Microstructure and growth mechanism of epitaxial SrRuO3 thin films on (001) LaAlO3 substrates

SrRuO3 thin films deposited on (001) LaAlO3 substrates by 90 degrees off-axis sputtering at 600 degreesC were studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Both AFM and cross-section TEM investigations show that the films have a rough surface. Plan-view TEM studies demonstrate that the films are composed of all three different types of orientation domains (twins). These domain structures and surface morphology are different from the SrRuO3 film deposited on the (001) SrTiO3 substrate which has an atomically flat surface and is composed of only the [110]-type domains. The reason for these differences was ascribed as the effect of lattice mismatch across the film/substrate interface. It is proposed that a SrRuO3 thin film grows on a (001) SrTiO3 substrate through a two-dimensional nucleation process, while a film on LaAlO3 grows with three steps: the coherent growth of a few monolayers at the initial stage through a two-dimensional nucleation process; the formation of misfit dislocations when the film reaches a critical thickness; and an island-like growth thereafter due to the nonuniform distribution of stress along the film surface. (C) 2001 American Institute of Physics.