Self-limiting and complete oxidation of silicon nanostructures produced by laser ablation in water.

Oxidized Silicon nanomaterials produced by 1064 nm pulsed laser ablation in deionized water are investigated. High-resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy allows to characterize the structural and chemical properties at a subnanometric scale. This analysis clarifies that laser ablation induces both self-limiting and complete oxidation processes which produce polycrystalline Si surrounded by a layer of SiO₂ and amorphous fully oxidized SiO₂, respectively. These nanostructures exhibit a composite luminescence spectrum which is investigated by time-resolved spectroscopy with a tunable laser excitation. The origin of the observed luminescence bands agrees with the two structural typologies: Si nanocrystals emit a μs-decaying red band; defects of SiO₂ give rise to a ns-decaying UV band and two overlapping blue bands with lifetime in the ns and ms timescale. [ABSTRACT FROM AUTHOR]