  The paper presents briefly some general points of the theory of Surface
Enhanced Raman Scattering on metals, semiconductors, dielectrics and graphene.
It is pointed out that the reason of SERS on graphene and some other 2D
materials is not the chemical enhancement mechanism as it is widely accepted in
literature, but ripples, which are necessarily present on a graphene surface
and are analogues of the surface roughness, which is a reason of SERS. In
addition, it is indicated that the quadrupole interaction, which arises in
strong SERS is practically absent in the system with graphene. The results are
confirmed by the analysis of the SERS, usual Raman and IR spectra of
phthalocyanine molecule and by some other experimental data.

Optics