Measurement of chromatic aberration in STEM and SCEM by coherent convergent beam electron diffraction

A simple method is described for the accurate and precise measurement of chromatic aberration under electron-optical conditions pertinent to scanning transmission electron microscopy (STEM) and scanning confocal electron microscopy (SCEM). The method requires only the measurement of distances in a coherent CBED pattern and knowledge of the electron wavelength and the lattice spacing of a calibration specimen. The chromatic aberration of a spherical-aberration corrected 300 kV thermal field emission TEM is measured in STEM and SCEM operating modes and under different condenser lens settings. The effect of the measured chromatic aberrations on the 3 dimensional intensity distribution of the electron probe is also considered.

► A method is presented to measure chromatic aberration (Cc) using coherent CBED.
► The Cc of the probe and imaging lens systems in STEM and SCEM modes is measured in a C3-corrected S/TEM.
► The effect of the measured Cc on the depth resolution in STEM is simulated for different energy spreads.