Polarized and diameter-dependent Raman scattering from individual aluminum nitride nanowires: The antenna and cavity effects

Abstract

Raman scattering of individual aluminum nitride (AlN) nanowires is investigated systematically. The axial direction of single nanowire can be rapidly verified by polarized Raman scattering. The angular dependencies of E2(high) mode show strongly anisotropic behavior in smaller nanowires, which results from optical antenna effect. Raman enhancement (RE) per unit volume of E2(high) increases with decreasing diameter of nanowires. Compared to the thin film, ∼200-fold increase of RE is observed in AlN nanowires having diameter less than 50 nm, which is far beyond the quantum confinement regime. Such a large RE can be attributed to the effects of resonant cavity and stimulated Raman scattering.