Epitaxial thin film growth of Ca₂RuO_4+δ by pulsed laser deposition

Epitaxial Ca2 Ru O4+δ thin films have been grown on (001) LaAl O3 substrate by pulsed laser deposition. X-ray diffraction and transmission electron microscopy studies show that the films are single crystal with good structural quality. The films are determined to have quasitetragonal structure with a=5.352 (8) Å, c=12.20 (9) Å and epitaxially grown on the substrate with in-plane tensile strains. C plane of the film is parallel to the substrate surface and its 〈100〉 is along 〈110〉 of the pseudocubic LaAl O3 cell. Resistivity versus temperature measurement reveals that the thin film has metallic-like behavior with low resistivity (<0.002 Ω cm) and no metal-to-insulator transition between 2 and 300 K, different from its bulk material property.