Investigation of C and Si-doped 2D germanene quantum dots for potential nanotechnology applications.

In this study, the structural, electronic, and optical properties of pristine and doped two-dimensional germanene quantum dots (GeQDs) were systematically investigated using first-principles calculations based on density functional theory (DFT). The model systems consist of monolayer GeQDs comprising 37 Ge atoms with hydrogen-passivated edges, including pristine, carbon-doped, and silicon-doped configurations. All structures are found to be dynamically stable, exhibit non-magnetic metallic behavior, and show distinctive structural modifications upon doping. Notably, carbon doping significantly reduces the buckling height of the quantum dots due to its smaller atomic radius and higher electronegativity. Multi-orbital hybridization analysis reveals substantial changes in electronic orbital interactions, particularly in the Si-doped structure. Charge density difference analysis indicates that carbon atoms act as charge acceptors, while silicon atoms donate charge to the surrounding Ge lattice. Optical property calculations show strong anisotropic absorption behavior, with all configurations demonstrating pronounced absorption in the ultraviolet region and moderate absorption in the visible range. These findings suggest that pristine and doped GeQDs hold promise for applications in nanoscale electronic and optoelectronic devices, including ultraviolet photodetectors, plasmonic components, and next-generation integrated circuits.