Ripples Of Graphene On Silicon Surface: Molecular Dynamics Study

Since graphene has been found in2004, it has pay much attention due to itsunique and outstanding electrical properties, as well as the applications onNano-electronic devices for future. Graphene should be placed on the suitablesubstrate in order to design and fabricate nano-electronic devices based on graphene.So, substrates will affect the morphology, the electrical properties and the transportproperties of graphene. Recent results have showed that graphene can be directlygrow on the silicon substrate in order to fabricate the quantum devices. It hasprovided a new approach for the application of graphene. So, it is important to studythe morphology controlling of graphene on various semi-conductor substrates such asSi and SiO2. It is useful for the understanding of controlling mechanism of grapheneand the design of quantum devices based on graphene. Using molecular dynamicssimulation (MD) and simulated annealing techniques, we have studied the atomicscale rippled morphology of single-atomic layer graphene on the ideal surface and thereconstructed surface of silicon in this paper. The effects of the annealing temperature,strain and reconstructed surface on the rippled morphology of graphene have beenanalyzed. We have mainly given the following conclusions.1.The atomic scale rippled morphology of graphene on the Si(100), Si(111) andSi(211) surface have been showed. We have found that the formation of rippledgraphene on Si substrate is result of the lattice mismatch between graphene andsubstrate. The rippled morphology of graphene is strongly depends on the annealingtemperature. The effects of rippled morphology on the stability of adsorbed grapheneon Si substrate have also been analyzed.2.The periodic ripples of graphene on the Si(111)7x7reconstructed surface haveshowed at room temperature. The periodicity of rippled graphene is about26.98,which is closely the lattice periodicity of Si(111)7x7reconstructed surface. Theformation mechanism differs from the roughening mechanism for the free-standingmonolayer graphene. Formation of periodic ripples in graphene on Si reconstructedsurface can be explained by the lattice coincidence between graphene and substrate.We have showed that the periodic ripples of graphene can be changed into the randomripples, as the annealing temperature increasing. In addition, the rippled morphology of graphene has been changed by means of the stretching or the bending substrate.3.The rippled morphology of graphene placed on the various reconstructed。surface of Si(111), such as Si(111)√3x√3, Si(111)2x2, Si(111)5x5and Si(111)7x7,have been displayed at atomic scale. A comparative analysis of the surface roughnessof graphene on various Si reconstructed surface has been performed. We have foundthat at room temperature the rippled behaviors of graphene on Si(111)5x5are thestrongest, while the rippled behvaviors of graphene on Si(111)2x2are the weakest.