Study On The Preparation Of Graphene On The Surface Of SiO₂/Si Substrate And Dendritic Copper Powder By Chemical Vapor Deposition

Graphene,as a kind of two dimensional nano-material,has quite broad application prospects in materials,biology and electronics because of its excellent mechanical properties as well as thermal conductivity.There are multiple methods to fabricate graphene such as mechanical stripping method,redox method,silicon carbide epitaxy method and chemical vapor deposition method?CVD?.The chemical vapor deposition,which contains good controllability and scalability,is considered to be the most effective method for preparing high quality graphene among these methods.Growing graphene by chemical vapor deposition mainly uses metal substrates,insulating substrates,or non-planar substrates.Metal substrates are widely used because they have high catalytic activity and can produce large-area,high-quality graphene.However,graphene grown on metal substrates needs to be transferred to an insulating substrate for assembly of electronic devices.The transfer process will cause defects of graphene and increase the cost of the experiment.If fabricating graphene on an insulating substrate,it can be directly used to prepare electronic devices,which will greatly promote the application of graphene.In addition,other existing methods for preparing graphene on non-planar copper powders,such as mechanical ball-milling and solution blending,also have a lot of defects:excessive graphene layer,easy agglomeration,poor dispersion uniformity.All these defects will make the electrical properties and elongation of copper-based graphene composite materials dropped significantly.However,the chemical vapor deposition method can solve the problem of uniform dispersion of graphene on copper powder substrate.Based on this,in order to solve this problem,we present a preparation method of graphene on the insulating substrate SiO₂/Si and on the non-planar base dendritic copper powder by chemical vapor deposition.Firstly,this thesis studies the effects of the growth temperature,growth time,carbon source concentration and other parameters on the preparation of graphene by chemical vapor deposition on SiO₂/Si substrate.Under the catalytic effect of gaseous copper atoms,single-layer graphene was prepared on the insulating substrate SiO₂/Si when adapting the parameter following a growth temperature of 1100°C,a hydrogen flow rate of 100 sccm,a CH₄ flow rate of 6 sccm,and a reaction time of 60 min.Graphene was characterized by Raman spectra,atomic force microscopy?AFM?and scanning electron microscopy?SEM?.The results show that the fabricated graphene possesses high quality.The resistance and transmittance of thin layer graphene were tested by four-probe and spectrophotometer.The resistance and the transmittance of thin layer graphene is 920?/sq and 97.6%respectively,indicating that graphene has good electrical conductivity and light transmission.In addition,the effects of different parameters such as growth temperature,growth time,carbon and hydrogen ratio on the growth of graphene on dendritic copper powder by chemical vapor deposition were investigated.Finally,the high content graphene was fabricated on the dendritic copper powder with the following growth conditions:the growth temperature 750?,the Plasma power 150 W,the ratio of C₂H₂ to H₂ is 1:4 and a growth time of 90 min.The obtained copper-based graphene composites were characterized by vertical electronic universal testing machine and digital eddy current metal conductivity meter.The results show that the tensile strength is 251.7 MPa and the elongation is 58.5%,and the electrical conductivity is greater than 99.9%.Comparing with other methods for the preparation of copper-based graphene composites,the conductivity and elongation of copper-based graphene composites fabricated under this experimental conditions is greatly improved.The experimental results show that the copper-based graphene composites fabricated on the dendritic copper powder by chemical vapor deposition method perform a higher tensile strength,electrical conductivity and elongation.