PNNL

Abstract

Gold nanoclusters dispersed in single crystal SrTiO3(001) have been prepared by ion implantation at both 300 K and 975 K followed by annealing at 1275 K for 10 hours. Transmission electron microscopy (TEM), high-resolution TEM, high angle annular dark-filed (HAADF) imaging in an aberration corrected dedicated scanning TEM (STEM), and image simulations were used to study the morphology, size, and crystallographic orientation of the Au nanoclusters with respect to the SrTiO3 matrix, as well as the interface structure between the Au nanoclusters and SrTiO3. Implantation of gold at 300 K leads to amorphization of SrTiO3 surface layer, which is corrugated to form bumps and valleys on the surface. Annealing at 1275 K for 10 hours leads to epitaxial re-crystallization of the amorphized layer within which Au clusters of several nanometers and a narrow size distribution were formed. Implantation at 975 K and subsequently annealing leads to Au cluster size of ~ 50 nm and a very wide size distribution. The precipitated Au clusters possess an epitaxial orientation with the SrTiO3, such that Au[001]//SrTiO3[001] and Au(100)//SrTiO3(100). The critical size of the Au cluster for transition from strain-matched interface to dislocation relaxed interface has been found to be ~ 7 nm. Cavities formed by condensation of vacancies were faceted along {001} and {011} planes in the SrTiO3 matrix. It is generally implied that implantation below a critical temperature may lead to a finer Au cluster size.