Preparation Of Graphene Based On Sapphire Substrate By Chemical Vapor Deposition

Graphene is a two-dimensional material composed by a single layer or several layers of carbon atoms,due to its excellent optical and thermodynamic,electrical performance,make it become a new hotspot in the research of the current material.So far,there are many methods for the preparation of graphene,mainly includes the mechanical exfoliation,oxidation-reduction,chemical vapor deposition,and so on.Graphene is widely used in field effect transistors,sensors,supercapacitors and metal matrix composites,and other fields.But the research of growing graphene on the insulating substrate is relatively few,which led to limit the applications of graphene in many fields.In this paper,chemical vapor deposition method is applied to grow graphene.Using CH₄ as the carbon source gas,H₂ as the reaction gas,Ar as the carrier gas,and the growth of graphene was studied on sapphire substrate surface under different growth conditions,meantime simulation studies H₂ etching on the surface of the sapphire substrate.The main research content is as follows:The growth of graphene on sapphire substrate surface was studied under different growth temperature of 1050?to 1300?.The results show that,when the temperature is under 1100?,there is no graphene.And when the temperature exceeds 1100?,with the increase of growth temperature,I_D/I_G reduces from 2.85 to0.85,I_2D/I_G increases from 0.06 to 0.58,which shows that the growth of the graphene quality is getting better and better.The growth of graphene on sapphire substrate surface was studied under different growth time of 10 min to 30 min.The results show that,with the increase of growth time,I_2D/I_G reduces from 0.56 to 0.42,contact Angle increases from 81.68°to129.96°,shows that growth of graphene layers is increasing,hydrophobic performance is also enhancing.The growth of graphene on sapphire substrate surface was studied under different CH₄ flow of 4sccm to 8 sccm.The results show that,when CH₄ flow is 4sccm,contact angle of the samples is similar to sapphire substrate,and Raman spectra shows that there is not growth of the graphene;when CH₄ flow is 4 sccm,Raman spectrum can be found that a better quality graphene is prepared.When CH₄ flow increase to 8 sccm,contact angle of samples is very high,from Raman spectra,we can know it is likely to generate the amorphous carbon or graphite flake.Simulation H₂ of etching the surface of the sapphire substrate was studied,and the results show that H₂ decomposes into H atoms which can capture O in the substrate and make O atoms escape from the surface of Al atoms restriction and taken away.At the same time,the effect of etching time of H₂ on the etching of sapphire substrate was also investigated by the experiment,and it was found that,with the increasing of etching time,etching condition was worse.At the same time,the effect of etching time of H₂ on the etching of sapphire substrate was also investigated by experimental research.