Solid Phase Epitaxy of SrRuO₃ encapsulated by SrTiO₃ membranes

Solid phase epitaxy (SPE) has been extensively studied for various thin film materials. This process involves annealing a pre-deposited amorphous layer on an epitaxial substrate, resulting in the formation of a single-crystalline thin film. Such films have found widespread use in industrial applications including metals and semiconductor thin films. In the case of complex oxides, achieving precise stoichiometric control during the growth of SPE-produced oxide thin films can be particularly challenging, especially when volatile phases are present at elevated temperatures.

In this study, we present our recent efforts to investigate the impact of encapsulation during the SPE process, using SrRuO₃ (SRO) as a model system. Amorphous SRO layers were deposited onto SrTiO₃ (STO) substrates at room temperature. Next, single-crystalline STO membranes were transferred onto the films, serving as encapsulation layers to prevent the evaporation of volatile species during the SPE process. Both unencapsulated and encapsulated SRO layers were successfully crystallized via SPE. However, we observed that the unencapsulated films experienced a substantial loss in Ru concentration (exceeding 20%) in comparison to the encapsulated counterpart. The study demonstrates that the encapsulation provided by oxide membranes effectively minimized stoichiometric loss during the traditional SPE procedure and enhanced surface quality, suggesting a promising avenue for the synthesis of functional oxide thin films.