Impact of beam size and diffraction effects in the measurement of long-range electric fields in crystalline samples via 4DSTEM.

Measuring long-range electric fields by 4-dimensional scanning transmission electron microscopy (4DSTEM) is on the verge to becoming an established method, though quantifying and understanding all underlying processes remains a challenge. To gain further insight into these processes, experimental studies employing the center-of-mass (COM) method of the model system of a GaAs p-n junction are carried out in which three ranges of the semi-convergence angle α are identified, with an intermediate one where measuring the built-in potential V is not feasible. STEM multislice simulations including both atomic and nm-scale fields prove that this intermediate range begins once diffraction disks start overlapping with the undiffracted beam.

Measuring Spatially-Resolved Potential Drops at Semiconductor Hetero-Interfaces Using 4D-STEM.

Characterizing long-range electric fields and built-in potentials in functional materials at nano to micrometer scales is of supreme importance for optimizing devices, e.g., the functionality of semiconductor hetero-structures or battery materials is determined by the electric fields established at interfaces which can also vary spatially.