Abstract

Bilayer graphene is a promising material to explore the physics of two-dimensional Nanoelectromechanical Systems (NEMS) due to its mechanical strength and low-onset nonlinearity. We describe a procedure to fabricate and anneal bilayer graphene NEMS (BG-NEMS) which are nearly disorder free (charge mobility μ ≈ 76000 cm2/V s, charge doping n0 < 6.6 × 10−9 cm−2, mass density ρ ≈ 1.01 ρgraphene).
We calibrate a current mixing measurement circuit for simultaneous resonance actuation, resonance detection, and conductivity measurement in annealed BG-NEMS. Using our circuit, we detect high-quality and reproducible BG-NEMS resonances with frequencies in the range f0 = 137MHz to f0 = 220MHz and quality factors of Q > 3000 at amplitudes between δz = 50 pm and δz = 1 nm.
Our data show significant Duffing nonlinearity (α ≈ −1.0 × 1035 Hz2/m2). When the resonators are strained, we observe anomalous frequency tuning. At higher powers our data show mode mixing with high cooperativity (C ≈ 4 and C ≈ 36). The mode mixing (α12 ≈ 6.9 × 1033 Hz2/m2 and α12 = 3.3×1036 Hz2/m2) matches the Duffing parameter and suppresses mobility (low μ) and electromechanical dissipation (high Q).
Disordered morphology of the samples accounts for decreased mobility (lattice disorder associated with ripples and wrinkles), mode mixing (nonlinear mode coupling to ripples), and anomalous membrane dispersion (catenary wrinkle deformation).