ABSTRACT
Phonon con nement (Piscanec et al. 2003; Adu et al. 2005, 2006; Fukata et al. 2006) e ects inside the waist of small diameter Si NWs (d− < 10 nm) have been demonstrated by several
groups via Raman scattering. Surface optical (SO) phonons that lie between the usual transverse optic (TO) and the higher frequency longitudinal optic (LO) phonons of binary semiconductors have been observed by Raman scattering in SNWs and proposed to be activated by quasiperiodic modulation of the surface potential via diameter modulations from a growth instability and from faceting (Gupta et al. 2003; Xiong et al. 2004). Indeed, the observation of a sharp SO peak in the Raman spectrum requires a periodic spatial perturbation of the surface potential of the semiconductor.
