Conductive single-phase SrMoO₃ epitaxial films synthesized in pure Ar ambience via plasma-assisted radio frequency sputtering

The cubic perovskite SrMoO₃ with a paramagnetic ground state and remarkably low room-temperature resistivity has been considered as a suitable candidate for the new-era oxide-based technology. However, the difficulty of preparing single-phase SrMoO₃ thin films by hydrogen-free sputtering has hindered their practical use, especially due to the formation of thermodynamically favorable SrMoO₄ impurity. In this work, we developed a radio frequency sputtering technology enabling the reduction reaction and achieved conductive epitaxial SrMoO₃ films with pure phase from a SrMoO₄ target in a hydrogen-free, pure argon environment. We demonstrated the significance of controlling the target-to-substrate distance (TSD) on the synthesis of SrMoO₃; the film resistivity drastically changes from 1.46 × 10⁵ μΩ·cm to 250 μΩ·cm by adjusting the TSD. Cross-sectional microstructural analyses demonstrated that films with the lowest resistivity, deposited for TSD = 2.5 cm, possess a single-phase SrMoO₃ with an epitaxial perovskite structure. The formation mechanism of the conductive single-phase SrMoO₃ films can be attributed to the plasma-assisted growth process by tuning the TSD. Temperature-dependent resistivity and Hall effect studies revealed metal-like conducting properties for low-resistive SrMoO₃ films, while the high-resistive ones displayed semiconductor-like behavior. Our approach makes hydrogen-free, reliable and cost-efficient scalable deposition of SrMoO₃ films possible, which may open up promising prospects for a wide range of future applications of oxide materials.