"Quantum confinement in Si- and Ge-capped nanocrystallites",
L.E. Ramos, J. Furthmüller, and F. Bechstedt,
Phys. Rev. B 72 , 045351 (2005).

We present an ab initio plane-wave-pseudopotential investigation of Si(Ge)-capped Ge (Si) nanocrystallites. The effects of capping Si and Ge nanocrystallites on the electron-hole pair excitation energies, optical absorption spectra, localization of the highest-occupied and lowest-unoccupied molecular orbitals, Stokes shifts, and radiative lifetimes are analyzed. The bond lengths and the localization of electrons and holes in the Si (Ge) capped nanocrystallites are similar to those found in the analogous Si/Ge heterostructures. Due to the changes in the quantum confinement properties caused by the capping, there are significant differences in the electronic and optical properties of Ge-capped Si nanocrystallites and Si-capped Ge nanocrystallites.