Synthesis of new silicene structure and its energy band properties

Silicene, silicon analogue to graphene which possesses a two-dimensional (2D) hexagonal lattice, has attracted increasing attention in the last few years due to predicted unique properties. However, silicon naturally possesses a three-dimensional (3D) diamond structure, so there seems to be not any natural solid phase of silicon similar to graphite. Here we report the synthesis of new silicene structure with a unique rectangular lattice by using a coherent electron beam to irradiate amorphous silicon nanofilm produced by pulsed laser deposition (PLD). Under the irradiation of coherent electron beam with proper kinetic energy, the surface layer of silicon nanofilm can be crystallized into silicene. The dynamic stability and the energy band properties of this new silicene structure are investigated by using first-principle calculations and density function theory (DFT) with the help of the observed crystalline structure and lattice constant. The new silicene structure has a real direct bandgap of 0.78 eV. Interestingly, the simulating calculation shows that the convex bond angle is 118° in the new silicene structure with rectangular lattices. The DFT simulations reveal that this new silicene structure has a Dirac-cone-like energy band. The experimental realization of silicene and the theoretically predicted properties shed light on the silicon material with potential applications in new devices. (paper)