Raman scattering in silicon disordered by gold ion implantation

Si (111) covered by a 250-nm thick SiO(2) surface layer has been disordered through implantation of 3.035 MeV gold ions within broad range of fluences from 1 x 10(13) ions/cm(2) to 1 x 10(16) ions/cm(2). Raman spectroscopy (514.5 nm laser) was applied for characterization of the silicon disordering. Variation of the Raman spectra of silicon after low-fluence implantation (fluences lower than 5 x 10(14) ions/cm(2)) in the vicinity of the transverse optical phonon (1TO) peak reflects the coexistence of bulk Si crystals (c-Si) and Si nanocrystals (nc-Si) in the implanted layer. Implantation with higher fluences yields only the stable 470 cm(-1) 1TO peak, corresponding to formation of amorphous phase (a-Si), in this region of the spectra. Detailed analysis of the silicon disorder was performed through calculation of the transverse acoustical phonon (1TA) peak area. The fluence dependence of the peak area reveals qualitative correlation with the depth profile of structural defects in the modified Si layer evaluated from RBS (Rutherford backscattering) experiment and from SRIM (stopping and range of ions in matter) code simulation. This correlation suggests a decrease of the structural disorder in the modified layer region enriched by vacancies. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim