Ferroelectric properties of vertically aligned nanostructured BaTiO ₃-CeO₂ thin films and their integration on silicon

Epitaxial (BaTiO₃)_0.5(CeO₂)_0.5 films have been deposited in vertically aligned nanocomposite form on SrTiO ₃/TiN buffered Si substrates to achieve high-quality ferroelectrics on Si. The thin TiN seed layer promotes the epitaxial growth of the SrTiO ₃ buffer on Si, which in turn is essential for the high-quality growth of the vertically aligned nanocomposite structure. X-ray diffraction and transmission electron microscopy characterization show that the films consist of distinct c-axis oriented BaTiO₃ and CeO₂ phases. Polarization measurements show that the BaTiO₃-CeO₂ films on Si are actually ferroelectric at room temperature, and the ferroelectric response is comparable to pure BaTiO₃ as well as the BaTiO ₃-CeO₂ films on SrTiO₃ single-crystalline substrates. Capacitance-voltage measurements show that, instead of decreasing, the Curie temperature increases to 175 and 150 C for the samples on SrTiO ₃ and Si substrates, respectively. This work is an essential step towards integrating novel nanostructured materials with advanced functionalities into Si-based devices.