Copper Foil Pretreatment And The Carbon Potential Impact On The Quality Of Graphene Prepared By Atmospheric Pressure Chemical Vapor Deposition

Graphene's application has been made greatly in sensor,optical,electrical,and heat devices.But the approach to fabricate a high-quality graphene film with defect is still the limit to improve its performance.In this paper,by using atmospheric pressure chemical vapor deposition?APCVD?,the graphene films were deposited onto pretreated copper foils.The effect of copper foil pretreatment and carbon potential(partial pressure of CH₃,P_CH3)on growth behavior and the quality of the graphene films were investigated carefully.The scanning electron microscopy,Raman spectroscopy,ultraviolet-visible spectrophotometer,four-probe sheet resistance tester,infrared spectrum analyzer and high-resolution transmission electron microscopy were used to characterize these graphene films.The following conclusion can be made:1)For those copper foils annealed at high temperature for long time,if their grain grows to a certain critical size,i.e.,around 1mm in this study,surface crystal grain orientation turns to Cu?111?plane.The proportion of grain with Cu?111?surface orientation increases with annealing time and temperature rising,but it's difficult to achieve a copper foil with 100%surface Cu?111?by means of purely annealing in this study.2)Graphene film can be prepared in the work gas within carbon potential(P_CH3)range between8.81-3.13 Pa.When carbon potential in the work gas is less than 1.87 Pa,a continuous graphene film covering the copper foil fully cannot be obtained,while only amorphous carbon film can be secured if the carbon potential is more than 8.81 Pa.In the carbon potential scope of 8.81-4.78 Pa,the as deposited endogenous graphene film is thick and with multi-layer.The double-layer and single layer graphene film can be deposited only if the carbon potential in the vicinity3.7 to 4.7 Pa.Especially at 4.32 Pa a single-layer graphene without defects and with high light transmittance can be fabricated.3)Under the carbon potential of 4.32 Pa we produced monolayer graphene,and its light transmittance was greater than 96%.Probably because of defects induced by transferring,the single layer graphene film did not hold an excellent electric conductivity in this study;in contrast,the few-layer graphene film presented a better conductivity,the sheet resistance 639?·?^-1.4)The graphene films of this study possessed C-H_n bonds,which were obvious in infrared absorption spectra?FTIR?and Raman spectra.In FTIR,the three peaks,i.e.,2850 cm^-1,2960^-1 cm,2930 cm^-1,were contributed to C-H_n bonds.Surly the C-H₂ bonds was the dominant form in the film.With lowering concentration of hydrogen in the work gas,the amount of C-H_n bonds increased.5)The high resolution TEM proved that the carbon film in this study was a single-or double-layer graphene crystal film,although the domain is small,less than 10mm.In the bright field,some chains or rings were tribute to carbon hydrogen functional group,which connected with the surface dangling carbon bond of the graphene layers.