Department of Chemical Engineering, University of Texas, Austin, Texas 78712, United States.
ACS Nano. 2011 Mar 22;5(3):1713-23. doi: 10.1021/nn102232u. Epub 2011 Mar 2.
Using a density functional theory approach, we examine the dielectric function (ε(ω)) optical spectra and electronic structure of various silicon nanowire (SiNW) orientations (<100>, <110>, <111>, and <112>) with amorphous oxide sheaths (-a-SiOx) and compare the results against H-terminated reference SiNWs. We extend the same methods to investigate the effects of surface passivation on <111> SiNW properties using functional group termination (-H, -OH, and -F) and three different thicknesses of oxide sheath passivation. Oxide layer growth is evidenced in the spectra by concomitant appearance of tail oxide character with signatures of increased Si disorder. Suboxide contributions and increased Si disorder from oxidation average out the band structure dispersion observed in the reference SiNWs. Furthermore, we plot average Seraphin coefficients for <111> passivations that clearly distinguish functional group termination from surface oxidation and discuss the suboxide and disorder contributions on the characteristic intersection of these coefficients. The substantial difference in properties observed between <111>-OH and <111>-a-SiOx SiNWs emphasizes the importance of using realistic oxidation models to improve understanding of SiNW properties.
我们采用密度泛函理论方法，研究了不同硅纳米线（SiNW）取向（<100>、<110>、<111>和<112>）的介电函数（ε（ω））光学谱和电子结构，这些硅纳米线带有非晶氧化物壳层（-a-SiOx），并将结果与氢终止的参考 SiNW 进行了比较。我们还采用相同的方法，使用官能团终止（-H、-OH 和-F）和三种不同厚度的氧化物壳层钝化，研究了表面钝化对<111> SiNW 性质的影响。通过同时出现具有增加 Si 无序特征的尾氧化特征，可以在光谱中证明氧化物层的生长。氧化引起的亚氧化物贡献和 Si 无序增加平均了参考 SiNW 中观察到的能带结构色散。此外，我们绘制了<111>钝化的平均 Seraphin 系数图，该图清楚地区分了官能团终止和表面氧化，并讨论了亚氧化物和无序对这些系数交点的影响。<111>-OH 和<111>-a-SiOx SiNW 之间观察到的性质差异很大，这强调了使用实际氧化模型来提高对 SiNW 性质的理解的重要性。
