Minh Tien Tran
In this study, detailed investigations of the structural, electronic, and optical properties of two-dimensional silicene quantum dots (SiQDs-2D) were carried out using first-principles calculations within the framework of density functional theory (DFT). The SiQDs-2D structure was constructed from 13 Si atoms arranged in a hexagonal lattice and passivated by 9 H atoms to enhance stability. The cohesive energy was calculated to be about –2.986 eV, confirming the dynamical stability of the system. The optimized geometry shows that the Si–Si bond lengths are approximately 2.247 Å (nearest neighbor), 3.637 Å (next-nearest neighbor), and 4.275 Å (opposite sites in a hexagon), with an average bond angle of 108.05° and a buckling height of about 0.8 Å. The electronic band structure and density of states (DOS) indicate that SiQDs-2D exhibits semiconducting behavior with a narrow HOMO–LUMO gap, strongly influenced by edge effects and hydrogen passivation. The charge density distribution shows that the HOMO states are mainly localized at the edges, while the LUMO states are more delocalized across the lattice, reflecting unique electronic transition mechanisms in the system. In terms of optical properties, SiQDs-2D presents strong absorption in the ultraviolet region (peak at ~5 eV) with an absorption coefficient of about 10⁸ m⁻¹, accompanied by a low reflectivity in the visible region. The real and imaginary parts of the dielectric function reveal the presence of intrinsic plasmon resonances in the range of 5–6 eV, while the JDOS confirms the role of dominant electronic transitions in the UV region. These results not only demonstrate the stability and unique electronic–optical features of SiQDs-2D but also highlight their potential applications in optoelectronic devices, UV sensors, and ultraviolet shielding materials