Raman scattering and photoluminescence studies on O+ implanted porous silicon

The effects of 125 keV O+ implantation on porous silicon (PS) in the fluence range from 10(14) to 10(16) cm(-2) have been investigated using Raman scattering and photoluminescence techniques. PS has been prepared by anodically etching (100) cut n-type crystalline silicon (c-Si). Raman spectra of PS have been generated using a model of phonon confinement in Si nanocrystallites and compared with experiment. As the fluence increases, the Si nanocrystallite size estimated from the Raman spectra decreases. Unimplanted PS shows a visible photoluminescence (PL) peak at 2.02 eV, with 0.3 eV FWHM coming from electron confinement in Si nanocrystallites. Its intensity decreases due to the creation of non-radiative recombination centers and the peak position increases due to nanocrystallites size reduction with increase of fluence. On O+ implantation, PS shows an additional visible PL at 2.35 eV with 0.3 eV FWHM due to amorphous silicon (a-Si) nanozones created by O+ single ion impact. Evidence for this PL peak is provided from O+ implanted c-Si. 2.35 eV PL intensity in O+ implanted PS is 10 times higher than that in O+ implanted c-Si. (C) 2004 Elsevier B.V. All rights reserved.