The team of project A5 of the SFB successfully measured the potential drop across a hetero interface using four-dimensional scanning transmission electron microscopy
Characterizing long-range electric fields and built-in potentials in functional materials at nano to micrometer scales is of supreme importance for optimizing devices. For example, the functionality of semiconductor heterostructures or battery materials is determined by the electric fields established at interfaces, which can also vary spatially. In this study, we propose momentum-resolved four-dimensional scanning transmission electron microscopy (4D-STEM) for the quantification of these potentials. So far, dynamic effects have inhibited the quantitative evaluation of fields at heterointerfaces. The scientists in SFB project A5 carefully adopted their experimental setup to overcome these challenges and for the first time quantitatively measured the potential drop across a GaAs/AlAs interface.
In detail, a precession electron diffraction (PED) system was introduced, which rocks the impinging electron beam at a rate of 1 kHz, while scanning across the sample. This significantly reduces the impact of dynamic effects in the 4D data. In turn, an energy filter minimizes the influence of inelastic scattering.
Using the method proposed, allows the quantification of intentional or parasitic electric fields even in the presence of heterointerfaces. Accordingly, the characterization of real-life devices, like solar cells or battery materials, which often involve a multitude of such internal interfaces, becomes feasibly to optimize their performance.
V. Chejarla, S. Ahmed, J. Belz, J. Scheunert, A. Beyer, K. Volz
Measuring spatially-resolved potential drops at semiconductor hetero-interfaces using 4D-STEM
Small Methods (2023) 2300453 DOI:10.1002/smtd.202300453
Prof. Dr. Kerstin Volz
SFB 1083 project A5, A14, B13
Tel.: 06421 28-22297