Local and transient nanoscale strain mapping during in situ deformation

Abstract

The mobility of defects such as dislocations controls the mechanical properties of metals. This mobility is determined both by the characteristics of the defect and the material, as well as the local stress and strain applied to the defect. Therefore, the knowledge of the stress and strain during deformation at the scale of defects is important for understanding fundamental deformation mechanisms. Here, we demonstrate a method of measuring local stresses and strains during continuous in situ deformation with a resolution of a few nanometers using nanodiffraction strain mapping. Our results demonstrate how large multidimensional data sets captured with high speed electron detectors can be analyzed in multiple ways after an in situ TEM experiment, opening the door for true multimodal analysis from a single electron scattering experiment.

Imaging Beam‐Sensitive Materials by Electron Microscopy

“…As a special type of segmented detectors, pixelated detectors provide an ultimate detector form for STEM imaging that incorporates the full range of reciprocal space information. Such detectors enable a versatile 4D‐STEM imaging mode, which is comprised of full diffraction (i.e., CBED) patterns, containing important information on the crystal structure,272 chemical composition,273 electric fields,274 defects/disorder,275 and strains,276–278 etc., for each probe position ( Figure ) 267,279,280…”

Functional Materials Under Stress: In Situ TEM Observations of Structural Evolution

“…Direct electron detector (DED) cameras can operate at thousands of frames per second, enabling time-resolved in-situ 4D-STEM experiments [46][47][48][49][50][51] , from which multi-modal characterization can be extracted from a single experimental dataset. Examples include orientation mapping [44,45] , strain evolution [52,53] , and local structural ordering [50] . As in-situ nanomechanical testing is usually conducted irreversibly, the multi-channel nature of 4D-STEM is essential to capture more of the information during dynamic processes.…”

4D-Data Acquisition in Scanning Confocal Electron Microscopy for Depth-Sectioned Imaging

“…4D-STEM can deliver much more structural information [1,2] than conventional STEM where only integrated electron intensities are acquired. The 4D dataset of CBED patterns can be utilized for structural analysis such as ptychographic reconstruction [3][4][5][6][7][8][9], strain mapping [10][11][12], electric and magnetic fields imaging using differential phase contrast [13,14], and composition and thickness measurements [15] with position-averaged CBED (PACBED) [16].…”