Raman scattering from nanopatterned silicon surface prepared by low-energy image-ion irradiation

We report a micro-Raman study of ordered self-organized dot patterns on silicon surface realized by low-energy Ar+-ion irradiation. Atomic force microscopy reveals that the average size of the silicon nanodots on the surface varies in the range 50–60 nm with an average height of about 12–13 nm. A gradual increase in downward shift and asymmetric broadening of the phonon peaks are observed in the Raman spectra from the nanopatterned Si(1 0 0) surfaces with increasing ion-beam energy. The downward shift of the phonon peak is due to the formation of silicon nanocrystallites embedded in amorphous matrices within the patterned Si surface, which are responsible for phonon localization, while the line shape broadening is a result of the combined influence of distribution of embedded nanosilicon phases and the ion-beam-induced amorphization caused by creation of damage within the patterned surface. The effect of rapid thermal annealing (RTA) on micro-Raman spectra shows significant change of the line shape due to removal of surface damage with transformation of embedded nanocrystalline silicon matrices to crystalline silicon, and gives clear evidence of spatial phonon localization.