Author(s): Rodrigues, Tiago ; Silva, José Pedro Basto ; Figueiras, Fábio ; Soares, M. R. ; Vilarinho, R. ; Moreira, J. Agostinho ; Çaha, Ihsan ; Deepak, Francis Leonard ; Almeida, B. G.
Date: 2024
Persistent ID: https://hdl.handle.net/1822/93938
Origin: RepositóriUM - Universidade do Minho
Subject(s): Ferroelectric thin films; Defect engineering; Polar topologies; Non-volatile memories
In this work, we show that epitaxially strained SrTiO3-δ thin films, grown by ion-beam sputtering onto (001)Nb: SrTiO3 substrates, exhibit a ferroelectric behavior. At the atomic-scale, through high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images, it was possible to identify the presence of polar nanoregions with non-trivial polar topological structures in the SrTiO3-δ film, which are induced through oxygen vacancies. To further confirm the presence of strained regions with a polar structure, Raman spectroscopy and high-resolution X-ray diffraction were employed and it was possible to confirm the presence of a tetragonal structure in the SrTiO3-δ film, with a tetragonality ratio (c/a) of 1.005. Scanning probe microscopy and macroscopic polarization-electric field hysteresis loops show ferroelectric behavior with maximum polarization of ~1.5 μC/cm2 , remnant polarization of ~0.4 μC/cm2 and coercive field of ~0.3 MV/cm. This work opens a window for exploring novel polar topological effects in sub-10 nm thin film materials for non-volatile memory application.
