Crystallographic investigation of Au nanoparticles embedded in a SrTiO₃ thin film for plasmonics applications by means of synchrotron radiation

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.