Saúl Estandía defens his PhD Thesis

Nanoscale Study of Epitaxial Ferroelectric Hf0.5Zr0.5O2 Thin Films and BaTiO3/SrTiO3 Superlattices

Date: Friday, 28 May 2021
Time: 11 am

Abstract: This thesis focuses on the characterization of ferroelectric Hf0.5Zr0.5Othin films and BaTiO3/SrTiOsuperlattices by combining scanning transmission electron microscopy, which allows to image the structure and chemistry locally with atomic resolution, with ferroelectric and structure measurements as x-ray diffraction. The first block revealed the ferroelectric dipole configurations in ferroelectric/paraelectric BaTiO3/SrTiO3 superlattices of different periods. A distinct configuration was found in the longest period BaTiO3/SrTiO3 superlattice (10 unit cell-BaTiO3/10 unit cell-SrTiO3), where unforeseen rotations of the polarization were directly imaged. The second block studied the stabilization of ferroelectric Hf0.5Zr0.5Oon perovskite substrates. Since the discovery of ferroelectricity in HfO2-based materials in 2011 these materials have attracted much attention, given their CMOS compatibility and robust nanoscale ferroelectricity, which bears profound advantages for applications. The strong effects of the bottom electrode and the epitaxial stress on the ferroelectricity of Hf0.5Zr0.5Othin films were studied in detail. 

Supervisors:

  • Florencio Sánchez, MULFOX group, ICMAB-CSIC
  • Jaume Gázquez, MULFOX group, ICMAB-CSIC