Preparation Of Graphene By Low-pressure Chemical Vapor Deposition (LPCVD) Method

Graphene, due to its excellent chemical and physical properties, has become the most dazzling star in the material and scientific fields in twenty-first century. There are many methods for the production of graphene, the most popular and promising way is chemical vapor deposition (CVD), because of its simple process and low cost.In this thesis, we used copper foil as the substrate, methane as the carbon source, to produce graphene by a low pressure chemical vapor deposition (LPCVD) method. By adjusting the experimental parameters, such as the flow rates of methane and hydrogen gas, we studied the influence of various experimental parameters on graphene. And we successfully synthesized high quality double-layer graphene, and novel graphene domains with a triangle structure.Firstly, we explored the effect of carbon source methane and buffer gas hydrogen on the growth of graphene. We found under certain experimental conditions, by increasing the amount of methane, the nucleation density of graphene increased and the grain size decreased, graphene quality declined; similarly, hydrogen as the buffer gas, its existence was essential to the growth of graphene, but excessive hydrogen would etch graphene. By adjusting the experimental parameters, we have prepared large scale and high quality graphene on copper foil.Secondly, we studied the morphology control of graphene; we prepared a novel triangular graphene structure. We found that the graphene domains were typically triangle, and the triangle graphene domains had a high degree of alignment, with low defect and high quality. We found that the quantity equilibrium of oxygen and hydrogen in the reaction process was the key to the formation of triangular graphene domains.Finally, we found hydrogen had an important role in the cooling process. As we all knew, hydrogen played an important role in the growth of graphene, where it protected graphene from the oxidizing gas and impurities. Few people knew that hydrogen in the cooling process was also indispensable, because there were residual oxygen or other oxidizing gas in reaction chamber during the graphene growth which would oxide graphene at a high temperature. This work may suggest a new theoretical basis for the preparation of graphene by chemical vapor deposition method.