Zeptogram Level Mass Sensing of Light Weight Gas Molecules Using Graphene Nanomechanical (GNEM) Resonator

In this work, we present zeptogram level mass sensing of Hydrogen and Argon mixture gas using top-gated graphene resonator. Monolayer chemical vapor deposition graphene was used to fabricate 1μm length and 500 nm width resonator along with co-planner waveguide for RF measurements. The resonant frequency of doubly clamped graphene resonator was measured to be 95.5 MHz in the vacuum condition of the chamber, which is consistent with the theoretical calculation based on continuum model. With the increase in the chamber pressure by injecting Hydrogen and Argon mixture gas, the resonant frequency of the resonator down shifted continuously along with the resonator Q factor degradation. This is attributed to the increase in the number adsorped molecules onto the resonator. We measured the increase in mass of ~886 zeptogram when the pressure level is changed from 5.6×10
^-3
Pa to 6.2×10
^-3
Pa. Binding energy of graphene-Ar and H
₂
molecules was calculated to be 0.141 and 0.287 eV, respectively, based on the first-principles simulation with van der Waals (vdW) correction. These measurement and simulation results clearly indicate the possibility of using graphene nanomechanical resonator for light weight molecules mass spectrometry applications.