Abstract
We investigated the electronic properties and second hyperpolarizabilities of hydrogenated silicon nanoclusters (H-SiNCs) by using the density functional theory method. The effects of cluster size, external electric field and incident frequency on the second hyperpolarizability were also examined, respectively. We found that small H-SiNCs exhibit large second hyperpolarizability. With the increase of the number of silicon atoms in H-SiNCs, the frontier molecular orbital energy gap decreases, attributed to the enhancement of the second hyperpolarizability. Interestingly, we also found the electric-field-induced gigantic enhancement of the second hyperpolarizability for H-SiNCs due to the change of electron density distributions. In addition, our results demonstrate a significant dependence on the frequency of incident light.
Highlights
In the present work, we systematically investigate the third-order NLO properties of H-SiNCs based on the first-principles method
The energy values of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and their energy gap EHL reflect the chemical activity of the cluster, which play an important role in the electronic and optical properties[21]
We found that the applied electric field induces the decrease of the gap EHL as a result of the increase of the HOMO (LUMO) energy, and leads to enhancement of the second hyperpolarizability
Summary
We systematically investigate the third-order NLO properties of H-SiNCs (see Fig. 1) based on the first-principles method. We aim to discover the relationship between the cluster size and the second hyperpolarizability for the H-SiNCs studied, and to assess the effects of external electric field and incident frequency on the second hyperpolarizability. Our theoretical results reveal that the third-order NLO properties of H-SiNCs are strongly dependent on the size, external electric field, and incident frequency, respectively. Our study may propose new strategies for enhancing the third-order NLO response of silicon-based nanomaterials by modulating the external electric field and the frequency of incident light
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