  The surface-enhanced Raman scattering in graphene deposited on AlxGa1-xN/GaN
axial heterostructure nanowires was investigated. The intensity of graphene
Raman spectra was found not to be correlated with aluminium content. Analysis
of graphene Raman bands parameters, KPFM and electroreflectance showed a
screening of polarization charges. Theoretical calculations showed that plasmon
resonance in graphene is far beyond the Raman spectral range. This excludes the
presence of an electromagnetic mechanism of SERS and therefore suggests the
chemical mechanism of enhancement.
