物理化学学报 >> 2009, Vol. 25 >> Issue (08): 1535-1544.doi: 10.3866/PKU.WHXB20090742

研究论文 上一篇    下一篇

不同覆盖度下Li原子在Si(001)表面上的吸附构型和电子结构

倪碧莲, 蔡亚萍, 李奕, 丁开宁, 章永凡   

  1. 福建医科大学药学院基础化学系, 福州 350108|福州大学化学化工学院, 福州 350108
  • 收稿日期:2009-02-10 修回日期:2009-04-16 发布日期:2009-07-16
  • 通讯作者: 章永凡 E-mail:zhangyf@fzu.edu.cn

Geometries and Electronic Structures for the Adsorption of Li on Si(001) Surface with Different Coverages

NI Bi-Lian, CAI Ya-Ping, LI Yi, DING Kai-Ning, ZHANG Yong-Fan   

  1. Department of Fundamental Chemistry, College of Pharmacy, Fujian Medical University, Fuzhou 350108, P. R. China|College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350108, P. R. China
  • Received:2009-02-10 Revised:2009-04-16 Published:2009-07-16
  • Contact: ZHANG Yong-Fan E-mail:zhangyf@fzu.edu.cn

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摘要：

采用基于赝势平面波基组的密度泛函理论, 对不同Li原子覆盖度下Li/Si(001)体系的吸附构型、电子结构以及吸附Li原子对表面性质的影响进行了系统研究. 计算结果表明, 在所考察的覆盖度范围内, Li原子倾向于吸附在相邻两个Si-Si二聚体之间各种对称性较高的空穴位, 其中覆盖度为0.75 ML(monolayer)时具有最小的平均吸附能. 由能带结构分析结果可知, 随着覆盖度的增大, Si(001)表面存在由半导体→导体→半导体的变化过程. 在覆盖度为1.00 ML时, 由于表层二聚体均受到显著破坏, 使得体系带隙明显增大. 吸附后, 有较多电子从Li原子转移到底物, 导致Si(001)表面功函显著下降, 并随着覆盖度的增加表面功函呈现振荡变化. 此外, 从热力学稳定性角度上看, 覆盖度为0.75 ML的Li/Si(001)表面较难形成.

关键词: 密度泛函理论, 碱金属, 表面吸附, 能带结构, Si(001)表面

Abstract:

Using density functional theory, based on the pseudo-potential plane wave basis set, the geometries and  electronic structures of Li/Si(001) systems with different Li atom coverages were investigated systematically. The effect of Li adsorption on surface properties was also investigated. Our results indicated that Li atoms preferred to adsorb on high symmetry sites between adjacent Si-Si dimers and that the smallest average adsorption energy was predicted for the 0.75 monolayer (ML) coverage. By analyzing the band structures, the Si(001) surface varied from semiconductor to conductor, then to semiconductor again with increasing Li coverage. The bandgap of the Si(001) surface increased obviously at 1.00 ML coverage because of the significant destruction of surface Si-Si dimers after Li adsorption. Since electrons obviously transferred from the Li atom to the substrate, the work function of the surface decreased and oscillated with an increase in coverage. Furthermore, according to the calculated surface formation energy, the phase corresponding to 0.75 ML coverage should be difficult to observe.

Key words: Density functional theory, Alkali metal, Surface adsorption, Band structure, Si(001) surface