Suppression of superconductivity by crystallographic defects in epitaxial Sr2RuO4 films

Epitaxial Sr2RuO4 thin films grown by pulsed-laser deposition from high-purity (99.98%) Sr2RuO4 targets on (001) LaAlO3 were found to be not superconducting down to 0.4 K. Structural disorder is believed to be responsible. A correlation was observed between higher resistivity ratios in electrical transport measurements and narrower x-ray diffraction rocking curve widths of the Sr2RuO4 films. High-resolution transmission electron microscopy revealed that the dominant structural defects, i.e., the defects leading to the observed variation in rocking curve widths in the films, are {011} planar defects, with a spacing comparable to the in-plane superconducting coherence length of Sr2RuO4. These results imply that minimizing structural disorder is the key remaining challenge to achieving superconducting Sr2RuO4 films.