Nestoklon Mikhail O, Avdeev Ivan D, Belolipetskiy Alexey V, Sychugov Ilya, Pevere Federico, Linnros Jan, Yassievich Irina N
Ioffe Institute, Politekhnicheskaya 26, St.-Petersburg, 194021, Russia.
Faraday Discuss. 2020 Jun 19;222(0):258-273. doi: 10.1039/c9fd00090a.
We develop an empirical tight binding approach for the modeling of the electronic states and optical properties of Si nanocrystals embedded in a SiO2 matrix. To simulate the wide band gap SiO2 matrix we use the virtual crystal approximation. The tight-binding parameters of the material with the diamond crystal lattice are fitted to the band structure of β-cristobalite. This model of the SiO2 matrix allows us to reproduce the band structure of real Si nanocrystals embedded in a SiO2 matrix. In this model, we compute the absorption spectra of the system. The calculations are in an excellent agreement with experimental data. We find that an important part of the high-energy absorption is defined by the spatially indirect, but direct in k-space transitions between holes inside the nanocrystal and electrons in the matrix.
我们开发了一种经验性紧束缚方法，用于模拟嵌入SiO₂基质中的硅纳米晶体的电子态和光学性质。为了模拟宽带隙SiO₂基质，我们使用虚拟晶体近似。具有金刚石晶格的材料的紧束缚参数被拟合到β-方石英的能带结构。这种SiO₂基质模型使我们能够重现嵌入SiO₂基质中的真实硅纳米晶体的能带结构。在该模型中，我们计算了系统的吸收光谱。计算结果与实验数据非常吻合。我们发现，高能吸收的一个重要部分是由纳米晶体内的空穴与基质中的电子之间在空间上间接但在k空间中直接的跃迁所定义的。
