Quantifying Nanoscale Chemical Heterogeneity with Coherent X-ray Microscopy

The very high brightness of synchrotron x-ray sources has enabled the continued development of coherent x-ray microscopy which is a powerful tool for the analysis of chemical and magnetic states in nano-materials. Scanning microscopes, which achieve the highest spatial resolution when using coherent light, are best suited to exploit the coherence gains expected from the new generation of diffraction limited synchrotron sources. High resolution, currently considered to be below 10 nanometers, can be achieved either with high numerical aperture x-ray optics or via computational imaging methods which reconstruct the image from coherent x-ray scattering patterns. The latter method replaces the need for high numerical aperture optics, which may be inefficient or suffer from very short working distances, with high speed imaging detectors and computational complexity. The advent of high speed x-ray pixel detectors and phase retrieval based reconstruction algorithms has led to the broad development of x-ray ptychography as a robust means of achieving high spatial resolution in an x-ray microscope. The ALS, as a soft x-ray synchrotron source, has pioneered the application of x-ray ptychography to the quantitative analysis of chemical phases in nanomaterials. I will present the design and performance of our newest x-ray microscope and data analysis infrastructure which can achieve a spatial resolution below 10 nm. I will also review several important scientific applications including redox reactions in energy storage materials and crystal orientation in biominerals. As a national scientific user facility, the ALS makes its experimental systems freely available to the general scientific community for open scientific research.

This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under Contract No. DE-AC02-05CH11231.