Strain-Controlled Dynamic Rotation of Twisted 2D Atomic Layers for Tunable Nanomechanical Systems

Achieving fine control over the twist angles of stacked two-dimensional (2D) layers is critical for device fabrication. Here, we demonstrate that the interplay between lattice mismatch strain and flake size can control the potential energy barriers for dynamic untwisting of stacked 2D sheets at elevated temperatures. These energy barriers scale with flake size and originate from periodically fluctuating quantities of unstable AA versus stable Bernal stacking during untwisting. However, the lattice mismatch strains are more readily accommodated coherently across Bernal versus AA stacking, leading to significantly reduced energy differences between these stacking arrangements. These competing effects enable strain-controlled engineering of twisted 2D layers for tunable nanomechanical systems.