Mechanism of single-domain selection in epitaxial CaRuO3 thin films

CaRuO3 thin films have been grown by on axis sputtering on various (110) SrTiO3, (110) LaAlO3, and (100) NdGaO3 substrates. The growth of high-quality twin free samples, having the a axis aligned with the substrate normal, and the b and c axis aligned with the principal in-plane substrate directions, is demonstrated. The mechanism of domain selection is addressed in terms of free energy minimization during the tetragonal to orthorhombic transition, taking into account both strain and surface energy contributions. On the base of experimental data, it is shown that minimization of surface energy plays a major role in determining film orientation. Obtained samples are especially suited for the investigation of anisotropy in the macroscopic properties of Ca/Sr ruthenates.