High frequency graphene nanomechanical resonators and transducers

This digest paper presents our initial explorations of engineering graphene 2D nanostructures into nanomechanical resonators and transducers vibrating at high frequencies (i.e., ~1-30MHz, in the HF band in radio frequency spectrum) at T ~300K. We explore very small graphene devices that are suspended over micrometer-scale trenches or cavities and are free to vibrate in out-of-plane modes. The devices are derived from single- or few-layer graphene flakes and membranes, made by either mechanical exfoliation of graphite, or transfer of monolayer graphene grown on polycrystalline copper (Cu) by a chemical vapor deposition (CVD) process. We report measured resonance characteristics from our typical exfoliated single- and bi-layer graphene resonators of ~1-5μm in size, with resonance frequency (f) in the ~10-20MHz range, and measured quality (Q) factors of ~800-1200. From a transferred CVD graphene membrane device of ~10μm in size, we have measured a nanomechanical resonance at f≈2.39MHz, with Q≈350. We further explore the potentials of these resonators for enabling sensitive transducers, by evaluating their sensitivities for detecting small displacements, forces, and mass loading effects. Moreover, in this study we have clearly identified and analyzed the striking discrepancies in the measurements and interpretations of both resonance frequency and strain from recently reported studies. Our analyses of these issues help find solutions toward gaining meaningful understandings that will be applicable to future designs and development of graphene nanomechanical devices.