Controlling the spatio-temporal dose distribution during STEM imaging by subsampled acquisition: In-situ observations of kinetic processes in liquids

Abstract

Subsampled image acquisition followed by image inpainting in a scanning transmission electron microscope is a novel approach to control dose and increase the image frame rate during experiments, thereby allowing independent control of the spatial and temporal dose envelope during image acquisition. Here, subsampled imaging is shown to permit precise in situ observations of the fundamental kinetic processes behind nucleation and growth of silver (Ag) nanoparticles from an aqueous solution. At high sampling-levels, nanoparticles can be observed with morphologies that are consistent with strong interface interactions, i.e., rafts and pillars, whereas at low sampling-levels, the particles exhibit regular spherical morphologies. The relative numbers of rafts/pillars and regular nanoparticles, their sizes, and their incubation times can be attributed to local changes in the molar concentration of the Ag ions in the aqueous solution; higher sampling-levels significantly increase the reactants in the vicinity of the window, leading to rapid supersaturation and the precipitation on the window surface. These precisely controlled kinetics highlight subsampled imaging as a method by which the driving force for nucleation and growth (i.e., the electron beam) can be disentangled from the spatial/temporal resolution of the observation in all in situ experiments, providing a pathway to identify and quantify the importance of individual kinetic factors behind nucleation and growth in a wide variety of complex materials systems and architectures.

Controlling radiolysis chemistry on the nanoscale in liquid cell scanning transmission electron microscopy

“…For STEM, this means that the deleterious effect of beam radiolysis can be significantly reduced by working at lower magnification or using a sub-sampled imaging approach, e.g. compressed sensing 9 . Using these models, we can predict the distribution of radiolysis products for a range of different illumination and sub-sampling conditions, allowing the beam to be used to create well-controlled reactive environments in the constrained in-situ liquid cells used in (S)TEM.…”

“…In the last decade, liquid cell electron microscopy has emerged as a unique technology for understanding nanoscale structures and processes in liquids or at the liquid/solid interface. [1][2][3][4][5] In particular, in-situ liquid cell (scanning) transmission electron microscopy ((S)TEM), has brought new insights and perspectives into various disciplines; for instance, observation of nucleation and growth [6][7][8][9] , electrochemical reactions 3,[10][11] , and investigation of oxidation states 12 and electronic structure of the electrodes [13][14] . However, despite these significant contributions, liquid cell electron microscopy has several outstanding challenges.…”

Simulation-Trained Sparse Coding for High-Precision Phase Imaging in Low-Dose Electron Holography

“…In many cases, the use of a learned dictionary, instead of predefined ones such as wavelets (Lee, 1996; Mallet, 1999) and curvelets (Candès & Donoho, 1999), can achieve the sparsity effectively, leading to better results of image processing, including image denoising, compression, and inpainting (Olshausen & Field, 1996, 2005; Engan et al, 1999; Aharon et al, 2006; Elad & Aharon, 2006). Hence, sparse coding has been widely applied to electron microscopy, such as scanning electron microscopy (Anderson et al, 2013; Ferroni et al, 2016; Tsiper et al, 2017), electron tomography (Binev et al, 2012; Leary et al, 2013; Deng et al, 2016; Ferroni et al, 2016; Saghi et al, 2016), in situ transmission electron microscopy (Stevens et al, 2015), and scanning transmission electron microscopy (Binev et al, 2012; Stevens et al, 2013, 2018 a , 2018 b ; Kovarik et al, 2016; Mehdi et al, 2019).…”

Minimising damage in high resolution scanning transmission electron microscope images of nanoscale structures and processes

“…This will be particularly important for in situ observations where sub-sampling has already demonstrated control over the kinetics of particular damage mediated nucleation and growth pathways. 20 Fig. 5 (a) An atomic resolution image of Ceria obtained using a 100% sampled 512 × 512 raster scan (b) the same atomic resolution image of Ceria obtained with a 6.25% line-hop sub-sampling (c) the reconstruction of the sub-sampled image shown in part (b) using inpainting algorithms.…”