Investigation of mechanical properties of graphene on silicon wafers
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Graphene is an atomically thin two-dimensional crystalline material with very low mass, high Young’s modulus, high elastic strength, high optical transparency, high-electron mobility, high thermal conductivity and high degree of biocompatibility. Due to these extraordinary properties, graphene has many promising applications. Graphene can be synthesized in vastly different ways, for example by chemical vapour deposition and micromechanical exfoliation. However, the invariably poor graphene/substrate adhesion energy is a major drawback for ensuring the reliability, stability and longevity of sensors and other micro- and nano-mechanical devices, precluding us from achieving semiconductor technology requirements and rendering manufacturing efforts futile. Therefore, synthesising wafer level graphene that has sufficient quality and adhesion with the substrate is still an open and critical research problem. To address these issues, we have demonstrated for the first time a fivefold improvement in adhesion between graphene and its underlying substrate, using a transfer-free, catalytic alloy approach for synthesising a monolayer of graphene on silicon carbide on silicon. An interfacial adhesion energy of 5.7 J/m² between graphene and silicon carbide is found using double cantilever beam testing, as compared to 1.02 J/m² reported for transferred graphene on silicon dioxide. As the obtained adhesion energy is a good starting point for achieving reliable resonant sensors, we have fabricated and evaluated graphene coated silicon carbide membranes, showing quality factor (𝒬) as high as 2.7x10⁴. We have also investigated the influence of graphene coating on the quality factor of the silicon carbide membrane resonators and reported a significant reduction in damping when a graphene overlayer is present on silicon carbide membranes instead of a conventional metal layer.
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