We report the effect of electrical current on the defects and microstructures from monolayer MoS2 to 100 nm palladium. The electrons move through the lattice but collide with defects and grain boundaries and lose the momentum. This provides a mechanical, electron ‚Äòwind force‚Äô that is highly localized to defects. The experiments are performed inside transmission electron microscope (in-situ TEM) so that we can directly visualize the migration of defects and interfaces.

In two-dimensional (2D) materials, we observe significant annealing effects. Experimental results show 5 times enhancement in electrical conductivity, which is supported by electron diffraction patterns indicating significant grain growth. Discrete spots in diffraction indicate evolution of high crystallinity even at room temperature. Our computational model shows the mechanisms behind healing lattice defects as well as reorienting the grain boundaries. Similar effects are also seen in 100 nm thick metal films. Here, the electron wind force interacts with the pre-existing defects to create very high density of Shockley partial dislocations. Shockley partials are extremely mobile and highly reactive to other defect species, which may obviate high temperature. Intriguingly, this imparts very high density of twins and high angle grain boundaries. The resultant microstructure has increased strength and without any loss in toughness, which are typically mutually exclusive.  


Moving Atomic Defects & Interfaces with the Electron Wind Force

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