  As the thinnest conductive and elastic material, graphene is expected to play
a crucial role in post-Moore era. Besides applications on electronic devices,
graphene has shown great potential for nano-electromechanical systems. While
interlayer interactions play a key role in modifying the electronic structures
of layered materials, no attention has been given to their impact on
electromechanical properties. Here we report the positive piezoconductive
effect observed in suspended bi- and multi-layer graphene. The effect is highly
layer number dependent and shows the most pronounced response for tri-layer
graphene. The effect, and its dependence on the layer number, can be understood
as resulting from the strain-induced competition between interlayer coupling
and intralayer transport, as confirmed by the numerical calculations based on
the non-equilibrium Green's function method. Our results enrich the
understanding of graphene and point to layer number as a powerful tool for
tuning the electromechanical properties of graphene for future applications.
