Raman spectral study of silicon nanowires: High-order scattering and phonon confinement effects

Raman-scattering spectra of silicon nanowires (SiNW's) with different diameters were obtained at room temperature, The Raman peaks of SiNW's were found to shift and to broaden with decreasing diameter of the SiNW's, In addition to the fundamental phonon modes, overtone and combination modes were also observed and identified according to the selection rules of overtone and combination bands. A phonon confinement model was used to explain the experimental results of observed phonon modes. The results show that the confinement effect becomes more obvious when the SiNW diameter is less than 22 nm. The present results should be of benefit to the applications of SiNW's.