The Effect Of Copper Substrate On The Growth Of Graphene By Chemical Vapor Deposition

Graphene is a two-dimensional material composed of sp2 hybrid carbon atoms arranged closely in honeycomb shape.It has excellent properties such as high transmittance,high conductivity and ultra-high mechanical strength.It has a very broad prospect in energy,materials,microelectronic devices and aviation fields.The preparation of graphene by chemical vapor deposition(CVD)is the most commonly used method in the laboratory because of its good controllability on the production oflarge-area graphene films.Copper substrate is the most commonly used metal substrate for CVD graphene because of its good surface catalysis and low carbon solubility.At present,most of the commercial copper foils used in the laboratory are rolled polycrystalline copper foils,which have rough surfaces and a lot of impurities induced by the rolling process.This introduces many uncontrollable factors for the CVD process.In this paper,the effects of copper substrates on the growth behavior of CVD graphene were studied from three aspects: annealing treatment,surface morphology,and crystal orientation.The main achievements are as follows:(1)The copper substrates were annealed in different atmosphere such as hydrogen and argon.It was found that the ability of removing impurities from copper substrate by argon was much higher than that of hydrogen.The impurities in the surface of copper substrates serve as the nucleation sites for graphene,thus increasing the nucleation density of graphene and affecting the orientations of graphene single crystals.(2)The effects of annealing,electrochemical polishing and other pretreatment processes on the surface morphology of copper substrates were systematically studied.Combined with various treatment methods,a simple and extremely efficient pretreatment method of copper substrate was achieved,which could effectively control the surface defects of copper substrates.(3)The effects of surface morphology of copper substrates on the growth behavior of CVD graphene was studied.The effective control of the nucleation density and adlayers of graphene was achieved,and the preparation of large-area high-quality adlayerfree graphene films was realized.(4)The growth of graphene on copper substrates with different orientations was studied.The oriented growth of graphene domains on copper substrates with multiple orientations was realized by adjusting parameters.On this basis,with the extention of the growth time,the oriented graphene domains were seamlessly attached and thus largescale graphene single crystal was achieved.