不同密度氢吸附金刚石(100)表面的微观结构

利用基于广义梯度近似的密度泛函理论,计算了金刚石(100)表面不同氢吸附密度的平衡态几何结构和态密度.结果表明对于2×1构型,在平行和垂直表面两个方向上发生弛豫,而1×1构型仅在垂直表面方向上发生弛豫.另外,清洁2×1,2×1 ∶0.5H和1×1 ∶1.5H表面,带隙中存在空表面态;而对于1×1 ∶2H和2×1 ∶H两种表面结构,空表面态上移进入导带,带隙中不存在表面态.结合电荷密度分布,探讨了金刚石(100)不同构型和氢吸附密度表面的表面态诱发机理. 关键词： 氢吸附 金刚石 弛豫 表面态

The microstructures of the diamond (100) surfaces with different density of hydrogen adsorption

By means of density functional theory on the basis of generalized gradient approximation, the equilibrium geometries and electronic properties of different hydrogenated diamond (100) surfaces were calculated. The results indicate that in the case of 2×1 reconstruction structure, the relaxation occurs along directions parallel and vertical to the surface. However, the relaxation does not appear in the direction parallel to the surface in the case of 1×1 structure. In addition, for the clean surfaces with C(100)-2×1, C(100)-2×1 ∶0.5H and C(100)-1×1 ∶1.5H structures, empty surface states exist in their band gaps. But with regard to the C(100)-1×1 ∶2H and C(100)-2×1 ∶H surface structures, which are configurations with full hydrogen coverage, the empty surface states shift upwards into the conduction band. With the help of analysis of charge density distribution, the inducing mechanisms of surface states were investigated.