Photoluminescence from Si nanocrystals obtained by electrochemical methods embedded in a silicon oxide matrix

Silicon rich oxide has shown photoemission. However, normally it is required a high temperature annealing in order to get intense emission. On the other hand, Si nanocrystals, nC, obtained by electrochemical methods and poured in a solutions have shown photoemission that depends on their size. Then, Si nC obtained by electrochemical methods are an alternative to obtain emissive silicon rich oxide without high temperature annealing. In this paper a study about photoluminescence (PL) spectra in silicon nanocrystal layers is presented. Si nc obtained by electrochemical process and suspended in colloidal solutions show photoluminescence. PL spectra show characteristics peaks in ~700 nm and ~400 nm. After that, the silicon nanocrystals are deposited on silicon substrates by evaporation of the colloidal and covered with a spin on glass (SOG) layer. FTIR spectroscopy show an increase of superficial Si-O defects in films after thermal annealing at 1100°C in Nitrogen environment. Finally, the PL spectra from annealed samples shifts toward 550 nm, compared to that in colloidal solution. The shift is due to superficial defects in silicon nanocrystals. Analysis of the FTIR data and PL spectra can be correlated to explain this and results are presented.