Synthesis Of Millimeter-Sized Graphene Single Crvstals And Adlayer Control

Graphene has great and unique physical, chemical and electrical properties, attracting manyresearch interests from different fields all over the world, such assynthesis, transfer and application. Although graphene now just need a small step to its mass-production, this distancestill seems to be along way to finish. Nowadays, the methods researchers use to prepare graphene in labshave problems in the samples such as small-size, defective, non-uniform, etc. In recent years chemical vapor deposition (CVD) has become the most frequently used method to prepare large-scale graphene films, however, problems remain in this method to obtain high quality samples.In this thesiswe first study the change and difference in size, morphology and nucleation ofmillimeter-sized single-crystal graphene grown under different parameters inside and outside a copper envelope. We discuss the possible growth mechanism based on the observation results. We further developed a "two-step" method to grow high-quality single-crystal graphene, and obtain graphene withgrain size as 0.68mm in average,50% increase compared with the "one-step" method, and its adlayer area is about 0.19 n m when the normal method is 0.32 μm, making the average coverage ofadlayers significantly reduced to 0.25%. This new method provesitsadvantages of growing largersize graphene grains with extremely low adlayer coverage. Finally, we also develop a new method to grow high quality polycrystalline graphene films, by adjusting the CVD parameters to not only enable the graphene grain size to millimeter scale but also form a continuous film. We believe the CVD methods we developed in this thesis will open a new way to more graphene applications.