硫化锡电子结构和光学性质的量子尺寸效应

Quantum confinement effect on electronic and optical properties of SnS

基于密度泛函理论的第一性原理计算,系统研究了硫化锡(SnS)晶体、纳米单层及多层的结构稳定性、电子结构和光学性质.结果表明:由于相对弱的层间范德瓦尔斯力作用,SnS单层纳米片可以像石墨烯等二维材料一样从块体中剥离出来;受制于量子尺寸效应和层间相互作用的影响,SnS的结构稳定性随层数减少而逐渐减弱,其带隙随层数减少而逐渐增大;由于材料的本征激发和吸收取决于电子结构,因此改变SnS材料的层数可以到达调控其光学性质的目的;SnS块体和纳米结构的主要光学吸收峰起源于Sn-5s,5p和S-2p轨道之间的电子跃迁;并且从块体到单层纳米结构,SnS的光学吸收峰出现明显的蓝移.本文的研究将有助于SnS材料在太阳能电池领域的应用.

The structural stabilities, electronic and optical properties of SnS bulk, monolayer, and multilayers are systematically studied by using the first-principles calculations within the density-functional theory. Our calculated results indicate that monolayer SnS can be exfoliated from its bulk, and the process is similar to the fabrication of graphene. With the reduction of layer number, the structural stabilities of SnS nanostructures become weak and their band gaps increase due to the quantum confinement effect and the layer interactions. Therefore, the optical properties of SnS can be controlled by adjusting the layer number due to the fact that the optical properties of materials depend on their electronic structures. The main optical absorption peaks of SnS bulk and nanostructures originate from the electron transitions among the orbitals of Sn-5s, 5p and S-2p. Moreover, the optical absorption peaks of SnS show obvious blue shift when SnS structure transforms from its bulk to monolayer. The present study will contribute to the application of SnS materials in the solar cells.