Soft X-ray 3-D Nanoscale Imaging

by Christoph Pratsch (HZB, Berlin)

Thursday 20 Oct 2016, 11:30 → 12:30 UTC

Marie Curie meeting room (ALBA Synchrotron)

3-D nanoscale soft X-ray imaging based on tomography is an established microscopy technique. However, as the lateral resolution of the zone plate objective improves to 10 nm, the depth of field shrinks significantly below the thickness of biological cells. To understand the effect of the depth of focus on tomographic reconstructions, we simulated the imaging process in the X-ray microscope. In agreement with our experimental observations, the simulations show that the obtainable 3-D resolution in biological specimens is limited to about 30 nm. As a consequence, new approaches to 3-D nanoscale X-ray imaging are required to resolve structures of extended samples at the 10 nm 3-D resolution level. 

In this talk we investigate the 3-D performance of a potential of confocal scanning transmission soft X-ray microscope. A completely new approach to 3-D X-ray imaging is based on scanning X-ray microscopy combined with focused ion beam milling, which we call FIB-SXM. We find that this method can achieve isotropic resolution of 10 nm due to the short escape length (< 10 nm) of the emitted electrons and the small size of the focal spot. Surprisingly, we also find that the electron detection mode can operate at a dose three orders of magnitude lower than any transmission technique. Finally we discuss potential improvements for dark field and Zernike phase contrast based X-ray microscopes.