CVD Growth Mechanism Of Graphene On The Surface Of Cu/Ni Alloy

Controllable preparation of graphene with high quality and large area is an important prerequisite for its industrial application.Chemical vapor deposition?CVD?of hydrocarbons on metal substrates is a promising method to achieve the goals of synthesizing large-area single-crystalline graphene in industry.However,the quality of graphene synthesized on the surface of single metal catalyst by CVD is still lower than our expected.One of the main reasons is that the metal catalysts which used for the growth of graphene in CVD have their own advantages and disadvantages.It is difficult to satisfy fast growth speed,high quality and good uniformity at the same time.Using alloy catalysts is an effective approach to solve this problem.At present,it has been found that the alloy catalyst has a special advantage in the rapid synthesis of high quality and large area single-crystalline graphene.But the growth mechanism of graphene on the alloy catalyst substrate is still unclear recently,which limit the application of alloy catalysts in the synthesis of high quality and large area graphene.In this paper,we based on the first principles calculations and studied the CVD growth mechanism of graphene on the surface of Cu/Ni alloy and the interaction between graphene and metal or alloy substrates.The paper is divided into two parts.1.The study of Nucleation density of graphene on Cu/Ni alloy surface.We studied the formation energy of C₂₄ consisting of seven hexatomic ring on the surface of Cu/Ni alloy.It was found that,the formation energy of C₂₄4 on alloy will decreased with the increase of Ni content.This is due to the strong interaction between C and Ni,which leads to the decrease of C₂₄ formation energy.Considering the introduction of Ni atoms will cause the dissolution change of C atoms,we further investigated the formation energy of C₂₄ on the surface of Cu/Ni alloy doped with a certain amount of C atoms.It is found that the formation energy of C₂₄4 on these metal surfaces is higher than that of Cu,which means graphene has higher nucleation energy and lower nucleation density on the surface of Cu/Ni alloy.Further,we found the rise of formation energy is because of the passivation of the surface Cu atoms by Ni,while the Ni atoms are passivated by the C atoms dissolved in alloy.The results of this theoretical study can be used to explain why the surface of Cu/Ni alloy is highly active in the decomposition of carbon source and the nucleation density decreases.2.The study of VDW interaction between graphene and metal substrate.Stripping graphene is a very important step in the synthesis of graphene CVD,and it is related to the strength of interaction between graphene and metal substrate.Therefore,it is necessary to study the VDW interaction between graphene and substrate,especially between graphene and alloy substrate.In this paper,we use the first principles calculations to study the different layers of graphene,different surface of the metal catalyst,and the alloy catalysts.We found that the VDW interaction between graphene and substrate becomes weaker with the increase of the number of graphene layers.The interaction between graphene and?111?surface is weaker than?100?.On the surface of the alloy catalyst,taking the dissolution of C atoms in the alloy into account,the VDW interaction of graphene on the alloy catalyst is weaker than that of the pure Cu.The results show that the catalyst not only has advantages in the synthesis of large area single crystal graphene,but also has a great advantage in the effective removal of graphene.