Investigation On Fabrication And Electronic Properties Of Graphene Grown By CVD

The ideal electron mobility of monolayer graphene at room temperature,up to15000 cm² V^-1 s^-1,attracts extensive attention of scholars in the element fabrication field.However,the intervention of non-ideal factors during the growth,transfer and test,leads to the far distance between the actual mobility and ideal value of the prepared graphene.In this paper,through the optimization of the technologies such as growth,transfer and doping,the mobility of graphene is improved to certain extent.The preparation of CVD graphene is firstly researched in this paper.The surface state of the Cu substrate is treated through double-polishing pretreatment,and thus the flatness of Cu substrate surface is improved.Besides,through the analysis of the change of the gas composition during growth,it is found that along with the increase of the proportion of hydrogen and methane,the shape of the single crystal of graphene transits from the hexagonal snowflake with a lot of branches at the edges to the hexagon with straight edges.It is researched that,the flatter the substrate surface is,the smoother the edges of the single crystal of graphene are,which is more favorable for the formation of large-area high-quality graphene.Next,the technological parameters including PMMA spin-coating speed,PMMA concentration,type of corrosive liquid,concentration of corrosive liquid,etc.are optimized.The experiment shows that when PMMA concentration is 40g/l,ferric trichloride concentration is 200g/l and PMMA spin-coating speed is 2500r,it is the optimal transfer condition.In addition,by soaking the transferred graphene in NaOH solution,the residual on the surface of the transferred CVD graphene is reduced,the surface of graphene is cleaner,and its electric properties are improved.Finally,a simple but effective graphene surface modification method is adopted,by which the hydroxyl in ascorbic acid is utilized to provide electrons,P-type doping introduced during growth and transfer is balanced,the nature of graphene is partially restored,and graphene mobility is further improved,which reaches 1.3 times of the original value.Therefore,the applications of CVD graphene in FET elements are more extensive.