Effect of oxygen on the optical properties of small silicon pyramidal clusters

Optical absorption and light emission of oxygen-incorporated small silicon (Si30H40Oi) pyramidal clusters as a function of oxygen content were theoretically studied using the self-consistent semiempirical molecular orbital method (modified neglect of diatomic overlap—parametric method). In the absolute majority of the cluster configurations with low oxygen content structures, a wide spread of the optical transition energies ranging from 1.60 to 3.00 eV is observed, due to the competition between two opposite tendencies. According to the first one, connected with the increasing of the quantum confinement effects due to oxidation, the optical transition energies tend to increase, whereas the enhanced possibility of involvement of oxygen or oxygen-adjacent silicon atoms in the process tends to decrease the energy transitions.