the stacking fault density. (orig.)

[en] We report here on the self-patterned growth of nanostructured epitaxial oxide thin films using a bottom-up approach. Different stepped (0001) sapphire surfaces have been used as templates to grow different nanostructured thin films of yttria-stabilized zirconia elaborated by a chemical solution deposition technique, namely sol-gel dip-coating. For such films, a morphological instability occurs during post-deposition thermal annealing that forces the film to split into isolated islands. Taking advantage of this effect, three distinct types of nanostructures have been produced depending on the step morphology of the substrate surface, and depending on the relative magnitude of the mean island diameter (D) and the mean terrace length (L). Flat-top islands, dome-shaped islands, tilted flat-top islands or self-organized arrays of nano-islands can be generated. Atomic force microscopy was used to observe nanostructures and quantitative characterizations of crystallographic and nanostructural aspects were carried out by high-resolution x-ray diffraction reciprocal space mapping

[en] Damage formation in implanted 4H-SiC was studied as a function of dose and temperature of implantation. At RT the maximal strain as well as the surface swelling linearly increases suggesting a point defects swelling. With increasing temperature the slope decreases due to irradiation-induced dynamic recovery with activation energy of 0.13±0.02eV. From 300°C the amorphisation is avoided and the strain build-up can be fitted according to a direct impact model. At 300°C the as-induced strain profile consists of three different zones of damage with depth, resulting from the damage accumulation in the near surface region, the formation of Xe-vacancy complexes in the ion distribution and beyond a zone of end-of-range strain associated with interstitial accumulation. (paper)