Scanning electron microscopy. A FEI Helios NanoLab 660 instrument equipped with a STEM III detector and the capacity to fit up to four micromanipulators (Kleindiek MM3A) inside the chamber was used for SEM imaging and in situ manipulation of dislocations. For manipulation experiments 2 or 3, MM3A manipulators were attached to the door of the microscope. The manipulators were equipped with commercial W tips (apex size of ca. 100 nm) or with focused ion beam–milled fine tips with apex sizes of ca. 25 nm. The microscope was operated at 20 kV in immersion mode. For tSEM imaging, the segmented STEM detector was read out according to the optimized contrast, as shown in fig. S2.

Transmission electron microscopy. A double-corrected FEI Titan Themis3 300 electron microscope was used for DF-TEM and aberration-corrected HRTEM. The microscope was operated at 80 kV to reduce knock-on damage. For HRTEM, the monochromator was excited to reduce chromatic aberration and thus enhance resolution. Micrographs were recorded on a FEI Ceta camera.