Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
Nano Lett. 2012 Oct 10;12(10):5068-73. doi: 10.1021/nl3013924. Epub 2012 Sep 19.
Using molecular dynamics simulations, we generate realistic atomic models for oxidized Si nanowires which consist of a crystalline Si core and an amorphous SiO(2) shell. The amorphous characteristics of SiO(2) are well reproduced, as compared to those for bulk amorphous silica. Based on first-principles density functional calculations, we investigate the stability and segregation of B and P dopants near the radial interface between Si and SiO(2). Although substitutional B atoms are more stable in the core than in the oxide, B dopants can segregate to the oxide with the aid of Si self-interstitials which are generated during thermal oxidation. The segregation of B dopants occurs in the form of B interstitials in the oxide, leaving the self-interstitials in the Si core. In the case of P dopants, dopant segregation to the oxide is unfavorable even in the presence of self-interstitials. Instead, we find that P dopants tend to aggregate in the Si region near the interface and may form nearest-neighbor donor pairs, which are energetically more stable than isolated P dopants.
利用分子动力学模拟，我们为氧化硅纳米线生成了逼真的原子模型，这些模型由晶态硅核和非晶态 SiO(2)壳层组成。与块状无定形二氧化硅相比，SiO(2)的非晶态特征得到了很好的再现。基于第一性原理密度泛函计算，我们研究了 B 和 P 掺杂剂在 Si 和 SiO(2)之间的径向界面附近的稳定性和偏析。尽管替位 B 原子在核中比在氧化物中更稳定，但在热氧化过程中产生的 Si 自间隙的帮助下，B 掺杂剂可以偏析到氧化物中。B 掺杂剂的偏析以氧化物中的 B 间隙形式发生，而自间隙则留在 Si 核中。对于 P 掺杂剂，即使存在自间隙，掺杂剂向氧化物的偏析也是不利的。相反，我们发现 P 掺杂剂倾向于在界面附近的 Si 区域聚集，并可能形成最近邻施主对，其能量比孤立的 P 掺杂剂更稳定。
