Electronic structure and interfacial properties of Ge nanoclusters embedded in amorphous silica

Silicon and germanium nanoparticles embedded in silica glass matrix have shown intriguing photoluminescence properties different from bulk crystals. In this paper, we report structural and electronic properties of a series diamond-structured germanium nanoparticles (diameter up to 1.6 nm) embedded in silica glass matrix obtained from periodic ab initio density functional theory (DFT) calculations based on models generated using the bond-switching algorithm. These large-scale DFT calculations involved hundreds of atoms and the results provide detailed atomic and electronic structural information of the embedded system including the semiconductor/glass interfaces. It was found that there exists 2–3% tensile strain in the embedded germanium nanocluster. The valance band and conduction band electron density distributions are mostly localized on the germanium cluster, different from silicon clusters. Particle size dependence of bandgap, i.e. the quantum confinement effect, has been observed in the embedded systems. The germanium/silica interfacial band energies are found to be around 1 J/m2 from DFT calculations.