Splitting of surface-related phonons in Raman spectra of self-assembled GaN nanowires

Micro Raman spectroscopy studies have been performed on GaN nanowires grown by Plasma‐Assisted Molecular Beam Epitaxy on Silicon (111) substrate. From the analysis of experimental data, the emergence of a two peaks band located near 700 cm−1 has been attributed to the Raman scattering by surface‐related phonons. We have analyzed the surface character of these two modes by changing the dielectric constant of the exterior medium and some experimental parameters. Furthermore, a theoretical model describing the nanowires ensemble by means of an effective dielectric function has been used to interpret the Raman scattering results. Those numerical simulations are in reasonable agreement with experimental observations and suggest that these two peaks resulting from the splitting of surface‐related phonon into axial and planar modes can be used as a probe of the dielectric properties of the nanowires environment (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)