Preparation Of Graphene By Chemical Vapor Deposition And The Raman Spectrum Characterization

Since the successful preparation of graphene in 2004,graphene has attracted wordwide intense attention because of its amazing physical performance.Graphene films with a single atomic layer,arranged in a perfect honeycomb lattice,have broad application in many aspects.There are many methods for prepaing graphene,such as liquid phase exfoliation,oxidation-reduction method,or chemical vapor deposition,etc.At present,chemical vapor deposition is one of the industrially controllable methods for large-scale preparation of layers.In this paper,we mainly discussed the effects of different reaction condition parameters by different chemical vapor deposition methods,the Raman spectral of different layers graphene,and the effects of different substrates.The conclusions are shown as follows:(1)Study on the growth condition parameters of graphene prepared by PECVDGraphene was synthesized on a Cu foil substrate by PECVD with CH4 and H2 precursors.The growth temperature,gas flow rate,and RF power on the morphology and quality of graphene was systematically investigated.We also got the optimal growth conditions of graphene,hydrogen,methane flow rate ratio was 3:1,growth temperature was 800℃,and RF power was 120 W.(2)Investigate on the growth condition parameters of graphene prepared by Thermal CVDGraphene prepared by thermal CVD methods has the advantages of controllable number of layers,high crystal quality and large-scale preparation.We explored the effects of different growth temperature,gas flow rate,and deposition time on the quality of obtained graphene films.We obtained the optimal parameters of CVD method through the specific parameters adjustion:the working temperature was 1000℃,the ratio ofhydrogen and methane flow ratio was 3:2,the estimated monolayer graphene growth time was 2 min,and consequently the estimated growth time was 4 min for double-layer graphene.(3)The difference of Raman spectrum between single and double layers of grapheneWe carried out Raman tests measurement on the prepared single-layer and double-layer graphene,respectively.The results showed that the half-peak widths of the G and 2D peaks of the single-layer graphene were smaller than those of the double-layer graphene.Their G peak positions were basically the same,but the 2D peak position of the double layer graphene was blue shifted 2.1 cm’1 compared with that of the single layer graphene.(4)Characteristics of Raman Spectral Single-and Double-layer Graphene transferred to different substratesBefore systematically studying the Raman spectroscopy of graphene with different layers under different substrates,we systematically explored the influence of the test system on graphene Raman information.We studied the Raman effect of different laser excitation energies and different excitation laser energies on single-layer graphene.When the laser irradiation power was increased,both of the G and 2D peaks of the graphene were shifted due to the heat generated by the laser.We obtained the bias of the G peak and the 2D peak at different laser irradiation powers by fitting.The shift slopes were-0.426 cm-1/mW and-1.988 cm-1/mW;respectively.We transferred graphene of different layers to 300 nm SiO2/Si,glass,sapphire,quartz and other substrates,and used Raman mapping technology to analyze the information of G peak and 2D peak position and half width of different substrates.(5)Preparation of three-dimensional graphene from daily used biomass carbonWe used carbonized waster paper as the substrate for growing three-dimensional graphene,and then studied the effects of the parameters:growth temperature and growth time.When the growth temperature was 1000℃,no graphene was detected on the biomass carbon substrate.The growth temperature was 1150℃,the hydrogen flow rate was 160 sccm,and the methane flow rate was 30 sccm.When the growth time less than 2 h,the ratio of ID/IG increased;when the growth time more than 2h,the ratio of ID/IG decreased.The reason for the increase was mainly because the substrate belongs to amorphous carbon,the degree of defects was high,while the degree of crystallization was low,and the Raman signal was adversely affected,and the less growth time also contributed to the higher ratio.When the growth time exceeds 2h,graphene develops toward a relatively high crystalline and a relatively small defect,which was a manifestation of a balance between graphene growth and hydrogen etching.This approach gaves us a new way of recycling waste.