Simulation And Experiment On Graphene Based Pressure Sensor And Resonator

Graphene is an ideal material for nanoelectromechanical systems(NEMS) due to its exceptional mechanical and electrical properties such as one atom thick, high carrier mobility and high Young's modulus. Recently, graphene based nano devices including pressure sensor and resonator become research hotspots, and these devices have some advantages including nanoscale, high sensitivity and high resonance frequency. In this paper, theoretical modeling, finite element simulation and experimental study for these devices are carried out, which provide strongly theoretical and experimental foundations for further design and fabrication of graphene pressure sensor and resonator. The main work in this paper is as follows:First, the nanomechanics of graphene membrane is researched using theoretical and finite element modeling, including the deflection, stress and strain of graphene membrane under surface pressure or point load. The effects of graphene size, material property and boundary conditions on the nanomechanics are further explored. Also, energy dispersion, Fermi velocity and guage factor of graphene are investigated using tight binding model, and the influence of strain on energy dispersion and Fermi velocity is also studied, respectively.Second, the vibration properties of graphene resonators with various shapes are studied. The dependences of vibration properties on graphene dimensions, built-in tension, material parameters and boundary conditions are further explored. Especially, the vibrational properties of electrostatically driven and doubly clamped graphene resonator are investigated using theoretical and finite element modeling. In addition, graphene resonator for the detection of tiny mass is modeled by theoretically expression and finite element. The simulation result shows that the resolution of graphene mass sensor can reach 10-22 g. The effects of attached mass location, graphene dimensions, boundary condition and built-in tension on the sensitivity and resolution of mass sensor are investigated in detail.Next, a novel resonant graphene pressure sensor is proposed. The theoretically and finite element calculation results show that its sensitivity is bigger than that of conventional resonant pressure sensors by two orders of magnitude. The influences of graphene dimensions, pressure membrane dimensions, built-in strain and temperature variation on the sensitivity are also demonstrated.Finally, piezoresistive graphene pressure sensor is fabricated using micromachining technology. Optical microscope, Raman spectrometer and scanning electron microscope(SEM) are used to characterize the pressure sensor.