Managing dose-, damage- and data-rates in multi-frame spectrum-imaging

Abstract

As an instrument, the scanning transmission electron microscope is unique in being able to simultaneously explore both local structural and chemical variations in materials at the atomic scale. This is made possible as both types of data are acquired serially, originating simultaneously from sample interactions with a sharply focused electron probe. Unfortunately, such scanned data can be distorted by environmental factors, though recently fast-scanned multi-frame imaging approaches have been shown to mitigate these effects. Here, we demonstrate the same approach but optimized for spectroscopic data; we offer some perspectives on the new potential of multi-frame spectrum-imaging (MFSI) and show how dose-sharing approaches can reduce sample damage, improve crystallographic fidelity, increase data signal-to-noise, or maximize usable field of view. Further, we discuss the potential issue of excessive data-rates in MFSI, and demonstrate a file-compression approach to significantly reduce data storage and transmission burdens.

Imaging Beam‐Sensitive Materials by Electron Microscopy

“…On the contrary, an “inverse” dose‐rate effect refers to decreased radiation sensitivity upon increased dose rate, which mainly originates from slower beam damage events such as diffusion‐limited mass loss, precipitation and segregation 57. The underlying dose‐rate dependent damage mechanisms, such as heating, charging (or damage that fits the “damage by the induced electric field, DIEF” model56) and diffusion allow the recovery of structures against beam damage,75,79 possibly through heat and charge dissipations,56 as well as back‐diffusion processes 69,80,81. Notably, under certain circumstances, the beam damages are affected by multiple mechanisms while the dominant mechanism as well as the overall dose‐rate effect may vary depending on the illumination conditions and material properties 21,56.…”

Direct Observation of High Densities of Antisite Defects in Ag2ZnSnSe4

“…While XRD is relatively insensitive to cation ordering in this system and provides only a view of aggregate structure across thousands of crystals/ grains, STEM allows us to select single crystal particles of Ag 2 SnZnSe and tilt them to "structure sensitive" orientations such as [010] where cation ordering can be examined in more detail. In order to unambiguously identify the elemental distribution, we have correlated HAADF images with simultaneous EDX mapping, using methods of data superposition described by Jones et al [16,17] The final results are shown in Figure 4 and more detail is shown in the Supplementary data. In summary, HAADF images and EDX spectra were recorded by scanning a 0.1nm probe, with 17pA current, over an 11nm x 11nm area of single crystal.…”

Joint non-rigid image registration and reconstruction for quantitative atomic resolution scanning transmission electron microscopy

“…In our case, the measurements were taken on the apex of a needle-shaped specimen prepared by focused ion beam milling, which introduces surface damage that obstructs the precise determination of lattice peak positions. The strain measurement suggests that even with the bias-corrected approach it is difficult to fully correct for the influence of slow scan instabilities, as also observed by [15]. The approach developed by Ophus et al [8] only relying on two orthogonally scanned images is also able to greatly reduce the influence of scan noise in comparison to individual slow scan images, but also in their case, residual non-local distortions remain.…”