The
creation and movement of dislocations determine the nonlinear
mechanics of materials. At the nanoscale, the number of dislocations
in structures become countable, and even single defects impact material
properties. While the impact of solitons on electronic properties
is well studied, the impact of solitons on mechanics is less understood.
In this study, we construct nanoelectromechanical drumhead resonators
from Bernal stacked bilayer graphene and observe stochastic jumps
in frequency. Similar frequency jumps occur in few-layer but not twisted
bilayer or monolayer graphene. Using atomistic simulations, we show
that the measured shifts are a result of changes in stress due to
the creation and annihilation of individual solitons. We develop a
simple model relating the magnitude of the stress induced by soliton
dynamics across length scales, ranging from <0.01 N/m for the measured
5 μm diameter to ∼1.2 N/m for the 38.7 nm simulations.
These results demonstrate the sensitivity of 2D resonators are sufficient
to probe the nonlinear mechanics of single dislocations in an atomic
membrane and provide a model to understand the interfacial mechanics
of different kinds of van der Waals structures under stress, which
is important to many emerging applications such as engineering quantum
states through electromechanical manipulation and mechanical devices
like highly tunable nanoelectromechanical systems, stretchable electronics,
and origami nanomachines.
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