The effects of surface reconstruction upon the absorption spectra and optical gaps of hydrogen-terminated silicon clusters were studied. The spectra and gaps were computed using an ab initio method based upon linear response theory within the time-dependent local-density approximation. The calculations showed that the structural reconstruction of cluster surfaces produced new absorption bands in the lower part of the spectrum and caused a significant reduction in the optical gap. The optical gaps in surface-reconstructed silicon clusters appeared to be similar in size to those in clusters with partially oxidized surfaces. The results suggested that both surface oxidation and surface reconstruction were essential in resolving disagreements between the optical gaps measured in experiments and theoretical predictions based upon a quantum confinement model.

Optical Properties of Hydrogenated Silicon Clusters with Reconstructed Surfaces. I.Vasiliev, R.M.Martin: Physica Status Solidi B, 2002, 233[1], 5-9