First - Principles Study On The Effect Of Adsorption Atoms On The Properties

Silicene is a very meaningful research carrier in two-dimensional material, because it has unique properties on electronic, thermal, and magnetic. And through adsorption, doping and other trim tools, the silicene can be modified on electronic level. In this paper, geometry structure, electronic properties and diffusion properties of different types of metals (alkali metals, alkaline earth metals, and transition metals, etc.) were studied based on first-principles density functional calculations.The most stable adsorption of Li, Na, and K on silicene is hollow site, the adsorption high monotonically increasing, while adsorption energy is decrease and then increase with increasing atomic radius. The most stable position of alkaline-earth metal on silicene substrate are the B-top site, and the transition metal for the bridge. Silicene appeared metal properties on electronic structure after adsorbed by Na.Compared with the perfect silicene, optimized structure of defected silicene decreases its symmetry, and Dirac point in the band has completely disappeared. Na atom on single vacancy-defected silicene occupy the position that lose one silicon atom, which means the stable adsorbed position is a bigger hollow site. Diffusion studies determined the best path of Na diffusion on silicene surface, and the diffusion barrier of Na on the perfect silicene is 0.25 eV, but on defected substrate is about 1.44 eV which is bigger than perfect one. So the single vacancy exhibits a more significant influence than the adsorption atom on electronic structure of silicene.In addition, we also studied the effect of silicene structures and electronic properties made by strain. In the paper, unidirectional tensile stress be given to perfect silicene, Si-Si bond become longer and the angle bigger with the increase of tensile stress. When pulling force to 8%, the interaction between Si atoms are very weak, the Dirac electronic properties of silicene disappeared.