Development of nanosystems in TiO2 by ion implantation

Au-ions were implanted into TiO2 single crystals with doses ranging from 2x1016Au+/cm2 to 6x1016Au+/cm2 at RT and 1000 K. At RT implanted samples were then thermally annealed at temperatures of 550 K to 1550 K. The Au-atoms precipitate to nanocrystals already during implantation at RT with an average particle size of 1.5 nm. HRTEM investigations revealed that the Au-nanocrystals, embedded in amorphous TiO2 regions, have a broad size and range distribution varying from large sizes in the near surface region to smaller sizes at larger depths. In the annealing process a reorientation of the Au-nanocrystals is observed, with the main effect of a decrease of the (111) peak and an increase of the (200)-peak in the XRD spectra. After annealing at 1000 K the particle size of the highly textured Au-implant was evaluated to ~ 6 nm; this means that during annealing the particles grow, leading to a partially coherent orientation in the disordered TiO2-matrix. Au implantation at RT performed through a metal mask with holes resulted in a narrow size distribution (2-6 nm) of the Au-nanocrystals in the near surface region.