Strong luminescence emission enhancement by wet oxidation of pyrolytic silicon nanopowders

A strong luminescence enhancement of several orders of magnitude was obtained using a wet chemical oxidation process on silicon nanopowders (Si-np) produced by laser-assisted pyrolysis of silane. IR absorption spectroscopy, X-ray diffraction analysis and Raman characterization of the as-prepared and processed Si-np show that the oxidation process acts on the oxide layer surrounding the particles by improving its stoichiometry, without affecting the inner crystalline silicon core. Accordingly, the luminescence emission band was centered at about 780 nm and was not shifted after the oxidation process. These results point out the importance of the quality of the oxide capping layer for the passivation of defects which can otherwise quench the luminescence emission.