Configuration And Electronic Properties Of Graphene And GNRs On Si Surface

Graphene, a single atomic layer honeycomb two-dimensional crystal has lots of interesting physical properties. As a new carbon nano-material, Graphene nanoribbons (GNRs), finite sized graphene of, draws increasing attention in theory and experiments due to their potential applications in nano-electronics. It is a research focus to realize the GNRs based device in micro-nanoelectronics. However, finding a suitable substrate for the graphene and GNRs is the premise their practical use. Silicon technology is the core of modern microelectronics industry. In view of the important role of the silicon material in the future nano-technology, the combination of graphene and GNRs and silicon should be a significant issue for their practical applications. Therefore, the study of the interaction between graphene and GNRs and Silicon substrate is significant importance. In this paper, we use first-principles method based on density functional theory to explore the modulation of electronic and structural of graphene or GNRs on the Si (211) surface or Si (111) surface. The main results are as follows:Firstly, we analyzed GNRs adsorbed on Si (211) substrate systematically, including the structural distortion, adsorption energy, electron density difference and density of states of GNRs. We considered the electronic and structural properties of both armchair and zigzag GNRs adsorbed on Si (211) surface along the directions of [0 1 -1] and [-1 1 1], respectively. We found that the adsorption energy is constrained not only by the GNRs edge states, but also by the band width and the substrate orientation. The adsorption configuration of GNRs on substrate depends on sp 3 hybridization btweeen the surface atoms of substrate and the edge atoms of GNRs. Substrate influence effectively the edge states of GNRs, the DOS peak around Fermi level caused the edge states of H-free GNRs adsorbed along [0 1 -1] direction of Si(211) surface and H-terminated GNRs along the two direction of Si(211) surface are reduced, and metallizing AGNRs. In comparison with H-free Si(211) surface, the adsorption energy of GNRs adsorbed on H-contaminative Si(211) surface is increased. H-contaminative Si(211) surface further reduce the metallic nature of ZGNRs, however, for the electronic properties of AGNRs are slightly changed.Secondly, we analyze the configuration and electronic properties of graphene adsorbed on clean and carbon decorated Si(111)surface, respectively. The adsorption energy, density of states and band structure of grapheme on both these Si(111) surfaces are analyzed. The sp 2 and sp 3hybridization passivates the surface and weaken the interactions between graphene and Si(111)surface. Through the analysis of density of states and the band structure of adsorption grapheme on this carbon decorated surface, we found that when the concentration of carbon atoms on Si 111)is 1/2 monolayer, 5/4 monolayer and 3/2 monolayer, the adsorbed graphene on this surface maintains good characteristics of insolated graphene.