Circular Electromechanical Resonators Based On Hexagonal-Boron Nitride-Graphene Heterostructures

2D materials such as graphene and hexagonal-boron nitride (h-BN), to name a few, when layered on top of each other offer a class of metamaterials with interesting properties. For example, the twisting degree of freedom between two layers has started the field of twistronics. The exceptional attributes of 2D materials like ultra-low mass, robustness, and high tunability make them very suitable for nanoelectromechanical systems (NEMS). Yet the mechanical properties of these heterostructures in the form of NEMS have not been studied extensively. Such 2D NEMS hold promise for various technological applications, namely, ultrafast sensors, actuators, etc. We report fabrication and characterization of h-BN graphene heterostructure-based circular nanoelectromechanical resonators on sapphire substrates. The devices are measured at cryogenic temperatures and exhibit multiple mode frequencies, which are highly tunable with gate voltage. A continuum mechanics model is employed to analyze the transmission (S-21) data of the fundamental mode. Parameters like built-in tension obtained from the fit are used to identify the indices (m, n) of higher mechanical modes observed for the device, providing further device characterization. Such 2D NEMS could offer a way to study diverse electronic phenomena such as superconductivity in twisted bilayer graphene (tBLG) heterostructures.