Ptychography Reduces Spectral Distortions Intrinsic to Conventional Zone-Plate-Based X-Ray Spectromicroscopy

• Published in: Microscopy and microanalysis Vol. 27; no. 6; pp. 1448 - 1453
• Main Authors: Marcus, Matthew A., Shapiro, David A., Yu, Young-Sang
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.12.2021; Oxford University Press
• Subjects: Coherent scattering; Heterogeneity; Microscopy; Photovoltaic cells; Point spread functions; Software and Instrumentation; Spatial discrimination; Spatial heterogeneity; Spatial resolution; Spectra; Spectrum analysis; X ray microscopy; STXM; spectromicroscopy; X-ray microscopy; ptychography; point spread function
• ISSN: 1431-9276; 1435-8115
• DOI: 10.1017/S1431927621012733

Scanning transmission X-ray microscopy is a powerful method for mapping chemical phases in nano-materials. The point spread function (PSF) of a conventional zone-plate-based microscope limits the achievable spatial resolution and also results in spatially resolved spectra that do not accurately reflect the spatial heterogeneity of the samples when the scale of the detail approaches the probe size. X-ray ptychography, a coherent-scattering-based imaging scheme that effectively removes the probe from the image data, returns accurate spectra from regions smaller than the probe size. We show through simulation how the long tails on the PSF of an x-ray optic can cause spectral distortion near a boundary between two spectrally distinct regions. The resulting apparent point spectra can appear mixed, with the species on one side of the boundary seeming to be present on the other even at a distance from the boundary equal to several times the spatial resolution. We further demonstrate the effect experimentally and show that ptychographic microscopy can return the expected spectra from a model system, whereas conventional microscopy does not.