Cristian Mocuta

This study explores the amorphization of a Te-poor Ge–Sb–Te alloy using single 800 nm femtosecond laser pulses. Before irradiation, the phase composition and microstructure of the investigated sample were characterized using synchrotron x-ray diffraction and high-resolution transmission electron microscopy. The threshold fluence required for amorphization with a single laser shot was identified, with a minimum fluence of ∼45 mJ cm−2 necessary to induce structural changes. At higher fluences (≥83 mJ cm−2), surface blistering and layer delamination occurred, also due to laser absorption by the TiN capping layer. This study revealed partial amorphization localized preferentially in the upper part of the layer with a few crystalline residuals closer to the substrate. The formation of cavities in the amorphized zones, close to the interface with the TiN layer, is supposed to be responsible for the delamination of the latter observed in the center of the irradiated zone. No long-range elemental diffusion was observed post-irradiation. These results provide valuable insights into the structural changes that can be induced by femtosecond laser irradiation in Ge–Sb–Te alloys.

High-throughput experimentation of synchrotron X-ray diffraction and fluorescence enabled the collection of the thermal expansion coefficients of an entire ternary system using a combinatorial library of LSCFM in a wide-surface furnace.

We report the development and synchrotron integration of a longitudinal magneto-optical Kerr effect (MOKE) magnetometer designed for in situ operation during x-ray diffraction (XRD) experiments under multiaxial mechanical loading. The optical layout, magnetic-field geometry, and mechanical compatibility were optimized to enable synchronized acquisition of MOKE hysteresis loops, XRD lattice strain, and digital image correlation (DIC) data within the constrained environment of a diffraction goniometer. The capabilities of the platform are demonstrated on a Co/W thin film deposited on a flexible Kapton® substrate subjected to equi-biaxial tensile loading. The combined MOKE–XRD–DIC measurements reveal three distinct mechanical regimes from elastic strain transfer to partial relaxation and ultimately full mechanical fragmentation, each associated with a characteristic magnetic response. Post-mortem image analysis provides a quantitative description of fragment morphology, linking crack topology to the evolution of magnetic properties and highlighting the role of fragment size, shape anisotropy, and mechanical isolation in strain-dependent magnetic behavior. The present approach establishes a multi-scale framework that integrates surface magnetometry, structural probes, and real-space imaging, opening new opportunities for studying magneto-mechanical coupling and damage-driven functional evolution in flexible magnetic thin films.

Chalcogenide ferroelectric Rashba semiconductors (FERSCs) offer a promising route to ultralow‐power spin–orbit devices, yet their integration into microelectronics has been hindered by the lack of high‐quality films grown using industry‐compatible methods. Here, we demonstrate CMOS‐compatible synthesis of rhombohedral α ‐GeTe(111) thin films on 200/300 mm Si wafers using an industrial deposition process based on van der Waals epitaxy, applied to this material class for the first time. Scanning Transmission Electron microscopy and advanced simulations of anomalous X‐ray diffraction measurements at synchrotron reveal that films are intrinsically self‐poled, exhibiting a robust upward out‐of‐plane ferroelectric polarization. The growth strategy is universal, enabling high‐quality α ‐GeTe(111) on metals and insulators without compromising structural or ferroelectric performance. Piezoresponse force microscopy confirms reversible 180° ferroelectric switching with performance comparable to molecular‐beam‐epitaxy benchmarks. This substrate‐independent growth strategy represents a decisive step toward the future large‐scale integration of FERSCs into functional spin‐orbit architectures, with the hope of bridging the gap between Rashba's fundamental physics and microelectronic implementation.

Flexible magnetoelectronics face a major challenge in maintaining functionality under mechanical strain. This research investigates how biaxial multicracking affects the magnetic properties of nanometric thin films, specifically by separating magnetoelastic from magnetostatic effects. Using a unique experimental platform, we show that in magnetostrictive Co films, the magnetic behavior is dominated by stress‐induced magnetoelastic effects. In contrast, in non‐magnetostrictive films, the magnetic changes only appear once multicracking begins, allowing us to demonstrate the magnetostatic contributions from fragmentation. Our findings reveal that the variation in the saturation field correlates directly with fragment shape. This work demonstrates that fragmentation is not just a failure mechanism but a controllable process whose magnetic effects can be understood and leveraged for designing next‐generation flexible devices.

X-ray diffraction pole-figure measurements are essential to analyze crystallographic texture in thin films and nanoparticles. Conventionally, large and equal incident and exit angles beyond the critical angle of the studied material are used, limiting surface sensitivity. This study demonstrates the use of grazing-incidence wide-angle X-ray scattering (GIWAXS) while rotating the sample azimuthally in its own plane to acquire pole figures that are more sensitive to the near-surface region compared with pole figures measured in standard Schulz geometry. Comparative measurements on supported Pt nanoparticles in GIWAXS and Schulz geometry at two different synchrotron beamlines confirm the improved sensitivity of the GIWAXS pole figures. By tuning the incident angle, the substrate diffraction background can be reduced and the information depth inside a Pt thin film can be selected. In addition, the near-horizontal sample orientation during GIWAXS – only tilted by the small incident angle – reduces constraints on sample environments compared with conventional Schulz geometry. The increased sensitivity to the near-surface region of a grazing-incidence X-ray beam, combined with the simpler measurement geometry, prove grazing-incidence pole figures to be powerful for future in situ and ex situ texture analysis on thin films and supported nanoparticles.

Ge-rich Ge–Sb–Te alloys exhibit a high (>350 °C) crystallization temperature, which is compatible with applications requiring a high thermal stability such as the use of non-volatile memories in cars. As the composition of these alloys does not correspond to any stable crystalline phase, crystallization from the amorphous phase is accompanied by phase separation (Ge2Sb2Te5 + Ge). The complexity of the elemental processes associated with this multiphase amorphous-to-crystal transition calls for in-depth materials studies. In this work, we focus on the influence of a thin (5 nm) underlayer (Ge2Sb2Te5 or Sb2Te3) on the crystallization of a Ge-rich Ge–Sb–Te alloy. Using in situ synchrotron x-ray diffraction, we demonstrate that the underlayers facilitate crystallization by decreasing crystallization temperature and suppressing incubation time. These results are interpreted in the framework of classical nucleation theory and are supported by crystallographic texture measurements, which evidence ⟨111⟩ fiber texture in the crystallized cubic Ge2Sb2Te5, particularly marked in the case of an Sb2Te3 underlayer. These results bear important consequences for the cycling of memory cells based on these materials.