Influence of SnO2 coating and annealing on the luminescence properties of porous silicon nanowires

Porous silicon (PS)-core/SnO2-shell nanowires (NWs) were synthesized by a two step process: electrochemical anodization of silicon followed by atomic layer deposition of SnO2. The photoluminescence spectrum of the PS nanowires showed a broad blue green emission band centered at approximately 510 nm. PL measurement also showed that the blue green emission was enhanced by SnO2 coating and enhanced further by thermal annealing. It appeared that annealing in a reducing atmosphere was more efficient in increasing the blue green emission intensity than annealing in an oxidizing atmosphere. Energy-dispersive X-ray spectroscopy revealed that the enhancement in the blue green emission by annealing in a reducing atmosphere was attributed to the formation of Sn interstitials in the PS cores due to the dissociation of the SnO2 shells followed by the diffusion of the Sn atoms, generated as a result of the dissociation of SnO2, into the PS cores during the annealing process. (C) 2011 Elsevier By. All rights reserved.