High-precision scanning transmission electron microscopy at coarse pixel sampling for reduced electron dose

Abstract

Determining the precise atomic structure of materials' surfaces, defects, and interfaces is important to help provide the connection between structure and important materials' properties. Modern scanning transmission electron microscopy (STEM) techniques now allow for atomic resolution STEM images to have down to sub-picometer precision in locating positions of atoms, but these high-precision techniques generally require large electron doses, making them less useful for beam-sensitive materials. Here, we show that 1-to 2-pm image precision is possible by non-rigidly registering and averaging a high-angle dark field image series of a 5-to 6-nm Au nanoparticle even though a very coarsely sampled image and decreased exposure time was used to minimize the electron dose. These imaging conditions minimize the damage to the nanoparticle and capture the whole nanoparticle in the same image. The high-precision STEM image reveals bond length contraction around the entire nanoparticle surface, and no bond length variation along a twin boundary that separates the nanoparticle into two grains. Surface atoms at the edges and corners exhibit larger bond length contraction than atoms near the center of surface facets.

Strain mapping accuracy improvement using super‐resolution techniques

“…Correcting image distortions using a series of images from the same object has been tackled by Recnik et al (2005) who introduced the IMAGE-WARP method; more recently Sang & LeBeau (2014) have developed the revolving STEM method, RevSTM, to remove drift distortion by acquiring a series of images and rotating the scan coordinate system between successive frames. Other proposals use registering algorithms to obtain a final averaged image with the same pixel density from a series of images (Saito, 2009;Kimoto et al, 2010;Yankovich, 2015), whereas restoration using nonlocal means (NLM) has been proposed by Binev et al (2012) and Mevenkamp et al (2014).…”

Achieve atomic resolution in in situ S/TEM experiments to examine complex interface structures in nanomaterials

“…when focusing on low voltage investigation [83,136,137]. At the same time, there is ongoing progress in enhancing S/N and contrast in atomic scale images while lowering electron dose (rates), such as drift corrected frame averaging [169], NCSI [61], in-line holography [12,55,63], integrated differential phase contrast (iDPC) [88], ptychography [122], supported by simultaneous development of innovative detection schemes and systems [13,50,117,122,151]. For instance, Steven et al [146] propose the application of a compressive sensing (CS) algorithm to increase frame rate recording in TEM videos.…”

Control of Knock-On Damage for 3D Atomic Scale Quantification of Nanostructures: Making Every Electron Count in Scanning Transmission Electron Microscopy

“…Using this analytical expression, the optimal dose has been computed for different combinations of adatoms on a substrate and microscope settings as shown in Table I. These predicted values can be compared against the experimental imaging conditions used in state-of-the-art STEM experiments where the atomic structure of Pt [31] and Au [32] nanoparticles has been characterised and where single N atoms on graphene have been detected [33]. This comparison suggests the possibility to reduce the electron dose by a factor of approximately 100, thus significantly decreasing the probability for beam-induced surface diffusion, σ sd d optimal .…”