Optimized fabrication and detection of nanomechanical resonators based on graphene membranes

Nanomechanical resonators based on two-dimensional materials offer opportunities to study the mechanical properties of atomically thin membranes and to develop sensitive detection schemes. However, these applications are limited by problems with nanofabrication. In addition, graphene is a pure surface that is sensitive to contamination. It is challenging to keep graphene clean during fabrication. Here we present our graphene resonator fabrication process. We control the geometry of the cavity over which graphene is suspended to prevent the membrane from collapsing. Then we minimize the occurrence of fabrication residues on the supporting substrate and optimize the cleanliness and flatness of the interface between graphene and electrodes used for electrostatic actuation. After optimizing the fabrication of the graphene resonator, we measure the frequency response of our resonators using an optical interferometry setup. We control the resonant frequency of vibrational modes by applying a dc voltage between the membrane and an electrode patterned at the bottom of the cavity and verify that the response of our resonators is tunable over a wide frequency range.