Applied Physics, School of Applied Sciences, RMIT University, Melbourne, Victoria 3001, Australia.
Nanoscale. 2012 Apr 28;4(9):2906-13. doi: 10.1039/c2nr30100h. Epub 2012 Apr 3.
We have shown, using density functional theory calculations, that the properties of Si nanosheets change as a function of thickness. While Si(111) oriented nanosheets that are 0.56 nm thick (2-layers) display a novel reconstruction, classified as Si(111)-2 × 2 on both surface layers (T. Morishita, M. J. S. Spencer, S. P. Russo, I. K. Snook and M. Mikami, Chem. Phys. Lett., 2011, 506, 221), nanosheets that are up to a thickness of 1.42 nm show the Si(111)-2 × 1 surface reconstruction, that is seen on the bulk Si(111) surface, on both sides of the nanosheet. For these thicker nanosheets, the relative orientation of the π-chain structure on each surface of the nanosheet can either be the same or different, resulting in unique electronic properties. When the orientation is the same, there is a widening of the band gap, indicating that the interaction between the surface π-chains is not present when they are oriented in different directions. The electronic properties of the nanosheets approach those of the bulk by 1.42 nm thick. The variation in structural and electronic properties of Si nanosheets with different thicknesses, as shown in this study, highlights the novelty of these materials and their significance for applications in electronic device technologies.
我们已经通过密度泛函理论计算表明，硅纳米片的性质随厚度而变化。虽然厚度为 0.56nm（2 层）的 Si(111)取向纳米片呈现出一种新颖的重构，在两个表面层上被归类为 Si(111)-2×2（T. Morishita、M. J. S. Spencer、S. P. Russo、I. K. Snook 和 M. Mikami，Chem. Phys. Lett.，2011，506，221），但厚度高达 1.42nm 的纳米片在纳米片的两侧呈现出在体硅（111）表面上看到的 Si(111)-2×1 表面重构。对于这些较厚的纳米片，纳米片每一侧的π链结构的相对取向可以相同或不同，从而产生独特的电子性质。当取向相同时，带隙变宽，表明当表面π链取向不同时，它们之间不存在相互作用。当厚度达到 1.42nm 时，纳米片的电子性质接近体相。本研究表明，不同厚度的硅纳米片在结构和电子性质上的变化突出了这些材料的新颖性及其在电子器件技术应用中的重要性。
