(4bx) First Principles Study of the Photodynamics of Oxidized Silicon Clusters

The effect of quantum confinement on the properties of semiconductor nanoparticles is well known, but also of interest are the properties which arise from the high surface-to-volume ratio of these systems. It is widely believed that imperfect surfaces result in the trapping and localization of charge carriers at the surfaces, and subsequently in recombination or emission. By modifying the surface chemistry of these nanoparticles one can therefore tune there electronic and optical properties, but the dynamics of such trapping at the atomic level is poorly understood. We have applied first principles quantum chemical and molecular dynamics methods to small silicon clusters in order to understand the effect of various surface treatments. Specific silicon-oxygen bonding configurations at the surface are found to introduce conical intersections within the band gap.  These intersections are dynamically accessible and facilitate fast nonradiative decay to the ground state.