Local crystal structure analysis with several picometer precision using scanning transmission electron microscopy

Picometre-precision analysis of scanning transmission electron microscopy images of platinum nanocatalysts

“…Registering two images, R and T, requires finding a deformation f of the image domain such that the composition T3f agrees with R. Figure 1a shows the conventional approach, in which f is a rigid translation 11,13,14 . A rigid f works for the unchanging pixel grid in Fig.…”

“…We demonstrate sub-picometre (pm) precision measurements of atom positions in aberration-corrected Z-contrast STEM images, more than five times better than previous methods 13,14 , based on NR registration and averaging of an image series. NR registered images of a Pt nanocatalyst show pm-scale contraction of atoms at a (1 11)/( 1 11) corner towards the particle centre and expansion of a (1 11) facet.…”

“…Precision is the statistical spread of repeated distance measurements in an image.) Precision smaller than the resolution is routinely achievable [11][12][13][14] : the best reported precision for TEM and STEM images is 1-3 picometre (pm) (refs 11,12) and 4-5 pm (refs 13,14), respectively. Precision is fundamentally limited by the signal-to-noise ratio (SNR) 15 ; however, in STEM serial acquisition of pixels translates instabilities in the sample and probe positions into displacements of the imaged atoms, limiting precision well above the SNR limit.…”

“…Precision is fundamentally limited by the signal-to-noise ratio (SNR) 15 ; however, in STEM serial acquisition of pixels translates instabilities in the sample and probe positions into displacements of the imaged atoms, limiting precision well above the SNR limit. Averaging many frames can reduce instabilities and increase SNR 11,13 ; however before averaging, the frames must be registered to one another to account for, for example, drift of the sample between frames.…”

Direct observation of charge mediated lattice distortions in complex oxide solid solutions

“…This enables direct identification of light and heavy elements within a structure, even single dopant atoms [10][11][12]. Crystallographic analysis using STEM, however, has been stymied by sample drift and noise that traditionally limit measurement precision to about 5-10 pm [11,13,14]. This challenge hindered the possibility to directly connect complex structural responses to local chemistry.…”