The study on Raman spectra of Si nanowires

Phonon confinement effect results in an redshift and asymmetric broadening in the low-frequency side of Raman spectra of intrinsic silicon nanowires(SiNWs), but is not the only factor impacting the Raman spectrum of SiNWs. At high incidence laser power densities, laser heating gives a redshift and symmetric broadening, and Fano interference between the scattering from the k = 0 optic phonon and the electronic continuum scattering from laser-induced carriers gives an asymmetric line shape, i.e. Fano line shape. Furthermore, due to phonon confinement effect, the fundamental k=0 Raman selection rule is relaxed, allowing phonons away from the Brillouin zone center to participate Raman scattering too, therefore, some new weak Raman signals appear at about 604 and 423 cm(-1) in addition to the usual silicon peaks at 520, 302 and 964 cm(-1) for silicon nanowires with small diameter.