乙炔和乙烯分子在Si(100)表面吸附的几何和电子结构的密度泛函研究

采用基于第一性原理的密度泛函理论和平板模型对Si(100)表面吸附乙炔和乙烯分子的构型稳定性以及电子结构进行系统研究. 结果表明: 无论是吸附乙炔还是乙烯分子, 当覆盖度为0.5 ML时, 最为稳定的吸附方式为dimerized模型; 当覆盖度增大到1.0 ML时, end-bridge模型为最稳定的吸附方式. 通过对各吸附模型的能带结构分析可知, 体系的带隙变化可以通过考察表层Si—Si二聚体中Si原子的配位环境来确定. 对于相同的吸附模型, 无论吸附分子是乙炔还是乙烯, 都具有非常相近的带隙. 吸附构型以及吸附分子的覆盖度对最小带隙及其来源有较大影响. 此外, 研究结果还表明, 杂化密度泛函方法更适合于描述Si(100)表面的电子结构, 尤其是对end-bridge吸附模型.

Density Functional Studies on the Geometries and Electronic Structures for the Adsorption of Acetylene and Ethylene Molecules on Si(100) Surface

Using the first-principle method with the density functional theory and the slab model, the ge- ometries and electronic structures of the adsorptions of acetylene and ethylene molecules on Si(100) surface have been investigated. Our results indicate that the dimerized model is the most stable configuration for both ethylene and acetylene when the converge is 0.5 ML, while the end-bridge configuration becomes the most favorable structure when the converge increases to 1.0 ML. The analyses of the band structures show that the variations of the band gap could be explained by considering the coordination environment of Si atoms of the dimer, and for the same adsorption model, nearly identical band gap was observed for both eth- ylene and acetylene. The configuration of adsorption and the converge have obvious effects on the value of the band gap, as well as the origin of the smallest band gap. Moreover, our results demonstrate that the hy- brid density functional method is suitable to describe the electronic structure of Si(100) surface, especially for the end-bridge model.