Strain Effect on Structural Transition in SrRuO3 Epitaxial Thin Films

We carried out detailed structural characterizations across the structural transition in SrRuO3 epitaxial thin films grown on SrTiO3 (001)(pc) substrate. The fabricated films undergo a structural transition from the low-temperature orthorhombic phase to the high-temperature pseudocubic phase at 280 degrees C. We find that, for films thinner than 20 nm, the transition becomes broader while thicker films display a sharp transition. Detailed X-ray diffraction measurements including reciprocal space mappings at various temperatures also reveal that the thinner films have a distorted orthorhombic unit cell resulting from the strain-induced additional rotation in the RuO6 octahedra, while, for the high-temperature pseudocubic phase, the film structure remains the same irrespective of film thickness. The results strongly suggest that the substrate-induced strain has a strong influence on the RuO6 rotation pattern in the epitaxial thin films