Robust elemental mapping of nanostructures at ultrahigh resolution using event-streamed spectrum imaging in an aberration-corrected analytical electron microscope

Abstract

We describe the application of X-ray energy dispersive spectroscopy (XEDS) event-streamed spectral imaging (ESSI) in an aberration-corrected analytical electron microscope (AEM) as a reliable method for the acquisition of ultra-high spatial resolution elemental maps. With the ESSI approach, the XEDS spectral image is acquired over multiple frames at rates typically reserved for imaging experiments. This approach differs significantly from that typically employed in the AEM, where spectrum image data is acquired serially (a pixel at a time) using per-pixel dwell times that are orders of magnitude larger. The ESSI approach provides numerous advantages, most notably the ability to use the relatively strong transmitted electron image signals as a reference to spatially register the sparse XEDS data. State-of-the-art implementations of ESSI allow this registration to be performed "on-the-fly", such that drift correction is performed in real time. In addition, the electron dose imparted to the specimen is spread over time, meaning the instantaneous dose at a given point in the specimen is orders of magnitude lower than that imparted using serial spectral imaging. Thus, ESSI enables the high spatial resolution analysis of dose-rate-sensitive specimens. The application of this technique to several nanoscale systems is discussed, along with the potential for its use in combination with improved detector designs.