Time-resolved X-ray Diffraction Measurements Research Articles

Development of a laser-driven shock compression platform for time-resolved XRD experiments at the ID09 beamline of the European Synchrotron Radiation Facility

ABSTRACT We present a newly developed laser-driven shock compression platform at the ID09 beamline of the European Synchrotron Radiation Facility (ESRF). This platform combines a custom high-power EKSPLA laser with ESRF's high-energy X-ray pulses to perform in situ, time-resolved X-ray diffraction (XRD) measurements in materials under well characterized, moderate pressure (up to 1 Mbar) and short-duration shock waves. Its purpose is to serve as a shock driver to study materials under dynamic pressure, focusing on phase transitions in condensed matter. We provide a detailed description of this platform's design and functionalities, along with preliminary experimental results obtained from iron and tin samples subjected to shock compression. These results not only demonstrate the platform's ability to acquire high-quality X-ray diffraction data but also highlight its potential for advancing research in material science and high-energy-density physics.

Ultrafast Switching of Interfacial Thermal Conductance.

Dynamical control of thermal transport at the nanoscale provides a time-domain strategy for optimizing thermal management in nanoelectronics, magnetic devices, and thermoelectric devices. However, the rate of change available for thermal switches and regulators is limited to millisecond time scales, calling for a faster modulation speed. Here, time-resolved X-ray diffraction measurements and thermal transport modeling reveal an ultrafast modulation of the interfacial thermal conductance of an FeRh/MgO heterostructure as a result of a structural phase transition driven by optical excitation. Within 90 ps after optical excitation, the interfacial thermal conductance is reduced by a factor of 5 and lasts for a few nanoseconds, in comparison to the value at the equilibrium FeRh/MgO interface. The experimental results combined with thermal transport calculations suggest that the reduced interfacial thermal conductance results from enhanced phonon scattering at the interface where the lattice experiences transient in-plane biaxial stress due to the structural phase transition of FeRh. Our results suggest that optically driven phase transitions can be utilized for ultrafast nanoscale thermal switches for device application.

(Invited) Structure and Dynamics of Interfacial Species in Electrical Double Layer

Understanding electrochemical processes is of importance for many industrial and scientific fields. Especially, interfacial species, such as electrolyte ions and solvent significantly affect electrochemical reaction activity. Surface oxide species also promote or inhibit various electrode reactions; therefore, the oxidation processes of metal electrode have been investigated using in situ vibrational spectroscopy. Infrared (IR) spectroscopy is an important tool because it can detect the complementary vibrational modes of surface oxide species. However, observation of the low-frequency mode is restricted by infusible IR windows such as CaF2, that are generally used in the IR reflection absorption spectroscopy (IRAS). We developed a complementary IR method that can be used to avoid contamination by dissolved ions from window material. The fusible low-pass IR window can be applied to in-situ IRAS measurements [1,2]. The adsorbed hydroxide was observed on the single crystal Pt electrodes depending on the surface orientation, its coverage was correlated with the decrease in oxygen reduction reaction activity [3]. Recent time resolved X-ray diffraction measurements revealed that there is a delay in the approach of alkali metal cations to surface because the interfacial water causes a blocking effect [4]. Therefore, the kinetics of approaching step in the EDL is significantly different from that of migration in the bulk phase, and the adsorption rate depends on the hydration structure, ionic valence, and ionic size. Although X-ray diffraction provides a distribution of interfacial species, it does not provide sufficient information about species identification and molecular orientation. We investigated the coadsorption dynamics of metal cation and (bi)sulfate anion using time resolved IR measurement [5]. Boron doped diamond (BDD) is a promising material of which properties are significantly different from those of metals and other carbon materials. However, the complex atomic arrangement and oxidation state of the polycrystalline BDD surface inhibit an atomic level study on the relationship between the electrochemical response and surface structure. More detailed surface analyses are necessary for the investigation of the electrode surface of BDD. We applied in situ ATR−IR spectroscopy to reveal the oxidative species and dopamine oxidation on the BDD electrode [6,7].[1] M. Nakamura, Y. Nakajima, N. Hoshi, H. Tajiri, O. Sakata, ChemPhysChem, 14, 2426 (2013).[2] M. Nakamura, Y. Nakajima, K. Kato, O. Sakata, N. Hoshi, J. Phys. Chem. C, 119, 23586 (2015).[3] T. Kumeda, H. Tajiri, O. Sakata, N. Hoshi, M. Nakamura, Nat. Commun., 9, 4378 (2018).[4] M. Nakamura, H. Kaminaga, O. Endo, H. Tajiri, O. Sakata, N. Hoshi, J. Phys. Chem. C, 118, 22136 (2014).[5] M. Nakamura, T. Banzai, Y. Maehata, O. Endo, H. Tajiri. O. Sakata, N. Hoshi, Sci. Rep., 7, 914 (2017).[6] T. Ogose, S. Kasahara, N. Ikemiya, N. Hoshi, Y. Einaga, M. Nakamura, J. Phys. Chem. C, 122, 27456 (2018).[7] R. Hosoda, N. Kamoshida, N. Hoshi, Y. Einaga, M. Nakamura, Carbon, 171, 814 (2021).

Effect of grain size on amorphization mechanism and kinetics of bridgmanite in shocked meteorites

Bridgmanite formation and amorphization in shocked meteorites constrain the pressure and temperature conditions during planetary impact. However, the effect of the bridgmanite grain size on its amorphization kinetics is still unclear. Here, the amorphization mechanism and kinetics of fine-grained polycrystalline bridgmanite were studied at high temperatures up to 1080 K. High-temperature time-resolved synchrotron X-ray diffraction measurements showed that significant volume expansion due to temperature-induced amorphization caused static stress, which then hindered amorphization progress. Further, the temperature required for the amorphization of fine-grained bridgmanite (~ 1 μm) was found to be approximately 100 K higher than that required for the amorphization of coarse-grained samples (> 10 μm). We also noted that amorphization preferentially commenced at the twin planes and subgrain boundaries of bridgmanite grains, resulting in lower amorphization temperatures for the coarse-grained samples. The limited number of such specific locations in fine-grained natural bridgmanite suggested that grain boundary amorphization may be the dominant mechanism for bridgmanite amorphization in shocked meteorites. This unique amorphization kinetics would support the preservation of bridgmanite during the post-shock annealing in the shocked meteorite. Although bridgmanite amorphization starts easily at temperatures above ~ 420 K, a small amount of bridgmanite grains can survive at temperatures above 800 K by the effect of amorphization-induced stress.

Compressibility of ferropericlase at high-temperature: Evidence for the iron spin crossover in seismic tomography

The iron spin crossover in ferropericlase, the second most abundant mineral in Earth's lower mantle, causes changes in a range of physical properties, including seismic wave velocities. Understanding the effect of temperature on the spin crossover is essential to detect its signature in seismic observations and constrain its occurrence in the mantle. Here, we report the first experimental results on the spin crossover-induced bulk modulus softening at high temperatures, derived directly from time-resolved x-ray diffraction measurements during continuous compression of (Mg0.8Fe0.2)O in a resistive-heated dynamic diamond-anvil cell. We present new theoretical calculations of the spin crossover at mantle temperatures benchmarked by the experiments. Based on our results, we create synthetic seismic tomography models to investigate the signature of the spin crossover in global seismic tomography. A tomographic filter is applied to allow for meaningful comparisons between the synthetic models and data-based seismic tomography models, like SP12RTS. A negative anomaly in the correlation between Vs variations and Vc variations (S-C correlation) is found to be the most suitable measure to detect the presence of the spin crossover in tomographic models. When including the effects of the spin crossover, the misfit between the synthetic model and SP12RTS is reduced by 63%, providing strong evidence for the presence of the spin crossover, and hence ferropericlase, in the lower mantle. Future improvement of seismic resolution may facilitate a detailed mapping of spin state using the S-C correlation, providing constraints on mantle temperatures by taking advantage of the temperature sensitivity of the spin crossover.

Axial vs equatorial: Capturing the intramolecular charge transfer state geometry in conformational polymorphic crystals of a donor-bridge-acceptor dyad in nanosecond-time-scale.

Two conformational polymorphs of a donor-bridge-acceptor (D-B-A) dyad, p-(CH3)2N-C6H4-(CH2)2-(1-pyrenyl)/PyCHDMA, were studied, where the electron donor (D) moiety p-(CH3)2N-C6H4/DMA is connected through a bridging group (B), -CH2-CH2-, to the electron acceptor (A) moiety pyrene. Though molecular dyads like PyCHDMA have the potential to change solar energy into electrical current through the process of photoinduced intramolecular charge transfer (ICT), the major challenge is the real-time investigation of the photoinduced ICT process in crystals, necessary to design solid-state optoelectronic materials. The time-correlated single photon counting (TCSPC) measurements with the single crystals showed that the ICT state lifetime of the thermodynamic form, PyCHDMA1 (pyrene and DMA: axial), is ∼3ns, whereas, for the kinetic form, PyCHDMA20 (pyrene and DMA: equatorial), it is ∼7ns, while photoexcited with 375nm radiation. The polymorphic crystals were photo-excited and subsequently probed with a pink Laue x-ray beam in time-resolved x-ray diffraction (TRXRD) measurements. The TRXRD results suggest that in the ICT state, due to electron transfer from the tertiary N-atom in DMA moiety to the bridging group and pyrene moiety, a decreased repulsion between the lone-pair and the bond-pair at N-atom induces planarity in the C-N-(CH3)2 moiety, in both polymorphs. The Natural Bond Orbital calculations and partial atomic charge analysis by Hirshfeld partitioning also corroborated the same. Although the interfragment charge transfer (IFCT) analysis using the TDDFT results showed that for the charge transfer excitation in both conformers, the electrons were transferred from the DMA moiety to mostly the pyrene moiety, the bridging group has little role to play in that.

Microstructure evolution induced by solidification and ferrite–austenite massive-like transformation in Fe–C alloys

The coarsening of austenite grains produced through a massive-like transformation from the ferrite to the austenite phase during/after solidification in Fe–0.45mass%C steel was examined through time-resolved X-ray diffraction measurements using time-resolved computed tomography. The δ phase solidification resulted in a single δ grain in the observation region (0.6 mm in diameter, 0.1 mm in height). The massive-like transformation produced multiple γ grains, and coarsening immediately followed the transformation. The coarsening in the observation region was completed even within 200 s. A correlation of crystallographic orientation between the γ grains was found in the γ grain structure. The massive-like transformation frequently produced fcc (111) twinned grains, and the twinned austenite grains tended to remain during coarsening because the twin interface energy is lower than the grain boundary energy. The massive-like transformation following the solidification contributed to the texture formation in the γ grain structure.

Optimized x-ray emission from 10ns long germanium x-ray sources at the National Ignition Facility.

This study investigates methods to optimize quasi-monochromatic, ∼10ns long x-ray sources (XRS) for time-resolved x-ray diffraction measurements of phase transitions during dynamic laser compression measurements at the National Ignition Facility (NIF). To support this, we produce continuous and pulsed XRS by irradiating a Ge foil with NIF lasers to achieve an intensity of 2 × 1015 W/cm2, optimizing the laser-to-x-ray conversion efficiency. Our x-ray source is dominated by Ge He-α line emission. We discuss methods to optimize the source to maintain a uniform XRS for ∼10ns, mitigating cold plasma and higher energy x-ray emission lines.

Dynamical criticality of spin-shear coupling in van der Waals antiferromagnets

The interplay between a multitude of electronic, spin, and lattice degrees of freedom underlies the complex phase diagrams of quantum materials. Layer stacking in van der Waals (vdW) heterostructures is responsible for exotic electronic and magnetic properties, which inspires stacking control of two-dimensional magnetism. Beyond the interplay between stacking order and interlayer magnetism, we discover a spin-shear coupling mechanism in which a subtle shear of the atomic layers can have a profound effect on the intralayer magnetic order in a family of vdW antiferromagnets. Using time-resolved X-ray diffraction and optical linear dichroism measurements, interlayer shear is identified as the primary structural degree of freedom that couples with magnetic order. The recovery times of both shear and magnetic order upon optical excitation diverge at the magnetic ordering temperature with the same critical exponent. The time-dependent Ginzburg-Landau theory shows that this concurrent critical slowing down arises from a linear coupling of the interlayer shear to the magnetic order, which is dictated by the broken mirror symmetry intrinsic to the monoclinic stacking. Our results highlight the importance of interlayer shear in ultrafast control of magnetic order via spin-mechanical coupling.

Structural measurement of electron-phonon coupling and electronic thermal transport across a metal-semiconductor interface

Scattering of energetic charge carriers and their coupling to lattice vibrations (phonons) in dielectric materials and semiconductors are crucial processes that determine the functional limits of optoelectronics, photovoltaics, and photocatalysts. The strength of these energy exchanges is often described by the electron-phonon coupling coefficient, which is difficult to measure due to the microscopic time- and length-scales involved. In the present study, we propose an alternate means to quantify the coupling parameter along with thermal boundary resistance and electron conductivity by performing a high angular-resolution time-resolved X-ray diffraction measurement of propagating lattice deformation following laser excitation of a nanoscale, polycrystalline metal film on a semiconductor substrate. Our data present direct experimental evidence for identifying the ballistic and diffusive transport components occurring at the interface, where only the latter participates in thermal diffusion. This approach provides a robust measurement that can be applied to investigate microscopic energy transport in various solid-state materials.

Synchrotron X-Ray-Driven Nitrogen Reduction on an AgCu Thin Film.

Nitrogen (N2 ) is an essential element for life, but kinetically stable N2 in the atmosphere needs to be reduced to biologically available forms as a nutrient for organisms. Abiotic nitrogen fixation is critical to the origin of life on the early Earth, which is due to lightning or mineral-based reduction. Here, synchrotron X-ray-induced silver nitrate formation on a silver copper (AgCu) thin-film is reported. Time-resolved X-ray diffraction measurements show that under intense X-ray exposure, initially formed silver oxides (AgOx) are quickly converted to silver nitrate (AgNO3 ). Interestingly, AgNO3 is first formed in its high-temperature phase with a space group of R3cH, which gradually transforms to the room temperature phase with a space group of Pbca under continuous X-ray irradiation. The result not only provides a new clue about the abiotic nitrogen reduction prior to life but also demonstrates a novel strategy of materials synthesis using synchrotron X-rays.

Ultrafast optical stress on BaFe2As2

We investigate the ultrafast lattice dynamics in ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ via time-resolved x-ray diffraction measurements using an x-ray free-electron laser at SPring-8 Angstrom Compact free-electron LAser (SACLA). The profile of the Bragg peaks substantially changes after strong photoexcitation, where the $c$ axis length of the lattice initially contracts, followed by expansion. These ultrafast lattice contractions and expansions significantly depend on the pump fluence, and it is suggested that a strong normal stress is applied along the $c$ axis. To obtain a phenomenological understanding of the observed lattice dynamics, we performed calculations based on a two-temperature model and an ultrafast thermoelasticity model. Our results showed that a steep gradient of the electron temperature induced by photoexcitation generates a blast force, which acts as a strong normal stress. We propose that a temporal stress can be applied by a strong optical pump, and this scheme can be another route for the application of uniaxial stress to superconductors.

Amino Acids and Their N-Acetylated Derivatives Maintain the Skin's Barrier Function.

The hydrocarbon-chain packing structure of intercellular lipids in the stratum corneum (SC) is critical to the skin's barrier function. We previously found that formation of V-shaped ceramide reduces the barrier function of skin. There are few agents, apart from ceramides and fatty acids that can improve the orthorhombic packing (Orth) ratio of the intercellular lipid packing structure. In this study, we investigated agents that directly increase the Orth ratio. We selected an intercellular lipid model consisting of ceramide, cholesterol, and palmitic acid and performed differential scanning calorimetry. We focused on natural moisturizing factor components in the SC, and therefore investigated amino acids and their derivatives. The results of our intercellular lipid model-based study indicate that N-acetyl-L-hydroxyproline (AHYP), remarkably, maintains the lamellar structure. We verified the effect of AHYP on the lamellar structure and hydrocarbon chain packing structure of intercellular lipids using time-resolved X-ray diffraction measurements of human SC. We also determined the direct physicochemical effects of AHYP on the Orth ratio of the hydrocarbon-chain packing structure. Hence, the results of our human SC study suggest that AHYP preserves skin barrier function by maintaining the hydrocarbon-chain packing structure of intercellular lipids via electrostatic repulsion. These findings will facilitate the development of skincare formulation that can maintain the skin's barrier function.

The fast multi-frame X-ray diffraction detector at the Dynamic Compression Sector.

A multi-frame, X-ray diffraction (XRD) detector system has been developed for use in time-resolved XRD measurements during single-event experiments at the Dynamic Compression Sector (DCS) at the Advanced Photon Source (APS). The system is capable of collecting four sequential XRD patterns separated by 153 ns, the period of the APS storage ring in the 24-bunch mode. This capability allows an examination of the temporal evolution of material dynamics in single-event experiments, such as plate impact experiments, explosive detonations, and split-Hopkinson pressure bar experiments. This system is available for all user experiments at the DCS. Here, the system description and measured performance parameters (detective quantum efficiency, spatial and temporal resolution, and dynamic range) are presented along with procedures for synchronization and image post-processing.

Long duration x-ray source development for x-ray diffraction at the National Ignition Facility.

We present the results of experiments to produce a 10 ns-long, quasi-monochromatic x-ray source. This effort is needed to support time-resolved x-ray diffraction (XRDt) measurements of phase transitions during laser-driven dynamic compression experiments at the National Ignition Facility. To record XRDt of phase transitions as they occur, we use high-speed (∼1ns) gated hybrid CMOS detectors, which record multiple frames of data over a timescale of a few to tens of ns. Consequently, to make effective use of these imagers, XRDt needs the x-ray source to be narrow in energy and uniform in time as long as the sensors are active. The x-ray source is produced by a laser irradiated Ge foil. Our results indicate that the x-ray source lasts during the whole duration of the main laser pulse. Both time-resolved and time-integrated spectral data indicate that the line emission is dominated by the He-α complex over higher energy emission lines. Time-integrated spectra agree well with a one-dimensional Cartesian simulation using HYDRA that predicts a conversion efficiency of 0.56% when the incident intensity is 2 × 1015 W/cm2 on a Ge backlighter.

Real-time stress evolution during laser surface line hardening at varying maximum surface temperatures using synchrotron X-ray diffraction

Multiple laser surface line hardening experiments on flat samples, made of tempering steel SAE 4140, were carried out under variation of the maximum control temperature in the range of 850 °C to 1150 °C at the sample surface. For each temperature, time resolved X-ray diffraction measurements using synchrotron radiation were performed at beamline P05@PETRA III at DESY (Deutsches Elektronen Synchrotron) in Hamburg, Germany. The samples were line hardened using a 4 kW High Power Diode Laser unit at a constant laser feed of 800 mm/min with a specific laser optics under pyrometer control of the maximum surface temperature. A special designed process chamber with 4 symmetrically attached fast silicon micro strip line detectors allows for stress analysis during the process according to the sin2ψ method in single exposure mode with a measurement frequency of 50 Hz. As a result of the time resolved analyses the elastic strains were separated from thermal ones and near surface local stress evolutions, longitudinal and transverse to the laser track direction in the center of the processed zone, were determined. The in situ experiments were complemented by high spatially resolved post-process residual stress analyses using conventionally generated X-rays and by metallographic investigations. The results are carefully discussed regarding mechanisms of local stress formation during the laser hardening process and their dependence on the maximum control temperature. The temporal stress course during laser surface line hardening is presented for the first time in both surface parallel directions, where temperature differences in the process zone lead to significant differences in the resulting residual stress profiles. In addition to the common validation of process simulations by comparison with experimentally determined data from the final state after processing, e.g. the resulting local residual stresses, the current work provides real-time data from in situ experiments during laser surface hardening for the validation of temporal stress courses of numerical process simulations.

Femtosecond Optical Laser System with Spatiotemporal Stabilization for Pump-Probe Experiments at SACLA

We constructed a synchronized femtosecond optical laser system with spatiotemporal stabilization for pump-probe experiments at SPring-8 Angstrom Compact Free Electron Laser (SACLA). Stabilization of output power and pointing has been achieved with a small fluctuation level of a few percent by controlling conditions of temperature and air-flow in the optical paths. A feedback system using a balanced optical-microwave phase detector (BOMPD) has been successfully realized to reduce jitter down to 50 fs. We demonstrated the temporal stability with a time-resolved X-ray diffraction measurement and observed the coherent phonon oscillation of the photo-excited Bi without the post-processing using the timing monitor.

Enhanced intrinsic piezoelectric response in (001)-epitaxial single c-domain Pb(Zr,Ti)O3 nanorods

In this study, (001)-epitaxial tetragonal phase Pb(Zr, Ti)O3 (PZT) nanorods were fabricated on SrRuO3/SrTiO3 substrates by pulsed laser deposition. The PZT nanorods were self-assembled and grown on the substrate at an elevated oxygen pressure, and showed a complete c-domain structure. Time-resolved x-ray diffraction measurements under an applied electric field show that the fabricated PZT nanorods exhibit a piezoelectric constant, d33, that is significantly higher than that of thin PZT films and comparable to that for unclamped single-domain bulk crystals, which is thought to be due to a significant reduction in substrate clamping. The obtained results demonstrate that the self-assembled nanorods can achieve an enhanced intrinsic piezoelectric response, which makes them attractive for a range of practical applications.

Strain-Rate Dependence of the Martensitic Transformation Behavior in a 10 Pct Ni Multi-phase Steel Under Compression

The deformation-induced transformation of metastable austenite to martensite can contribute to improved performance of many steel alloys in a range of applications. For example, one class of Ni-containing steels that has undergone consecutive heat treatments of quenching (Q), lamellarization (L), and tempering (T) exhibits improved ballistic resistance and low-temperature impact toughness. To better understand the origin of this improvement, we tracked the volume fraction of austenite present in a QLT 10 wt pct Ni steel during compression at low and high strain rates ( $$\dot{\varepsilon }={0.001}\,{{\text{s}}^{-1}}$$ and $$\dot{\varepsilon }\simeq {2500}\,{{\text{s}}^{-1}}$$ , respectively) using ex situ vibrating sample magnetometry measurements and in situ time-resolved X-ray diffraction measurements. We observe that the austenite-to-martensite transformation occurs more readily during quasi-static loading than during dynamic loading, even at small values of applied strain, which is qualitatively different from the behavior of steels known to undergo a strain-induced martensitic transformation mechanism. We propose that the strain-rate dependence of transformation in the QLT 10 pct Ni steel is dominated by the transformation in small austenite particles, where stress-assisted martensitic transformation is likely to be the dominant mechanism. Indirect evidence for this hypothesis is provided by electron backscatter diffraction measurements of deformed specimens.

A resistively-heated dynamic diamond anvil cell (RHdDAC) for fast compression x-ray diffraction experiments at high temperatures.

A resistively-heated dynamic diamond anvil cell (RHdDAC) setup is presented. The setup enables the dynamic compression of samples at high temperatures by employing a piezoelectric actuator for pressure control and internal heaters for high temperature. The RHdDAC facilitates the precise control of compression rates and was tested in compression experiments at temperatures up to 1400 K and pressures of ∼130 GPa. The mechanical stability of metallic glass gaskets composed of a FeSiB alloy was examined under simultaneous high-pressure/high-temperature conditions. High-temperature dynamic compression experiments on H2O ice and (Mg, Fe)O ferropericlase were performed in combination with time-resolved x-ray diffraction measurements to characterize crystal structures and compression behaviors. The employment of high brilliance synchrotron radiation combined with two fast GaAs LAMBDA detectors available at the Extreme Conditions Beamline (P02.2) at PETRA III (DESY) facilitates the collection of data with excellent pressure resolution. The pressure-temperature conditions achievable with the RHdDAC combined with its ability to cover a wide range of compression rates and perform tailored compression paths offers perspectives for a variety of future experiments under extreme conditions.