Films Grown Via a Novel Hybrid MBE Approach

Functional oxide heterostructures grown using molecular beam epitaxy (MBE) can have atomically abrupt interfaces, enabling the systematic study of their intrinsic properties. In particular, heterostructures using epitaxial SrRuO₃ as metallic electrodes for electronic devices have been widely studied. SrRuO₃ exhibits itinerant ferromagnetism at low temperatures and topological behavior which are of significant interest in magnetic devices. The conventional MBE growth of SrRuO₃ has been challenging due to the low vapor pressure of Ru, requiring electron beam evaporation. Ru also has a higher electronegativity than most B-site cations in ABO₃-type compounds, requiring stronger oxidants like ozone to form Ru⁴⁺. The conventional process is, therefore, prone to flux instabilities and demands highly reactive oxidants during growth. Here, we report a novel MBE approach with scalable growth rates for the growth of (110)_O SrRuO₃ on (001) SrTiO₃. Initial growth optimization yielded atomically smooth, epitaxial, phase pure SrRuO₃ films with a rms roughness of ~230 pm. Films were conductive with room temperature resistivities of ~200 µΩ cm. We will discuss the effect of substrate temperature and Sr/Ru flux ratio on stoichiometry, surface morphology, carrier density and magnetic properties.