We report first-principles calculations for optical absorption spectra of hydrogenated silicon clusters in the presence of oxygen on the surface. Our computational technique is based on linear-response theory within the time-dependent local-density approximation (TDLDA). The calculated spectra show that oxidation substantially reduces the size of optical gaps in silicon nanocrystals. This result may explain a seeming disagreement between the measured photoluminescence and theoretical predictions based on a quantum confinement model in the limit of small clusters.

• Received 22 August 2001

DOI:https://doi.org/10.1103/PhysRevB.65.121302