四面体$Si_xGe_{47-x}:H_{60}$纳米晶的结构、电子和光学性质的密度泛函研究
Structural, electronic and optical properties of tetrahedral $Si_xGe_{47-x}:H_{60}$ nanocrystals: A Density Functional study
摘要：
通过密度泛函理论（DFT）计算，研究了混合SiGe：H量子点的结构、内聚、电子和光学性质，并对具有代表性的$Si_xGe_{47-x}:H_{60}$形式的中等尺寸纳米颗粒进行了研究。计算是在Becke，Lee，Parr和Yang的混合非局域交换相关泛函（B3 LYP）框架下进行的。除了基态的DFT/B3 LYP值外，我们还基于含时DFT（TDDFT/B3 LYP）计算得到了自旋和对称性允许的最低电子跃迁的可靠结果。结果表明，光学带隙不仅取决于硅、锗和氢的相对浓度，还取决于硅和锗壳层相对于晶体表面的相对位置。这对于允许可能的电子和光学间隙工程的结构、内聚和电子性质也是如此。此外，它被发现的情况下，与纯Ge或Si核的纳米粒子，光学性能主要是由纳米粒子的Ge部分，而硅似乎作为钝化剂。
英文摘要：
The structural, cohesive, electronic and optical properties of mixed SiGe:H quantum dots are studied by Density Functional Theory (DFT) calculations on a representative ensemble of medium size nanoparticles of the form $Si_xGe_{47-x}:H_{60}$. The calculations have been performed in the framework of the hybrid non-local exchange-correlation functional of Becke, Lee, Parr and Yang (B3LYP). Besides the ground state DFT/B3LYP values we provide reliable result for the lowest spin and symmetry allowed electronic transition based on Time Dependent DFT (TDDFT/B3LYP) calculations. Our results show that the optical gap depends not only on the relative concentrations of silicon, germanium and hydrogen, but also on the relative position of the silicon and germanium shells relative to the surface of the nanocrystal. This is also true for the structural, cohesive and electronic properties allowing for possible electronic and optical gap engineering. Moreover, it is found that for the cases of nanoparticles with pure Ge or Si core, the optical properties are mainly determined by the Ge part of the nanoparticle, while silicon seem to act as a passivant.
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