A Parametric Study on the Influence of Synthesis and Transfer Conditions on the Quality of Graphene

In this paper, a systematic and comprehensive study has been carried out to observe the effect of synthesis and transfer conditions on the quality and uniformity of graphene deposition in an atmospheric pressure chemical vapour deposition set up. It was observed that the quality of graphene was highly affected by the synthesis conditions, such as, synthesis temperature, synthesis duration, methane and hydrogen flow rate ratio and total flow rate during deposition and cooling cycles. The quality of graphene was observed to be significantly improved upon increasing the synthesis temperature while increase in methane and hydrogen flow rates beyond a particular limit resulted into degradation in the quality of graphene. From the comparison of scanning electron microscopy images of graphene grown at different times, it was found that the nucleation and growth of graphene domains strongly depend on the growth time. The process of transfer of monolayer graphene was significantly improved by controlling the PMMA concentration using a modified three step technique. Raman spectroscopy and the high mobility (˜8153 cm2V−1s−1) of graphene after transferred onto a SiO2/Si substrate confirm the high quality of monolayer graphene obtained by the optimizations of synthesis and transfer conditions in this study.