Fabrication and structure analysis of freestanding BaTiO₃-CeO₂ epitaxial nanocomposite membranes

Vertically aligned nanocomposite films hold the promise of making a significant contribution to the performance enhancement and multifunctional integration of flexible thin-film devices but are hindered by the difficulty of direct epitaxial growth on flexible substrates. In this work, freestanding BaTiO3-CeO2 epitaxial nanocomposite membranes were prepared by using water-soluble Sr3Al2O6 as the sacrificial buffer during film deposition. The membrane's lattice parameters as well as their epitaxial relationship, before and after its removal from the single-crystal substrates, were quantitatively measured and analyzed by combining x-ray diffraction and TEM. In addition, synchrotron soft x-ray absorption spectroscopy reveals the discrepancy in the surface and internal electron states of Ce and Ti via comparative studies in total electron yield mode and transmission mode, respectively. This work exemplified that freestanding membranes provide a convenient platform for (1) the study of in-plane lattice information of epitaxial oxide films via TEM and for (2) the comparative study of surface and internal electron band information of epitaxial oxide films.