Oxygen role on the optoelectronic properties of silicon nanodots

The optoelectronic properties of Si nanodots have been investigated using ab initio total energy calculations within the density functional theory. Structural relaxations have been considered. We have studied two types of nanodots: isolated clusters covered by H, studying the substitution of Si/H bonds with different Si/O bonds, and nanocrystals embedded in SiO2 matrix. In the first case, we find that the optoelectronic properties strongly depend on the type and the number of Si/O bonds, especially for the gap value and the arrangement of the energy levels. In the second case, the close interplay between chemical and structural effects is pointed out.