Improved 4D STEM strain mapping of Ge/SiGe heterostructure defects via energy-filtered, precession-assisted 4D STEM 

Instruments used

STEMx^® Precession, STEMx system, GIF Continuum^® K3^®, eaSI™ technology, and DigitalMicrograph^® software

Background

4D STEM is an excellent tool for analyzing strain distributions at nanometer resolution. To achieve this, strain mapping algorithms used by DigitalMicrograph and other open-source packages use peak finding methods to measure small shifts in diffraction spot positions and calculate the resulting strain. Mapping results are best when the diffraction patterns in a 4D STEM dataset have a high signal-to-noise ratio (SNR) and the diffraction peaks are easy for the algorithm to accurately find. Common effects like dynamical diffraction and inelastic scattering backgrounds can negatively affect data quality, which in turn worsens strain mapping results. However, these effects can be minimized with energy filtering and precession-assisted 4D STEM methods as discussed in this experiment brief.