Heteroepitaxial growth of $RuO2$ thin films on $α-Al2O3$ substrates with $CeO2$ buffer layers by pulsed laser deposition

Metallic conductive ruthenium oxide thin films have been grown epitaxially on sapphire (01 $1̄$ 2) with a cerium oxide buffer layer by pulsed laser deposition. We used transmission electron microscopy, high-resolution electron microscopy, and x-ray diffraction to characterize the growth behavior of the films and the orientation relationship between the films and the substrate. Our electron diffraction and x-ray diffraction studies indicate that the orientation relationships are $(200)RuO2 //(200)CeO2 //(011̄2)Al2O3$ and $〈011〉RuO2//〈001〉CeO2//〈22̄01〉Al2O3.$ All of the interfaces were seen to be atomically sharp by cross-sectional, high-resolution transmission electron microscopy in the as-grown samples. No precipitates or additional phases were found in the films or at their interfaces.