Dielectric mismatch and central-cell corrections in doped silicon nanodots

摘要

The effect of the central-cell corrections on the shallow donor states in Si spherical quantum dot is studied within the effective mass approximation. Finite step-like spatial confining potential, Coulomb and image charge potentials arising from the dielectric mismatch at the interface of the media are taken into account. We found that it is possible to tune the impurity energies by varying the dot radius and dielectric constant of the barrier material. In the strong confinement regime, due to the enhanced weight of the donor wave functions on the impurity atoms, large values of the chemical shifts for typical donors in Si compared to the ones in bulk are obtained. The calculated size-dependence of the effective Bohr radius in donor doped nanocrystals is in reasonable accord with electron spin resonance measurements on Si quantum dots embedded in insulating glass matrices. We conclude that both the dielectric mismatch and central-cell corrections must be considered in the study of these systems in order to obtain satisfactory agreement with experimental data.