Abstract

The microstructures of Ru-excess SrRuO 3 films, which were grown epitaxially on SrTiO 3 substrates by ion-beam sputtering, were studied by transmission electron microscopy. The excess Ru can be accommodated by forming extended defects on the {100} planes, faulted dislocation loops, by making RuO 2 double layers. However, the most stable crystalline phase of the excess Ru in SrRuO 3 film was metallic Ru with a hexagonal structure. The orientation relationship between the Ru precipitates, the SrTiO 3 substrate, and the SrRuO 3 film can be described as follows: Ru // STO // SRO and [100] Ru //[110] STO //[110] SRO where the subscripts STO and SRO indicate SrTiO 3 and SrRuO 3 respectively. Owing to the difference between the crystal symmetries of Ru and SrTiO 3 , the precipitates showed different in-plane alignments along two perpendicular directions on the substrate and accordingly different anisotropic growth morphologies. The precipitates degrade the film surface by making deep trenches and act as sources for defect generation