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

The cubic perovskite SrMoO 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 SrMoO thin films by hydrogen-free sputtering has hindered their practical use, especially due to the formation of thermodynamically favorable SrMoO impurity. In this work, we developed a radio frequency sputtering technology enabling the reduction reaction and achieved conductive epitaxial SrMoO films with pure phase from a SrMoO target in a hydrogen-free, pure argon environment. We demonstrated the significance of controlling the target-to-substrate distance (TSD) on the synthesis of SrMoO; the film resistivity drastically changes from 1.46 × 10 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 SrMoO with an epitaxial perovskite structure. The formation mechanism of the conductive single-phase SrMoO 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 SrMoO films, while the high-resistive ones displayed semiconductor-like behavior. Our approach makes hydrogen-free, reliable and cost-efficient scalable deposition of SrMoO films possible, which may open up promising prospects for a wide range of future applications of oxide materials.