Introduction to Ptychography
Ptychography is a high resolution, scanning-based coherent diffractive imaging (CDI) technique. The sample is illuminated with a focused, coherent (laser-like) X-ray beam and small angle scattering patterns are collected as the sample is raster scanned through the beam. The scattering patterns and the precise beam positions on the sample are fed into a Fourier transform-based, iterative algorithm which returns a real-space image that contains both the phase and absorption information of the sample. The resulting image has a resolution better than the size of the focused X-ray beam. Therefore, the resolution of the technique is not limited by the size of the focused beam footprint on the sample, which allows imaging below the current resolution limits of the most state-of-the-art X-ray optics. Ptychography does not require a crystalline sample as with standard X-ray diffraction nor an isolated sample as with standard, full-field CDI.
Energy storage devices are complex, hierarchical systems which have operational and failure mechanisms occurring across a wide range of length scales from a few Ångstroms to hundreds of microns. The aim of this project is to establish a novel enabling capability within SLAC through the development of a new sub-5 nm resolution imaging capability in the soft X-ray regime. The new imaging capability will be achieved through the development of soft X-ray ptychography with X-ray absorption near edge spectroscopy (XANES), which will improve SSRL’s soft X-ray imaging resolution from around 40 nm to below 5 nm and give access to oxygen chemistry and the valence states of 3d transition metals.
Anna Wise working at beamline 13-1 to implement high resolution ptychographic imaging.