Morphological studies of Ni clusters on SrTiO3 (001) and (110)

Abstract Ni clusters grown on SrTiO 3 (0 0 1) and (1 1 0) substrates were studied with UHV-TEM. Before Ni deposition, both surfaces were cleaned effectively by electron beam annealing and showed atomic level flatness. Both surfaces seemed to have simple 1 × 1 structures. SrTiO 3 (1 1 0) substrates are supposed to have O-vacancies on surfaces and inside. Ni clusters grow about 2–5 nm in sizes, and their interfacial structures and morphologies depend on substrate surface orientations. While clusters on SrTiO 3 (0 0 1) grow with cube-on-cube epitaxial relationship, those on SrTiO 3 (1 1 0) have two kinds of interfaces. In both cases, most of the clusters match the Winterbottom construction. On SrTiO 3 (0 0 1) surfaces this appears as truncated pyramids. On SrTiO 3 (1 1 0) surfaces they are either huts or hexagons. Those clusters are under the condition of partial wetting. Interface bonding energies are estimated based on their morphologies.