Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore.
Nano Lett. 2011 Nov 9;11(11):4794-9. doi: 10.1021/nl2026212. Epub 2011 Sep 30.
First-principles density functional theory calculations on hydrogenated silicon nanowires (SiNWs) with diameters up to 7.3 nm are carried out for comparing to experimentally relevant SiNWs and evaluating its radial doping profiles. We show that the direct band gap nature of both the small diameter (110) and (100) SiNWs fades when the diameter reaches beyond about 4 nm, where the difference of direct and indirect band gaps are close, within the experimental measurement uncertainty of ±0.1 eV, suggesting the diameter size where the gap nature transition starts. In addition, we reveal that core-surface boron (B) codoped SiNW forms more preferably at large diameter than that of the surface-surface codoped one, attributing to the lower energy configuration raised by the core B dopant at large diameter SiNW. More importantly, the diameter for such a preferential transition increases as the doping concentration decreases. Our results rationalize photoluminescent measurements and radial doping distributions of SiNWs.
我们对直径高达 7.3nm 的氢化硅纳米线（SiNWs）进行了第一性原理密度泛函理论计算，以与实验相关的 SiNWs 进行比较，并评估其径向掺杂分布。我们表明，当直径超过约 4nm 时，小直径（110）和（100）SiNW 的直接带隙性质会消失，此时直接带隙和间接带隙之间的差异接近，在实验测量不确定度±0.1eV 范围内，这表明了带隙性质转变开始的直径大小。此外，我们揭示了核心-表面硼（B）共掺杂 SiNW 在大直径下比表面-表面共掺杂的更易形成，这归因于大直径 SiNW 中核心 B 掺杂剂降低了能量结构。更重要的是，这种优先转变的直径随着掺杂浓度的降低而增加。我们的结果合理化了 SiNW 的光致发光测量和径向掺杂分布。
