Origin of preferential orthorhombic twinning in SrRuO3 epitaxial thin films

In order to elucidate the driving forces which promote oriented in-plane crystallographic texture in SrRuO3 thin films deposited on stepped SrTiO3 substrates, a high-temperature x-ray analysis of both SrRuO3 thin films and powders was conducted. Structural phase transitions were found at temperatures near 350 °C and slightly above 600 °C. The transitions are tentatively indexed as orthorhombic to tetragonal and tetragonal to cubic, respectively. These results suggest that SrRuO3 thin films grow with cubic symmetry. As such, film–substrate interfacial characteristics, rather than a preferred growth direction, are believed to determine the orientation of orthorhombic twins.