College of Material Engineering, Shanghai University of Engineering Science, 333 Long Teng Road, Shanghai 201620, People's Republic of China.
Nanotechnology. 2016 Aug 12;27(32):325702. doi: 10.1088/0957-4484/27/32/325702. Epub 2016 Jun 27.
We present a detailed investigation into the origin of blue emission from colloidal silicon (Si) nanocrystals (NCs) fabricated by femtosecond laser ablation of Si powder in 1-hexene. High resolution transmission electron microscopy and Raman spectroscopy observations confirm that Si NCs with average size 2.7 nm are produced and well dispersed in 1-hexene. Fourier transform infrared spectrum and x-ray photoelectron spectra have been employed to reveal the passivation of Si NCs surfaces with organic molecules. On the basis of the structural characterization, UV-visible absorption, temperature-dependent photoluminescence (PL), time-resolved PL, and PL excitation spectra investigations, we deduce that room-temperature blue luminescence from colloidal Si NCs originates from the following two processes: (i) under illumination, excitons first form within colloidal Si NCs by direct transition at the X or Γ (Γ25 → Γ'2) point; (ii) and then some trapped excitons migrate to the surfaces of colloidal Si NCs and further recombine via the surface states associated with the Si-C or Si-C-H2 bonds.
我们详细研究了通过飞秒激光烧蚀硅粉在 1-己烯中制备的胶体硅（Si）纳米晶体（NCs）中蓝色发射的起源。高分辨率透射电子显微镜和拉曼光谱观察证实，平均尺寸为 2.7nm 的 Si NCs 被制造出来并在 1-己烯中很好地分散。傅里叶变换红外光谱和 X 光电子能谱被用来揭示 Si NCs 表面与有机分子的钝化。基于结构特征、紫外-可见吸收、温度依赖光致发光（PL）、时间分辨 PL 和 PL 激发光谱研究，我们推断胶体 Si NCs 的室温蓝色发光源于以下两个过程：（i）在光照下，激子首先通过 X 或 Γ 点（Γ25→Γ'2）的直接跃迁在胶体 Si NCs 中形成；（ii）然后一些被捕获的激子迁移到胶体 Si NCs 的表面，并通过与 Si-C 或 Si-C-H2 键相关的表面态进一步复合。
