Epitaxial Ca₂RuO_4+δ thin films grown on (001) LaAlO₃ by pulsed laser deposition

Ca₂RuO_4+δ single crystal has shown intriguing physical properties that are the focus of many recent studies. In this work, epitaxial Ca₂RuO_4+δ thin films have been grown by pulsed laser deposition technique. The crystallinity and microstructures of the films were studied by both X-ray diffraction and transmission electron microscopy. Under carefully controlled conditions, Ca₂RuO_4+δ grows epitaxially on (001) LaAlO₃ substrate with a in-plane relationship of 〈110〉_film//〈100〉_sub. The lattice parameters of films are consistent with a strained long phase. The growth conditions that influence the film quality, such as substrate temperature, target composition, oxygen pressure and flow rate, have been systematically studied. The thin film's magnetic and electrical transport properties differ drastically from the bulk counterpart. In contrary to the bulk, our films show overall metallic behavior with no magnetic transition in temperature range of 4-300 K. A weak metal to non-metal transition at about 200 K was observed, which could be correlated to the imperfect microstructures of the thin films.