Crystal Surface Atomic Dissociation And Adsorption Behavior Of SiC:First-principles Study

Graphene is a new type of two-dimensional carbon material with peculiar electronic properties, such as zero electronic band gap, high electron mobility, long coherent length and long length of the elastic scattering. It possesses very important application prospect in many scientific fields and thus is received extensive attention of people. At present, based on the crystal surface of silicon carbide(SiC), epitaxial growth method of graphene is generally expected as one of the most effective method to realize industrialization of graphene preparation and production. However, the micro kinetics and mechanism of epitaxial growth of graphene on the surface of SiC crystal is not so clear, especially the affect of the disintegration, adsorption and diffusion behavior of silicon, carbon atoms on the SiC surface on large area and high quality graphene growth.In this paper, we adopt the density functional theory based first principles method to investigate the dissociation, adsorption and diffusion behaviors of carbon and silicon atoms on the 6H-SiC(000-1) surface. The research task of our thesis is to explorer the mechanism of the nucleation and growth process of large area growth of graphene on SiC surface from a atomic scale, which will provide us useful theoretical data for understanding the process of graphene growth and improving the preparation technology of graphene. And thus, two detail tasks are designed as:1) Based on first principles method, he dissociation and adsorption behavior of C and Si atoms on 6H-SiC(000-1) surface were systematically studied. We found that it is more easy to form carbon vacancy defect than silicon vacancy defect on perfect SiC surface according to the relatively low dissociation energy of carbon atom. After the formation of carbon vacancy defect, Si atoms can easy dissociate from the surface.About the adsorption, carbon atoms are more favorable than silicon atoms. We find that H3 position is the most possible adsorption position. Interestingly, the increasing of the number of dissociation atom will reduces the adsorption energy of Si atom on the defected surface.2) Based on first principles method, the diffusion behavior of silicon atoms on the interface between graphene and SiC substrate surface is investigated. We find that in the process of diffusion, the diffusion barrier of silicon will increases before passinggraphene and decreases after passing graphene. Further investigation indicates that defects in graphene will effectively decrease the diffusion barrier of silicon, which is good for the growth of graphene on the surface.