Temperature-Dependent Structure of Epitaxial (Ba,Sr)TiO₃ Films Grown on SrRuO₃-Covered SrTiO₃ Substrates

Growth dynamics of epitaxial (Ba,Sr)TiO₃ thin films deposited at different temperatures on SrRuO₃/SrTiO₃ substrates by pulsed laser deposition is investigated by transmission electron microscopy. The films exhibit a layered structure comprising sublayers with distinctive features in regard to the remaining strain, density of misfit dislocations and/or lattice defects, and growth habit. We correlate these temperature-dependent features with the predominant misfit-strain relaxation mechanisms for each one of the detected growth regimes. The thickness dependence of the film structure is discussed within the framework of the predictions for a kinetically modified Stranski--Krastanov growth mode.