Graphene Nanoelectromechanical Systems as Stochastic-Frequency Oscillators

We measure the quality factor <i>Q</i> of electrically driven few-layer graphene drumhead resonators, providing an experimental demonstration that <i>Q</i> ∼ 1/<i>T</i>, where <i>T</i> is the temperature. We develop a model that includes intermodal coupling and tensioned graphene resonators. Because the resonators are atomically thin, out-of-plane fluctuations are large. As a result, <i>Q</i> is mainly determined by stochastic frequency broadening rather than frictional damping, in analogy to nuclear magnetic resonance. This model is in good agreement with experiment. Additionally, at larger drives the resonance line width is enhanced by nonlinear damping, in qualitative agreement with recent theory of damping by radiation of in-plane phonons. Parametric amplification produced by periodic thermal expansion from the ac drive voltage yields an anomalously large line width at the largest drives. Our results contribute toward a general framework for understanding the mechanisms of dissipation and spectral line broadening in atomically thin membrane resonators

Visualizing Electrical Breakdown and ON/OFF States in Electrically Switchable Suspended Graphene Break Junctions

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 voltages of 2.5 to ∼4.5 V, corresponding to an ON pulse, and ∼8 V, corresponding to an OFF pulse. 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

Visualizing Electrical Breakdown and ON/OFF States in Electrically Switchable Suspended Graphene Break Junctions

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 voltages of 2.5 to ∼4.5 V, corresponding to an ON pulse, and ∼8 V, corresponding to an OFF pulse. 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