  Interest for layered Ruddlesden-Popper strongly correlated manganites of
Pr$_{0.5}$Ca$_{1.5}$MnO$_4$ as well as to their thin film polymorphs is
motivated by the high temperature of charge orbital ordering above room
temperature. We report on the tailoring of the c-axis orientation in epitaxial
RP-PCMO films grown on SrTiO$_3$ (STO) substrates with different orientations
as well as the use of CaMnO$_3$ (CMO) buffer layers. Films on STO(110) reveal
in-plane alignment of the c-axis lying along to the [100] direction. On
STO(100), two possible directions of the in-plane c-axis lead to a mosaic like,
quasi two-dimensional nanostructure, consisting of RP, rock-salt and perovskite
building blocks. With the use of a CMO buffer layer, RP-PCMO epitaxial films
with c-axis out-of-plane were realized. Different physical vapor deposition
techniques, i.e. ion beam sputtering (IBS), pulsed laser deposition (PLD) as
well as metalorganic aerosol deposition (MAD) are applied in order to
distinguish between the effect of growth conditions and intrinsic epitaxial
properties. For all deposition techniques, despite their very different growth
conditions, the surface morphology, crystal structure and orientation of the
thin films reveal a high level of similarity as verified by X-ray diffraction,
scanning and high resolution transmission electron microscopy. We found that
for different epitaxial relations the stress in the films can be relaxed by
means of a modified interface chemistry. The charge ordering in the films
estimated by resistivity measurements occurs at a temperature close to that
expected in bulk material.
