Realization of Closed Cavity Resonator Formed by Graphene-PMMA Membrane for Sensing Audio Frequency

Large area graphene-poly (methyl methacrylate) (PMMA) closed cavity resonator has been fabricated. The resonator has been formed by transferring an ultra-large graphene-PMMA membrane over 3.5 mm diameter circular closed cavity with 220 μm depth. The graphene-PMMA membrane includes 6-layer graphene and 450 nm PMMA film. A modified graphene-PMMA dry transfer method has been developed in this work. Using the Kapton tape supporting frame, the graphene-PMMA membrane has been dry transferred onto the substrate with a small membrane's static deformation of around 180 nm. The membrane's static deformation aspect ratio (suspended membrane's diameter over the membrane's deformation) is around 19,500. The graphene-PMMA closed cavity resonator has been actuated mechanically, acoustically and electro-thermally. The dynamic behaviour of the membrane suspended over the closed cavity shows that the (1, 1) mode dominates the graphene-PMMA membrane's resonance with a resonant frequency of around 10 kHz and suggests the device is under good gas encapsulation. Acoustic vibration amplitude sensitivity of graphene-PMMA membrane over the closed cavity is measured to be around 6 μm/Pa. The membrane's dynamic behaviour, simulated under similar mechanical and electro-thermal actuation conditions, has been shown to be consistent with the trend of the device's experimental results. The strain in the suspended graphene-PMMA membrane is estimated to be 0.04 ± 0.01 %.