Highly enhanced Raman scattering from coupled vertical silicon nanowire arrays

Abstract

Vertical silicon nanowire (SiNW) arrays were fabricated in square lattices with varying diameters, pitches, and lengths, in order to investigate the effects on Raman scattering enhancement. An increase in absolute intensity of the 520 cm−1 vibrational mode by a factor of 15 was achieved for 1.1 μm long SiNWs with diameter of 115 nm arranged 400 nm apart. An oscillatory behaviour in the Raman intensity was also observed with increasing diameter, which is a result of constructive and destructive interferences within the array. A maximum Raman enhancement per unit volume (REV) of 838 was achieved for 115 nm diameter SiNWs with a length of 1.1 μm. The experimental REV results were supported and modelled quantitatively using finite difference time domain simulations.