Ultraviolet and Long-Lived Blue Luminescence of Oxidized Nano-Porous Silicon and Pure Nano-Porous Glass

Abstract

Heavily oxidized porous silicon exhibits a strong blue light emission band including a long-lived phosphorescence component, particularly strong below 200 K. Its origin is related to molecular species in the silicon/silicon oxide nanostructure. In this paper, we show that porous glass also exhibits the same phenomenon, supporting the fact the silicon phase in oxidized porous silicon is not involved in the blue emission process. In addition, a new emission band, in the ultraviolet (UV) region (270–295 nm), has been identified in both of these porous materials. It is associated to a very narrow absorption band, with a very small Stokes shift. It was not found correlated to the blue emission band. Moreover, the effect of sample exposure to liquid ethanol, resulting in the removal of carbon-related contaminants from the surface, was studied. The blue band was almost not affected, whereas the UV band was dramatically enhanced. The latter band was attributed to molecular species, present in air, adsorbed at the surface.