Raman scattering and photoluminescence studies on O+ implanted silicon

The effects of 125 keV oxygen ion implantation with fluences from 10(14) to 10(16) ions/cm(2) on (100) cut crystalline silicon (c-Si) have been investigated by Raman scattering and photoluminescence techniques. A systematic decrease in the area and frequency of longitudinal optical (LO) phonon Raman mode and increase in its full-width at half-maximum (FWHM) have been observed with increase of fluence. The temperature at the incident laser spot on the implanted Si increases with fluence. The behavior of peak position and FWHM is due to implantation-induced lattice damage. The decrease in area of the mode is due to the decrease in the volume fraction of c-Si in the implanted layer. The disappearance of the Raman LO mode of c-Si and the appearance of the Raman mode for the amorphous Si (a-Si) have been observed for 10(16) O+ /cm(2) fluence, suggesting the amorphization of the implanted layer. The increase in the temperature is due to the poor thermal conductivity of a-Si and increased photon absorption due to implantation induced lattice disorder. Photoluminescence (PL) in the range of 1.8-2.52eV shows a peak at 2.35eV with 0.4eV FWHM for all fluences. Its area increases with fluence and saturates. These results are due to a-Si nanozones created by the O+ impact and coalesce of such nanozones at high fluences. The average size of the a-Si nanozone estimated from PL peak position (2.05 nm) and that from the critical fluence for amorphization (1.9 nm) match very well. (C) 2003 Elsevier B.V. All rights reserved.