Microstructure of heteroepitaxially grown RuO2 thin films on MgO by pulsed-laser deposition

Conductive ruthenium oxide (RuO 2 ) thin films with a room-temperature resistivity of 35 μΩ cm and a residual resistivity ratio above 5 have been heteroepitaxially grown on MgO(100) substrates by pulsed-laser deposition. The heteroepitaxial growth of RuO 2 on MgO is confirmed by both the strong in-plane and the strong out-of-plane orientation of the film with respect to major axes of the substrate. The orientation relationship between the RuO 2 film and the MgO substrate, deduced from both X-ray and electron diffraction, is (100) RuO2 ∥(100) MgO and [001] RuO2 ∥[011] MgO (and [110] RuO2 ∥[011] MgO ). High-resolution electron microscopy reveals that the epitaxial RuO 2 film contains two variants that are consistent with the X-ray diffraction measurement.