Atomic resolution imaging is now routine in STEM. However, it is well-established that possessing atomically-resolved features does not guarantee that the image can be quantitatively analysed at atomic resolution. This is because the probe scatters within the crystal well beyond its initial point of incidence [1,2,3,4].
In this work, we investigate whether there exists a form of the incident electron probe that can generate a STEM signal with a predictable spatial origin that does not necessarily require a priori information about the specimen. We consider whether there exist probe conditions for which the spatial resolution of the image matches that of the information contained within it. Using Ge as a study case, we simulate and compare the scattering behaviour and resultant spatial origin of the STEM signals generated by a variety of different incident electron probes, including the commonly-used large convergence angle aberration-corrected probes, unit-cell resolution probes, under-focussed, tilted and ‘exotic’ probes. We discuss the relative strengths and weaknesses of the different geometries depending on the information sought and consider the optimum conditions for a given material science application.
The authors acknowledge the use of facilities and staff support at the Monash Centre for Electron Microscopy
This research was supported under the Discovery Projects funding scheme of the Australian Research Council (Project nos. DP120101573 and DP110101570).