Transition from three- to two-dimensional growth in strained SrRuO3 films on SrTiO3(001)

The morphology of strained SrRuO3 films grown on SrTiO3(001) has been investigated as a function of thickness. A transition of growth mode has been observed. At the early stages, there is a fingerlike structure originated by three-dimensional (3D) islands that nucleated along the substrate steps. Afterward, adatoms stick preferentially in the valleys of the structure and the films become progressively smoother. At a thickness above 10–20 nm, the films are extremely flat and have a self-organized structure of terraces and steps, with the growth proceeding mainly by a step flow (two-dimensional) mechanism. Relevance on film properties and possible use of the initial, nanometric, 3D structures are discussed.