The Investigation On The Growth And Intercalation Structure Of Graphene

Graphene is a new two-dimensional material,who has many outstanding physical and chemical properties which attractes wide attention all over the world.It has been found that graphene has a broad application prospect in the fields of catalysis,energy storage,microelectronic devices,functional composites,high sensitivity sensors,etc.In this paper,the intercalation of metals underneath graphene and the growth of graphene on metal substrates were studied by means of scanning tunneling microscope(STM).The interaction between graphene/intercalated-molecule/substrate,and the effect of interaction between graphene/substrate on the growth of graphene were investigated by density functional theory(DFT).In this dissertation,the adsorption,packing and the conversion into graphene of 1,3,5-Benzenetribenzoic Acid(BTB)on Ru(0001)were investigated.Firstly,BTB clusters were formed on Ru(0001)upon deposition.After annealing to 400?,graphitized flakes formed from the dehydrogenated BTB molecules coexisted with the adsorbed BTB molecules.The further annealing to a higher temperature would bring the system from such an intermediate stage to the stage of forming epitaxial graphene.Then,the intercalation of Co into graphcne overlayers on 6H-SiC(0001)were investigated.Upon adsorption,no ordered adsorption structure could be observed due to the Volmer-Weber growth mode of Co clusters.After annealing,the intercalation process took place both through the 1L and 2L graphene.By comparing the simulated and the experimental STM image,the most stable intercalation sites for Co underneath 1L and 2L graphene were determined.Taking the preference of the hollow site for Co adsorption onto pristine graphene into account,it could be inferred that in the 1L intercalation system,the interaction between the above 1L graphene and the intercalated Co atom influence the intercalation site mainly,while for the 2L case,the interaction between Co atom and the graphene layer sandwiching it were both influential for determining the intercalation site.Further calculations based on NEB theory showed that the intercalation barrier for the penetration of Co through a monovacancy in the 1L and 2L intercalation process were 0.60 eV and 0.41 eV,indicating that there should be an annealing temperature window within which the 2L intercalation process was activated while the 1L intercalation was forbidden.At the end,we report on the fabrication of Ca-intercalated graphene on SiC(0001)substrate by annealing the Ca-adsorbed graphene to 900?.The morphologies for Ca-intercalated structures underneath BL,1L and 2L were characterized by STM images.More details about the intercalation including the most energetically favoured intercalation sites,energies,and the corresponding electronic structures were further investigated by density functional theory(DFT)simulations.The charge transfer and the corresponding doping effect resulted from the intercalation were calculated for Ca-intercalated BL,1L and 2L structures.