中文摘要：

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0.75ML（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1.00ML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0.75ML的Li/Si（001）表面较难形成.

英文摘要：

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.