In Bragg Coherent Diffraction Imaging (BCDI), Phase Retrieval of highly strained crystals is often challenging with standard iterative algorithms. This computational obstacle limits the potential of the technique as it precludes the reconstruction of physically interesting highly-strained particles. Here, we propose a novel approach to this problem using a supervised Convolutional Neural Network (CNN) trained on 3D simulated diffraction data to predict the corresponding reciprocal space phase. This method allows to fully exploit the potential of the CNN by mapping functions within the same space and leveraging structural similarities between input and output. The final object is obtained by the inverse Fourier transform of the retrieved complex diffracted amplitude and is then further refined with iterative algorithms. We demonstrate that our model outperforms standard algorithms on highly strained simulated data not included in the training set, as well as on experimental data.

Thermal management is a major challenge in densely integrated photonic systems, yet the mechanisms governing heat generation in operating nanoscale devices remain poorly understood. Here, the spatio-temporal evolution of thermal loads in an electrically driven GeSn/SiGeSn multiple-quantum-well microdisk laser is resolved using a multimodal approach combining time-resolved operando Dark-Field X-ray microscopy, electro-thermal finite-element simulations, and three-dimensional focused ion beam–scanning electron microscopy tomography. With nanosecond temporal and sub-200 nm spatial resolution, this methodology directly visualises heat-induced lattice strain and enables quantitative reconstruction of the corresponding temperature field under realistic electrical injection conditions. Heat generation is strongly localised within the electrical contact area in Ge layer rather than in the gain medium. Current crowding at the contacts creates nanoscale hot areas that induce asymmetric strain fields extending into the active region, resulting in spatially non-uniform optical gain. Contact architecture, current injection uniformity, and interfacial defects emerge as the primary factors governing thermal loading and device-to-device performance variability. These results establish contact-mediated Joule heating as the dominant thermal bottleneck in electrically pumped group-IV microlasers and identify contact engineering as a direct route to improved performance. More broadly, they show that thermal behaviour in nanoscale photonic devices is governed primarily by current injection pathways and structural design, thereby providing a framework for developing thermally robust, CMOS-compatible light sources.

Understanding how the real-time motion of individual dislocations collectively produces macroscopic plastic deformation in strained crystalline materials remains a central open problem. Here, dislocation propagation in epitaxial heterostructures is tracked using in-situ dark-field X-ray diffraction microscopy in a grazing-incidence geometry, providing similar to 100 nm spatial resolution over a similar to 200 & times; 200 mu m(2) field of view with second-scale temporal resolution. Rather than gliding continuously, dislocations advance through intermittent, stop-and-go bursts with a broad distribution of stopping times and a progressive loss of activity at fixed temperature. Statistical analysis of hundreds of propagation events enables a stochastic jump-process model in which dislocation segments either become immobile or traverse a heterogeneous sequence of energy barriers arising from glide-induced changes in the dislocation core. The model explains the observed decay of activity as a rare-event-driven form of temporal hardening intrinsic to dislocation motion. This work establishes a general framework for analyzing real-time plasticity in materials with complex dislocation kinetics.

LiNi0.8Mn0.1Co0.1O2 (NMC811) is a promising cathode material for high-energy-density Li-ion batteries (LiBs). However, its practical application is limited by capacity fading during electrochemical cycling, mainly associated with cation mixing, structural degradation, and lattice collapse at high voltages. In this work, zirconium (Zr) doping was introduced during the co-precipitation step to improve the structural stability of NMC811 and mitigate its degradation mechanisms. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) measurements confirmed the incorporation of Zr into the NMC811 host structure at low doping concentrations, whereas concentrations above 0.1 mol% promoted the formation of an additional Li2ZrO3 (LZO) phase. The excess Zr was found to segregate locally on the surface of NMC811 particles rather than forming a homogeneous protective coating. Although higher Zr concentrations improved the rate capability, combined electrochemical and morphological analyses revealed that this enhancement primarily originates from the formation of smaller secondary particles induced by Zr addition during co-precipitation. However, the increased fraction of smaller particles negatively affects long-term cycling stability by promoting a larger electrode–electrolyte interfacial area and enhanced parasitic reactions. These results highlight that controlling the Zr concentration is essential to maximize lattice incorporation while minimizing secondary-phase formation and undesired morphological changes.

The technological advancement of mobile devices for virtual and augmented reality requires displays that are faster, more energy-efficient, and of higher resolution. InxGa1-xN-based micro-light-emitting diodes (LEDs) have the potential to realize such advanced displays thanks to their ability to provide emission of red, green, and blue light simply by tuning the In concentration. However, efficient emission in the red still remains a challenge, as it requires high In contents (approximate to 30-40%) that are unobtainable in InxGa1-xN epitaxial layers pseudomorphically strained to GaN substrates. Research efforts have therefore focused on achieving elastic relaxation of the active InxGa1-xN portion of the LED device to allow greater In incorporation, e.g., through the addition of partially relaxed intermediate InxGa1-xN layers in the heterostructure. Herein, the extent of strain relaxation in InxGa1-xN pseudosubstrates grown on GaN-on-sapphire substrates as induced by patterning in mesas 10 mu m2 in size is evaluated. Using synchrotron-based scanning X-ray diffraction microscopy, the lattice strain and tilt are mapped in a single mesa as well as in an ensemble of mesas with approximate to 60 nm spatial resolution, demonstrating the effectiveness of the processing route in producing high-quality, partially relaxed InxGa1-xN pseudosubstrates.

Surface acoustic wave devices are key components for processing radio frequency signals in wireless communication because these devices offer simultaneously high performance, compact size and low cost. The optimization of the device structure requires a quantitative understanding of energy conversion and loss mechanisms. Here we use stroboscopic full-field diffraction x-ray microscopy to reveal an unanticipated acoustic loss in a prototypical one-port resonator device. A non-uniform acoustic excitation in the active area was responsible for the substantial end and side leakages observed at the design frequency. Quantitative analysis of the strain amplitude using a wave decomposition method allowed the determination of several key device parameters. This high-resolution high-throughput spatiotemporal strain imaging technique is more generally applicable to the study of dynamic strain modulation in nanoscale acoustic, electronic, optical and quantum devices. The high sensitivity allows precise measurement of the strain modulation with picometer-scale amplitude.

The palladium-hydrogen system plays a crucial role in catalysis, hydrogen production and storage, hydrogen embrittlement, and sensing technologies. Understanding the transition of palladium nanocrystals (NCs) from the hydrogen-poor (α) phase to the hydrogen-rich (β) phase is crucial for elucidating hydrogen absorption/desorption mechanisms as well as related phenomena such as hydrogen trapping. In this study, we carefully minimized undesired X-ray beam effects and used in situ Bragg coherent diffraction imaging under electrochemical control to map the strain and lattice parameter distribution within individual palladium NCs across electrochemical potentials relevant to hydrogen absorption and desorption. Lattice parameter changes in both α and β phases are tracked, and reversible strain inversion during the α-to-β phase transition is observed. Through strain and reciprocal space analysis and molecular simulations, a model for the α-to-β phase transition is proposed, which includes a hydrogen-saturated subsurface shell, hydrogen depletion from the α phase during β phase nucleation, and propagation of the β phase in a spherical-cap fashion.

Palladium hydrogen is a useful model in the study of both hydrogen absorption for energy storage, and lattice gas systems for fundamental thermodynamic models. Using in situ time-resolved X-ray nanodiffraction at the fourth generation Extremely Brilliant Source of the European Synchrotron (ESRF-EBS), the kinetics of hydrogen absorption in individual alpha phase Pd nanoparticles is examined. Hydrogen absorption kinetics in a gas reactor and an electrochemical cell are compared. Combining the individual nanoparticle X-ray measurements with chronoamperometry measurements, the kinetics of the ensemble of Pd nanoparticles on the glassy carbon substrate is compared with kinetics at the single nanoparticle level. Hydrogen absorption in alpha phase Pd in the electrochemical system is found to be slower than that of the gas system. Furthermore, the absorption in the electrochemical system slows down as the electrochemical potential is lowered. This slow down is found to be directly related to the increasing hydrogen absorption per step in electrode potential. Furthermore, differences between absorbed-quantity normalized absorption times is seen between the hydrogen and deuterium absorbates. Sieverts's law of absorption is also shown to hold for individual Pd nanoparticles in the alpha phase.

The manipulation of light through its interactions with artificially structured media is a cornerstone of photonics. The rescaling of this concept to the X-ray realm-which will enable us to control X-ray light with the same precision routinely available in the visible/IR range-has so far been hindered by the inherent difficulty of realizing photonic structures with the sub-nanometric resolution dictated by X-ray wavelengths. A promising approach to this challenge is based on the so-called Berry-phase effect, the large beam translations undergone by X-ray photons propagating in a deformed crystal, due to the simultaneous presence of Berry curvatures in real and reciprocal space. In this work, the controlled crystal distortions required to rein in this effect are obtained by pairing the lattice expansion observed upon H irradiation of GaAsN with a spatially selective hydrogenation technique. The macroscopic beam translations measured here are striking manifestations of the Berry curvatures associated with the sub-nanometric lattice distortions induced by H incorporation. Through the comparison with a dedicated theoretical model, the individual translation branches observed in X-ray transmission can be traced back to specific deformation features present within the samples, establishing a predictive framework for the control of X-ray propagation in the fabricated structures.

LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising cathode materials for high energy density Li-ion batteries (LiBs). However, NMC811 suffers from capacity fading during electrochemical cycling because of its structure instability at voltages >4.2 V vs Li|Li+ due to the known hexagonal H2→H3 phase transition. Zr doping has proven to be effective in enhancing electrochemical performances of the NMC811. In depth investigations are conducted through operando x-ray diffraction (XRD) and ex situ x-ray absorption spectroscopy (XAS) measurements to mechanistically understand the benefits of Zr-doping in a NMC811 material when doped during the co-precipitation step. Herein, Zr-doping in NMC811 reduces the formation of the detrimental H3 phase and mitigates the transition metal dissolution upon cycling.

The core principles and nanoscale mechanisms of ion deintercalation in battery cathode materials remain poorly understood, in particular, the relationship between crystallographic defects (dislocations, small angle grain boundaries, vacancies, etc.) and microscopic features of Li deintercalation. Here, we used operando scanning X-ray diffraction microscopy (SXDM) to investigate the local strain and lattice tilt inhomogeneities inside Li1−xMn1.5Ni0.5O4 cathode crystals (diameter from 1 to 2 µm) during electrochemical delithiation and lithiation. The technique has been combined to operando multi crystal X-ray diffraction (MCXD) to differentiate between inter- and intra-particle heterogeneity in the sample. Operando SXDM revealed three distinct domains within the crystal that displayed metastable angular rotations of the lattice during both of the phase transitions. These rotations, reaching up to 0.4°, likely arise due to a dynamic lattice mismatch between phases with different unit cell parameters coexisting within the particle. The persistent location of tilt boundaries implies the presence of inherent structural defects locally facilitating the defect formation. Residual misorientations were observed in the particle even after the full discharge suggesting an irreversible change of the lattice structure. Tilt boundaries, affecting ionic conductivity, may impede the rate capability and lead to localized strain, stress, and potential capacity fade due to cracking. However, the observed self-healing angular lattice reorganization could enable the coexistence of two phases in a single crystal. Understanding this phenomenon can optimize cathode material microstructure.

Bragg coherent diffraction imaging struggles to phase data from nanocrystals exhibiting large strain inhomogeneities, which significantly limits its applicability across many scientific scenarios. Here, we demonstrate the experimental realization of Bragg coherent modulation imaging, an approach that incorporates wavefront modulation into the diffracted beam, enabling unambiguous structure recovery and resolving highly strained crystals. This method provides a more robust tool for three-dimensional lattice strain measurements in nanocrystals.

We performed operando Bragg coherent X-ray diffraction imaging under CO oxidation, as well as oxidizing conditions on a precharacterized single PtRh nanoparticle. We found that this (111) oriented particle with truncated octahedral shape is twinned with a Σ3 twin boundary parallel to the SrTiO3 (001) support, at the height of the nanoparticle edges. We observed that the average strain at the twin boundary is higher under CO oxidation conditions compared to pure CO or O2. In addition, we observed that two new facets were forming during the oxidizing/reducing cycles. Furthermore, we observed mixed edge/screw dislocations at the twin boundary, but only where the {111} side facets meet. Inducing such dislocations changes the local strain and the atomic structure of the nanoparticles, which may create more active sites close to the nanoparticle edges.

The resolution of a measurement system is fundamentally constrained by the wavelength of the used wave packet and the numerical aperture of the optical system. Overcoming these limits requires advanced interferometric techniques exploiting quantum correlations. While quantum interferometry can surpass the Heisenberg limit, it has been confined to the optical domain. Extending it to x-rays enables sub-angstrom spatial and zeptosecond temporal resolution, unlocking atomic-scale processes inaccessible to existing methods. Here, we demonstrate x-ray quantum interferometry using 17.5-kilo-electron volt ( [Formula: see text] = 70 picometers) photon pairs. Our approach introduces a phase measurement technique with exceptional noise resilience, mitigating the impact of mechanical instabilities, vibrations, and photonic noise-key challenges in x-ray interferometry. By generating and using entangled x-ray photons, we lay the foundation for next-generation techniques with unprecedented phase precision. This breakthrough carries far-reaching consequences for fundamental physics, high-resolution imaging, and spectroscopy, bringing to light quantum optical effects never before accessed in the x-ray regime.

Ni-rich layered oxides LiNi1-x-yMnxCoyO2 (NMC811, x = 0.1 and y = 0.1) are considered promising cathode materials in lithium-ion batteries (LiBs) due to their high energy density. However, those suffer a severe capacity loss upon cycling at high delithiated states. The loss of performance over time can be retarded by Zr doping. Herein, a small amount of Zr is added to NMC811 material via two alternative pathways: during the formation of the transition metal (TM) hydroxide precursor at the co-precipitation step (0.1%-Zr-cp) and during the lithiation at the solid-state synthesis step (0.1%-Zr-ss). In this work, the crystallographic Zr uptake in both 0.1%-Zr-ss and 0.1%-Zr-cp is determined and quantified through synchrotron X-ray diffraction and X-ray absorption spectroscopy. We prove that the inclusion of Zr in the TM site for 0.1%-Zr-cp leads to an improvement of both specific capacity (156 vs 149 mAh/g) and capacity retention (85 vs 82%) upon 100 cycles compared to 0.1%-Zr-ss where the Zr does not diffuse into the active material and forms only an extra phase separated from the NMC811 particles.

The necessity of mapping crystal defects in battery materials after synthesis is crucial in understanding heterogeneity within a single crystal domain and among particles to develop superior crystal quality materials. Numerous imaging techniques have been developed over the past years to study these materials at the nanoscale. However, most of them use electron beams which demand many hours of sample preparation, and they are incompatible with the investigation of batteries under realistic working conditions. Techniques such as Scanning X-ray Diffraction Imaging (Scanning X-ray Diffraction Microscopy) or Bragg Coherent Diffraction Imaging are increasingly available on the latest generation synchrotron sources. Their progressive deployment will allow for a standardized method for imaging crystal lattice imperfections such as lattice tilt and strain in individual particles without any prior sample preparation. In this paper, we exploited Scanning X-ray Diffraction Microscopy to probe the strain variation in single crystals and polycrystalline particles and Bragg Coherent Diffraction Imaging to reconstruct the volume of a single crystal particle. Presented case studies were performed on particles of different active cathode materials ($$ \rm{LiNi_{0.6}Mn_{0.2}Co_{0.2}O_{2}} $$ , $$ \rm{LiNiO_{2}} $$ and $$ \rm{LiMn_{1.5}Ni_{0.5}O_{4}} $$ ); however, these techniques can also be employed on other battery components for a more holistic structural understanding of used materials and (de)lithiation dynamics on the microscale.

The local lattice distortion in a crystal, the lattice strain, greatly influences the physical mechanisms underlying the operating principles of semiconductor devices. For example, strain is widely used in the bandgap engineering of group IV-based optoelectronic devices to improve their performance. In the case of GeSn-based light emitters, optimization of the lattice strain allowed the demonstration of optically pumped lasing at room temperature [1] and cw operation in an electrically pumped µ-disk laser [2], thanks to its beneficial effect on the "directness" of the bandgap, leading to increased material gain. It is therefore of paramount importance to characterize the strain with high sensitivity and sub-micron spatial resolution. Here we show how scanning X-ray diffraction microscopy, a recently developed model-free method based on synchrotron radiation [3,4], can be used to fully determine the landscape of mechanical deformation and stoichiometry fluctuation in a lithographically fabricated Ge1-xSnx/Ge suspended µ-disk, a structure of the same type as that used to demonstrate the first GeSn laser [5]. The full strain tensor of the entire microstructure, including all normal and shear components, is tomographically reconstructed with a lateral resolution of less than 100 nm and a sensitivity to strain variations of the order of 10-4. By comparing the lattice deformation in different sections of the microdisk, we observe a marked difference between the central pillar region in contact with the virtual Ge substrate and the free-standing outer rim where the Ge layer has been removed. Interestingly, although the misfit dislocation network at the GeSn/Ge relaxed heterointerface in the rim region has been removed during the fabrication process, we observe that a "fossilized" footprint of the dislocations is still present in the strain landscape of the layer. We attribute this to stoichiometric fluctuations that we measure in the Ge1-xSnx alloy generated by dislocation-driven strain fields during epitaxial growth, which are unaffected by etching and in turn generate a local strain field. We then exploit the symmetries of both the microdisk and the Ge1-xSnx material system itself. This allows us, for the first time, to calculate maps of the surface normal stress in an alloyed epitaxial thin film, which is traditionally difficult to impossible to disentangle from stoichiometric fluctuations in diffraction-based data, and is a key piece of information to evaluate in epitaxial layer growth. We complement the synchrotron experiments with electron microscopy and dedicated finite element method (FEM) simulations of both elastic and plastic relaxation processes in the model system, finding excellent agreement between experiment and theory. Furthermore, the effects of strain on the band structure are predicted in the light of the measured local variations in strain and composition. [1] A Elbaz, et al. Nature Photon. 14, 375 (2020) [2] L. Siedel et al. Nature, submitted (2024) [3] C. Corley-Wiciak et al. ACS Appl. Mater. & Interfaces 15, 3119 (2023) [4] C. Richter et al. Phys. Rev. Applied 18, 064015 (2022) [5] S Wirths, et al. Nature Photonics 9, 88 (2015)