  Gallium nitride nanowire and nanorod substrates with different morphology are
prospective platforms allowing to control the local strain distribution in
graphene films top of them, resulting in an induction of pseudomagnetic fields.
Atomic force microscopy measurements performed in a HybriD mode complemented by
scanning electron microscopy allow for a detailed visualization of the strain
distribution on graphene surface. Graphene in direct contact with supporting
regions is tensile strained, while graphene located in-between is characterized
by lower strain. Characteristic tensile strained wrinkles also appear in the
areas between the supporting regions. A detailed analysis of the strain
distribution shows positive correlation between strain gradient and distances
between borders of supporting regions. These results are confirmed by Raman
spectroscopy by analysis the D' band intensity, which is affected by an
enhancement of intravalley scattering. Furthermore, scanning tunneling
spectroscopy shows a local modification of the density of states near the
graphene wrinkle and weak localization measurements indicate the enhancement of
pseudomagnetic field-induced scattering. Therefore, we show that nanowire and
nanorod substrates provide strain engineering and induction of pseudomagnetic
fields in graphene. The control of graphene morphology by a modification of
distances between supporting regions is promising for both further fundamental
research and the exploration of innovative ways to fabricate pseudomagnetic
field-based devices like sensors or filters.
