  Self-organized monocrystalline Au nanoparticles with potential applications
in plasmonics are grown in a SrTiO$_3$ matrix by a novel two-step deposition
process. The crystalline preferred orientation of these Au nanoparticles is
investigated by synchrotron hard x-ray diffraction. Nanoparticles
preferentially align with the (111) direction along the substrate normal (001),
whereas two in-plane orientations are found with $[110]_{SrTiO_3} \: || \:
[110]_{Au}$ and $[100]_{SrTiO_3} \: || \: [110]_{Au}$. Additionally, a smaller
diffraction signal from nanoparticles with the (001) direction parallel to the
substrate normal (001) is observed; once again, two in-plane orientations are
found, with $[100]_{SrTiO_3} \: || \: [100]_{Au}$ and $[100]_{SrTiO_3} \: || \:
[110]_{Au}$. The populations of the two in-plane orientations are found to
depend on the thickness of the gold film deposited in the first step of the
growth.
