Progress In Transfer Technologies And Characterization For Graphene Syntheized By Chemical Vapor Deposition

Graphene,with its remarkable physical and chemical properties,has attracted great attention from the scientific and commercial circles.With the wide application of graphene in various fields,the research on graphene has become more and more in-depth.It is found that some major problems must be overcome in order to commercialize graphene,such as the growth of controllable layers of graphene,the optimization of graphene transfer process,and the rapid characterization of graphene layers.In this paper,a series of studies on the growth,transfer and characterization of graphene have been carried out.The results are as follows:Copper foil is the most suitable substrate for the preparation of high quality graphene.The surface quality of copper foil has an important impact on the growth of graphene.By polishing and annealing,clean and smooth copper foil substrate surface is obtained,which effectively reduces the nucleation density of graphene domain and reduces the point defects in graphene.Graphene was grown by chemical vapor deposition(CVD)along the surface of copper foil.The coverage and number of layers of graphene were mainly affected by the optimum growth time.The carbon flux determined the amount of carbon infiltrated into copper foil in a unit time.The nucleation and growth of graphene on the surface of copper foil were affected.Characterizations such as optical microscope and Raman spectroscopy confirmed that the graphene layers were controllable and the graphene quality was good and the homogeneity was high.On the basis of the conventional substrate transfer process,we improved the concentration of etchant,compared the surface effect of different etchant on graphene,and chose ferric chloride as the etchant solution without damage to graphene.At the same time,the graphene was transferred to the target substrate and the heating step was introduced.The experiment proved that the bonding between the target substrate and the graphene could be effectively strengthened by slow heating.The annealing process can further remove residual substances and improve the transfer quality of graphene.Carrier mobility of graphene was measured by Hall device.The results show that the optimized transfer process can ensure the integrity of graphene and high cleanliness.Single crystal graphene and graphene continuous films were successfully transferred by dry process using thermal release tape.This new dry transfer process avoids the steps of corrosion of copper foil,saves metal materials,and makes the transfer process more environmentally friendly.Atomic force microscopy(AFM)characterization of this transfer process allows graphene to have significantly fewer wrinkles and higher surface smoothness.The digital characterization of the number of layers and the distribution rate of the number of layers of graphene,combined with the optical microscope CCD imaging system and MATLAB software operation,avoids the destruction of the structure of graphene in the conventional layer characterization methods and the long-term test,realizes the rapid judgment of the number of layers of grapheneand the intuitive,full and rich three-layer distribution law.The visualization of graphene layer number and its distribution rate can be comprehensively and accurately understood.This digital characterization method is convenient,fast and reliable.