Microstructure of Precipitated Au Nanoclusters in TiO_2

摘要

Gold nanoclusters dispersed in single crystal TiO_2 (110) have been formed by 2MeV Au~(2+) implantation to an ion fluence of 1x10~(17) cm~(-2) at 300 K and 975 K followed by annealing at 1275 K for 10 hours. The morphological features, size and crystallographic orientation of the Au nanoclusters with respect to the TiO_2 matrix have been investigated using conventional transmission electron microscopy and electron diffractions. In particular, the interface structure between the Au nanoclusters and TiO_2 was investigated. Atomic structural model of interface between Au and TiO_2 was established based on high-resolution transmission electron microscopy (HRTEM) imaging and HRTEM image simulations. Two types of orientation relationship can be identified, Au<110>//TiO_2[001] and Au{111}//TiO_2(200), and Au<110>//TiO_2[001] and Au{111}//TiO_2(110). Au clusters are faceted along Au{112}and Au{111} or Au{220} and Au{002} planes. The precipitated Au clusters show extensive (111) twins. These orientation relationships are the same for Au clusters grown on TiO_2(110) surface, indicating that lowering interfacial energy to be a governing factor for setting the orientation relationship.