| Graphene is a carbonaceous two-dimensional material composed of single-layered carbon atoms arranged in a hexagonal lattice.It possesses many unique physicochemical properties,and has great application prospects in semiconductor devices,optoelectronic devices,capacitors,and energy reserves.Growth of graphene by chemical vapor deposition(CVD)involves many process parameters.How to prepare large-scale,high-quality graphene on a large scale by optimizing the process parameters of CVD growth of graphene is an urgent problem to be solved.With the increase of computing capabilities of computers,the growth of thin films under complex process parameters can be simulated by computer modeling,and finally the optimal process parameters for thin film growth can be obtained,thereby guiding industrial production.kinetic Monte Carlo method(KMC)is a method that combines Monte Carlo(MC)and molecular dynamics theory.Its algorithm structure is clear and simple,and it is particularly suitable for simulating the motion process of large-scale particles.In this paper,a KMC model of graphene growth on a copper substrate is established,and the growth of graphene on Cu(111)surface is simulated under different conditions of temperature,pressure,and methane/hydrogen ratio.In order to establish a KMC reaction event model of graphene growth,the growth kinetics of graphene on the Cu(111)surface was studied by first-principles calculations in this paper and find the energy required for the dehydrogenation of methane was higher.Therefore,the carbon atoms mainly participate in the growth of graphene as CHx groups;Secondly,the stable structure of carbon polymers on the Cu(111)surface is a chain-like arch structure,and the carbon ring can be stably present on the Cu(111)surface.Therefore,the growth of graphene is mainly determined by the combination of carbon ring and carbon atom,and between carbon ring and carbocyclic ring;The close proximity of carbon atoms will cause the deformation of the Cu substrate near the surface,forming a C-Cu-C chain,so that the polymerization between carbon atoms has a certain energy barrier.Finally,the Cu(111)surface lattice model is established.The [0001] crystal orientation is used as the z-axis,the [2001] crystal orientation is used as the x-axis,and the [1210] crystal orientation is used as the y-axis to establish a rectangular coordinate system;The KMC model of graphene grown by CVD on a copper substrate was established by using the graphene growth kinetics process on the Cu(111)surface as the reaction event model.The growth of graphene on the Cu(111)surface was simulated at different temperatures,pressures and methane/hydrogen ratios.The simulation results show that:(1)graphene growth is achieved through the coalescence,nucleation and aggregation of carbon atoms.The carbon atoms first aggregate into carbon clusters,and then continue to adsorb carbon atoms to form graphene sheets.As the growth time advances,the graphene sheets continue to expand,gaps between the graphene sheets are continuously filled with carbon atoms,and a complete film is eventually formed;(2)High temperature can increase the growth rate of graphene,and reduce the nucleation density,promoting the quality of graphene to a certain extent,and the number of defects on the surface of graphene first decreases with temperature and then rises.Therefore,a large area of single crystal graphene can be obtained at 1290 K.(3)High pressure will increase the growth rate of graphene and promote the diffusion of carbon atoms,making the surface morphology of graphene become irregular,while graphene has a regular hexagonal shape at low pressure.(4)The higher CH4:H2 dominates the deposition and diffusion of the lower carbon atoms.At this time,the growth rate of graphene is faster,the diffusion of carbon atoms is enhanced,and the graphene easily forms a large area of irregular leaf-like shapes.When CH4:H2 is low,the etching effect of H2 dominates,and the graphene morphology presents a regular hexagonal shape. |
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