Design of a MEMS-based tunable graphene resonator with precision strain and force metrology
Made of only on sheet of carbon atoms, graphene is the thinnest yet strongest material ever exist. Since its discovery in 2004, graphene have attracted tremendous research effort worldwide. Guaranteed by the superior electrical and excellent mechanical properties, graphene is the ideal building block for Nanoelectromechanical System (NEMS). However, one of the major challenges in producing highly accurate graphene-based nanoelectromechanical (NEMS) resonators is the poor fabrication repeatability of graphene-based NEMS devices due to small variations in the residual stress and initial tension of the graphene film. This has meant that graphene-based nanoelectromechanical resonators tend to have large variations in natural frequency and quality factor from device to device. However, by actively controlling the tension on the graphene resonator it is possible both to increase repeatability between devices and to increase the force/mass sensitivity of the nanoelectromechanical resonators produced. Such tension control makes it possible to produce electrometrical filters that can be precisely tuned over a frequency range of up to several orders-of-magnitude. In order to controllably strain the graphene resonator, a microelectromechanical system (MEMS) is designed and used to apply tension to the graphene. The MEMS device consists of a graphene resonator, electro-thermal actuator and two differential capacitive sensors. Using this setup, it is not only possible to tune the natural frequency of the graphene resonator, but also possible to perform high precision force and strain metrology on graphene beam. In addition to designing devices that can compensate for manufacturing errors in nanomanufactured devices, this thesis will present several methods that can greatly expand the scope and rate at which nanomaterials-based devices can be fabricated.