Influence of growth mode on stoichiometry in epitaxial calcium ruthenate thin films

Clear evidence about the influence of growth orientation on the stoichiometry of sputtered oxide thin films is reported and discussed. The growth of stoichiometric and of non-stoichiometric films is respectively obtained, from the same CaRuO3 target, on the surface of (110) and (100) perovskite substrates. Such phenomenon has been systematically investigated by deposition of pairs of samples in the same deposition run. Our data show that in samples deposited on (100) perovskites, Ca excess leads to the formation of a single Ca-rich phase with stoichiometry Ca1+xRu1-xO3, resulting in a dramatic effect on transport properties. Structural characterization based on X-ray diffraction proves that the orthorhombic structure is preserved in a wide stoichiometry range. The striking evidence that substrate orientation influences film stoichiometry is discussed in terms of growth kinetics and chemical properties of sputtered species.