Epitaxial lift-off of La2/3Sr1/3MnO3 membranes enabled by BaO sacrificial layers and restoration of the Curie temperature

Ultrathin complex-oxide membranes provide a powerful platform for strain engineering, interfacial control, and heterogeneous integration; however, their formation remains constrained by the availability and performance of suitable water-soluble sacrificial layers. This study demonstrates that barium oxide (BaO) serves as a highly efficient and rapidly dissolving water-soluble sacrificial layer, enabling the epitaxial lift-off and transfer of ultrathin La2/3Sr1/3MnO3 (LSMO) membranes onto SiOx/Si substrates. LSMO membranes with a thickness of ∼8 nm are released using a BaO sacrificial layer grown by molecular beam epitaxy, while high crystallinity is preserved and Ba interdiffusion is limited to a narrow interfacial region of ∼0.5 nm. Post-transfer oxygen annealing at 600 °C increases the Curie temperature (TC) from 342 to 346 K by eliminating Mn2+ states associated with oxygen vacancies generated through oxygen extraction into the BaO layer. These results show that BaO provides a fast, scalable, and compositionally simple route for complex-oxide membrane release, while brief oxygen annealing is essential to restore the optimal Mn valence state and achieve the intrinsic high TC. These findings are directly relevant to oxide-based electronic and spintronic applications.