半导体纳米晶体中的屏蔽：从头算结果与 Thomas-Fermi 理论
摘要
presented. We show that isocoric screening gives results in agreement with both the linear response and the point-charge approximations. Based on the present ab initio results, and by comparison with previous calculations, we propose a physical real-space interpretation of the several contributions to the screening. Combining the Thomas-Fermi theory and simple electrostatics, we show that it is possible to construct a model screening function that has the merit of being of simple physical interpretation. The main point upon which the model is based is that, up to distances of the order of a bond length from the perturbation, the charge response does not depend on the nanocrystal size. We show in a very clear way that the link between the screening at the nanoscale and in the bulk is given by the surface polarization. A detailed discussion is devoted to the importance of local field effects in the screening. Our first-principles calculations and the Thomas-Fermi theory clearly show that in Si and Ge nanocrystals, local field effects are dominated by surface polarization, which causes a reduction of the screening in going from the bulk down to the nanoscale. Finally, the model screening function is compared with recent state-of-the-art ab initio calculations and tested with impurity activation energies.
引用
@article{arxiv.0801.2312,
title = {Screening in semiconductor nanocrystals: \textit{Ab initio} results and Thomas-Fermi theory},
author = {F. Trani and D. Ninno and G. Cantele and G. Iadonisi and K. Hameeuw and E. Degoli and S. Ossicini},
journal= {arXiv preprint arXiv:0801.2312},
year = {2008}
}