Nanoscale Study of Epitaxial Ferroelectric Hf_0.5Zr_0.5O₂ Thin Films and BaTiO₃/SrTiO₃ Superlattices

by Saúl Estandía, Multifunctional Thin Films and Complex Structures (MULFOX) group, ICMAB, CSIC

Date: Friday, 28 May 2021
Time: 11 am
Venue: ICMAB Seminar Room "Carles Miravitlles" and online session by Zoom. Register here to attend by Zoom.

Abstract: This thesis focuses on the characterization of ferroelectric Hf_0.5Zr_0.5O₂ thin films and BaTiO₃/SrTiO₃ superlattices 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 Hf_0.5Zr_0.5O₂ on 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 Hf_0.5Zr_0.5O₂ thin films were studied in detail. 

Supervisors:

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

PhD Committee:

• President: Fabio Miletto Granozio, National Research Council of Italy
• Secretary: Francesca Peiró Martínez, Universitat de Barcelona (UB)
• Vocal: José Ángel Pardo Gracia, Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-UNIZAR

University: Universitat Autònoma de Barcelona (UAB)
PhD Programme: Materials Science