Atomic-Resolution Chemical Analysis in Aberration-Corrected Analytical Electron Microscopy
Speaker: Masashi Watanabe, Lehigh U.
Date & Time: April 21, 2011 - 12:00pm
Location: Chem. 260
Chemical analysis at atomic-level spatial resolution with single-atom detection sensitivity is one of the ultimate goals in materials characterization. Such atomic-level materials characterization would be feasible by electron energy-loss spectrometry (EELS) and X-ray energy dispersive spectrometry (XEDS) in the latest aberration-corrected scanning transmission electron microscopes (STEMs) because more probe current can be added into the incident probe by aberration-correction. Especially for EELS analysis, sufficient amounts of core-loss signals can be generated within a short acquisition time by higher current probes, and hence atomic-resolution EELS mapping has already been applied. For XEDS analysis, spatial resolution reaches ~ 0.4 nm, which implies atomic-level analysis is feasible, in aberration- corrected STEM. However, atomic-level chemical analysis is even more challenging in the XEDS approach since detection of X-ray signals is more limited than that in EELS (~100 times difference). The limited signals can be improved by applying spectrum-imaging (which records a full spectrum at individual pixels) in combination with multivariate statistical analysis.