Haq Atta Ul, Buerkle Marius, Alessi Bruno, Svrcek Vladimir, Maguire Paul, Mariotti Davide
School of Engineering, Ulster University, York Street, Belfast BT15 1ED, UK.
Renewable Energy Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8568, Japan.
Nanoscale Horiz. 2024 Oct 21;9(11):2042-2050. doi: 10.1039/d4nh00235k.
Creating tin-alloyed silicon nanocrystals with tailored bandgap values is a significant challenge, primarily because a substantial concentration of tin is essential to observe useful changes in the electronic structure. However, high concentration of Sn leads to instability of the silicon-tin nanocrystals. This work introduces a completely new approach to doping and the modification of the electronic structure of nanoparticles by incorporating few-atom clusters in nanocrystals, deviating from isolated atom doping or attempting alloying. This approach is exemplified a combined theoretical and experimental study on tin (Sn) 'cluster-doping' of silicon (Si) nanocrystals, motivated by the opportunities offered by the Si-Sn system with tailored band energy. First-principles modelling predicts two noteworthy outcomes: a considerably smaller bandgap of these nanocrystals even with a modest concentration of tin compared to an equivalent-sized pure silicon nanocrystal and an unexpected decrease in the bandgap of nanocrystals as the diameter of nanocrystals increases, contrary to the typical quantum confined behaviour. Experimental verification using atmospheric pressure microplasma synthesis confirms the stability of these nanocrystals under ambient conditions. The plasma-synthesised nanocrystals exhibited the predicted atypical size-dependent behaviour of the bandgap, which ranged from 1.6 eV for 1.4 nm mean diameter particles to 2.4 eV for 2.2 nm mean diameter particles.
制备具有特定带隙值的锡合金化硅纳米晶体是一项重大挑战，主要原因是要观察到电子结构的有用变化，锡的浓度必须相当高。然而，高浓度的锡会导致硅锡纳米晶体的不稳定。这项工作引入了一种全新的掺杂方法以及通过在纳米晶体中引入少量原子团簇来改变纳米颗粒电子结构的方法，这与孤立原子掺杂或尝试合金化不同。这种方法通过对硅（Si）纳米晶体的锡（Sn）“团簇掺杂”进行理论与实验相结合的研究得以例证，这一研究受到具有特定带隙能量的Si-Sn体系所带来的机遇的推动。第一性原理建模预测了两个值得注意的结果：与同等尺寸的纯硅纳米晶体相比，即使锡的浓度适中，这些纳米晶体的带隙也会显著变小；并且随着纳米晶体直径的增加，纳米晶体的带隙会出现意外的减小，这与典型的量子限域行为相反。使用大气压微等离子体合成进行的实验验证证实了这些纳米晶体在环境条件下的稳定性。等离子体合成的纳米晶体表现出预测的带隙非典型尺寸依赖性行为，平均直径为1.4 nm的颗粒带隙为1.6 eV，平均直径为2.2 nm的颗粒带隙为2.4 eV。
