Graphene Enhanced Ultra-high Frequency Piezoelectric Nanoelectromechanical Systems
Micro and nano-electromechanical systems (MEMS and NEMS) are key drivers behind a number of advanced applications such as radio frequency (RF) wireless communications, single-molecule detection, switches, infrared-imaging, magnetometers, and chemical sensors. Many of these are driven by on-chip piezoelectric actuation and sensing of ultra-high frequency (UHF) vibration in miniaturized free-standing micro and nano mechanical structures thanks to their unique advantages of extremely high sensitivity to external perturbations and ultra-low noise performance. In this context, designing “ideal electrodes” that simultaneously guarantee low mechanical damping and electrical loss as well as high electromechanical coupling in such ultralow-volume piezoelectric nanomechanical structures is a key challenge. In this talk, I will show that mechanically transferred graphene, floating at van der Waals proximity, can closely mimic “ideal electrodes” for UHF piezoelectric nanoelectromechanical resonators with negligible mechanical mass and interfacial strain and perfect electric field confinement. These unique attributes enable graphene-electrode-based piezoelectric nanoelectromechanical resonators to operate at their theoretically “unloaded” frequency-limits with significantly improved electromechanical performance compared to metal-electrode counterparts, despite their reduced volumes. This represents a spectacular trend inversion in the scaling of piezoelectric electromechanical resonators, opening up new possibilities for the implementation of NEMS with unprecedented performance. Furthermore, the transparent and chemically active natures of the atomically-thin graphene electrode enable unique IR detection and chemical sensing capabilities of such graphene enhanced nanomechanical resonators, making them a promising candidate for the development of both high resolution resonant IR detectors and chemical sensors.