Structure and surface morphology of highly conductive RuO₂ films grown on MgO by oxygen-plasma-assisted molecular beam epitaxy

Metallic RuO₂(110) thin films were grown by oxygen-plasma-assisted molecular beam epitaxy (MBE) on MgO(100) and (110) at 425 °C. RuO₂ films on MgO(100) are epitaxial with two variants, while RuO₂ films on MgO(110) are highly oriented with the (110) face parallel to the substrate surface. The two variants in the RuO₂(110) epitaxial films resulted in a twofold mosaic microstructure. The RuO₂(110) epitaxial films are very smooth and exhibit a low resistivity of ∼ 36 μΩ-cm. In contrast, the RuO₂(110) textured films are very rough, and consist of small grains with a poor in-plane alignment. A slight higher resistivity (49 μΩ-cm) was found for the RuO₂ (110) textured films grown on MgO(110).