Dielectric Constants of Silicon Quantum Dots

Quantum mechanical pseudopotential calculations of the absorption spectra and static dielectric constant ₒ of Si quantum dots with 100-1300 atoms are presented. The predicted ₒ is found to be significantly reduced relative to the bulk value, but is considerably larger than the value deduced from currently available model calculations. A convenient parametrization of ₒ vs size R is provided. We find that for quantum dots with R<20 the electron-hole pair is confined by the physical dimension of the dot, not by the Coulomb attraction.