Raman scattering study on pristine and oxidized n-type porous silicon

We have investigated the effects of oxidation on Raman spectra of porous silicon (PS). Many Si–H x bonds were indicated in as-anodized PS. Compared to crystalline silicon, the background in the spectrum was stronger which indicates that the PS surface was rough due to the presence of pores. When oxidation was performed, the Raman spectrum revealed the presence of nanocrystalline silicon in freshly prepared PS whose diameter was around 5.22 nm. The Raman analysis showed that the peak intensities sharply decrease after oxidation compared to the as-prepared because the bonds of Si–H x on the PS surface are greatly reduced after oxidation. The oxidation of PS by thermal oxidation is complete; therefore, thermal oxidation is very well suited for a passivation of PS films.