  In crystalline materials, the creation and modulation of dislocations are
often associated with plastic deformation and energy dissipation. Here we
report a study on the energy dissipation of a trilayer graphene ribbon
resonator. The vibration of the ribbon generates cyclic mechanical loading to
the graphene ribbon, during which mechanical energy is dissipated as heat.
Measuring the quality factor of the graphene resonator provides a way to
evaluate the energy dissipation. The graphene ribbon is integrated with silicon
micro actuators, allowing its in-plane tension to be finely tuned. As we
gradually increased the tension, we observed, in addition to the well-known
resonance frequency increase, a large change in the energy dissipation. We
propose that the dominating energy dissipation mechanism shifts over three
regions. With small applied tension, the graphene is in elastic region, and the
major energy dissipation is through graphene edge folding; as the tension
increases, dislocations start to develop in the sample to gradually dominate
the energy dissipation; finally, at large enough tension, graphene layers
become decoupled and start to slide and cause friction, which induces the more
severe energy dissipation. The generation and modulation of dislocations are
modeled by molecular dynamics calculation and a method to count the energy loss
is proposed and compared to the experiment.
