Atomic resolution imaging of Au nanocluster dispersed in TiO ₂, SrTiO ₃, and MgO

Gold nanoclusters dispersed in single crystal TiO2, MgO, and SrTiO3 have been prepared by ion implantation at 300-975 K and subsequent annealing at 1275 K for 10 h. High-resolution transmission electron microscopy and high-angle annular dark field (HAADF) imaging in aberration corrected scanning transmission electron microscope (STEM) have been used to characterize the microstructure of the gold nanoclusters dispersed materials. STEM-HAADF imaging with atomic resolution has directly revealed for all three materials that Au atoms partially occupy cation lattice positions. Cavities up to several tens of nanometers were observed in MgO and SrTiO3. The cavities and gold clusters are spatially associated in MgO and SrTiO3, indicating a strong interaction between the Au cluster and cavities. For MgO and SrTiO3, the faceting planes appear to be the same for both nanometer-sized cavity and the Au cluster, demonstrating that both the surface energy and the interfacial energy between Au cluster and the matrix are lowest on these planes.