| Metadata | Details |
|---|
| Publication Date | 2025-10-24 |
| Journal | Proceedings of the National Academy of Sciences |
| Authors | Tang Li, Ken Vidar Falch, Jan Garrevoet, Leonid Dubrovinsky, Mikhail Lyubomirskiy |
| Institutions | University of Bayreuth, MAX IV Laboratory |
| Analysis | Full AI Review Included |
- Novel Imaging Paradigm: Demonstrated X-ray ptychography using beam scanning via tilting reflective optics, successfully decoupling high-resolution imaging from the need for precise translation of heavy or bulky samples (e.g., Diamond Anvil Cells).
- Resolution and Sensitivity: Achieved sub-50 nm resolution (42 nm edge response) and high phase contrast sensitivity, crucial for visualizing minimal density changes resulting from melting or chemical reactions.
- Extreme Conditions Capability: Applied the method to visualize the melting and oxidation of iron (Fe) inside a DAC under extreme conditions: 51 GPa pressure and 2,350 K temperature.
- Precision Tracking: Beam position on the sample is tracked with subnanometer precision using laser interferometers monitoring the mirror angle, ensuring accurate data reconstruction despite beam movement.
- Speed and Efficiency: The mirror oscillation acts as a fast scanning axis, delivering unmatched scanning speed compared to conventional motorized sample stages.
- Broad Applicability: This approach enables operando nanoscopy for fields previously limited by sample environment size and weight, including geoscience, high-pressure physics, and industrial catalysis studies requiring large reactors.
| Parameter | Value | Unit | Context |
|---|
| Achieved Resolution (Edge Response) | 42 | nm | Mirror scanning validation (12.3 keV) |
| Achieved Resolution (FRC, 1 bit criterion) | 36 | nm | Mirror scanning validation (12.3 keV) |
| X-ray Energy (DAC Experiment) | 13 | keV | Fe oxidation study |
| Maximum Pressure Achieved | 51 (±2) | GPa | Fe oxidation in DAC |
| Laser Heating Temperature | 2,350 (±150) | K | Fe oxidation reaction zone |
| Fe Foil Thickness (Compressed) | 0.4 to 0.5 | ”m | Estimated thickness at 51 GPa |
| Fe Foil Phase Shift (Reconstructed) | -0.23 | rad | Corresponds to 0.4 ”m material thickness |
| KB Mirror Working Distance | 200 | mm | Last mirror edge to sample |
| Scanning Mirror Coating | Ru | 35 nm | Total reflective mirror |
| Scanning Mirror Figure Error | 2 | nm rms | - |
| Mirror-Sample Distance | 110 | mm | Scanning mirror to sample |
| Detector Type | Eiger (In-vacuum) | 2,048 x 2,048 | Pixel array size |
| Detector Pixel Size | 75 | ”m | - |
| Cumulative Fluence (Mirror Scan) | 1.891 x 108 | photos/”m2 | Siemens Star validation |
- Beamline and Focusing Optics: Experiments were performed at the P06 beamline (PETRA III SRF). The X-ray beam was focused using Kirkpatrick Baez (KB) mirrors, providing a 200 mm working distance.
- Beam Scanning Hardware: A total reflective mirror (35 nm Ru coated) mounted on a piezo tilting stage was inserted between the last KB mirror and the sample (110 mm distance).
- Scanning Strategy: The sample area was raster scanned by oscillating the reflective mirror in the vertical direction (fast scanning axis) while the sample stage translated horizontally (slow scanning axis).
- Position Determination: Two laser interferometers tracked the angular displacement (d1 and d2) of the scanning mirror with high frequency (12.2 kHz). These measurements were averaged and optimized to calculate the precise vertical beam position at the sample plane.
- Ptychography Data Processing: Diffraction patterns were numerically recentered based on the calculated beam positions (horizontal and vertical shifts on the detector).
- Reconstruction Algorithms: Ptychographic reconstructions utilized a combination of the ePIE algorithm (with position refinement) for initial iterations, followed by the maximum likelihood algorithm for final refinement.
- High-Pressure Cell Preparation: A BX-90 Diamond Anvil Cell (DAC) with 250 ”m culets was used. A 3 ”m thick Fe foil was placed in the chamber (110 ”m diameter) and cryogenically loaded with O2, serving as both reactant and pressure medium.
- Reaction Induction: The Fe foil was laser-heated double-sided to 2,350 K for 2 seconds at 51 GPa, resulting in the formation of cubic FeO2.
- Geoscience and High-Pressure Research: Operando imaging of phase transitions, melting, and chemical reactions (e.g., Fe oxidation) in materials relevant to planetary interiors, overcoming the weight and size constraints of DACs and large-volume presses.
- Industrial Catalysis and Reactor Studies: Non-destructive, in situ morphological study of catalysts and reaction products within large-volume industrial reactors, where conventional sample translation is impractical.
- Advanced Materials Synthesis: Visualization of dynamic processes, such as material flow and grain growth, during synthesis under extreme temperature and pressure conditions, enabling optimization of novel material creation.
- High-Speed Failure Analysis: Tracking dynamic processes in functional devices (e.g., high-power electronics) that require exceptionally high scanning speeds, bypassing the limitations of conventional slow piezo scanning stages.
- Free-Electron Laser (FEL) Science: Enabling particle tracking for serial femtosecond crystallography by quickly and precisely manipulating the X-ray beam position, reducing the need for large statistical ensembles of data.
- X-ray Optics and Instrumentation: Provides a robust platform for testing and validating the performance and aberration characteristics of reflective X-ray optics under dynamic tilting conditions.
View Original Abstract
We present an approach to nanoscale-resolution high-sensitivity imaging of internal material structure under in situ/operando conditions for virtually any sample environment. When bulky or heavy sample environment is required state-of-the-art X-ray imaging techniques, such as scanning and full-field microscopy or holography fail to deliver high-resolution imaging capabilities due to either i) extremely small opticsâ working distance for magnification-based methods or ii) the inability to precisely control heavy sample position in the case of lens-less methods. In this work, we address those challenges for a scanning lens-less imaging method called ptychography. Instead of precisely controlling the sample position during raster scan in a focused, confined X-ray beam, we are scanning that beam across the sample. This overcomes the constraints on scanning procedure imposed by sample size/weight and delivers unmatched scanning speed while maintaining high precision of beam position during the scan. We directly applied our approach, showcasing phase contrast nanoimaging with diamond anvil cells, and visualized intricate details of the melting and oxidation of laser-irradiated iron under pressure of 50 GPa.