  Graphene-based electromechanical resonators have attracted much interest
recently because of the outstanding mechanical and electrical properties of
graphene and their various applications. However, the coupling between
mechanical motion and charge transport has not been explored in graphene. Here,
we studied the mechanical properties of a suspended 50-nm-wide graphene
nanoribbon, which also acts as a single-electron transistor (SET) at low
temperature. Using the SET as a sensitive detector, we found that the resonance
frequency could be tuned from 82 MHz to 100 MHz and the quality factor exceeded
30000. The strong charge-mechanical coupling was demonstrated by observing the
SET induced ~140 kHz resonance frequency shifts and mechanical damping. We also
found that the SET can enhance the nonlinearity of the resonator. Our
SET-coupled graphene mechanical resonator could approach an ultra-sensitive
mass resolution of ~0.55*10^(-21) g and a force sensitivity of ~1.9*10^(-19)
N/(Hz)^(1/2), and can be further improved. These properties indicate that our
device is a good platform both for fundamental physical studies and potential
applications.
