Theoretical Prediction Of Two Dimensional Silicon On Diamond Surface

In recent years,two-dimensional materials have become a new research hotspot because of their excellent electrical and mechanical properties.In these two-dimensional materials,the band structure of silicene is similar to that of graphene.Dirac cone exists at the high symmetry point K in Brillouin region,which makes its effective mass of electrons very small and has very high carrier mobility.At present,most of the silicene is synthetized by chemical vapor deposition on metal surfaces,such as Ag(111),Ag(110),Ir(111).However,the strong interaction between the silicene grown on these surfaces and the base leads to many kinds of reconstruction phenomena,which will destroy the lattice symmetry of the silicene and the electrical properties of the silicene.Therefore,it is of great significance for the practical application of silicene to find a new substrate and obtain a new kind of silicene reconstruction by growing on the surface.Diamond has compact crystal lattice,and carbon element is easily bonded with silicon element.In addition,silicon is often used as the base material in diamondheteroepitaxy.Therefore,we choose diamond as the base for the growth of silicene.The interfacial structure of diamond and silicon has not been fully studied.The study of the interfacial structure of diamond and silicon will be of great significance to the study of diamond growth and application.The research contents of this paper are as follows:1.Prediction of two-dimensional silicon structure on diamond(111)surface by particle swarm optimization(PSO).A new silicene structure named rhombic silicene has been found.It can be seen from phonon spectra that rhombic silicene possesses dynamic stability.When this silicene exists on the surface of diamond,it can be seen from phonon spectra that it is dynamically stable.The diamond surface can be stabilized by rhombic silicene at 500 K.When diamond surface contains rhombic silicene,the carbon on silicon and diamond surface forms polar covalent bonds,while the weak covalent bonds between silicon and silicon atoms.We found that the rhombic silicene has the same space group P6/mmm and similar bond length as a kind of silicon at high pressure.This may be due to the strong covalent bond formed between carbon atoms and silicon atoms on the diamond surface,which results in the equivalent high pressure effect on the surface and makes silicon exist as a high pressure phase.We also studied the electrical properties of rhombic silanes and found that the structure exhibited metallic properties,and the density of states near the Fermi plane was mainly derived from rhombic silanes.It can be seen from the energy band diagram that the special structure of node line exists in the energy band of diamond-shaped silicene,which indicates that diamond-shaped silicene has a bright future in the field of electronic devices.2.We choose Ge and Sn as the fourth main group elements to calculate whether they have similar rhombic single layer structure on the diamond surface.The thermal stability at 500 K was calculated by molecular dynamics.It was found that neither Ge nor Sn could exist on diamond surface with r-silicene-like structure.This is because the atomic radius of Ge and Sn is much larger than that of Si,so there are internal stresses in the results of Ge and Sn under the same lattice conditions,which make them unstable on the surface of diamond.3.According to the conditions of diamond heteroepitaxy,we have explored the interface structure of diamond(100)and silicon(100)surfaces.Two possible interface structures are predicted using particle swarm optimization(PSO).One is the diamond structure with silicon atoms at the interface between diamond and silicon,the other is the interface structure with quadrilateral silicon.We calculated the bonding between the two interfacial structures and found that the two interfacial structures are covalent bonds with silicon atoms and two interfacial atoms.It can be seen from the density-of-states diagram that the structureexhibits metallic properties,while both diamond and silicon are semiconductors.This semiconductor-metal-semiconductor structure may play a role in the electronic field.The above research will broaden the research of diamond in two-dimensional materials and provide ideas.Fill in the gap of the interface structure between diamond and silicon.