  Narrow gaps are formed in suspended single to few layer graphene devices
using a pulsed electrical breakdown technique. The conductance of the resulting
devices can be programmed by the application of voltage pulses, with a voltage
of 2.5V~4.5V corresponding to an ON pulse and voltages ~8V corresponding to OFF
pulses. Electron microscope imaging of the devices shows that the graphene
sheets typically remain suspended and that the device conductance tends to zero
when the observed gap is large. The switching rate is strongly temperature
dependent, which rules out a purely electromechanical switching mechanism. This
observed switching in suspended graphene devices strongly suggests a switching
mechanism via atomic movement and/or chemical rearrangement, and underscores
the potential of all-carbon devices for integration with graphene electronics.
