Orientation-dependent growth of Ni clusters on SrTiO

TLDR: In this article, the effects of surface orientations and preparation conditions on Ni clusters were investigated using a combined ultrahigh-vacuum transmission electron microscopy/scanning tunnelling microscopy (UHV-TEM/STM) system.

Abstract: Surface conditions of oxide substrates greatly influence the physical properties of clusters and films grown on them. To investigate the effects of surface orientations and preparation conditions, Ni clusters were grown on SrTiO3 (001), (110), and (111) substrates, and studied using a combined ultrahigh-vacuum transmission electron microscopy/scanning tunnelling microscopy (UHV-TEM/STM) system. Before Ni deposition, SrTiO3 (111) surfaces showed a partial formation of the (5 × 5) superstructure on STM samples and the (3 × 3) structure on TEM samples. The (5 × 5) superstructure formation is attributed to oxygen depletion during electron beam annealing. The (3 × 3) superstructure formation is assumed to be due to amorphization and oxygen removal during ion milling followed by enhanced oxygen self-diffusion and re-oxidation. Some of the Ni clusters have equilibrium shapes, such as square, rectangle, and hexagon, when grown on the SrTiO3 (001), (110), and (111) substrates, respectively. These can be interpreted on the basis of Winterbottom construction and are clarified as truncated pyramids, huts, and hexagons, respectively. No particular epitaxial relationship was obtained for clusters on SrTiO3 (111).