Detecting weak core-loss signals with dose-fractionated spectrum imaging

Gatan instruments used

GIF Continuum^® with Stela^®* system

Background

Energy loss near-edge fine structure (ELNES) in transition metal (TM) K-edges can be used to study local symmetry, coordination, and covalency of the surrounding TM environment [1]. TM K-edge interpretation is less complex than corresponding L-edges as 1s core hole does not strongly interact with the 3d or 4p (pre-edge) valence electrons. However, the inelastic cross-sections for TM K-edges are three orders of magnitude smaller than the corresponding L-edges. Proportionally, longer acquisition times are required, increasing the likelihood that sample damage and spatial drift will occur. In-situ spectrum image (SI) acquisition saves each pass of the SI individually, fractionating the dose over several passes. This strategy allows users to inspect the condition of samples pass-by-pass post-acquisition, preventing the incorporation of anomalous data.