The demand for fast and reliable data storage is strongly rising, with the IoT and Cloud Computing sectors being big drivers. This is reflected by the estimated global next-generation data storage market size in 2018 was 53.1 billion USD with an expected compound annual growth rate of 12.5% until 2025 [1]. Coming to automotive applications (elevated temperatures), the current state of the art for non-volatile data storage employing flash technology (e.g. in SSDs), is reaching fundamental limits because of its physical principle. Owing to their properties, phase change materials (PCMs) can solve the problem. PCMs can be reversibly switched between an amorphous and a crystalline phase through controlled (local) heating, e,g, by lasers or by an electrical current. Thus, PCMs open the path to Phase Change Random Access Memories (PCRAM), a very promising alternative to replace flash technology [2]. In this contribution investigations on the PCM GST-theta a Ge-rich material within the Ge-Sb-Te ternary system are presented. GST-theta reaches crystallization temperatures above 350°C, which is needed in automotive applications [3]. In a previous study on 50 nm thick films of GST-theta [4], we have shown that the crystallization of that PCM proceeds in two steps (fig 1). Ge crystallization precedes the crystallization of Ge₂Sb₂Te₅, a cubic, metastable phase [5]. In the present work we aim at investigating the effects of N-doping and H₂-treatment on the structural evolution of GST-theta (crystallization temperatures, evolution of grain sizes, elastic strains). Therefore, a series of annealing experiments was performed and followed by in-situ X-ray diffraction at the DiffAbs beamline of SOLEIL synchrotron. All samples are annealed up to 500°C under N₂-atmosphere using an Anton Paar® heating stage mounted on the six-circle diffractometer. The diffraction patterns were recorded with an XPAD hybrid pixel detector and corrected and transformed into 1D patterns following previously developed procedures [6]. The 1D patterns are then indexed and diffraction peaks are fitted. A fitting procedure was developed in-house to find and handle also very weak peaks on a strong background. We will discuss here the influence of H₂-treatment, N doping and lateral confinement on the crystallization and microstructure development in GST-theta thin films and nanostructures. It is worth mentioning that some investigated samples are very close to final products (several metallization layers on top), which demonstrate the capability of synchrotron X-ray diffraction to investigate the PCM in its “real” environment.

Here should be a figure.

Fig 1. areas of the Ge 111 and Ge₂Sb₂Te₅ 200 reflections upon heating of an amorphous film show a phase separation

[1] https://www.grandviewresearch.com/industry-analysis/next-generation-data-storage-market

[2] M. Gallard, PhD thesis, Aix Marseille Univ. (2019)

[3] P. Zuliani, E. Palumbo, et al. (2015). Solid State Electronics. 111, 27

[4] O. Thomas et al. (2021). Microelectronic Engineering

[5] T. Matsunaga, N. Yamada, and Y. Kubota (2004). Acta Crystallogr. Sect. B Struct. Sci. 60, 685

[6] C. Mocuta, M.I. Richard, et al. (2014). J. Appl. Crystallogr. 47, 482

Keywords: chalcogenides; data storage; in-situ synchrotron X-ray diffraction; phase change materials; nanostructures

Acknowledgments We would like to thank SOLEIL synchrotron for allocating beamtime on DiffAbs beamline. Ph. Joly (Synchrotron SOLEIL, DiffAbs) is thanked for technical support. IPCEI/Nano 2022 program is acknowledged for partial funding of this work.

In the case of alloy films and multilayers, measure of composition may be hard, since the volume of film is far less than that of substrate. Therefore, the surface sensitive measurements, such as X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), are employed frequently. Alterative way is the chemical etching of film followed by the concentration analysis of the aqueous solution. However, all these methods are destructive and can be performed only under ex-situ condition. Also, diffraction stress analysis of alloy films may be difficult, since the composition is required for estimating the diffraction elastic constants.
Considering the situation described above, we proposed the self-consistent diffraction stress analysis method for analysing composition and stress (Fig. 1) [1]. This method is based on the strain-free lattice parameter, which is generally treated as a by-product of diffraction stress analysis and receives less attention. However, we here tried to utilize it, since it contains the information of composition. The main concept of the proposed method is the feedback of the strain-free lattice parameter in the form of composition. Due to the feedback, the diffraction stress analysis can be performed even when the exact composition is unknown. After the convergence of feedback calculation, the final results are composition and stress; they have self-consistency.
The validity of this analysis method was experimentally confirmed using example specimens of (111) fibre-textured palladium cobalt (PdCo) alloy films with different composition. Note that PdCo alloy films are expected as the next generation magnetism-based hydrogen sensor, since they absorb hydrogen and show both perpendicular magnetic anisotropy and large magnetostriction constant [2-4]. The lattice spacings measured at the different tilt angles are analysed using the proposed method. It was revealed that the self-consistent calculation converged well and the resultant composition is in a good agreement with the result of AES. The difference of composition is 1 at.%, even though this method only provides the estimated composition from the strain-free lattice parameter. The resultant stress also shows an agreement with one of the conventional diffraction stress analysis.
The proposed self-consistent method is suitable for cases, such as in-situ measurement, where the measure of composition is difficult. This method expands the applicability of diffraction stress analysis.

Scandium nitride (ScN) has attracted a great deal of attention in recent years due to its promising properties as high hardness, temperature stability and high electrical conductivity [1], [2]. Twin domains have been already studied in this interesting material for some other configurations including ScN crystalline and polycrystalline growth on different substrates[3]–[5]. Five epitaxial (001) ScN films from 145 nm to 1080 nm thicknesses were deposited at the same conditions on MgO (001) substrate by DC reactive magnetron sputtering. The presence of twins has been analyzed through 2theta scans, 002, 022 and 111 pole figures and 2D reciprocal space maps (RSM). Four twin domains are present in all samples being (111) the twining plane. This gives rise to twelve distinguished peaks of 002 reflection (labelled on the inset pole figure for the thickest sample in Figure 1). Special care must be taken for thinner samples, since the presence of twins can be hidden under the strong contribution arisen from the epitaxial layer. The twins/epitaxial layer diffracted intensity ratio seems to rise with the layer thickness. Further research must be done to elucidate if there is a limiting layer thickness for twin formation.

The tungsten carbide films were deposited by reactive magnetron sputtering in an industrial-scale coating chamber at different bias voltages and gas (argon/acetylene) flows. As substrate materials, silicon wafers and 100Cr6 steel sheets were used. The films were characterized using electron probe microanalysis with wavelength-dispersive X-ray spectroscopy (EPMA/WDX) and in situ high-temperature X-ray diffraction (HTXRD). EPMA revealed the chemical composition of the films; HTXRD gave overview over the thermally activated phase transformations and stabilization of metastable phase through the microstructure defects. The as-deposited films contain metastable phases WC_1-x and W₂C with distorted crystal structures. With increasing temperature and/or longer annealing time, the crystal structure of the high-temperature W₂C phase recovered, although the annealing temperature was below the temperature, which is required to make W₂C thermodynamically stable. The density of the microstructure defects in W₂C was reduced, but some defects persisted. The structure relationships between individual phases will be discussed. Further heat treatment resulted in a decomposition of W₂C, which was accompanied by the formation of metallic tungsten. The EPMA results confirmed that this decomposition is accelerated by the reaction of carbon with oxygen impurities in the annealing atmosphere. When the 100Cr6 steel is used as substrate material, W₃Fe₃C forms at the interface between the substrate and the coating. The presence of this carbide influences the decomposition of W₂C.

Recently the rocking curve imaging (RCI) technique has been transferred from synchrotron to laboratory set-ups. RCI is an X-ray diffraction technique which combines full-field X-ray digital topography and Bragg-diffraction rocking curve recording. A large almost parallel monochromatic beam irradiates a crystalline sample with a misorientation distribution characterized by local tilt angles. Series of digital topographs are measured by a two-dimensional detector at different sample orientations from which peak characteristics of millions of local Bragg peaks from each series are extracted. The field of view and lateral resolution is given by the camera size, its pixel size and the Bragg angle, while the angular resolution is given by the rocking curve width being typically much smaller than the misorientation angles of the studied crystal. Simultaneous high spatial resolution provided by the two-dimensional detector and high angular resolution (0.001°) allows to quantify crystalline structure perfectness over large sample area which scales with the area of the detector. Therefore the rocking curve imaging is an imaging method with faster recording compared to usual scanning area diffractometry which requests measurement of the rocking curve at each surface point.

Synchrotron RCI [1,2] profits from large parallel beam, high flux and small detector pixel size downto one micrometre. For small misorientations, detector can have any distance from the sample, while larger misorientations due to inherent focusing/defocusing of the diffracted (micro)beams require a dedicated reconstruction procedure.

Laboratory RCI [3] with a slightly divering beam requires small misorientation angles and very small sample to detector distance, thus a home-made extension for a commercial diffractometer is necessarily. Current two-dimensional detectors available at laboratory diffractometers have typical spatial resolution downto 0.1 mm which make it possible to analyze a large sample area at once. On several examples, we will show suitability of the method for a characterisation of several large-area semiconductor wafers. In particular, we demonstrate application of the method on mapping of local lattice tilt distortion of large array of SiGe microcrystals epitaxially grown on silicon.

[1] P. Mikulík, et al. (2003) Journal of Physics D: Appl. Phys. 36, A74–A78.

[2] D. Lübbert, et al. (2005) Journal of Applied Crystallography 38, 91–96.

[2] M. Meduňa, et al. (2021) Journal of Applied Crystallography 54.

Titanium alloys are material that is often used in aerospace industry and in biomedical engineering for their excellent properties as low density, high tensile strength and corrosion resistance in some common environments. On the other hands the disadvantages of these materials are in general poor performance in sliding, hardness and wear. Enriching the surface area of pure titanium by nitrogen lead to improve hardness, corrosion resistance and abrasion resistance. Moreover, the required low modulus of elasticity of bulk material is maintained which is susscesfully used for example in joint replacements and dental crowns.

In our contribution we would like to present the study of surface area of alfa-titanium after implantation of nitrogen ions. The X-ray diffraction and x-ray reflectivity were used for characterization of these surfaces. The special cheap home-made improvement of incident beam that enable to reach lower angles during reflectivity measurements will be presented.

Zr/Nb nanometric multilayers deposited on Si substrate by magnetron sputtering, having a periodicity from 6 to 167 nm were subjected to room temperature irradiation by carbon, silicon and copper ions. The mechanical proprieties, ion profiles, and disordering behavior have been investigated by Secondary Ion Mass Spectrometry - SIMS, nanoindentation, X-ray diffraction - XRD, and scanning transmission electron microscopy - STEM. The damaged regions are clearly visible on STEM bright field micrographs of cross-section lamellae prepared by focused ion beam technique - FIB. Damage starts from the surface side of the multilayer, and the most damaged and disordered zone is located close to the maximum ion concentration. Near the substrate, no damage was observed. The C and Si concentration profiles detected by SIMS were not affected by the nanolayers periodicity. This agrees with the Stopping and Range of Ions in Matter - SRIM software simulations. Diffraction analyses – selective area electron diffraction, and XRD suggest a structural evolution in relation to the multilayer periodicity. For the multilayer with a periodicity of 6 nm, and 27 nm, Si, C and Cu-ion irradiation led to a tensile strain in Nb layers and compressive strain in Zr layers. In contrast, for periodicity higher than 27 nm, both Zr and Nb layers are subjected to compressive out-of-plane strain.