| Two-dimensional(2D) materials have physical properties in optics,magnetism, electric conduction, heat conduction and so on due to its unique structure. As the representative of transition-metal-sulfides-like structure, MoS2 and stanene have attracted much attention. They have great application potential in many optoelectronic devices. MoS2,as new material of 2D, has excellent semiconductor properties, and its direct band gap is about 1.74eV, which has great potential in industrial applications. In recent years, it has been a hot research topic to improve the performance of MoS2 by doping different atoms. However, there is no systematic study on the doping Li into different phases of MoS2.In addition, since graphene opened a new wave of 2D IV- materials, stanene,as its 'brother',has gradually aroused widespread concern. Stanene is a kind of topological insulator with excellent electric and heat conductivity while it has defects such as zero band gap and there is little experimental study on its growth substrate. Recently,the research on the growth of IV-materials on the substrate has emerged frequently, so it is the main research point of this paper that the stanene could combine with the substrate which could tune the performance of stanene. In this paper, we use the first principle based on density functional theory and the main research contents are concluded as follows:1. In this paper, we investigate the effect of adsorbed Li atoms concentration on the stability and electronic properties of 1H-MoS2,1T-MoS2 and 2H-MoS2, respectively. Our calculated results show that the stability of 1H and 2H phase is not sensitive to Li concentration than that of 1T phase. The results about electronic properties suggest that the increasing concentrations of adsorbed Li atoms can change the direct band gap semiconductor to be metallic for 1H-MoS2; while the 2H-MoS2 switches from direct band gap semiconductor to indirect band gap n-type semiconductor of 1.62eV. For 1T-MoS2, the adsorption of Li atoms will lead to the opening of a direct gap of 0.05eV compared to the metallic instinct one.2. We have proposed a question that if stanene could grow on the WS2 substrate to form a hybrid structure and make an improvement of the performance of it? In this paper, we present the calculations to study the stability and electronic properties of stanene on WS2 hybrid structure. It can be seen that the stanene is bound to WS2 substrate with an interlayer distance of about 3.0A with a binding energy of -51.8meV per Sn atom,suggesting a weak interaction between stanene and WS2.The nearly linear band dispersion character of stanene can be preserved with a sizeable band gap in the stanene on WS2 hybrid structure due to the difference of onsite energy induced by WS2 substrate, which is more helpful to the on-off current rotio in logical devices need made of stanene/WS2.Moreover, the band gaps, the position of Dirac point respect to Fermi level, and electron effective mass (EEM) of stanene on WS2 hybrid structure can be tuned by interlayer distance, external electric field, and strains. The part of the results indicate that stanene on WS2 hybrid structure are promising candidates for stanene-based FET with finite band gap and high carrier mobility. |
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