Research On The Initial Tension Of Graphene NEMS Resonator Based On Molecular Dynamics

As a typical nanoelectromechanical systems(NEMS) device, the NEMS resonator has been used in the field of sensor, accelerometer, high frequency signal processing and communication, etc. Due to the existence of the thermal mismatch in processing technic, the lattice mismatch in crystal growth, and other defects such as evaporation and sputtering, a certain initial tension will be produced in the resonant beam. Because of its excellent mechanical and electrical properties, graphene becomes an ideal material for producing NEMS resonator. The initial tension has a great impact on the graphene NEMS resonator. In this thesis, series of numerical simulations were carried out to investigate the factors that affect the initial tension of the graphene resonant beam through molecular dynamics(MD). The main work is introduced as follows:Firstly, a briefly introduction of NEMS, graphene and the research actuality of graphene resonator was given in this thesis, as well as the relevant theory of NEMS resonator, including the principle of operation and incentives. Then the modeling method of resonant beams and the calculation method of stress were also presented.Secondly, the definition and basic principle of MD was introduced along with the explanation of corresponding initial conditions including initial value, time step, ensemble, boundary conditions and interaction potential functions. Meanwhile the initial conditions utilized in our simulations were described briefly in this part.Then, the models of GNR were built and a lot of MD simulations were carried out to investigate the effects of the aspect ratio of GNR, the temperature and pressure of simulation system on the initial tension of the double-clamped GNR through the analysis of their relaxation process. It was shown that the effect of the aspect ratio of the GNR and system temperature on initial tension is relatively large, while the effect of the pressure is small.Finally, the effect of substrate on the initial tension of GNR was also investigated through MD method. The influence of the initial distance between the graphene and substrate on the initial tension was studied by establishing Si O2 substrate models. In addition, in order to investigate the influence of different metal substrates on the initial tension of the free-standing graphene, the Cu, Au and Ni substrates were established with the same size The results indicated that the initial distance has great influence on the initial tension of GNR; the initial tension of the graphene on metal substrate is very small, and the substrate material has a little impact on the initial tension.In this thesis, the factors affecting the initial tension of the graphene resonant beam were explored through MD method, which might give some theoretical reference to improve the mechanical properties of the graphene NEMS resonator, and provide theoretical basis and data support in the following related experimental research.