Molecular Dynamics Study Of Nanoelectromechanical Resonator Based On Graphene With Defects

Graphene has excellent mechanical,electrical and thermal properties and it is an ideal material for micro-nano devices.The graphene-based nanoresonators with low power consumption,high sensitivity,and high mechanical resonance frequency have wide application prospects in sensors,signal generator,signal processing and other fields.However,due to the limitations of the manufacturing technology,the obtained graphene actually contains a large number of defects,and these defects will have a certain influence on the macroscopic properties of the graphene.At present,there is little report on how the defects affect the resonance characteristics of the graphene.In this paper,the nanoelectromechanical resonators based on defective graphene has been studied via molecular dynamics method and this provides the necessary theoretical basis for design and performance optimization of graphene nanoresonators.This paper mainly includes the following contents:1.Based on the electrostatically-actuated principle of nano-electromechanical resonator and the structural characteristics of graphene,a graphene-based nanoresonator model is established.The resonant characteristics are analyzed by using molecular dynamics software LAMMPS.The resonant frequency variation characteristics of defect-free graphene under different external forces are analyzed.The results show that the resonant frequency of perfect graphene exhibits a non-linear increasing trend with the external force.When the external force is between 10.715 n N and 29.765 n N,the resonant frequency is 469 GHz.2.The graphene nanoribbon model with vacancy defects in different positions,sizes and concentrations was established.The molecular dynamics method was used to simulate the vibration process of graphene under external force.The results show that:(1)A single atomic vacancy has no effect on the resonance frequency of graphene.(2)The resonance frequency of graphene decreases with the increase of vacancy defect concentration.When the concentration is 5%,its resonant frequency decreases by 12.77%.(3)Large vacancy defects,ie holes,reduce the graphene resonance frequency.The closer the holes are to the fixed ends of the graphene,the lower the frequency is.3.A graphene nanoribbon containing different atomic mass,position and concentration for adsorption of atomic defects was analyzed.The results show that the adsorption atom causes the decrease of graphene resonance frequency.The resonance frequency decreases with the mass and concentration of the adsorbent.The resonant frequency shows a decreasing trend as the distance from the adsorption site to the graphene center decreases.4.The graphene nanoribbon models with different positions and numbers of 5-5-8 grain boundaries are established.The results show that:(1)The presence of grain boundaries make the resonant frequency of graphene decrease.(2)The grain boundary position has little effect on the resonance frequency of graphene.(3)The graphene resonance frequency shows a decreasing trend with the increase of the number of grain boundaries.5.The frequency response characteristics of bilayer graphene under different external forces are analyzed.The results show that the resonant frequency of double-layer graphene is higher than that of single-layer graphene under the same external force,and the difference between the two gradually increase as the external force increases.