NBED strain measurements enhanced via energy-filtered 4D STEM

Gatan instruments 

eaSI™ is an exclusive technology from Gatan that delivers the most efficient and effective workflow for advanced STEM experiments. eaSI leverages the GIF Continuum^® system upgraded with the STEMx^® system to enable energy-filtered 4D STEM studies.

Background

A better understanding of materials’ behavior under tension or compression is vital for various engineering fields. For instance, in many common silicon devices, strain engineering is used to tailor their electronic properties for different applications. Similarly, in the case of metallics, understanding and then predicting the material behavior under deformation requires strain measurement. One of the standard strain mapping (scanning transmission electron microscopy (STEM) methods is nanobeam electron diffraction (NBED) [1, 2]. In this technique, the electron probe is scanned over a two-dimensional (2D) array on the specimen, while a 2D electron diffraction pattern is recorded at each probe position, hence the name 4D STEM. Strain is then calculated by measuring changes to the positions of the diffraction disks compared to a reference diffraction pattern acquired from an unstrained area of the sample. NBED strain mapping depends greatly on how precise the position of the diffraction disks is measured.