Tuning the Bandgap Character of Quantum-Confined Si-Sn Alloyed Nanocrystals
Tuning the Bandgap Character of Quantum-Confined Si-Sn Alloyed Nanocrystals
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DOI：
10.1002/adfm.201907210
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发表时间：
2020-04-02
影响因子：
19
通讯作者：
Svrcek, Vladimir
中科院分区：
文献类型：
--
作者：
Burkle, Marius;Lozac'h, Mickael;Svrcek, Vladimir
分子和块体之间的纳米晶体产生独特的电子特性。这里提供了一项针对量子限制纳米晶体（NC）的全面研究。在密度泛函理论的层面上，计算了一个近似（准）能带结构，它解决了有限尺寸NC的分子和体积方面的问题。特别是，显示了带状特征如何随着粒径的增加而出现。准带结构用于讨论技术相关的直接带隙NC。研究发现，超小型 Sn NC 在纳米级稳定的 α 相中具有直接带隙，并且当 Sn 浓度足够高（约 41%）时，Si-Sn NC 合金从间接带隙半导体转变为直接带隙半导体。这些计算有力地支持了最近的实验，表明这些系统存在直接带隙。为了进行定量比较，执行多体 GW + Bethe-Salpeter 方程 (BSE) 计算。预测的光学间隙与实验数据接近，计算的吸收光谱与相应的测量结果吻合良好。
Nanocrystals in the regime between molecules and bulk give rise to unique electronic properties. Here, a thorough study focusing on quantum-confined nanocrystals (NCs) is provided. At the level of density functional theory an approximate (quasi) band structure which addresses both the molecular and bulk aspects of finite-sized NCs is calculated. In particular, how band-like features emerge with increasing particle diameter is shown. The quasiband structure is used to discuss technological-relevant direct bandgap NCs. It is found that ultrasmall Sn NCs have a direct bandgap in their at-nanoscale-stable alpha-phase and for high enough Sn concentration (approximate to 41%) alloyed Si-Sn NCs transition from indirect to direct bandgap semiconductors. The calculations strongly support recent experiments suggesting a direct bandgap for these systems. For a quantitative comparison many-body GW + Bethe-Salpeter equation (BSE) calculations are performed. The predicted optical gaps are close to the experimental data and the calculated absorbance spectra compare well with the corresponding measurements.