Tunable Electronic and Optical Properties of Silicene Quantum Dots under External Electric Fields: A DFT Investigation

Abstract:

In this study, the effect of external electric fields on the electronic and optical properties of silicene quantum dots (SiQDs) was investigated using density functional theory (DFT) within the Quantum Espresso package. The optimized SiQD structure shows a Si–Si bond length of about 2.25 Å in the central hexagon, a buckling height of 0.50 Å, and a cohesive energy of –4.05 eV/atom, confirming structural stability. When the external electric field increases from 0 to 3.0 V/Å, the Fermi level shifts significantly from –4.43 eV to –12.35 eV, while the bandgap gradually decreases, leading to an increase in the density of states at the Fermi level and a semiconductor–metal transition. Charge density and Bader charge analysis reveal uneven redistribution of electrons: atom Si1 accumulates up to 7.8 e at 3.0 V/Å, while Si4 and Si10 lose nearly all electrons in their Bader regions. For optical properties, both dielectric and absorption spectra exhibit a pronounced red-shift; the absorption peak around 1.8 eV decreases to about 1.5 eV at 3.0 V/Å, while the reflection intensity is strongly reduced in the 1–2 eV range. These results demonstrate the controllable tuning of the electronic and optical properties of SiQDs by external electric fields, highlighting their potential for optoelectronic devices, sensors, and next-generation solar technologies.

• Periodical: Advanced Materials Research (Volume 1190)
• Pages: 23-37
• DOI: https://doi.org/10.4028/p-D7fPyL
• Online since: July 2026
• Authors: Minh Tien Tran*
• Keywords: Density Functional Theory (DFT), Electronic Properties, External Electric Field, Optical Properties, Silicene Quantum Dots (SiQDs)

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