Giant step bunching in epitaxial SrRuO3 films on vicinal SrTiO3(001)

We report here on the giant step bunching, with steps reaching 20–40 unit cells high, observed in SrRuO3 epitaxial films on vicinal SrTiO3(001). Bunching develops in films thicker than tens of nanometers, whereas three-dimensional (3D) islands were found in thinner films. We show that bunching forms when these islands coalesce. The growth of the 3D islands on substrates having varied miscut angles is investigated. In spite of the formation of bunching from initial nucleation of islands, the final morphology of the film surface is highly ordered as statistical analysis confirmed. The influence of processing parameters on the bunching morphology was investigated, and it has been demonstrated that lateral and vertical dimensions can be separately adjusted with a proper combined selection of film growth rate and substrate miscut angle.